Category: Class 9

Tamilnadu State Board New Syllabus Samacheer Kalvi 9th Science Guide Pdf Chapter 23 Economic Biology Text Book Back Questions and Answers, Notes.

Tamilnadu Samacheer Kalvi 9th Science Solutions Chapter 23 Economic Biology

9th Science Guide Economic Biology Text Book Back Questions and Answers

I. Choose the correct answer :

Question 1.
The production and management of fish is called
(a) Pisciculture
(b) Sericulture
(c) Aquaculture
(d) Monoculture
Answer:
(a) Pisciculture

Question 2.
Which one of the following is not an exotic breed of cow?
(a) Jersey
(b) Holstein-Friesan
(c) Sahiwal
(d) Brown Swiss
Answer:
(c) Sahiwal

Question 3.
Which one of the following is an Italian species of honey bee?
(a) Apis mellifera
(b) Apis dorsata
(c) Apis florae
(d) Apis cerana
Answer:
(a) Apis mellifera

Question 4.
Which one of the following is not an Indian major carp?
(a) Rohu
(b) Catla
(c) Mrigal
(d) Singhara
Answer:
(d) Singhara

Question 5.
Drones in the honey bee colony are formed from
(a) unfertilized egg
(b) fertilized egg
(c) parthenogenesis
(d) both b and c
Answer:
(a) unfertilized egg

Question 6.
Which of the following is an high milk yielding variety of cow?
(a) Holstein-Friesan
(b) Dorset
(c) Sahiwal
(d) Red Sindhi
Answer:
(a) Holstein-Friesan

Question 7.
Which Indian variety of honeybee is commonly used for apiculture?
(a) Apis dorsata
(b) Apis florea
(c) Apis niellifera
(d) Apisindica
Answer:
(d) Apis indica

Question 8.
…………….. is the method of grafting plants without soil.
(a) Horticulture
(b) Hydroponics
(c) Pomology
(d) None of these
Answer:
(b) Hydroponics

Question 9.
The symbiotic association of fungi and vascular plants is
(a) Lichen
(b) Rhizobium
(c) Mycorrhizae
(d) Azotobacter
Answer:
(c) Mycorrhizae

Question 10.
The plant body of mushroom is
(a) Spawn
(b) Mycelium
(c) Leaf
(d) All of these
Answer:
(b) Mycelium

II. Fill in the blanks :

1. Quinine drug is obtained from …………………
Answer:
Cinchona (cinjona maram)

2. Carica papaya leaf can cure disease.
Answer:
Dengue

3. Vermicompost is a type of soil made by …………… and microorganisms.
Answer:
Earthworm

4. …………… refers to the culture of prawns, pearl and edible oysters.
Answer:
Aquaculture

5. The largest member in a honey bee hive is is the ……………
Answer:
Queen Bee

6. …………… is a preservative in honey.
Answer:
Formic acid

7. …………… is the method of culturing different variety of fish in a water body.
Answer:
Polyculture

III. Say true or false. If false, correct Hie statement:

1. Mycorrhiza is an algae.
Answer:
Correct statement: Mycorrhiza is a tumgi

2. Milch animals are used in agriculture and transport.
Answer:
False
Correct statement: Milch animals are used in milk production

3. Apis florea is a rock bee.
Answer:
False
Correct statement: Apis florea is a rock bee.

4. Ongole is an exotic breed of cattle.
Answer:
False.
Correct statement: Ongole is an Indian breed of cattle.

5. Sheep manure contains high nutrients than farm yard manure.
Answer:
True.

IV. Differentiate the following :

(a) Exotic breed and Indigenous breed.
Answer:

Exotic Breed	Indigenous Breed
The exotic breeds are imported from foreign countries.	Indigenous Breeds are native of India.
They include Jersey, Brown Swiss, Holstein – Friesian.	They include Sahiwal, Red Sindhi, Deoni and Gir.

(b) Pollen and Nectar
Answer:

Pollen	Nectar
It is fine powder of microscopic particles from the male flower.	It is a‘sweet sdbstance, produced by plants to attract pollinators such as bee, butterfly.
Pollen is produced by anther, male reproductive organ.	Nectar is converted into Honey.

(c) Shrimp and Prawn
Answer:

Shrimp	Prawn
Marine inhibited prawns are called Shrimps, which breed in deep sea.	Prawn are crustaceans inhibited in fresh water, marine water, estuaries, etc

(d) Farmyard manure and Sheep manure
Answer:

Farmyard manure	Sheep manure
It is a mixture of cattle dung, urine, litter material, and other dairy wastes.	This is the manure of sheep or Goat
0.5% Nitrogen, 0.2% Phosphate, 0.5% potash.	3% Nitrogen, 1% phosphorus pentoxide 2% potassium oxide.
Less compared to sheep manure	High nutrients.

V. Match the following :

Column A	Column B
1. Lobsters	Marine fish
2. Catla	Pearl
3. Sea bass	Shell fish
4. Oysters	Paddy
5. Pokkali	Fin fish
6. Pleurotus sps	Psoriosis
7. Sarpagandha	Oyster mushroom
8. Olericulture	Reserpine
9. Wrighta tinctoria	Vegetable farming

Answer:

Column A	Column B
1. Lobsters	Shell fish
2. Catla	Fin fish Pearl
3. Sea bass	Marine fish
4. Oysters	Pearl
5. Pokkali	Paddy
6. Pleurotus sps	Oyster mushroom
7. Sarpagandha	Reserpine
8. Olericulture	Vegetable farming
9. Wrighta tinctoria	Psoriosis

VI. Answer briefly :

Question 1.
What are the secondary metabolites?
Answer:
Most medicines are obtained either directly or indirectly from plants. All the major system of medicines such as Ayurveda, Yoga, Unani, Siddha, Homeopathy (AYUSH) use drugs obtained from plants and animals. These drugs from medicinal plants are called secondary metabolites.

Question 2.
What are the types of vegetable gardens?
Answer:
Types of vegetable gardens are

1. Kitchen or Nutrition gardening
2. Commercial gardening
3. Vegetable forcing
4. Greenhouse (or) Poly House
5. Organic Vegetable Gardening.

Question 3.
Mention any two mushroom preservation methods.
Answer:
Drying and Vacuum Cooling are some methods used to preserve mushrooms.

Question 4.
Enumerate the advantages of vermicompost over chemical fertilizer.
Answer:

• Vermicompost is free from pathogens and toxic elements.
• It enhances the decomposition of organic matter in soil.
• It is rich in beneficial microflora.
• It contains valuable vitamins, enzymes and growth regulator substances.

Question 5.
What are the species of earthworm used for vermiculture?
Answer:
Among the vast community of earthworms, only very few species can be used for vermicompost production. They are Perionyx excavatus (Indian blue worm), Eisenia fetida (Red worms), Eudrilus eugeniae (African nightcrawler).

Question 6.
List the medicinal importance, of honey.
Answer:

• Honey has an antiseptic and antibacterial property.
• It is a blood purifier.
• It helps in building up hemoglobin content in the blood.
• It prevents cough, cold, fever, and relieves sore throat.
• It is a remedy for ulcers of the tongue, stomach, and intestine.
• It enhances digestion and appetite.

VII. Answer in detail :

Question 1.
Enumerate the advantage of hydroponics.
Answer:
Hydroponics was demonstrated by a German Botanist Julius Von Sachs in 1980.
Advantages:

• Crops can be grown in places where the land is limited, doesn’t exist, or is heavily contaminated.
• The climate – temperature, humidity, light intensification, the composition of the air can be monitored.
• Conservation of water and nutrients.
• Controlled plant growth.
• No intrusion by weeds.
• Fewer pests & diseases
• Minimal use of insecticide or herbicides
• In deserts and Arctic regions hydroponics can be an effective alternative method.
• Hydroponics is successfully employed for the commercial production of seedless cucumber and tomato.

Question 2.
Define Mushroom culture. Explain the mushroom cultivation methods.
Answer:
Mushroom is a fungus belonging to basidiomycetes. It is rich in proteins, fibres, vitamins and minerals. Mushroom culture is the process of producing food, medicine, and other products by the cultivation of mushrooms.
Mushrooms can be cultivated either on paddy straw or on the wood log.
Major stages of mushroom cultivation are;

• Composting: Compost is prepared by mixing paddy straw with a number of organic materials like cow dung and inorganic fertilizers. It is kept at about 50°C for one week.
• Spawning: Spawn is the mushroom seed. It is prepared by growing fungal mycelium in grains under sterile conditions. Spawn is sown on the compost.
• Casing: Compost is covered with a thin layer of soil. It gives support to the growing mushroom, provides humidity, and helps regulate the temperature.
• Pinning: Mycelium starts to form a little bud, which will develop into mushrooms. Those little white buds are called pins.
• Harvesting: Mushroom grows better in 15°C – 23°C. They grow 3 cm in a week which is the normal size for harvesting. In the third week, the first flush mushroom can be harvested.

Question 3.
What are the sources of organic resources for vermicomposting?
Answer:
Biologically degradable organic wastes are used as potential organic resources for vermicomposting.
They are :

• Agricultural wastes (Crop residue, Vegetable waste, Sugarcane trash).
• Crop residues (rice straw, tea wastes, cereal and pulse residues, rice husk, tobacco wastes, coir wastes).
• Leaf litter.
• Fruit and vegetable wastes.
• Animal wastes (cattle dung, poultry droppings, pig slurry, goat and sheep droppings).
• Biogas slurry.

Question 4.
Give an account of different types of fish ponds used for rearing fishes.
Answer:
Types of ponds for fish culture
The fish farm requires different types of the pond for the various developmental stages of fish growth. They are:

1. Breeding pond: Healthy and sexually mature male and female fishes are collected and introduced in this pond for breeding. The eggs released by the female are fertilized by the sperm and fertilized eggs float in water as frothy mass.
2. Hatchling pits: The fertilized eggs are transferred to hatching pits for hatching. Two types of hatching pits are hatcheries and hatching hapas.
3. Nursery ponds: The hatchlings are transferred from hatching pits after 2 to 7 days. The hatchlings grow into fry and are cultured in these ponds for about 60 days with proper feeding till they reach 2 -2.5 cm in length.
4. Rearing ponds: Rearing ponds are used to culture the fry. The fish fry are transferred from nursery pond to rearing ponds and are maintained for about three months till they reach 10 to 15 cm in length. In these rearing ponds the fry develops into fingerlings.
5. Stocking pond: The stocking pond is also called a culture pond or production pond. These ponds are used to rear fingerlings upto the marketable size. Before releasing the fingerlings, the pond is manured with organic manure and inorganic fertilizers.

Question 5.
Classify the different breeds of the cattle with suitable examples.
Answer:

VIII. Higher Order Thinking Skills :

Question 1.
Biomanuring plays an important role in agriculture. Justify.
Answer:

• Biomanuring reduces soil pollution, water pollution and air pollution, etc.
• It protects soil health and promotes soil fertility.
• It provides healthy production of vegetables, fruits etc.
• It makes the soil fertile by adding nutrients like nitrogen.

Question 2.
Each bee hive consists of hexagonal cells. Name the material in which the cell is formed and mention the significance of the hexagonal cells.
Answer:

• The comb of the bees is formed mainly by the secretion of the wax glands present in the abdomen of the worker bee.
• A comb is a vertical sheet of wax with double layer of hexagonal / cells.
• Hexagonal cells serve as storage vessels for honey as well as homes to raise the young bees.

9th Science Guide Economic Biology Additional Important Questions and Answers

I. Choose the correct answer :

Question 1.
Olericulture refers to the farming of ………………..
(a) Vegetable
(b) Flowers
(c) Fruits
(d) All of these
Answer:
a) Vegetable

Question 2.
India is the ………………..largest producer of vegetables next to China.
(a) First
(b) Second
(c) Third
(d) Fourth
Answer:
(b) Second

Question 3.
Tuber rose is cultivated from ………………..
(a) Madurai zone
(b) Hill area zone
(c) Coimbatore zone
(d) Hosurzone
Answer:
(c) Coimbatore zone

Question 4.
Green manure also helps in reclamation of ……………….. soils.
(a) Acidic
(b) Alkaline
(c) neutral
(d) None of these
Answer:
(b) Alkaline

Question 5.
Azolla having a cyanobacterial symbiotic association with ………………..
(a) Azotobacter
(b) Azospirillum
(c) Mycorrhizae
(d) Anabaena
Answer:
(d) Anabaena

Question 6.
Quinine is a best drug for treatment of ………………..
(a) Dengue
(b) Psoriasis
(c) Malaria
(d) Leukemia
Answer:
(c) Malaria

Question 7.
Nilavembu kashayam is givep to patients/people to protect from . ………………..
(a) Dengue
(b) Chikungunya
(c) Diabetes
(d) All of these
Ans :
(d) All of these

Question 8.
Reserpine is derived from ………………
(a) Cathyranthusroseus
(b) Rauwolfia serpentina
(c) Hemidesmus indicus
(d) Aloe vera
Answer:
(b) Rauwolfia serpentina

Question 9.
Casing is done on the mushroom to ………………..
(a) support the growth of mushroom
(b) provide humidity to mushroom
(c) regulate the temperature
(d) All the above
Answer:
(d) All the above

Question 10.
The growth medium of Aeroponics is
(a) Nutrients
(b) Water
(c) air
(d) soil
Answer:
(c) air

Question 11.
The Indigenous Draught breed from Thanjavur district is ………………..
(a) Pulikulam
(b) Bargur
(c) Ongole
(d) Umblachery
Answer:
(d) Umblachery

Question 12.
………………..are low in fibre and contain a high level of carbohydrates, protein, and other
nutrients.
(a) Silage
(b) Concentrates
(c) Roughage
(d) None of these
Answer:
(b) Concentrates

Question 13.
Operation Flood is the programme for ………………..development.
(a) Dairy
(b) Cattle
(c) Marine
(d) Agriculture
Answer:
(a) Dairy

Question 14.
Air-breathing fishes are cultured in ………. water.
(a) Brackish
(b) Fresh
(c) Marine
(d) All of these
Answer:
(b) Fresh

Question 15.
Central Marine Fisheries Research Institute (CMFRI) is situated at …………………
(a) Chennai
(b) Mumbai
(c) Cochin
(d) Vizag
Answer:
(c) Cochin

Question 16.
Culture of fishes along with Agricultural crops is known as ………………..
(a) Polyculture
(b) Extensive culture
(c) Integrated culture
(d) Intensive culture
Answer:
(c) Integrated culture

Question 17.
The longest marine water prawn is
(a) Penaeus Indicus
(b) Penaeus monodon
(c) Macro brachium rosenbergii
(d) Macro brachium malcoumsonii
Answer:
(b) Penaeus monodon

Question 18.
Earthworms are sacred – This statement was made by ………………..
(a) Aristotle
(b) Darwin
(c) Plato
(d) Cleopatra
Answer:
(d) Cleopatra

Question 19.
Vermicompost is similar to ……………….. in colour and appearance.
(a) sheep manure
(b) Farmyard manure
(c) Green manure
(d) All of these
Answer:
(b) Farmyard manure

Question 20.
………………..is an enzyme present in Honey
(a) Sucrose
(b) Dextrose
(c) Invertase
(d) Maltase
Answer:
(c) Invertase

Question 21.
Fastest growing sector in Agriculture is ………………..
(a) Vegetable forcing
(b) Hydroponics
(c) Greenhouse
(d) Aqua ponies
Answer:
(c) Greenhouse

Question 22.
Which of the following are Indian cattle?
(i) Bos indicus
(ii) Bos domesticus
(iii) Bos bubalis
(iv) Bos vulgaris
(a) (i) and (ii)
(b) (i) and (iii)
(c) (ii) and (iii)
(d) (iii) and (iv)
Answer:
(b) (i) and (iii)

Question 23.
Which one of the following is referred as red worms?
(a) Eudrilus fetida
(b) Eudrilus eugieniae
(c) Eisenia fetida
(d) Lampito mauritii
Answer:
(c) Eisenia fetida

Question 24.
Mehsana is a breed of
(a) Cow
(b) Buffalo
(c) Goat
(d) Sheep
Answer:
(b) Buffalo

Question 25.
Binomial name of Nilavemubu is ………………..
(a) Leucas Aspera
(b) Andrographis paniculata
(c) Crotalaria juncea
(d) Cassia fistula
Answer:
(b) Andrographis paniculata

II. Fill in the blanks:

1. ………….. is the most intensive type of vegetable growing.
Answer:
Vegetable forcing

2. India stands first in the world in the production of…………………… and …………………….
Answer:
Potato, Lady’s finger

3. Compost is a …………………… as well as a fertilizer, which is rich in nutrients.
Answer:
Soil conditioner

4. Earthworms eat …………………… and excrete it in a digested form.
Answer:
biomass

5. Green manure is obtained from undecomposed green material derived from …………………… plants.
Answer:
Leguminous

6. …………………… is a type of Bio-fertilizers that are capable of producing antifungal and antibacterial compounds.
Answer:
Azotobacter

7. Mycorrhizae increase the uptake of …………………….
Answer:
Phosphorous

8. …………………… is the study of chemical substances derived from plants .
Answer:
Phytochemistry

9. …………………… is used as an antidote for snake bite.
Answer:
Chivan Amalpodi (Sarpagandha)

10. Alkaloids, Terpenoids, flavonoids etc are called …………………… metabolites.
Answer:
Secondary

11. India’s first anti-diabetic ayurvedic drug is …………………….
Answer:
BGR-34

12. Mushroom is a fungi belonging to …………………….
Answer:
Basidiomycetes

13. Hydroponics was first demonstrated by German botanist …………………….
Answer:
Julius Von Sachs

14. Milk production in cattle depends upon the duration of ……………………
Answer:
Lactation

15. Jallikattu madu belongs to …………………… breed.
Answer:
Indigenous Draught

16. Young female calf is called as……………………
Answer:
Heifer

17. Dr.Verghese Kurien is the Father of …………………….
Answer:
White revolution

18. Panchagavya is an…………………… Fertilizer .
Answer:
organic liquid

19. The Central Institute of Brackish Water Aquaculture (CIBA) was established in …………………….
Answer:
1987

20. India holds …………………… position in Marine fish production in the world.
Answer:
10th

21. The eggs released by the female fish are fertilized by the sperm and fertilized eggs float in water as …………………….
Answer:
frothy mass

22. Hatching period in Hatchling pits is …………………….
Answer:
2-7days

23. PUFA stands for ……………………
Answer:
Poly Unsaturated Fatty Acid

24. ………………….. culture is the oldest and traditional method of prawn culture practiced in Kerala.
Answer:
Pokkali

25. The nutrient rich materials that are excreted by earthworms knows as …………………….
Answer:
worm castings

26. The …………………… cells contain honey and pollen.
Answer:
Storage

27. …………………… and…………………… give sweet taste to the honey.
Answer:
Dextrose, Sucrose

28. One kilogram of honey contains …………………… calories.
Answer:
3200

29. …………………… is widely used in cosmetic and pharmaceutical industries.
Answer:
Bee wax

30. …………………… is a nodulating type of microorganism associating symbiotically with the root of legume plants.
Answer:
Rhizobium

31. …………………… is the maintenance of bee colonies in modem hives.
Answer:
Beekeeping

III. Match the following:

I.

(1) Homeopathy	a) Hippocrates
(2) Siddha	b) Patanjali
(3) Unani	c) Charaka Samhita
(4) Ayurveda	d) Agasthya
(5) Yoga	e) Samuel Hahnemann

Answer:
1-e, 2-d,3 -a,4-c,5-b

II.

(1) Rhizobium	a) Crop plants
(2) Azolla	b) Antifungal and antibacterial compounds
(3) Azotobacter	c) vascular plants
(4) Mycorrhizae	d) leguminous plants
(5) Azospirillum	e) Floating nitrogen factory

Answer:
1-d, 2-e, 3-b, 4-c, 5-a

III.

(1) Paddy straw Mushroom	a) Volvariella volvacea
(2) Lingzhi Mushroom	b) Agaricus bisporus
(3) Oyster Mushroom	c) Pieurotussps
(4) Button Mushroom	d) Ganoderma lucidum

Answer:
1-a, 2-d, 3-c, 4-b

IV.

(1) Bargur	a) Indigenous dairy breeds
(2) Tharparkar	b) Buffalo breeds
(3) Murrah	c) Indigenous Draft breeds
(4) Gir	d) Dual-purpose breeds

Answer:
1 – c, 2d, 3 – b, 4 – a

IV. Say true or false. If false, correct the statement:

1. Edible mushrooms are valuable source of supplementary lipids.
Answer:
False.
Correct statement: Edible mushrooms are valuable source of supplementary proteins.

2. The yield of greenhouse is very high compared to outdoor cultivation.
Answer:
True.

3. Rhizobium fix atmospheric nitrogen and convert them to nitrates.
Answer:
False.
Correct statement: Rhizobium fix atmospheric nitrogen and convert them to ammonia.

4. The roots in hydroponic plant absorb water and nutrients but do not perform the anchoring function.
Answer:
True.

5. Spawn is prepared by growing fungal mycelium in grains under fertile conditions.
Answer:
False.
Correct statement: Spawn is prepared by growing fungal mycelium in grains under sterile conditions.

6. Local breed animals show excellent resistance to diseases.
Answer:
True

7. Milk production of Buffaloes are less than that of cow.
Answer:
False.
Correct statement: Milk production of Buffaloes are more than that of cow.

8. The salinity of brackish water ranges from 30-35 ppt.
Answer:
False.
Correct statement: The salinity of brackish water ranges from 1-32 ppt.

9. Fish meal is used as a feed for cattle and poultry farming animals.
Answer:
True.

10. Earthworm feeds on inorganic wastes and excrete it in digested form known as castings.
Answer:
False.
Correct statement: Earthworm feeds organic wastes and excrete it in a digested form known as castings.

11. Medicinal plants contain compounds that can be used for therapeutic purposes.
Answer:
True.

12. Anthraquinones is obtained from Ocimum sanctum.
Answer:
False.
Correct statement: Anthraquinones is obtained from Aloevera.

13. Aquaponics is a technique of growing plants with their root supplied with moisture present in the air.
Answer:
False.
Correct statement: Aeroponics is a technique of growing plants with their root supplied with moisture present in the air.

V. Assertion and Reason :

(a) Direction: In each of the following questions, a statement of Assertion is given and a corresponding statement of Reason is given just below it. Of statements, given below, mark the correct answer as
a. If both Assertion and Reason are true and Reason is the correct explanation of Assertion.
b. If both Assertion and Reason are true that Reason is not the correct explanation of Assertion.
c. If Assertion is true but Reason is false.
d. If Assertion is false but Reason is true.

Question 1.
Assertion : Apiculture, vermiculture are gaining more importance.
Reason : They have economical and commercial values.
Answer:
(a) Both Assertion and Reason are true and Reason is the correct explanation of Assertion

Question 2.
Assertion : Foreign dairy breeds are preferred over local breeds.
Reason: The foreign breeds have shorter lactation periods.
Answer:
(c) Assertion is true but Reason is false
Reason : The foreign breeds have longer lactation periods.

Question 3.
Assertion : Bullocks are good draft animals in draft breeds.
Reason : Cows are poor milk yielders in draft (or) Draught breeds.
Answer:
(b) Both Assertion and Reason are true that Reason is not the correct explanation of Assertion

Question 4.
Assertion : Porous soil permits both aeration and quick absorption of water.
Reason : The burrowing and soil feeding habits of earthworm make the soil
porous.
Answer:
(a) Both Assertion and Reason are true and Reason is the correct explanation of Assertion

Question 5.
Assertion : Hydroponics can be defined as a soilless growing system in which plants grow in water.
Reason : If a plant is provided with water, minerals and required nutrients, it will grow well and yield more even in the absence of soil.
Answer:
(a) Both Assertion and Reason are true and Reason is the correct explanation of Assertion

Question 6.
Assertion : Fish and other varieties of aquatic animals are used as food.
Reason : Fish and other varieties of sea food constitute good source of nutrition
Answer:
(a) Both Assertion and Reason are true and Reason is the correct explanation of Assertion

Question 7.
Assertion : The production of food from animal sources has increased greatly in the last few decades.
Reason : Operation flood and blue revolution production has increased in recent years.
Answer:
(b) Both Assertion and Reason are true and Reason is not the correct explanation of Assertion

Blue revolution is the concept of rapid increase in the production of fish and marine product.

VI. Define the following.

a. Pisciculture
Answer:
Pisciculture or Fish culture is the process of breeding and rearing of fishes in ponds, reservoirs (dams), lakes, rivers, and paddy fields.

b. Apiculture
Answer:
Apiculture is the rearing of honey bee for honey. It is called Beekeeping

c. Vermiculture
Answer:
Vermiculture involves the artificial rearing or cultivation of earthworms and using them for the production of compost from natural organic wastes.

d. Maricuiture (or) Marine water aquaculture
Answer:
The cultivation of aquatic organisms in seawater is referred as Mariculture (or) Sea farming.

e. Floriculture (or) Flower Farming
Answer:
Floriculture is the art of cultivation of flowering and ornamental plants in garden for beauty or floristry.

f. Compost
Answer:
Compost is a soil conditioner as well as a fertilizer, which is rich in nutrients.

g. Pomiculture
Answer:
Pomiculture is cultivation, development, entrancement of Fruits.

h. Pinning
Answer:
Pinning is the development of little white buds from mycelium.

VII. Very Short Answer questions :

Question 1.
Name the main classes of Horticulture.
Answer:
They are four main classes of Horticulture

1. Pomology (fruit farming),
2. Olericulture (vegetable farming),
3. Floriculture (flowers farming),
4. Landscape gardening.

Question 2.
What is Floriculture?
Answer:
Floriculture is the art of cultivation of flowering and ornamental plants in garden for beauty (or) floristry.

Question 3.
What is spawning?
Answer:
Spawn is the mushroom seed. It is prepared by growing fungal mycelium in grains under sterile conditions. Spawning is the sowing or planting of spawn on the compost.

Question 4.
What is Vermicompost?
Answer:
Vermicompost is a method of making compost with the use of earthworms, which ^ generally live in soil.

Question 5.
List the leguminous plants providing green manure.
Answer:

• Sunhemp (Crotolariajuncea)
• Dhaincha (Sesbania aculeata)
• Sesbania (Sesbania speciosa)

Question 6.
Define: phytochemistry.
Answer:
Phytochemistry is the study of phytochemicals which are chemical substances derived from various parts of the plant.

Question 7.
Name any three edible mushrooms.
Answer:

1. Button mushroom (Agaricus bisporus)
2. Oyster mushroom (Pleurotus sps),
3. Paddy straw mushroom (Volvariella volvacea).

Question 8.
Mention the main problems of harvesting mushrooms.
Answer:

1. Discolouration
2. Weight and flavour loss.

Question 9.
Name any three methods to increase mushroom life.
Answer:

1. Freezing
2. Vacuum Cooling
3. Gamma radiation and storing at 15°C.

Question 10.
Write classification of cattle breeds.
Answer:
Cattle breeds are classified into three types:

1. Dairy breeds
2. Drought (or) Draft breeds
3. Dual-purpose breeds.

Question 11.
How is the Fish Meal prepared?
Answer:
Fish meal is prepared from the wastes of fish oil (or) from whole fish.

Question 12.
List the methods employed in Prawn Culture,
Answer:

1. Seed collection and hatchery method.
2. Paddy cum prawn culture method.

Question 13.
What is Bee wax?
Answer:
Bee wax is the natural by-product secreted by the wax glands of worker bee to construct the combs of a beehive.

Question 14.
Mention the aim of operation Flood.
Answer:
Operation Flood is based on dairy commodity aid to increase milk supply in urban y areas.

Question 15.
What does NDDB stand for?
Answer:
NDDB – National Dairy Development Board.

VIII. Short Answer questions :

Question 1.
How is compost prepared?
Answer:
Compost is produced by the decomposition of organic matter such as crop residues,
animal wastes, food wastes, industrial and municipal wastes by microorganisms under controlled conditions.

Question 2.
Mention the advantages of Green Manure.
Answer:

• Green Manure improves soil structure.
• It increases water holding capacity and decreases soil loss by erosion.
• It also helps in reclamation of alkaline soils and reduces weed proliferation.

Question 3.
Write short notes on Mushrooms;
Answer:

• Mushroom is a fungi belonging to basidiomycetes.
• It is rich in proteins, fibres, vitamins and minerals.
• Cultivation of Mushroom takes one to three months.

Question 4.
Explain briefly about Aquaponics.
Answer:

• Aquaponics is a system of a combination of conventional aquaculture with hydroponics in a symbiotic environment.
• Two main parts are (i) Aquaculture – for raising aquatic animals like fish (ii) hydroponics – for raising plants.

Question 5.
Write short notes on Intensive Cattle Development Programme.
Answer:

• Intensive Cattle Development Programme is based on cross-breeding of indigenous cows with exotic European breeds to increase milk production.
• New methods and modem equipments are made available for machine – milking of cows.

Question 6.
Differentiate Extensive and Intensive Fish culture.
Answer:
Extensive Fish culture

1. Culture of fishes in large areas.
2. Low stocking density
3. Natural feeding

Intensive Fish culture

1. Culture of fishes in small areas.
2. High stocking density
3. Artificial feeding

Question 7.
What is green manure? How is it beneficial?
Answer:
Green manure is obtained by collection and decomposition of green leaves, twigs of trees, shrubs, and herbs growing in wastelands, field bunds etc. Green manure improves soil structure, increases water-holding capacity, and decreases soil loss by erosion. It also helps in the reclamation of alkaline soils and reduces weed proliferation. It is manure obtained from undecomposed green material derived from leguminous plants e.g. Sunhemp, Dhaincha, etc.

Question 8.
Enumerate the nutritional values of prawns.
Answer:

• Prawns are a rich nutritive source of protein, vitamin A & D, Glycogen and Amino acids.
• They contain less amount of fat.
• Cultured prawns provide Poly Unsaturated Fatty Acid (PUFA).

Question 9.
List the important methods of vermicomposting.
Answer:

• Bin or Container method.
• Vermicomposting of organic wastes in field pits.
• Vermicomposting of organic wastes on ground heaps.

Question 10.
What do you know about AYUSH?
Answer:

• AYUSH is the ministry of Government of India for Indian (or) Alternative Medicine. ‘
• AYUSH refers to Ayurveda, Yoga, Unani, Siddha and Homeopathy.

Question 11.
Why do we call Haryana and Kankrej breed of cattle as dual-purpose breeds?
Answer:
Haryana, Kankraj breeds

• provide milk ,
• also useful for farm work.
  So, they are called Dual-purpose breeds.

Question 12.
How is the division of labour observed in honey bees?
Answer:
Division of labour by Honey bees :
Queen Bee: Responsible for laying eggs in a colony.
Drones: They fertilize the eggs, produced by Queen Bee.
Worker Bee :
Functions

• Collect Honey
• Look after the young ones
• Clean the comb
• Defend the hive
• Maintain the temperature of beehive.

Question 13.
What is the nutritional importance of fish liver oils? Name any two marine fishes which yield these oils.
Answer:
Nutritional Importance of Fish liver oil:

• Great medicinal value
• They are rich in Vitamin A, D, and E.

Two marine fishes: Shark, Tuna.

IX. Long Answer questions :

Question 1.
Compare types of Bio fertilisers with their functions.
Answer:

Question 2.
What are the types of honey bees found in a colony?
Answer:
There are three types of individuals in a colony namely the Queen bee, the drones and the worker bees.

1. Queen Bee: The queen is the largest member and the fertile female of the colony. They are formed from fertile eggs. The queen is responsible for laying eggs in a colony. The life span of the queen bee is 3-4 years.
2. Drones: They are fertile males. They develop from unfertilized eggs. They are larger than the workers and smaller than the queens. Their main function is to fertilize the eggs produced by the queen.
3. Worker Bees: They are sterile female bees and are the smallest members of the colony. Their function is to collect honey, look after the young ones, clean the comb, defend the hive and maintain the temperature of the beehive.

Question 3.
Discuss various types of Honey bees with their functions.
Answer:

Question 4.
Explain the structure of Honey Bee Comb.
Answer:
The comb of the bees is formed mainly by the secretion of the wax glands present in the abdomen of the worker bee.
Comb : It is a vertical sheet of wax with double layer of hexagonal cells.

Types of Cells:
(i) Storage cell:

• They are built in the margin and at the top of the comb.
• It contains honey and pollen.

(ii) Brood cells : They are built in the centre and the lower part of the comb. They
are dividecf into three cells such as

• Worker chamber
• Drone chamber
• Queen chamber

Where the larvae developing into worker, drone and queen aye reared.

Question 5.
How is honey formed?
Answer:

• The honey bees suck the nectar from various flowers.
• The nectar passes to the honey sac, where sucrose mixes with nectar.
• By enzymatic action, Nector along with sucrose is converted into Honey.
• Honey is stored in the special chambers of the hive.

Question 6.
Discuss the various nutrients present in Honey.
Answer:
Honey is a sweet viscous, edible natural food product. ‘

• Sweet taste : Dextrose and sucrose give sweet taste to the honey.
• Honey contains protein, free amino acids, vitamins like ascorbic acid etc.
• Acids such as citric acid, gluconic acid and formic acid are found in honey.
• Minerals such as calcium, Iron, Phosphorous and manganese are present.
• Invertase is the enzyme present in honey.

Question 7.
Give an account on medicinal plants.
Answer:

(1) Katralai (Aloe vera)
It is herbal leaves.
The drug derived from it, is Anthraquinones.
This is best treatment for skin problems and cancer. It heal wounds.

(2) Tulsi (Octimum sanctum)
It is an important herb.
Leaves have medicinal value.

Uses :

• Best medicine for cold and fever.
• It is also useful for cardiac diseases, gynecological disorder.
• Skin disorders and respiratory problems can also be treated.
  Sura’s o Science – 9th Std o Unit 23 o Economic Biology

(3) Nilavembu (Andrograhis paniculata)
It is a herbal plant with roots and leaves have medicinal values.
Uses :

• It is the best tonic for dengue fever.
• It is also used to treat diabetes and malaria.
• It is best remedy for ulcer, Influenza, Chikungunya etc.,

(4) Vepalai (Neem) – (Wrightia tinctoria)
It is a medicinal plant with eVtry part has medicinal values.
Uses:

• It has antipyretic, antibacterial and antitumour.
• It gives best immunity power.
• It is used to treat 4rin infections (or) diseases such as Psoriasis.
• It is also good for respiratory disorders, diarrhoea and Swellings.

(5) Pappali (Carica papaya)
Like neem, every part of papaya has medicinal benefits.
Uses:

• Best medicine for Dengue.
• It reduces risk of heart diseases, diabetes arid cancer.
• It lowers blood pressure and heals wounds.

Question 8.
What are biofertilisers? Give examples. Why are biofertilisers better than other fertilisers?
Answer:
Biofertilisers are substances that contain living microorganisms, when applied to plant promote growth by increasing primary nutrients to host plant.
Examples: (1) Rhizobium (2) Azospirillum (3) Azotobacter (4) Mycorrhizae (5) Azolla

Advantages of Biofertiser over chemical fertilisers :

• Biofertilizers are environmental friendly fertilizers.
• They enrich the nutrient quality of soil.
• They sustain soil health.
• They improve texture, structure and water-holding capacity of soil.
• No adverse effect on plant growth and soil fertility.

Question 9.
Write short notes on
a) Importance of greenhouses
b) Uzahavan mobile Application
c) Major floriculture zones
d) Azospirillum
Answer:
(a) Importance of Greenhouses

• Continuous production of disease-free plants.
• Very less water requirement and less pesticide usage.
• Very high yield and protection from uncertain weather.

(b) Uzhavan App:

• Launched by the Government of Tamilnadu.
• It provides information to farmers about subsidies, crop insurance, and stock of seeds and fertilizer.

(c) Major Floriculture zones :

• Hosurzone
• Chennai zone
• Madurai zone
• Trichy zone
• Coimbatore zone
• Kanyakumari zone
• Hill area zone

(d) Azospirillum :

•  It has the ability to use Atmospheric Nitrogen and transport to this nutrient crop plants
•  It increases grain productivity, (e.g.) cereals 5-20%, millets 30% and Fodders 50%.

Question 10.
Explain the feeding management of dairy cattle.
Answer:

1. Dairy cattle need balanced rations containing all nutrients in a proportional amount.
2. Food additives should contain minerals, vitamins, antibiotics and hormones to
   promote the growth of animals, good yield of milk, and protect from diseases.
3. The daily average feed ratio of milking cow is:
   • 15 – 25 kg of roughage (dry grass and green fodder)
   •  4 – 5 kg of green mixture.
   • 100- 150 litres of water.

X. Thinking Skills.

Question 1.
Arun and Akash were given fertilisers and earthworm compost both to be used in the fields. Akash preferred to use earthworm compost. Why did not select the fertilizers?
Answer:

• Inorganic fertilizers pollute the soil.
• Inorganic fertilizers contain chemicals that are toxic in nature and will result in health problems.

Question 2.
What is pasturage and how is it related to honey production?
Answer:

• Pasturage is land with herbaceous vegetation cover used for unregulated livestock ; as a part of farms in arid regions.
• Better pasturage provides better habitat for honey bee and honey production.

Tamilnadu State Board New Syllabus Samacheer Kalvi 9th Science Guide Pdf Chapter 15 Carbon and its Compounds Text Book Back Questions and Answers, Notes.

Samacheer Kalvi 9th Science Solutions Chapter 15 Carbon and its Compounds

9th Science Guide Carbon and its Compounds Text Book Back Questions and Answers

I. Choose the correct answer :

Question 1.
A phenomenon in which an element exists in different modification in same physical state is called
(a) isomerism
(b) allotropy
(c) catenation
(d) crystallinity
Answer:
(b) allotropy

Question 2
Carbon forms large number of organic compounds due to
(a) Allotropy
(b) Isomerism
(c) Tetravalency
(d) Catenation
Answer:
(d) Catenation

Question 3.
Nandhini brings her lunch every day to school in a plastic container which has resin code number 5. The container is made of
(a) Polystyrene
(b) PVC
(c) Polypropylene
(d) LDPE
Answer:
(c) Polypropylene

Question 4.
Plastics made of Polycarbonate (PC) and Acrylonitrile Butadiene Styrene (ABS) . are made of resin code …………………
(a) 2
(b) 5
(c) 6
(d) 7
Answer:
(a) 7

Question 5.
Graphene is one atom thick layer of carbon obtained from
(a) diamond
(b) fiillerene
(c) graphite
(d) gas carbon
Answer:
(c) graphite

Question 6.
The legal measures to prevent plastic pollution come under the Protection …………….. Act 1988.
(a) Forest
(b) Wildlife
(c) Environment
(d) Human rights
Answer:
(c) Environment

II. Fill in the blanks :

1. ………………. named carbon.
Answer:
Antoine Lavoisier

2. Buckminster Fullerene contains ………………… carbon atoms.
Answer:
60

3. Compounds with same molecular formula and different structural formula are known as ………………….. .
Answer:
Isomers

4. …………….. is a suitable solven for Sulphur.
Answer:
Allotropy

5. There are ……………. plastic resin codes.
Answer:
seven

III. Match the following :

Alkyne	Bucky Ball
Andre Geim	Oxidation
C60	Graphene
Thermocol	Triple bond
Combution	Polystyrene

Answer:

Alkyne	Triple bond
Andre Geim	Graphene
C60	Bucky Ball
Thermocol	Polystyrene
Combution	Oxidation

IV. Answer in briefly :

Question 1.
Differentiate graphite and diamond.
Answer:

Graphite	Diamond
Each carbon atom has three covalent bonds.	Each carbon atom has four covalent bonds.
Soft, slippery to touch and opaque	Hard, heavy and transparent
It has planar layers of hexagon units.	It has tetrahedral units linked in three dimension
It is conductor of heat and electricity.	It is non-conductor of heat and electricity

Question 2.
Write all possible isomers of C₄H₁₀
Answer:

Question 3.
Carbon forms only covalent compounds. Why?
Answer:
Carbon forms only covalent compounds because it has 4 electrons, in its.

Question 4.
Define Allotrophy.
Answer:
Allotrophy is a property by which are element can exist in more than one form that are physically different and chemically similar.

Samacheer Kalvi 9th Science Guide Chapter 15 Carbon and its Compounds 1

Question 5.
Why are one-time use and throwaway plastics harmful?
Answer:

1. Use and throwaway plastics cause short and long-term environmental damage.
2. Half of all the plastic made today is used for throwaway plastic items. These block drains and pollute water bodies.
3. One-time use plastic causes health problems for humans, plants and animals.
4. Some examples are plastic carry bags, cups, plates, straws, water pouches, cutlery and plastic sheets used for food wrapping.

V. Answer in detail :

Question 1.
What is catenation? How does carbon form catenated compounds?
Answer:
Catenation is binding of an element to itself or with other elements through covalent bonds to form open chain or closed chain compounds.

• Carbon is the most common element which undergoes catenation and long chain compounds.
• Carbon atom links repeatedly to itself through covalent bond to form linear branched chain (or) ring structure

• This property of carbon itself is the reason for the presence of large number of organic carbon compounds.
• So organic chemistry essentially deals with catenated carbon compounds.
• Example: Starch and cellulose contain chains of hundreds of carbon atoms.

Question 2.
What are the chemical reactions of carbon?
Answer:
Elemental carbon undergoes no reaction at room temperature.
Oxidation : Carbon combines with oxygen to form its oxides such as carbon monoxide (CO) and carbon dioxide (CO₂), with evolution of heat. Organic carbon compounds like hydrocarbon also undergo oxidation to form oxides and steam with evolution of heat and flame.

This reaction is also called ‘Combustion’.

Reaction with Steam : Carbon reacts with steam to form carbon monoxide hydrogen. This mixture is called water gas.
C_(S) + H₂O_(g) → CO_(g) + H_2(g)

Reaction with Sulphur: With sulphur, carbon forms its disuiphide at high temperature.
C_(S) + S_(g) → CS_2(g)

Reaction with Metals : At elevated temperatures, carbon reacts with some metals like iron, tungsten, titanium, etc., to form their carbides
W_(S)+C_(g) → WC_(S)

Question 3.
Name the three safer resin codes of plastics and describe their features.
Answer:

VI. Higher Order Thinking Skills:

Question 1.
Why do carbon exist mostly in combined state?
Answer:
Carbon is an element that can form many different compounds, as each carbon atom can form 4 chemical bonds with other atoms and because the carbon atom is just the right size to fit in comfortably as parts of very large molecules.

Question 2.
When a carbon fuel burns in less aerated room, it is dangerous to stay there. Why?
Answer:

• When a carbon fuel bums in less aerated room, the fuel may undergo incomplete combustion.
• It results in the formation of carbon monoxide.
• When exposed to carbon monoxide (CO) it enters human body, through breathing, affects the function of haemoglobin.
• Sometimes, it will lead to death.

Question 3.
Explain how dioxins are formed? Which plastic-type they are linked to and why they are harmful to humans?
Answer:
Dioxin formation:

• Dioxin compounds are not created intentionally but are formed inadvertently by a number of human and natural activities.
• These activities include combustion and incineration, forest fires, chlorine bleaching of pulp and paper, certain types of chemical manufacturing and processing, and other industrial processes.
• Cigarette smoke, some home-heating systems, and exhaust from vehicles using leaded and unleaded petrol as well as diesel fuels also produce small amounts of dioxins.
• Burning materials that may contain chlorine such as plastics, wood treated with pentachlorophenol (PCP), pesticide-treated wastes, other chemicals such as polychlorinated biphenols (PCB_s), and even bleached paper can produce dioxins.

Their link with plastic :

• Dioxins are linked with PVC (Polyvinyl Chloride plastics).
• The most dangerous emissions can be caused by burning PVC, as it releases dioxins.

Harmful effects of Dioxins to humans :

• Dioxins are the most toxic to human organisms.
• Dioxins can cause cancer, disrupt the endocrine system, alteration in pituitary and thyroid gland functions, immune suppression, neurobehavioral effects and cause reproductive and developmental effects.
• They are carcinogenic and a hormone disruptor and persistent, and they accumulate in our body-fat and thus mothers give it directly to their babies via the placenta.

Question 4.
Yugaa wants to buy a plastic water bottle. She goes to the shop and sees four different kinds of plastic bottles with resin codes 1, 3, 5, and 7. Which one should she buy? Why?
Answer:

• Yugaa should buy a plastic water bottle with Resin Code No.5, which is considered as one of the safer plastics. It is light and hard.

Reasons to avoid resin codes 1,3,7

• Bottle with Resin Code 1 is to be used only once. This plastic can release a chemical additive called antimony, which is not good for health.
• Bottle with Resin Code 3 is the most toxic plastic. It will have a smell of a new shoe. It should be avoided.
• Bottle with Resin Code 7 has the plastic types PC and ABS which are unsafe and toxic.

Intext Activities

ACTIVITY -1
With the help of your teacher, try to classify the following as organic and inorganic compounds.
HCN, CO₂, Propane, PVC, CO Kerosene, LPG, Coconut oil, Wood, Perfume, Alcohol, Na₂CO₃, CaCO₃. MgO, Cotton, Petrol.
Solution:

Inorganic	Organic
CO2	Propane
CO	Wood, kerosene, coconut oil
MgO	Parfume
HCN	Alcohol
Na2CO3	Cotton
PVC	Petrol
	LPG

[End of the activity]

ACTIVITY – 2

Take a football since it resembles Buckminsterfullerene. Count how many hexagonal and pentagonal panels are in it very comer is considered as one carbon. Compare your observation with fullerene and discuss with your friends.
Aim:
To compare the structure of fullerene with football.
Materials required:
Football

Procedure:

1. Take football.
2. Count the hexagonal and pentagonal rings shapes in football.

Observation:

Shapes	Fullerene (C60)	Football
Pentagon	12 Pentagonal rings	12 Black pentagons
Hexagon	20 Hexagonal rings	20 White hexagons
Structure	Closed cage-like structure	Polyhedron Structure

Conclusion :
The structure of football is compared with fullerene.

9th Science Guide Carbon and its Compounds Additional Important Questions and Answers

I. Choose the correct answer :

Question 1.
Carbon is one of the most important ………………….element.
(a) Metallic
(b) Non-metallic
(c) Metalloid _
(d) None of these
Answer:
(b) Non-metallic

Question 2.
The most recently discovered allotrope of carbon is ……………….
(a) Graphite
(b) Fullerene
(c) Graphene ‘
(d) Gas carbon
Answer:
(c) Graphene

Question 3.
……………. is the first organic compound synthesized in the laboratory.
(a) Urea
(b) Acetic acid
(c) Methane
(d) Ethanol
Answer:
(a) Urea

Question 4.
The main component of water gas is …………….
(a) Carbon dioxide
(b) Carbon monoxide
(c) Calcium carbide
(d) Methane
Answer:
(b) Carbon monoxide

Question 5.
The ability of carbon to form …………… is the main reason for the formation of various classes of carbon compounds.
(a) Tetravalency
(b) Catenation
(c) Isomerism
(d) Multiple bonds
Answer:
(d) Multiple bonds

Question 6.
Arrangement of atoms in diamond is …………………
(a) Hexagonal
(b) Trigonal
(c) Tetrahedral
(d) Pentagonal
Answer:
(c) Tetrahedral

Question 7.
The amorphous allotropic carbon used for making electrodes in dry cell
(a) Coke
(b) Charcoal
(c) Lampblack
(d) Gas carbon
Answer:
(d) Gas carbon

Question 8.
Elemental carbon undergoes …………. reaction at room temperature.
(a) Oxidation
(b) Reduction
(c) Free radical
(d) no.
Answer:
(d) no

Question 9.
Amorphous forms of carbon and graphite are almost …………… in colour.
(a) Grey
(b) brownish
(c) black
(d) dirty white
Answer:
(c) black

Question 10.
Carbon monoxide displaces ………………. from hemoglobin.
(a) nitrogen
(b) oxygen
(c) hydrogen
(d) carbon dioxide
Answer:
(b) oxygen

Question 11.
Burning of PVC releases
(a) Dioxins
(b) Carbon monoxide
(c) Sulphur dioxide
(d) Chlorine
Answer:
(a) Dioxins

Question 12.
Which among the following plastics release antimony when we reuse.
(a) PVC
(b) HDPE
(c) PP
(d) PET
Answer:
(d) PET

Question 13.
According to the Octet rule, carbon requires ……………. electrons to attain the nearest noble gas.
(a) One
(b) two
(c) Three
(d) Four
Answer:
(d) Four

Question 14.
Most one-time use plates are made from ……………
(a) Polypropylene
(b) Polystyrene
(c) Polyethylene
(d) Polyvinylchloride
Answer:
(b) Polystyrene

Question 15.
Which among the following compound is soluble in water?
(a) Methane
(b) Ethylene
(c) Ethanol
(d) Phenol
Answer:
(c) Ethanol

Question 16.
The number of free electrons in each carbon of diamond is
(a) Zero
(b) One
(c) Two
(d) None of these
Answer:
(a) zero

Question 17.
The carbon atoms in Graphene are arranged in
(a) Hexagon
(b) Pentagon
(c) octagon
(d) Tetragon
Answer:
(a) Hexagon

Question 18.
Resin Code” represents the type of …………….. used to make the plastic.
(a) Polymer
(b) Rubber
(c) monomer
(d) Polymerisation
Answer:
a) Polymer

Question 19.
Diamond is not a good conductor of electricity because
(a) it is very hard
(b) it has no free electron
(c) its structure is uniform
(d) it is insoluble in water
Answer:
(b) it has no free electron
Hint: Diamond contains no free electron and it behaves as an insulator

Question 20.
Which of the following is highly toxic?
(a) Carbon dioxide
(b) Carbon monoxide
(c) Calcium carbonate
(d) Sodium bicarbonate
Answer:
(b) Carbon monoxide
Hint: CO easily binds with Haemoglobin and then causes death

Question 21.
Which of the following plastic items are banned by the Government of Tamil Nadu as of 1st January 2019?
(a) Plastic sheets
(b) Plastic teacups
(c) Plastic water packet
(d) All the above
Answer:
(d) All the above

Question 22.
Graphite is used as a lubricant in machines because
(a) it is a good conductor of electricity
(b) it is made of slippery layers and  has a high melting point
(c) it has a high density
(d) it is strong and soft
Answer:
(b) it is made of slippery layers and has a high melting point

Question 23.
Plastic resin codes are shown as three chasing arrows in a ………………. with a number in the middle or letters (an acronym of that plastic type).
(a) Logo
(b) Recycling Symbol
(c) Square
(d) Triangle
Answer:
(d) Triangle

II. Fill in the blanks :

1. …………… is the main constituent of coal.
Answer:
Carbon

2. Carbon chemistry is also called as ……………..
Answer:
Living chemistry

3. Graphene has a thickness of just …………… atom.
Answer:
One

4. ……………. is the Father of Modem Organic Chemistry
Answer:
Friedrich Wohler

5. The inorganic carbon compound that takes past in photosynthesis is …………………….
Answer:
Carbon dioxide

6. The carbon cycle is the …………….. cycle.
Answer:
Biogeochemical

7. ……………….. structure accountable for hardness and rigidity of diamond.
Answer:
Three dimensional

8. Hexagonal layers in Graphite are held together by ……………………
Answer:
weak VanderWaals forces

9. Pet name for Buckminster Fullerene is ………………….
Answer:
Bucky ball

10. A large family of fullerene exists, starting at ………………… and reaching upto .
Answer:
C₂₀, C₅₄₀

11. Graphene is ………………. shaped hexagonal ring
Answer:
Honeycomb

12. Cigarette smoking is a source of ……………….
Answer:
Carbon Monoxide

13. Carbon monoxide enters into human body through …………………
Answer:
breathing

14. Do not use _______ for school projects.
Answer:
Thermocol

15. Polycarbonate (PC) plastic contains ……………..
Answer:
Bisphenol A

III. Match the following :
(I)

1. Graphite	a) Honeycomb
2. Fullerene	b) Tetrahedral
3. Graphene	c) Hexagonal
4. Diamond	d) Dome-shaped

Answer:
1 – c, 2 – d, 3 – a, 4 – b

(II)

Answer:
1-b,2-c,3-a,4-d

(III)

Answer:
1-c, 2 -a, 3-b, 4-c

IV. True or False :

1. About 18% of the weight of the human body is carbon.
Answer:
True.

2. There is more abundance of carbon in the earth
Answer:
False.
Correct statement: There is less abundance of carbon in the earth.

3. Carbon has the tendency to lose its four electrons with that of other atoms to complete its octet.
Answer:
False.
Correct statement: Carbon has the tendency to share its four electrons with that of other atoms to complete its octet

4. All the allotropic forms of carbon are solids.
Answer:
True.

5. Carbon’s amorphous forms have high melting and boiling poult compared to crystalline forms.
Answer:
False.
Correct statement: Carbon’s amorphous forms have low melting and boiling point compared to crystalline forms.

6. Used plate is easy to recycle.
Answer:
False.
Correct statement: Used plate difficult to recycle.

7. Do not eat hot food items in plastic containers.
Answer:
True.

V. Assertion and Reason type questions :

Mark the correct choice as:
(a) If both Assertion and Reason are true and Reason is the correct explanation of Assertion.
(b) If both assertion and reason are true but the reason is not the correct explanation of assertion.
(c) If Assertion is true but the reason is false.
(d) Both assertion and reason are false.

Question 1.
Assertion (A) : The number of carbon compounds alone is more than the number of compounds of all the elements taken together.
Reason (R) : Carbon has some unique properties such as
1) Catenation, 2) Tetravalency, 3) Multiple bonds, 4) Allotropy, 5) Isomerism.
Answer:
(a) Both Assertion and Reason are true and Reason is the correct explanation for Assertion

Question 2.
Assertion (A) : There are various classes of carbon compounds formed.
Reason (R) : The property of Isomerism is the main reason.
Answer:
(c) Assertion is true but reason is false
Reason : The ability to form multiple bonds is the main reason.

Question 3.
Assertion (A) : Carbon monoxide is a toxic gas of carbon.
Reason (R): smoking is a source of carbon monoxide.
Answer:
(b) Both assertion and reason are true but reason is not the correct explanation for assertion

Question 4.
Assertion (A): PVC is an unsafe plastic.
Reason (R)Burning PVC releases dioxins, a most toxic chemical.
Answer:
(a) Both Assertion and Reason are true and Reason is the correct explanation for Assertion

VI. Answer the following by rearranging the jumbled letters :

Question 1.
It is the hardest allotrope of carbon
mnodaid
Answer:
Diamond

Question 2.
Organic compounds having a double bond between carbon atoms are
knelaes
Answer:
Alkenes

Question 3.
Reaction of carbon with oxygen gives
osdiex
Answer:
Oxides

Question 4.
In this molecule, carbon is attached to four hydrõgen atoms.
emathen
Answer:
Methane

Question 5.
Carbon combines with other elements through the _______ bond.
lnaocvet
Answer:
Covalent

Question 6.
Plastics made of________ are represented by resin code #6.
sytlopynere
Answer:
Polystyrene

Question 7.
One-time use plastics are also known as ______ plastics.
áwyrhotwa
Answer:
throwaway

Question 8.
One-time use plastics cause ________ damage.
trnvomenialne
Answer:
Environmental

Question 9.
Expanded polystyrene is commercially known as
mthreolco
Answer:
Thermocol

VII. Very Short Answer questions :

Question 1.
How can graphite be transformed to diamond?
Answer:
Graphite could be transformed to the diamond at high temperature and high pressure.

Question 2.
How did the ancients obtain charcoal?
Answer:
Ancients manufactured charcoal by burning organic compounds.

Question 3.
Which theory was challenged by the synthetic preparation of Urea?
Answer:
Vital force theory.

Question 4.
Name two inorganic carbon compounds which are used as an antacid?
Answer:
Calcium carbonate (CaCO₃), Sodium bicarbonate (NaHCO₃)

Question 5.
What is tetravalency?
Answer:
Carbon has the tendency to share~its four electrons with other atoms to complete its octet. This is called Tetravalency.

Question 6.
Name the primary factor that determines the physical and chemical properties of compounds.
Answer:
Nature of bonding in a compound.

Question 7.
Why do elements show allotropy?
Answer:
It’s a method of formation or preparation.

Question 8.
Why is graphite softer than a diamond?
Answer:
The hexagonal layers in graphite are held together by weak Vander Waals forces of attraction.

Question 9.
What are Polymer resins?
Answer:
Plastics, made from long-chain organic compounds, are called “Polymer resins”.

Question 10.
List the three unsafe plastics.
Answer:

1. Polyvinyl chloride (PVC)
2. Polystyrene (Thermocol)
3. Polycarbonates (PC).

Question 11.
How many valence electrons are there in carbon?
Answer:
There are 4 valence electrons in carbon, out of 6 total electrons.

Question 12.
Who is called ‘Father of Modern Organic Chemistry’?
Answer:
Friedrich Wohler is called the ‘Father of Modern Organic Chemistry’.

Question 13.
Which three resin codes are unsafe?
Answer:
Resin Code Nos. 3, 6, and 7 unsafe.

VIII. Short Answer questions:

Question 1.
Prove that a diamond is a pure form of carbon?
Answer:

• When an equal weight of charcoal and diamond were burned, they produced the same amount of carbon dioxide.
• So like charcoal, diamond is also a pure form of carbon.

Question 2.
Write the classification of carbon compounds.
Answer:

1. Organic Carbon Compound	2. Inorganic Carbon Compounds
These are the compounds of carbon obtained from living organisms such as plants and animals. (e.g) Cellulose, Ethanol, Starch.	These are the compounds containing carbon but obtained from non-living matter. (e.g) Calcium carbonate, Carbon dioxide, Carbon monoxide

Question 3.
Write short notes on the carbon cycle.
Answer:

1. The carbon cycle is the biogeochemical cycle.
2. Carbon is exchanged among the biosphere, geosphere, hydrosphere, and atmosphere of the Earth.
3. Carbon is the main component of biological compounds as well as a major component of many minerals such as limestone.

Question 4.
Define: (i) Allotropy (ii) Allotrope
Answer:
(i) Allotropy: It is a property by which an element can exist in more than one form that is physically different and chemically similar.
(ii) Allotrope: The different forms of an element.

Question 5.
Differentiate crystalline and amorphous forms of allotropes of carbon.
Answer:

Crystalline allotropes of carbon	Amorphous allotropes of carbon
1. Diamond	1. Charcoal
2. Graphite	2. Lampblack
3. Fullerene	3. Coke
4. Graphene	4. Gas Carbon

Question 6.
Why is carbon monoxide harmful to health? (or) What happens when we breath Carbon monoxide?
Answer:

• On exposition, carbon monoxide (CO) enters the human body through breathing.
• It affects the function of hemoglobin by displacing oxygen from hemoglobin.
• It will lead to death.

Question 7.
Why. do we remove plastics safely? How can it be done?
Answer:

• Plastics are non-biogradable.
• Plastics can be recycled (or) disposed safely without harming environment.

Question 8.
Mention two reasons for the harmful nature of plastics.
Answer:

1. Plastics contain chemicals that are harmful to our health.
2. Most of the plastics are one-time use (or) throwaway in nature and pollutes the environment.

Question 9.
Give some examples of one-time-use plastic.
Answer:

• Plastic carry bags,
• Cups,
• Plastic plates,
• Straws,
• Water pouches, 6. Plastic sheets.

Question 10.
What we can do to prevent plastic pollution?
Answer:

• Share scientific knowledge on plastics and their effects with our family, friends, and relatives.
• Create awareness to avoid harmful plastics by educating about the resin codes.
• Educate about the new rules to stop one-time use of plastics.

IX. Long Answer questions

Question 1.
Draw a timeline of carbon chemistry depicting the contribution by scientists.
Answer:

Year	Scientist	Contribution
1772	Antoine Lavoisier (France)	Diamond and charcoal are carbon allotropes
1779	Carl Scheele (Sweden)	Graphite is another form of carbon
1796	Smithson Tennant	Diamond is a pure carbon like charcoal.
1855	Benjamin Brodie (England)	Pure graphite from carbon, proving graphite is a form of carbon
1955	Francis Bundy (USA)	Transformed graphite into diamond.
1985	Robert Curl, Harry Kroto and Richard Smalley	Discovered a new form of carbon called fullerenes.
2004	KostyaNovoselov Andre Geim	Graphene – lightest carbon

Question 2.
Give an account of (I) Isomerism (II) Isomers with an illustration.
Answer:
(1) Isomerism: The Phenomenon in which an element has the same molecular formula may exhibit different structural arrangement is called Isomerism.
(II) Isomers: Compounds that have the same molecular formula but different structural formula are called isomers.
Illustration: Molecular formula: C₂H₆O, is having two kinds of the arrangement of atoms as shown below.

In the above illustration, the molecular formula C₂H₆O has two different structural formulae
(a) Alcohol (CH₃CH₂OH) [Oxygen at the end of Chain
(b) Ether (CH₃OCH₃) [Oxygen at the middle
Both structural formulae will show different physical and chemical properties.

Question 3.
Write the salient features of Graphene.
Answer:

• Graphene is the most recently produced allotrope of carbon.
• It is honey comb-shaped hexagonal rings repeatedly arranged in a plane.
• It is the thinnest compound known to man at one atom thick.
• It is the lightest material known and the strongest compound discovered.
• Layers of graphene are stacked to form graphite by Vander Waals forces.

Question 4.
Briefly note the harmful effects of any four plastics.
Answer:

Question 5.
How can you minimise plastic pollution by your daily practices?
Answer:

• Don’t litter the environment by throwing plastic items.
• Don’t burn plastics since it causes the evolution of highly toxic gases.
• Avoid one-time use (or) throw away plastics like plastic bags, teacups, carry bags, plastic plates, etc.
• Don’t eat hot (or) spicy food items in plastic containers. ‘
• Segregate the plastic wastes and hand this over to the municipal authorities so that it can be recycled.
• Know about the resin codes and avoid unsafe plastics.
• Don’t use thermocol for school projects.

Tamilnadu State Board New Syllabus Samacheer Kalvi 9th Science Guide Pdf Chapter 25 Computer – An Introduction Text Book Back Questions and Answers, Notes.

Tamilnadu Samacheer Kalvi 9th Science Solutions Chapter 25 Computer – An Introduction

9th Science Guide Computer – An Introduction Text Book Back Questions and Answers

I. Choose the correct answer.

Question 1.
………………. is an electronic device which stores data and information.
(a) Telescope
(b) Television
(c) Computer
(d) Radio
Answer:
(c) Computer

Question 2.
………………. belongs to the generation IV of the computer
(a) Microprocessor
(b) Artificial Intelligence
(c) Transistor
(d) Vaccum Tubes
Answer:
(a) Microprocessor

Question 3.
Data processing involves……………….steps.
(a) seven
(b) four
(c) six
(d) eight
Answer:
(c) six

II. Match the following:

III generation computer	Integrated circuit
Text,	Information
Transistor	Father of computer
Directly used	Data
Charles Babbage	II generation

Answer:

III generation computer	Integrated circuit
Text, number	Data
Transistor	II generation
Directly used	Information
Charles Babbage	Father of computer

III. Answer briefly :

Question 1.
Define computer.
Answer:
A computer is an electronic device, which manipulates and stores data and information through commands or program codes.

Question 2.
Differentiate data and information.
Answer:
Data
Data is the set of values of qualitative and quantitative variables. The data that is fed to the computer can be text, numbers, or statistics. These data stored in computer memory cannot be used directly. It has to be processed.

Information
The information we get or obtain or receive using the data from the computer can be used directly.

Question 3.
What is data processing?
Answer:
The data processing in a computer is collecting data and converting it into information according to our needs and requirements.

IV. Answer in detail :

Question 1.
What are the different steps involved in data processing?
Answer:
Data processing has six steps. They are,

• Data collection
• Data storage
• Data sorting
• The data processing
• Data analysis
• Data presentation and conclusions

Question 2.
List out the generations of computers.
Answer:
The history of computers has been classified into many stages. The main difference between the generations is the speed and efficiency of the computer. On the basis of performance and speed, the generations of the computer was categorised as follows.

Generations of Computer:

Period	Generation	Digital devices
1940-1956	I Generation	Vacuum tubes
1956-1963	II Generation	Transistor
1964-1971	III Generation	Integrated circuits
1972-2010	IV Generation	Microprocessors
After 2010	V Generation	Artificial Intelligence

9th Science Guide Computer – An Introduction Additional Important Questions and Answers

I. Choose the correct answers :

Question 1.
The people of China used ……………….
(a) abacus
(b) transistor
(c) vacuum tubes
(d) microprocessors
Answer:
(a) abacus

Question 2.
ENIAC computer had approximately ………………. vacuum tubes.
(a) 16,000
(b) 14,000
(c) 18, 000
(d) 12,000
Answer:
(c) 18,000

Question 3.
ATM machine works with the help of …………… only.
(a) calculator
(b) mobile
(c) transistor
(d) computer
Answer:
(d) computer

Question 4.
How many generations of computers are there?
(a) 2
(b) 5
(c) 3
(d) 6
Answer:
(b) 5

Question 5.
………………. was used by the American Military.
(a) ENIAC
(b) Computer
(c) Transistor
(d) Calculator
Answer:
(a) ENIAC

Question 6.
The main difference between the generations is the ………… and …………….. of the computer.
(a) size, shape
(b) hardware, software
(c) speed, efficiency
(d) shape, performance
Answer:
(c) speed, efficiency

Question 7.
………….. is one of the steps in the data processing.
(a) Data management
(b) Data storage
(c) Data calculation
(d) Data transformation
Answer:
(b) Data storage

Question 8.
………………….. stored in computer memory cannot be used directly.
Information
a) Information
(b) Words
(c) Data
(d) Numbers
Answer:
(c) Data

Question 9.
Which of the following is the period of the first generation of computers?
(a) 1956- 1963
(b) 1964- 1971
(c) 1940- 1956
(d) 1972-2010
Answer:
(c) 1940 – 1956

Question 10.
(i) The computer operates by the exchange of commands between hardware and
software.
(ii) Lady Augusta Ada Lovelace gave the first programming to do arithmetic operations.
(a) Both the statements are Wrong
(b) Statement (i) is correct but’ statement (ii) is wrong
(c) Statement (i) is wrong but statement (ii) is correct
(d) Both the statements are correct
Answer:
(d) Both the statements are correct

II. Match the following :

ATM	set of values
Lady Augusta Ada Lovelace	step in the data processing
Data analysis	withdraw money
Data	general-purpose computer
ENIAC	1956 – 1963
II Generation	1972 – 2010
IV Generation	First programmer

Answer:

ATM	withdraw money
Lady Augusta Ada Lovelace	First programmer
Data analysis	step in the data processing
Data	set of values
ENIAC	general-purpose computer
II Generation	1956 – 1963
IV Generation	1972 – 2010

III. Answer briefly:

Question 1.
Define ENIAC.
Answer:

• ENIAC (Electronic Numerical Integrator And Computer) was designed in the year 1946 was equivalent to the size of a huge classroom.
• ENIAC had approximately 18,000 vacuum tubes.
• ENIAC, which was used by the American Military in 1946 to predict the trajectory of artillery shells, recognized as the world’s first general-purpose computer.

Question 2.
What is meant by hardware and software?
Answer:

• The computer operates by the exchange of commands between the hardware and software.
• Hardware can be touched and felt.
• The software cannot be touched and felt.

Question 3.
Name the fields where computers are used.
Answer:
The fields where computers are used are:

• Banks
• Hospitals
• Post offices
• Transport
• Market
• Media
• Defense sector
• Education and space research

IV. Answer in detail :

Question 1.
Explain the history of computers.
Answer:

• Around 2000 years ago, the people of China used Abacus.
• This was considered as the most basic model of a computer.
• Nineteenth century was considered as the birth of the computer when Charles Babbage designed the basic construction of a computer.
• ENLAC, which was used by the American Military in 1946 to predict the trajectory of artillery shells, recognized as the world’s first general-purpose computer.
• ENIAC had approximately 18,000 vacuum tubes.
• The size occupied by the ENIAC could be equivalent to a classroom.
• Lady Augusta Ada Lovelace was honored as the first programmer as she gave the first programming to do arithmetic operations.

Question 2.
Write the history of computers.
Answer:

• Around 2000 years ago, the people of China used Abacus. This was considered as the most basic model of a computer.
• Nineteenth-century was considered as the birth of the computer when Charles Babbage designed the basic construction of a computer.
• ENIAC, which was used by the American Military in 1946 to predict the trajectory of artillery shells was recognized as the world’s first general-purpose computer.
• Lady Augusta Ada Lovelace was honored as the first programmer as she gave the first programming to do arithmetic operations.

Question 3.
Explain in detail about data and data processing.
Answer:
Data:

• Data is the set of values of qualitative and quantitative variables.
• The data that is fed to the computer can be text, numbers or statistics.
• These data stored in computer memory cannot be used directly.
• It has to be processed.

Data Processing:
The data processing in a computer is collecting data and converting it into information according to our needs and requirements.

Steps in data processing:
Data processing has six steps. They are:

• Data collection
• Data storage
• Data sorting
• Data processing
• Data analysis
• Data presentation and conclusions

Question 4.
What are the different generations of computers?
Answer:

• The main difference between the generations is the speed and efficiency of the computer.
• On the basis of performance and speed, the generations of the computer were categorised.

Generations of Computer:

Period	Generation	Digital devices
1940-1956	I Generation	Vacuum tubes
1956-1963	II Generation	Transistor
1964-1971	III Generation	Integrated circuits
1972-2010	IV Generation	Microprocessors
After 2010	V Generation	Artificial Intelligence

Tamilnadu State Board New Syllabus Samacheer Kalvi 9th Science Guide Pdf Chapter 26 Parts of Computer Text Book Back Questions and Answers, Notes.

Tamilnadu Samacheer Kalvi 9th Science Solutions Chapter 26 Parts of Computer

9th Science Guide Parts of Computer Text Book Back Questions and Answers

I. Choose the correct answer:

Question 1.
Which one of the following is an output device?
(a) Mouse
(b) Keyboard
(c) Speaker
(d) Pendrive
Answer:
(c) Speaker

Question 2.
Name the cable that connects CPU to the Monitor.
(a) Ethernet
(b) VGA
(c) HDMI
(d) USB
Answer:
(b) VGA

Question 3.
Which one of the following is an input device?
(a) Speaker
(b) Mouse
(c) Monitor
(d) Printer
Answer:
(b) Mouse

Question 4.
Which one of the following is an example for wireless connections?.
(a) Wi-Fi
(b) Electric wires
(c) VGA
(d) USB
Answer:
(a) Wi-Fi

Question 5.
Pen drive is a/an ………….. device.
(a) output
(b) input
(c) storage
(d) connecting cable
Ans :
(c) storage

II. Match the following:

Question 1.

VGA	Input device
Bluetooth	Connecting cable
Printer	LDMI
Keyboard	Wireless connection
HDMI	Output device

Answer:

VGA	Input device
Bluetooth	Wireless connection
Printer	Output device
Keyboard	LDMI
HDMI	Connecting cable

III. Answer briefly :

Question 1.
Name the parts of a computer.
Answer:
Three parts of the computer are:

1. Input Unit
2. Central Processing Unit (CPU)
3. Output Unit.

Question 2.
Bring out any two differences between input and output devices.
Answer:
Input devices

1. The Input units help to send the data and commands for the processing.
2. Input devices only allow for the input of data to a computer.

Output devices

1. The Output units convert the command received by the computer in the form of binary signals into easily understandable characters.
2. Output devices only receive the output of data from another device.

9th Science Guide Parts of Computer Additional Important Questions and Answers

I. Choose the correct answer:

Question 1.
………………… plays an important role in a computer as an input device.
(a) Keyboard
(b) Scanner
(c) Printer
(d) Mouse
Answer:
(a) Keyboard

Question 2.
………………….. is an essential part of the computer.
(a) Keyboard
(b) CPU
(c) Mouse
(d) Wi-Fi
Answer:
(c) Mouse

Question 3.
A bit has a single binary value either ……………….. or ………………..
(a) 1,-1
(b) 0,1
(c) 1,2
(d) 2,0
Answer:
(b) 0,1

Question 4.
The personal computer comes under the ……………….. computer.
(a) mainframe
(b) mini
(c) micro
(d) super
Answer:
(c) micro

Question 5.
………………..cable transmits high quality and high bandwidth streams of audio and video.
(a) VGA
(b) USB
(c) Data
(d) HDMI
Answer:
(d) HDMI

Question 6.
………………..is used to connect the speaker to the computer.
(a) Audio jack
(b) Power card
(c) Data cable
(d) USB cable
Answer:
(a) Audio jack

Question 7.
………………..cable helps to establish internet connectivity.
(a) Power card
(b) Audio jack
(c) Ethernet
(d) USB
Answer:
(c) Ethernet

II. Answer the following :

Question 1.
What are the input devices?
Answer:
The input unit helps to send the data and commands for processing. The devices that are used to enter data are called injfut devices.

Question 2.
Write some examples of input and output devices of a computer system.
Answer:
Input devices:
Keyboard, Mouse, Scanner, Barcode reader, Microphone, Web camera, Light pen are some of the input devices.

Output devices:
Monitor, Printer, Speaker, Scanner, are some of the output devices.

Question 3.
What is Keyboard?
Answer:

• The keyboard plays an important role in a computer as an input device.
• Numbers and alphabet play a role of data in the computer.
• The keyboard helps to enter data.;
• Keyboard has two types of keys, namely number keys and alphabet keys.
• The keys with numbers are called number keys and the keys with letters are called alphabet keys.

Question 4.
Explain CPU.
Answer:
CPU (Central Processing Unit)

(i) Memory Unit
(ii) Arithmetic Logic Unit (ALU)
(iii) Control Unit

(i) Memory Unit: The memory unit in the computer saves all data and information temporarily. The data is measured in units which is called as Bit. A Bit has a single binary value either 0 or 1. We can classify memory unit into two types namely primary and secondary memory. Memory can be expanded externally with the help of Compact Disk (CD), Pendrive, etc.

(ii) Arithmetic Logic Unit : Arithmetic and Logic unit performs all arithmetic computations like addition, subtraction, multiplication and division.

(iii) Control Unit: The control unit controls the functions of all parts of the computer.

Question 5.
What is Bit?
Answer:
The memory unit in the computer saves all data and information temporarily. The data is measured in units which is called as Bit.

Question 6.
What are the types of monitors?
Answer:
There are two types of monitors namely.

1. Cathode Ray Tube monitors (CRT)
2. Thin Film Transistor Monitors (TFT)

Question 7.
What is the classification of the computer?
Answer:
The computers can be classified as follows based on their design, shape, speed, efficiency, working of the memory unit, and their applications.

• Mainframe Computer
• Mini Computer
• Micro or personal compute
• Supercomputer

Question 8.
Explain the types of cables.
Answer:
Video Graphics Array (VGA), High Definition Multimedia Interface (HDMI), Universal Serial Bus (USB), Data cable, Power Cord, Mic cable, Ethernet cable.

• VGA Cable: It is used to connect the computer monitor with the CPU.
• USB cable /cord: Devices like Printer, Pendrive, Scanner, Mouse, Keyboard, web camera, and Mobile phone devices are connected with the computer using a USB cord or cable.
• HDMI Cable: HDMI cable transmits high quality and high bandwidth streams of audio and video. It connects the monitor, projector with the computer.
• Data Cable: Data cable transmits data and it is used to connect a tablet, mobile phone to the CPU for data transfer.
• Audio jack: The audio jack is used to connect the speaker to the computer.
• Power cord: Power cord temporarily connects an appliance to the main electricity supply.
• Mic cable: To connect the Mic (Microphone) to the CPU, Mic wire/cord is used.

Question 9.
Explain wireless connections.
Answer:
Bluetooth, Wi-Fi is used to connect to the internet without using any connecting cables/devices.

• Bluetooth: Mouse, Keyboard can be connected to the computer using Bluetooth. Using Bluetooth the data can be shared with nearby devices.
• Wi-Fi: Net connectivity can be obtained using Wi-Fi without any connecting cables. Any data from anywhere can be shared using Wi-Fi.

Tamilnadu State Board New Syllabus Samacheer Kalvi 9th Science Guide Pdf Chapter 27 Hardware and Software Text Book Back Questions and Answers, Notes.

Tamilnadu Samacheer Kalvi 9th Science Solutions Chapter 27 Hardware and Software

9th Science Guide Hardware and Software Text Book Back Questions and Answers

I. Choose the correct answer :

Question 1.
Find out the part which is not found in CPU?
(a) Mother Board
(b) SMPS
(c) RAM
(d) Mouse
Answer:
(d) Mouse

Question 2.
Which of the following is correct?
(a) Free and Open source
(b) Free and Traditional software
(c) Passive and Open source
(d) Passive and Traditional source
Answer:
(a) Free and Open source

Question 3.
LINUX is a
(a) Paid Software
(b) Licensed Software
(c) Free and Proprietary software
(d) Free and Open source software
Answer:
(d) Free and Open source software

Question 4.
Find out the Paid and Proprietary software from the given list
(a) Windows
(b) MAC OS
(c) Adobe photoshop
(d) All the above
Answer:
(d) All the above

Question 5.
……………… is an Operating system.
(a) Android
(b) Chrome
(c) Internet
(d) Pendrive
Answer:
(a) Android

II. Match the following :

MAC OS	Free and Open source Software
Software	Paid and Proprietary Software
Hardware	Input Device
Keyboard	RAM
LINUX	Geogebra

Answer:

MAC OS	Paid and Proprietary Software
Software	Geogebra
Hardware	RAM
Keyboard	Input Device
LINUX	Free and Open-source Software

III. Answer in brief:

Question 1.
What are Hardware and Software?
Answer:
Hardware is the parts of a computer which we can touch and feel. Hardware includes Input and Output devices, Cabinet, Hard Disk, Mother Board, SMPS, CPU, RAM, CD Drive, and Graphics Card.

Software is programmed and coded applications to process the input information. The software processes the data by converting the input information into coding or programmed language.

Question 2.
What do you mean by Operating System? How does it work?
Answer:
Operating System (System software): Operating system is software that makes the 1 hardware devices process the data fed by the user.
Working of Operating system: It works by displaying the results on the output devices ‘ like Monitor.

Question 3.
What is Free and Open Source Software? Give any two examples.
Answer:
Free and open software is available free of cost and can be shared with many end-users. Free software is editable and customizable by the user and this leads to the update or development of new software. Examples of Free and Open source software are LINUX, Open office, Geogebra, etc.

9th Science Guide Hardware and Software Additional Important Questions and Answers

I. Choose the correct answer :

Question 1.
The Software gives …………… in the monitor.
(a) input
(b) output
(c) a & b
(d) None of these
Answer:
(b) output

Question 2.
Word Processing Software is ………………
(a) Application Software
(b) System Software
(c) Hardware
(d) None of these
Answer:
(a) Application software

Question 3.
Windows is ……………..
(i) Application Software
(ii) Operating System
(iii) Free and Open-source Software
(iv) Paid and Proprietary Software
(a) i and ii
(b) (ii) and (iii)
(c) (i) and (iv)
(d) (ii) and (iv)
Answer:
(d) (ii) and (iv)

Question 4.
Which one of the following is an Application Software?
(a) Mac
(b) Chrome
(c) Windows
(d) Android
Answer:
(b) Chrome

II. Fill in the blanks :

1. Graphic Card is a …………….
Answer:
Hardware

2. The Software processes the data by converting the input information into coding (or) programming ……………..
Answer:
Language

3. Free software is…………….. and …………….. by the user.
Answer:
editable, customizable

4. The application programmes can be installed in the …………….. for usage on a particular computer.
Answer:
Hard Disk

III. State whether true or false. If false, correct the statement:

1. The functions of Hardware and Software are separate.
Answer:
False.
Correct statement: The functions of Hardware and Software combine together.

2. We cannot see the functions of Software.
Answer:
False.
Correct statement: We can see the functions of the software in the form of output.

3. Application Software completes more than one work of the end-user.
Answer:
True.

4. The end users can legally use the pirated version of the paid and proprietary software.
Answer:
False.
Correct statement: The end users are legally prohibited to use the pirated versions of the paid and proprietary software.

IV. Assertion and Reason type questions : 

Mark the correct choice as :
(a) If both assertion and reason are hue and Reason is the correct explanation of Assertion.
(b) If both assertion and reason are true but the reason is not the correct explanation of assertion.
(c) If the assertion is true but the reason is false.
(d) If the assertion is false but the reason is true.

Question 1.
Assertion (A) : The functions of hardware and software combine together to make the computer functional.
Reason (R) : A computer is a device comprising both hardware and software.
Answer:
(a) Both assertion and reason are true and Reason is the correct explanation of Assertion

Question 2.
Assertion (A) : The free and open-source software cannot be updated (or) developed to new software.
Reason (R) : Free software is editable and customizable by the user.
Answer:
(d) Assertion is false but the reason is true
Assertion (A) : The free and open-source can be updated (or) developed to new software.

V. Answer very briefly :

Question 1.
How are parts of a computer compared to humans?
Answer:
A computer is like a human body, where the human body is the hardware and the soul is the Software.

Question 2.
What are the two forms of the operating system and application software?
Answer:
The Operating system and application software are available in two forms.
They are:

• Free and Open-source.
• Paid and Proprietary Software.

Question 3.
WhatisOSI?
Answer:
The Open Source Initiative (OSI), is an organization dedicated to promoting Open Source Software.

VI. Answer in detail :

Question 1.
What is Application software? How is it utilised?
Answer:
Application software is a program (or) a group of programs designed for the benefit of the end-user to work on a computer.

UTILISATION:

• The application programs can be installed on the hard disk for usage on a particular computer.
• This type of application program completes one or more than one works of the end-user.
  The following are examples of the application program:
  (e.g) Drawing tools, Editing software, Word Processing Software, Video player, Audio player, etc.

Question 2.
Write the conditions in the use of Paid and Proprietary Software.
Answer:
Conditions of Paid and Proprietary Software :

• The software needs a license to use it.
• We have to pay to use the software permanently (or) temporarily.
• The end-user is legally prohibited to steal the software program.
• The end-user is also prohibited to use the pirated versions of the software.
  (e.g.) Windows, Microsoft Office, Adobe Photoshop.

Tamilnadu State Board New Syllabus Samacheer Kalvi 9th Science Guide Pdf Chapter 14 Acids, Bases and Salts Text Book Back Questions and Answers, Notes.

Samacheer Kalvi 9th Science Solutions Chapter 14 Acids, Bases and Salts

9th Science Guide Acids, Bases and Salts Text Book Back Questions and Answers

I. Choose the correct answer :

Question 1.
Zn + 2HCl → ZnCl₂ + ….↑ (H₂, O₂, CO₂)
Answer:
H₂

Question 2.
Apple contains malic acid. Orange contains …………………(citric acid, ascorbic acid).
Answer:
ascorbic acid

Question 3.
Acids in plants and animals are organic acids. Whereas Acids in rocks and minerals are …………………. (Inorganic acids, Weak acids).
Answer:
Inorganic acids

Question 4.
Acids turn blue litmus paper to …………….. (green, red, orange).
Answer:
Red

Question 5.
Since metal carbonate and metal bicarbonate are basic, they react with acids to give salt and water with the liberation of ……………….. (NO₂, SO₂, CO₂).
Answer:
CO₂

Question 6.
The hydrated salt of copper sulphate has …………….colour (red, white, blue).
Answer:
Blue

II. Answer in briefly :

Question 1.
Classify the various types of Acids based on their sources.
Answer:
The acids are classified based on their sources and organic and inorganic acids.
Organic acids – acids present in plants and animals.
Inorganic acids – acids prepared from rocks and minerals.

Question 2.
Write any four uses of acids.
Answer:

• Sulphuric acid is called King of Chemicals because it is used in the preparation of many other compounds. It is used in car batteries also.
• Hydrochloric acid is used as a cleansing agent in toilets.
• Citric acid is used in the preparation of effervescent salts and as a food preservative.
• Nitric acid is used in the manufacture of fertilizers, dyes, paints and drugs.
• Oxalic acid is used to clean iron and manganese deposits from quartz crystals. It is also used as bleach for wood and removing black stains.
• Carbonic acid is used in aerated drinks.
• Tartaric acid is a constituent of baking powder.

Question 3.
Give the significance of p^H of .soil in agriculture.
Answer:
In agriculture, the p^H of soil is very important. Citrus fruits require slightly alkaline soil, while rice requires acidic soil and sugarcane requires neutral soil.

Question 4.
What are the various uses of Aquaregia.
Answer:

• It is used chiefly to dissolve metals such as gold and platinum.
• It is used for cleaning and refining gold.

Question 5.
What are the uses of Plaster of Paris?
Answer:

• It is used for plastering bones.
• It is used for making casts for statues.

Question 6.
Two acids ‘A’ and ‘B’ are given. Acid A gives one hydrogen ion per molecule of the acid in solution. Acid B gives two hydrogen ions per molecule of the acid in solution.
(i) Find out acid A and acid B.
(ii) Which acid is called the King of Chemicals?
Answer:
(i) Acid A – HCl – Hydrochloric acid. Acid B – H₂SO₄ – Sulphuric acid.
(ii)Sulphuric acid – H₂SO₄.

Question 7.
Define aquaregia.
Answer:
It is the mixture of hydrochloric acid and nitric acid prepared optimally in a molar ratio of 3 : 1.

Question 8.
Correct the mistakes :
(a) Washing soda is used for making cakes and bread soft, spongy.
(b) Calcium sulphate hemihydrate is used in textile industry.
Answer:
(a) Baking soda (Sodium bicarbonate – NaHCO₃) is used for making cakes and bread soft spongy, (or) Washing soda is used for softening hard water.
(b) Calcium sulphate hemihydrate (CaSO₄, 1/2 H₂O)is used for plastering bones (or) Bleaching powder (Calcium oxy Chloride – CaOC₁₂) is used in textile industry.

Question 9.
What is neutralization reaction? Give an example.
Answer:
Neutralization reaction is a reaction in which an acid reacts with a base to form salt and water and H⁺ ion and OH^– ion combines to generate water. The neutralization of a strong acid and strong base has a p^Hequal 7.

III. Answer in detail :

Question 1.
Differentiate hydrate and anhydrous salts with examples.
Answer:

Hydrated	Anhydrous
1. Hydrons is a term used to explain a substance that contains water as a constituent	Anhydrous is a term used to explain a substance that does not contain water as a constituent.
2. Composed of water molecules.	Not composed of water molecules.
3. These are known as hydrates.	Known as anhydrates
4. Hydroscopic compounds can form hydrous compounds by Absorption of water from the air.	Anhydrous compounds can absorb water from the air.
Ex : CuSO4 5H2O – Blue vitrol.	Ex: NaCl

Question 2.
Give the tests to identify Acids and Bases.
Answer:

• Acids turn blue litmus. Red bases turn red litmus blue.
• In acid phenolphthalein is colourless. In base Phenolphthalein is pink in colour.
• In acid methyl orange is pink. In bases methyl orange is yellow

Question 3.
Write any four uses of bases.
Answer:

• Sodium hydroxide is used in the manufacture of soap.
• Calcium hydroxide is used in the whitewashing of buildings.
• Magnesium hydroxide is used as a medicine for a stomach disorder.
• Ammonium hydroxide is used to remove grease stains from cloth.

Question 4.
Write any five uses of salts.
Answer:
Common Salt (NaCl) :
It is used in our daily food and used as a preservative
Washing Soda (Sodium Carbonate – Na₂CO₃) :

• It is used in softening hard water.
• It is used in glass, soap and paper industries.

Baking Soda (Sodium bicarbonate -NaHCO₃):

• It is used in making of baking powder which is a mixture of baking soda and tartaric acid.
• It is used in soda-acid fire extinguishers.
• Baking powder is used to make cakes and bread, soft and spongy.
• It neutralizes excess acid in the stomach and provides relief.

Bleaching powder (Calcium Oxychloride – CaOCl₂):

• It is used as a disinfectant.
• It is used in textile industry for bleaching cotton and linen.

Plaster of Paris (Calcium Sulphate Hemihydrate – CaSO₄ .1/2 H₂O):

• It is used for plastering bones
• It is used for making casts for statues.

Question 5.
Sulphuric acid is called King of Chemicals. Why is it called so?
Answer:
Sulphuric acid is called King of Chemicals because it is used in the preparation of many other compounds

Intext Activities

ACTIVITY – 2

Take solutions of hydrochloric acid or sulphuric acid. Fix two nails on a cork and place the cork in a 100 ml beaker.
Connect the nails to the two terminals of a 6 V battery through a bulb and a switch as shown in Figure. Now pour some dilute HCl in the beaker and switch on the current. Repeat the activity with dilute sulphuric acid, glucose and alcohol solutions. What do you observe now? Does the bulb glow in all cases?

Answer:

• The bulb glows when sulphuric acid and hydrochloric acid are used.
• The bulb does not glow when the activity is done with alcohol and glucose solution.

ACTIVITY – 3

Collect the following samples from the science laboratory – Hydrochloric acid, Sulphuric acid and Nitric acid, Sodium hydroxide, Potassium hydroxide. Take 2 ml of each solution in a test tube and test with a litmus paper and indicators phenolphthalein and Methyl orange. Tabulate your observations.

Answer:

ACTIVITY-4

Answer:

ACTIVITY – 5
Boil about 100 ml of groundwater in a vessel to dryness. After all the water get evaporated observe the inner wall of the vessel. Can you observe any deposits? This is the deposit of dissolved salts present in water.
Answer:
This is the deposit of dissolved salts present in water.

9th Science Guide Acids, Bases and Salts Additional Important Questions and Answers

I. Choose the correct answer :

Question 1.
Acid secreted in our stomach is ……………….
(a) hydrochloric acid
(b) sulphuric acid
(c) nitric acid
(d) carbonic acid
Answer:
(a) hydrochloric acid

Question 2.
Hydrochloric Acid reacts with metal bicarbonates to give ……………
(a) metal chloride
(b) water
(c) carbon di – oxide
(d) all the above
Answer:
(d) all the above

Question 3.
…………… & ………….. metals do not react with HCl or HNO₃.
(a) Gold & Magnesium
(b) Silver & Magnesium
(c) Gold & Silver
(d) Zinc & Silver
Answer:
(c) Gold & Silver

Question 4.
The molar ratio of hydrochloric acid and nitric acid in aquaregia is ………………..
(a) 1 : 3
(b) 6 : 3
(c) 2 : 3
(d) 3 : 1
Answer:
(d) 3 : 1

Question 5.
Bases ionise in water to form ……………………. ions.
(a) H⁺
(b) H₃O⁺
(c) OH^–
(d) O^2-
Answer:
(c) OH ^–

Question 6.
Which of the following pairs are weak base?
(a) NH₄OH & NaOH ‘
(b) Ca(OH)₂ & KOH
(c) NH₄OH & Ca(OH)₂
(d) NaOH&KOH
Answer:
(c) NH₄OH & Ca(OH)₂

Question 7.
NaOH & KOH are …………….
(a) strong bases
(b) metal Oxides
(c) weak bases
(d) diacidic bases
Answer:
(a) strong bases

Question 8.
Which of the following solution is soapy to touch?
(a) Acidic
(b) Basic
(c) Salt
(a(d) Aquaregia
Answer:
(b) Basic

Question 9.
Which of the following solutions do not conduct electricity?
(a) alcohol
(b) glucose
(c) sulphuric acid
(d) both a & b
Answer:
(d) both a & b

Question 10.
The p^H value of neutral solution is ………………
(a) = 7
(b) <7
(c) none of the above
(d) -7
Answer:
(a) = 7

Question 11.
The p^H of stomach fluid is ……………….
(a) 4
(b) 2
(c) 6
(d) 7
Answer:
(b) 2

Question 12.
A salt which is formed by complete neutralization of an acid and a base is called ………………. salt.
(a) basic
(b) acid
(c) double
(d) normal
Answer:
(d) normal

Question 13.
The number of water molecules present in one molecule of copper sulphate is
(a) 2
(b) 3
(c) 4
(d) 5
Answer:
(d) 5

Question 14.
The molecular formula of copper sulphate pentahydrate is ………………..
(a) CuSO₄. H₂O
(b) CuSO₄. 2H₂O
(c) CuSO₄. 5H₂O
(d) CuSO₄. 3H₂O
Answer:
(c) CuSO₄ . 5H₂O

Question 15.
……………is the gas produced when HCl is added with carbonate salt.
(a) H₂
(b) N₂
(C) CO₂
(d) O₂
Answer:
(c)CO₂

Question 16.
The formula of bleaching powder is ……………..
(a) CaCl₂
(b) CaOCl₂
(c) Ca(OH)₂
(d) CaO
Answer:
(b) CaOCl₂

Question 17.
The chemical name of plaster of paris is ……………………..
(a) Calcium sulphate hemihydrate
(b) Calcium sulphate monohydrate
(c) Calcium sulphate dihydrate
(d) Calcium sulphate trihydrate
Answer:
(a) Calcium sulphate hemihydrate

Question 18.
Which of the following metal does not react with sodium hydroxides?
(a) Cu
(b) Ag
(c) Cr
(d) All the above
Answer:
(d) All the above

Question 19.
Curd contains …………….acid.
(a) malic ‘
(b) formic
(c) lactic
(d) ascorbic
Answer:
(c) lactic

Question 20.
Which one of the following acids undergoes complete ionisation?.
(a) HCl
(b) CH₃COOH
(c) H₂SO₄
(d) all the above
Answer:
(a) HCl

II. Fill in the blanks :

1. Acid reacts with base to form a neutral product called ………………
Answer:
Salt

2. The taste of acid is ………………..
Answer:
Sour

3. …………….. contain one or more replaceable hydrogen atoms.
Answer:
Acids

4. ………………..acids have a relatively smaller amount of acids dissolved in a solvent.
Answer:
Dilute

5. Acids react with metallic oxides to produce ……………….
Answer:
salt and water

6. _________ acid is used in aerated drinks.
Answer:
Carbonic acid

7. Chemical formula of aquaregia is ________
Answer:
3HCl + HNO₃

8. Water soluble bases are called ________
Answer:
alkali

9. Non-metallic oxides are ___________ in nature.
Answer:
acid

10. __________ are bitter in taste.
Answer:
Bases

11. __________ alkali has a relatively high percentage of alkali in its aqueous solution.
Answer:
Concentrated

12. Acids turn blue litmus to ………….
Answer:
red

13. Phenolphthalein and methyl Orange are ………………
Answer:
indicators

14. p^H stands for …………….. in a solution.
Answer:
power of hydrogen ion concentration

15. The p^H value of acids are …………….. than 7.
Answer:
lesser

16. White enamel coating of our teeth is…………….
Answer:
Calcium phosphate

17. Salt is ………….. in nature.
Answer:
hygroscopic

18. Salt which is formed by the partial replacement of hydrogen ions of an acid by a metal is called ………………………..
Answer:
acid salt

19 Salts contaíning water of crystallisation are called …………. salts.
Answer:
hydrated

20. Salts that do not contain water of crystallisation is called …………..
Answer:
anhydrous salt

21. p^H value of human blood is ……………..(7.0, 7.4, 7.6).
Answer:
7.4

22. The nature of the toothpaste commonly used is ……………. in nature (acidic, basic, neutral)
Answer:
basic

23. You are given pure water to test the p^H value using p^H paper. It shows colour (White, black, green)
Answer:
green

III. To Match:

Question 1.

Source	Acid present
1) Apple	?
2) ?	Citric acid
3) ?	tartaric acid
4) Tomato	?
5) Vinegar	?

Answer:

Source	Acid present
1) Apple	Malic acid
2) Lemon	Citric acid
3) Grapes	tartaric acid
4) Tomato	Oxalic acid
5) Vinegar	Acetic acid

Question 2.

Answer:

Question 3.

Answer:

Question 4.

Answer:

IV. Complete the following equations.

Question 1.
HCl + H₂O → ? + ?
Answer:
HCl + H₂O → H₃O⁺ + Cl^–

Question 2.
H⁺ + H₂O → ?
Answer:
H⁺ + H₂O → H₃O⁺

Question 3.
Mg+ ? → ? + H₂
Answer:
Mg + H₂SO₄ → MgSO₄ + H₂↑

Question 4.
Na₂CO₃ + 2HCl → ? + ? + CO₂↑
Answer: Na₂CO₃ + 2HCl → 2NaCl + H₂O + CO₂↑

Question 5.
ZnO + 2HCl → ? + ?
Answer:
ZnO + 2HCl → ZnCl₂ + H₂O↑

Question 6.
Zn + ? → Na₂ZnO₂ + H₂ ↑
Answer:
Zn + 2NaOH → Na₂ZnO₂+ H₂↑

Question 7.
CaO + H₂SO₄ → ? + H₂O
Answer:
CaO + H₂SO₄ → CaSO₄ + H₂O

Question 8.
HCl + ? → NaCl + H₂O
Answer:
HCl + NaOH → NaCl + H₂O

Question 9.
Ca(OH)₂ + ? → ? + H₂O
Answer:
Ca(OH)₂ + CO₂ → CaCO₃ + H₂O

Question 10.

Answer:
A = NH₄Cl, B = NH₃↑
C = HCl
D = NaHSO₄,E = H₂O

V. Answer in briefly :

Question 1.
What are organic acids? Given examples.
Answer:
Acids present in plants and animals (living things) are organic acids.
Example: HCOOH, CH₃COOH

Question 2.
How are acids classified based on ionisation? Give examples.
Answer:
Acids get ionise in water (produce H⁺ ions) completely or partially. Based on the extent of ionisation, acids are classified as follows:
Strong Acids:
These are acids that ionise completely in water.
Example: HCl

Weak Acids :
These are acids that ionise partially in the water.
Example: CH₃COOH.

Question 3.
What is Aquaregia? Mention its uses.
Answer:
It is a mixture of hydrochloric acid and nitric acid prepared optimally in a molar ratio of 3:1. It is a yellow-orange fuming liquid. It is a highly corrosive liquid, able to attack gold and other resistant substances.

• Aquaregia is used tp dissolve noble metals such as gold, platinum, and palladium.
• It is used Tor cleaning and refining gold.

Question 4.
What does the acidity of base mean?
Answer:
It means the number of replaceable hydroxyl groups present in one molecule of a base.

Question 5.
What is Potash alum? Write its formula.
Answer:
Potash alum is a mixture of potassium sulphate and aluminium sulphate. KAl(SO₄)₂.12H₂O.

Question 6.
What are double salts? Give an example?
Answer:
Double salts are the salts formed by the combination of the saturated solution of two simple salts in equimolar ratio followed by crystallization. For example : Potash alum.

Question 7.
What are basic salts? Give suitable reaction for this.
Answer:
Basic salts are the product formed by the partial replacement of hydroxide ions of a diacidic or triacidic base with an acid radical.
Pb(OH)₂ + HCl → Pb(OH)Cl + H₂O

Question 8.
Why are tooth pastes basic?
Answer:
Toothpastes which are generally basic and used for cleaning the teeth can neutralise the excess acid and prevent tooth decay.

Question 9.
What is water of crystallisation?
Answer:
Many salts are found as crystals with water molecules they contain. These water molecules are known as water of crystallisation.

Question 10.
Why do blue colour copper sulphate becomes white on heating?
Answer:
On heating, blue colour copper sulphate loses its water molecules and becomes white.

Question 11.
Acidic or basic solutions are good conductors of electricity. Justify your answer.
Answer:
Acidic and basic solutions in water conduct electricity because they produce hydrogen and hydroxide ions respectively.

Question 12.
What are hygroscopic substances?
Answer:
Substance which absorbs water from the surroundings are called hygroscopic substances.

Question 13.
Define indicator. Give examples
Answer:
Chemical substances used to find out whether the given solution is acid or base are called indicators. Eg: Phenolphthalein, methyl orange.

Question 14.
Define ionisation.
Answer:
Ionisation is the condition of being dissociated into ions by heat or radiation or chemical reactions or electrical discharge.

Question 15.
How is normal salt obtained? Give a suitable reaction.
Answer:
A normal salt is obtained by complete neutralization of an acid by a base.
NaOH + HCl → NaCl + H₂O

Question 16.
How are bases classified based on ionisation?
Answer:
Based on Ionisation
(a) Strong Bases :
These are bases which ionise completely in aqueous solution.
Example: NaOH, KOH

(b) Weak Bases:
These are bases that ionise partially in aqueous solution.
Example: NH₄OH, Ca(OH)₂

VI. To Interpret:

Question 1.
CH₄ and NH₃, are not acids.
Answer:
CH₄ and NH₃ do not produce hydrogen ion (H⁺) in its aqueous solution.

Question 2.
Acetic acid (CH₃COOH) is a mono basic acid.
Answer:
Though acetic acid contains four hydrogen atoms only one hydrogen can be replaced in its aqueous solution. So CH₃COOH is a mono basic acid.
CH₃COOH → H⁺+ + CH₃COO^–

Question 3.
Al(OH)₃ & Zn(OH)₂ are not alkalis.
Answer:
Al(OH)₃ & Zn(OH)₂ are water insoluble bases. So they are bases not alkalies.

Question 4.
NaOH & KOH are strong bases.
Answer:
These are bases which ionise completely in aqueous solution.

Question 5.
NaHSO₄ is an acid salt.
Answer:
It is formed by the partial replacement of hydrogen ion of sulphuric acid (H₂ SO₄ ) by a metal present in sodium hydroxide (NaOH).
NaOH + H₂ SO₄ → NaHSO₄ + H₂O

Question 6.
Non-metallic oxides are acidic is nature.
Answer:
When non – metallic oxides react with bases, they can form a salt and water similar to the reaction of base with acids. So non-metallic oxides are acidic in nature.

VII. Complete the following table:

Question 1.

Answer:

Question 2.

Answer:

Question 3.

1) Hydrochloric acid	a) Fertilizer
2) Citric acid	b) Baking powder
3) Nitric acid	c) Car batteries
4) Oxalic acid	d) Cleansing agent in toilets
5) Sulphuric acid	e) Removing black stains
	f) Effervescent salts

Answer:
1. – d, 2. – f, 3. – a, 4. – e, 5. – c

Question 4.

1) Hardest substance in our body	a) Aluminium phosphate
2) Citrus fruits	b) Potash alum
3) Rice plant	c) Insoluble in water
4) Double salts	d) Acidic soil
5) Silver chloride	e) Calcium phophate
	f) Alkaline soil

Answer:
l.-e,2.-f,3.-d,4-b,5.-c

VIII. Find odd one out & give reason :

Question 1.
HCl, HNO₃, HCOOH, H₃PO₄
Answer:
H₃PO₄,
It is a tribasic acid whereas other three are monobasic acids.

Question 2.
Acetic acid, formic acid, tartaric acid, sulphuric acid.
Answer:
Sulphuric acid.
It is a mineral acid whereas other three are organic acids.

Question 3.
CaO, Na₂O, ZnO, NaOH
Answer:
NaOH.
It is a base containing replaceable hydroxyl ion. whereas other three bases contain replaceable oxide ions.

Question 4.
Bitter taste, soupy to touch, turns red litmus to blue, produce pink colour with methyl orange.
Answer:
Produce pink colour with methyl orange.
It is the property of acids whereas other three are properties of bases.

Question 5.
Litmus paper, phenolphthalein, methyl orange, Aquaregia.
Answer:
Aquaregia.
It is a mixture of two acids namely, hydrochloric acid and nitric acid, used to dissolve metals such as gold and platinum whereas other three are indicators used to identify the nature of the solution.

IX. Spot the error / Correct the wrong statement given below :

Question 1.
An acid is the compound which are capable of forming hydroxyl ions (OH^– ) in aqueous solution. .
Answer:
An acid is the compound which are capable of forming hydrogen ions (H+) in aqueous , solution, (or) A base is the compound which are capable of forming hydroxyl ion (OH-) in aqueous solution.

Question 2.
Nitric Acid is a constituent of baking powder.
Answer:
Tartaric acid is a constituent of baking powder.

Question 3.
The p^H value of the base in lesser than 7.
Answer:
The p^H value of the base is greater than 7. (or) p^H value of an acid is lesser than 7.

Question 4.
Ca(OH)₂ is a triacidic base.
Answer:
Ca(OH)₂ is a diacidic base (or) Al(OH)₃ is a triacidic base.

Question 5.
Magnesium hydroxide is used in whitewashing of buildings.
Answer:
Magnesium hydroxide is used as an antacid. (or) Calcium hydroxide is used in whitewashing of buildings.

X. Answer in detail :

Question 1.
Explain the classification of acids based on their basicity.
Answer:
Monobasic Acid :
Acid that contain only one replaceable hydrogen atom per molecule is called monobasic acid. It gives one hydrogen ion per molecule of the acid in solutions.
Example: HCl, HNO₃
.
Dibasic Acid :
An acid which gives two hydrogen ions per molecule of the acid in solution.
Example : H₂SO₄, H₂CO₃
‘
Tribasic Acid :
An acid which gives three hydrogen ions per molecule of the acid in solution.
Example: H₃PO₄.

Question 2.
Write notes on the properties of acids.
Answer:
(a) They have sour taste.
(b) Their aqueous solutions conduct electricity since they contain ions
(c) Acids turns blue litmus red.
(d) Acids react with active metals to give hydrogen gas.
Mg + H₂SO₄ → MgSO₄ + H ₂↑
Zn + 2HCl → ZnCl₂ + H₂↑

(e) Acids react with metal carbonate and metal hydrogen carbonate to give carbon dioxide.
Na₂CO₃ + 2HCl → 2NaCl + H₂O + CO₂↑
NaHCO₃ + HCl → NaCl + H₂O + CO₂↑

(f) Acids react with metallic oxides to give salt and water.
CaO + H₂SO₄ → CaSO₄+ H₂O

(g) Acids react with bases to give salt and water.
HCl + NaOH → NaCl + H₂O.

Question 3.
Write notes on the properties of bases. .
Answer:
(a) They have bitter taste.
(b) Their aqueous solutions have soapy touch.
(c) They turn red litmus blue.
(d)Their aqueous solutions conduct electricity.
(e) Bases react with metals to form salt with the liberation of hydrogen gas.
Zn + 2 NaOH → Na₂ZnO₂ + H₂↑

(f) Bases react with non-metallic oxides to produce salt and water. Since this is similar to the reaction between a base and an acid, we can conclude that non-metallic oxides are acidic in nature,
Ca(OH)₂ + CO₂ → CaCO₃+ H₂O

(g) Bases react with acids to form salt and water.
KOH + HCl → KCl + H₂O
The above reaction between a base and an acid is known as Neutralisation reaction.

(h) On heating with ammonium salts, bases give ammonia gas.
NaOH + NH₄Cl → NaCl + H₂O+ NH₃↑

Question 4.
Describe the classification of bases based on their acidity.
Answer:
(a) Monoacidic Base :
It is a base that ionises in water to give one hydroxide ion per molecule.
Example: NaOH, KOH

(b) Diacidic Base:
It is a base that ionises in water to give two hydroxide ions per molecule.
Example: Ca(OH)₂, Mg(OH)₂

(c) Triacidic Base :
It is a base that ionises in water to give three hydroxide ions per molecule.
Example: Al(OH)₃, Fe(OH)₃

Question 5.
Write notes on importance of pH in everyday life.
Answer:
p^H in our digestive system :
Hydrochloric acid produced in our stomach helps in the digestion of food without harming the stomach. During indigestion, the stomach produces too much acid and this causes pain and irritation. pH of stomach fluid is approximately 2.0

p^H changes is the cause of tooth decay :
White enamel coating of our teeth is calcium phosphate, the hardest substance in our body. Toothpaste which are generally basic and used for cleaning the teeth can neutralise the excess acid and prevent tooth decay.

p^H of soil:
In agriculture, the pH of soil is very important. Citrus fruits require slightly alkaline soil, while rice requires acidic soil and sugarcane requires neutral soil.

p^H of rain water:
The pH of rainwater is approximately 7 which means that it is neutral and also represents its high purity. If the atmospheric air is polluted with oxides of sulphur and nitrogen, they get dissolved in rainwater and make its pH less than 7. Thus, if the pH of rainwater is less than 7, then it is called acid rain. When acid rain flows into the rivers it lowers the pH of the river water. The survival of aquatic life in such rivers becomes difficult.

Question 6.
List the properties of salts.
Answer:

•  Salts are mostly solids which melt as well as boil at high temperature.
• Most of the salts are soluble in water.
  For example, chloride salts of potassium and sodium are soluble in water. But silver chloride is insoluble in water.
• They are odourless, mostly white, cubic crystals or crystalline powder with a salty taste.
• Salt is hygroscopic in nature.

Tamilnadu State Board New Syllabus Samacheer Kalvi 9th Science Guide Pdf Chapter 13 Chemical Bonding Text Book Back Questions and Answers, Notes.

Samacheer Kalvi 9th Science Solutions Chapter 13 Chemical Bonding

9th Science Guide Chemical Bonding Text Book Back Questions and Answers

I. Choose the correct answer:

Question 1.
Number of valence electrons in carbon is
(a) 2
(b) 4
(c) 3
(d) 5
Answer:
(b) 4

Question 2.
Sodium having atomic number 11, is ready to ______________ electron/electrons to attain the nearest noble gas electronic configuration.
(a) gain one
(b) gain two
(c) lose one
(d) lose two
Answer:
(c) lose one

Question 3.
The element that would form anion by gaining electrons in a chemical reaction is ………………..
(a) potassium
(b) calcium
(e) fluorine
(d) iron
Answer:
(c) fluorine

Question 4.
Bond formed between a metal and non metal atom is usually …………………..
(a) ionic bond
(b) covalent bond
(e) co-ordinate bond
Answer:
(a) ionic bond

Question 5.
______________ compounds have high melting and boiling points.
(a) Covalent
(b) Coordinate
(e) Ionic
Answer:
(c) Ionic

Question 6.
Covalent bond is formed by …………………
(a) transfer of electrons
(b) sharing of electrons
(c) sharing a pair of electrons
Answer:
(b) sharing of electrons

Question 7.
Oxidising agents are also called as …………………. because they remove eletrons form other substances.
(a) electron donors
(b) electron acceptors
Answer:
(b) electron acceptors

Question 8.
Elements with stable electronic configurations have eight electrons in their valence shell. They are ……………….
(a) halogens
(b) metals
(c) nobel gases
(d) non metals
Answer:
(c) noble gases

II. Answer briefly :

Question 1.
How do atoms attain Noble gas electronic configuration?
Answer:
Atoms of all elements, other than inert gases, combine to form molecules because they have incomplete valence shell and tend to attain a stable electronic configuration similar to noble gases. Atoms can combine either by transfer of valence electrons from one atom to another or by sharing of valence electrons in order to achieve the stable outer shell of eight electrons.

Question 2.
NaCl is insoluble in carbon tetrachloride but soluble in water. Give reason.
Answer:
NaCl is an ionic compound, it is soluble in polar solvent (water). Whereas CCl₄ is a covalent compound. So.it is insoluble in polar solvent (water). But it is soluble in nonpolar solvents.

Question 3.
Explain the Octet rule with an example.
Answer:
The tendency of atoms to have eight electrons in the valence shell is known as the ‘Octet rule’ or the ‘Rule of eight’ For example, Sodium with atomic number 11 will readily loose one electron to attain Neon’s stable electronic configuration. Similarly, chlorine has electronic configuration 2,8,7. To get the nearest noble gas (i.e. Argon) configuration, it needs one more electron. So chlorine readily gains one electron from another atom and obtains stable electronic configuration. Thus elements tend to have stable valence shell (eight electrons) either by losing or gaining electrons.

Question 4.
Write a note on different types of bonds.
Answer:
There are different types of chemical bonding possible between atoms which make the molecules. Depending on the type of bond they show different characteristics or properties.

Question 5.
Correct the wrong statements.
(a) Ionic compounds dissolve in non-polar solvents.
(b) Covalent compounds conduct electricity in molten or solution state.
Answer:
(a) Covalent compounds dissolve in non-polar solvents. (or) Ionic compounds dissolve in polar solvents.
(b) Ionic compounds conduct electricity in molten or solution state.

Question 6.
Complete the table given below.

Answer:

Question 7.
Draw the electron distribution diagram for the formation of Carbon dioxide (CO₂) molecule.
Answer:

Question 8.
Fill in the following table according to the type of bonds formed in the given molecule.
CaCl₂, H₂O, CaO, CO, KBr, HCl, CCl₄, HF, CO₂, Al₂Cl₆

Answer:

Question 9.
The property which is characteristic of an Ionic compound is that
(a) it often exists as a gas at room temperature.
(b) it is hard and brittle.
(c) it undergoes molecular reactions
(d) it has a low melting point.
Answer:
(b) it is hard and brittle

Question 10.
Identify the following reactions as oxidation or reduction.
(a) Na → Na⁺ + e^–
(b) Fe³⁺ + 2 e^– → Fe⁺
Answer:
(a) oxidation
(b) reduction

Question 11.
Identify the compounds as Ionic/Covalent/Coordinate based on the given characteristics.
(a) Soluble in non-polar solvents
(b) Undergoes faster/instantaneous reactions
(c) Non-conductors of electricity
(d) Solids at room temperature
Answer:
(a) Co-ordinate Covalent compound.
(b) Ionic compound.
(c) Covalent compound.
(d) Ionic compound.

Question 12.
An atom X with atomic number 20 combines with atom Y with atomic number 8. Draw the dot structure for the formation of the molecule XY
Answer:

Question 13.
Considering MgCl₂ as ionic compound and CH₄ as covalent compound give any two differences between these two compounds.
Answer:

MgCl (ionic compound)	CH4(covalent compound)
1. It is formed by the transfer of electrons (2e– ) from metal magnesium (Mg) to a non – metal atom chlorine (Cl)	It is formed by the sharing of electrons between the non-metal atoms carbon and hydrogen
2. In MgCl2 , strong electrostatic force of attraction exist between magnesium cation (Mg2+) and chlorine atoms (Cl– )	In CH4, weak force of attraction exist between the carbon atom and four hydrogen atoms.

Question 14.
Why are Noble gases inert in nature?
Answer:
Noble gases are inert in nature due to the completely filled subshells and thus have stable electronic structures which is very difficult to change. The elements Helium, Neon, Argon, Krypton, Xenon and Radon of group 18 in the periodic table are Noble gases.

III. Answer in detail :

Question 1.
List down the differences between Ionic and Covalent compounds.
Answer:

Ionic Compounds	Covalent Compounds
Formed by the transfer of electrons from a metal to a non-metal atom	Formed by sharing of electrons between non-metal atoms.
The strong electrostatic force of attraction between cations and anions.	Mutual sharing of electrons and so weak force of attraction between atoms.
Solids at room temperature.	Gases, liquids, and soft solids.
Conducts electricity in molten state or in solutions	Non-conductors of electricity.
Have high melting and boiling points.	Have low melting and boiling points.
Soluble in polar solvents	Soluble in non-polar solvents.
Hard and brittle.	Soft and waxy.
Undergo ionic reaction which is fast and instantaneous	Undergo molecular reactions which are slow.

Question 2.
Give an example for each of the following statements.
(a) A compound in which two Covalent bonds are formed.
(b) A compound in which one ionic bond is formed.
(c) A compound in which two Covalent and one Coordinate bond are formed.
(d) A Compound in which three covalent bonds are formed.
(e) A compound in which a coordinate bond is formed.
Answer:
(a) Oxygen molecule (O₂) (O = O)
(b) Sodium’Chloride (NaCl)
(c) Carbon monoxide?

(d) Nitrogen molecule (N₂) (N ≡N)
(e) NH₃ → BF₃

Question 3.
Identify the incorrect statement and correct them.
(a) Like covalent compounds, coordinate compounds also contain charged particles (ions). So they; are good conductors of electricity.
(b) Ionic bond is a weak bond when compared to Hydrogen bond.
(c) Ionic or electrovalent bonds are formed by the mutual sharing of electrons between atoms.
(d) Loss of electrons is called Oxidation and gain of the electron is called Reduction.
(e) The electrons which are not involved in bonding are called valence electrons.
Answer:
(a) Incorrect statement. Like covalent compounds, co-ordinate compounds also do not contain charged particles (ions), so they are bad conductors of electricity.
(b) Incorrect statement. An ionic bond is a strong bond when compared to a hydrogen bond.
(c) Incorrect statement. Covalent bonds are formed by the mutual sharing of electrons between atoms, (or) Ionic or electrovalent bonds are formed by the transfer of electrons between atoms.
(d) Correct statement
(e) Incorrect statement. The electrons which are not involved in bonding are called lone pair of electrons.

Question 4.
Discuss in brief the properties of coordinate covalent compounds.
Answer:
The compounds containing coordinate covalent bonds are called coordinate compounds.
(a) Physical state – These compounds exist as gases, liquids or solids.
(b) Electrical conductivity-Like covalent compounds, co-ordinate compounds also do not contain charged particles (ions), so they are bad conductors of electricity.
(c) Melting point – These compounds have to melt and boiling points higher than those of purely covalent compounds but lower than those of purely ionic compounds.
(d) Solubility – Insoluble in polar solvents like water but are soluble in non-polar solvents like benzene, CCl₄, and toluene.
(e) Reactions – Co-ordinate covalent compounds undergo molecular reactions which are slow.

Question 5.
Find the oxidation number of the elements in the following compounds.
(a) C in CO₂
(b) Mn in MnSO₄
(c) N in HNO₃
Answer:
(a) C in CO₂
1(C) + 2(0) = 0
1x + 2(-2) = 0
x-4 = 0 ‘
x = +4 .
ON of C in CO₂ is +4

(b) Mn in MnSO₄
1 (Mn) + 1 (S) + 4(0) = 0
x + 1(+6) + 4(-2) = 0
x + 6 – 8 = 0
x – 2 = 0
x = +2
ON of Mn in MnSO₄ is +2,

(c) N in HNO₃
1(H) + 1 (N) +3(0) =0
1 (+1) + 1 (x) + 3 (-2) =0
+ 1 + x – 6 =0
x – 5 =0
x = +5
ON of N in HNO₃ is + 5.

9th Science Guide Chemical Bonding Additional Important Questions and Answers

I. Choose the correct answer:

Question 1.
Which of the following atom can exist independently?
(a) Magnesium
(b) Chlorine
(c) Hydrogen
(d) Neon
Answer:
(d) Neon

Question 2.
Alkali and alkaline earth metals form ………… compound when they react with non-metals.
(a) ionic
(b) covalent
(c) co-ordinate covalent
(d) all the above
Answer:
(a) ionic

Question 3.
……………..compounds are highly brittle.
(a) Ionic
(b) Covalent
(c) Co-ordinate covalent
Answer:
(a) Ionic

Question 4.
The bond which is formed by mutual sharing of electrons is called ……………….. bond.
(a) ionic
(b) covalent
(c) co-ordinate covalent bond
(d) all the above
Answer:
(b) covalent

Question 5.
………………. is an example of a covalent compound having a high melting point.
(a) Magnesium oxide
(b) Silicon carbide
(c) Ammonia
(d) All the above
Answer:
(b) Silicon carbide

Question 6.
Which of the following compound(s) possesses a high melting point?
(a) NaCl
(b) MgCl₂
(c) CCl₄
(d) Both a & b
Answer:
(d) Both a & b

Question 7.
The element that would form cation due to the loss of electron during the chemical reaction is ………………..
(a) calcium
(b) Fluorine
(c) Chlorine
(d) all the above
Answer:
(a) calcium

Question 8.
Fajan’s rule is formulated by considering …………… the cation and ………………..of the cation and anion.
(a) charge
(b) size
(c) charge & size
(d) none
Answer:
(c) charge & size

Question 9.
The formation of brown colour on the freshly unit surface of vegetables and fruits is because ………………. of organic compounds present in them.
(a) oxidation
(b) reduction
(c) both a & b
(d) none
Answer:
(a) oxidation

Question 10.
Which of the following compounds has melting and boiling points higher than covalent compounds but lower than ionic compounds?
(a) NaCl
(b) MgCl₂
(c) H₂O
(d) NH₃→BF₃
Answer:
(d) NH₃→BF₃

Question 11.
Atoms having 1,2 or 3 electrons in their valence shell will readily form ……………..
(a) cation
(b) anion
Answer:
(a) cation

II. Fill in the blanks:

1. ……………theory explains the formation of molecules.
Answer:
Kossel – Lewis theory

The valency of noble gases is ……………..
Answer:
zero

3. …………….. is the only noble gas which does not have eight electrons in their valence shell.
Answer:
Helium

4. The atom that loses electrons will from a ________
Answer:
cation

5. ______ compounds have high density.
Answer:
Ionic

6. In covalent bond formation, the sharing of ………….. electrons takes place in their outermost shell.
Answer:
unpaired

7. Polar solvents contain bond between atoms with ………………
Answer:
different electronegativities

8. ……………….. & ………….. atoms have similar electronegativities.
Answer:
Carbon & hydrogen

9. Molecular reactions are ……………… in the covalent compound.
Answer:
slow

10. Ionic compounds are ……………..in nature.
Answer:
solid

11. The tendency of atoms to have eight electrons in the outer shell is known as ……………….
Answer:
Octet rule

12. As per Fajan’s rule, A1I₃is ……………..
Answer:
covalent

13. Oxidising agents are otherwise called as ………………..
Answer:
electron acceptors

14. The tarnishing of metals is due to the formation of ……………….
Answer:
metal oxide

15. The tarnishing of metals is an example of ……………. reaction.
Answer:
oxidation

16. The sum of oxidation number of all atoms in a compound is ………………..
Answer:
Zero

17. The ……………….. is a metal that has a high resistance to corrosion.
Answer:
Gold

III. Spot the error / correct the wrong statement:

Question 1.
In the formation of compounds, the inner shell electrons of an atom involved in bonding.
Answer:
In the formation of compounds, the valence electrons of an atom involved in bonding.

Question 2.
The atom that gains electrons will form a cation.
Answer:
The atom that gains electrons will form an anion.

Question 3.
Ionic compounds have low melting and boiling point.
Answer:
Ionic compounds have high melting and boiling point, (or) Covalent compounds have low melting and boiling point.

Question 4.
Non-polar solvents contain bonds between atoms with different electronegativities.
Answer:
Non-polar solvents contains bonds between atoms with similar electronegativities.

Question 5.
Covalent compounds are soluble in polar solvents.
Answer:
Covalent compounds are readily soluble in non-polar solvents, (or) Ionic compounds are soluble in polar solvents.

Question 6.
Greater the charge of the cation greater will be the ionic character.
Answer:
Greater the charge of the cation greater will be the covalent character.

IV. Match the following :

Question 1.

1) Monoatomic gaseous atom	a) Electrovalent bond
2) Octet rule	b) Benzene
3) Ionic bond	c) Water
4) Non-polar solvent	d) Electronic theory of valence
5) Polar solvent	e) Noble gases

Answer:
1. – e, 2. – d, 3. – a, 4. – b, 5. – c

Question 2.

1) Atomic bond	a) Oxygen and hydrogen
2) Atoms with different electronegativities	b) acceptor bond
3) Atom which accepts electron pair	c) covalent bond
4) Rusting of iron	d) donor atom
5) Atom which provides electron pair	e) oxidation
	f) ionic bond

Answer:
1. – c, 2. – a, 3. – b, 4. – e, 5, – d.

V. Find the odd one out and write the reason:

Question 1.
Water, acetone, benzene, toluene turpentine.
Answer:
Water. It is a polar solvent where a^ others air non-polar solvents.

Question 2.
Addition of oxygen, removal of hydrogen, loss of an electron, gain of electron.
Answer:
Gain of electron. It is a reduction reaction whereas other three are oxidation reactions.

Question 3.
Platinum, palladium NaBH₄, CrO₃.
Answer:
CrO₃ It is an oxidising agent whereas the other three are reducing agents.

Question 4.
Ionic bond, metallic bond, Coordinate covalent bond, Hydrogen bond.
Answer:
Hydrogen bond. It is a weak bond whereas the other three are strong bonds.

Question 5.
Soft & waxy, a bad conductor of electricity, low boiling point, solid at room temperature.
Answer:
Solid at room temperature.
It is the property of ionic compounds whereas the other three are the properties of covalent compounds.

.
VI. Answer in brief :

Question 1.
What is a chemical bond?
Answer:
A chemical bond may be defined as the force of attraction between the two atoms that bind them together as a unit called a molecule.

Question 2.
Write the basic concept of Kossel – Lewis theory.
Answer:
Kossle – Lewis theory is based on the concept of electronic configuration of noble gases.

Question 3.
Define the ionic bond.
Answer:
An ionic bond is a chemical bond formed by the electrostatic attraction between positive and negative ions. The bond is formed between two atoms when one or more electrons are transferred from the valence shell of one atom to the valence shell of the other atom.

Question 4.
The following shows the electronic distribution diagram for the formation of MgCl₂ molecule. Based on this answer the following questions.

(a) Which of the above atom loses electrons to form a cation?
(b) Which of the above atom gain electrons to form an anion?
(c) How many electrons are transferred from Mg to Cl?
(d) Write the name of the anion formed.
(e) Which noble gas configuration do these ions resemble?
(f) Write the electronic configuration of Mg²⁺ & Cl^–
Answer:
(a) Magnesium atom loses electrons to form a cation.
(b) Chlorine atom gains 1 electron to from anion.
(c) Two electrons are transferred from Mg – atom to 2 Cl – atoms (each Cl – atom gains 1e^– from Mg – atom).
(d) Chloride anion (Cl^– )
(e) Mg²⁺ ion resembles noble gas configuration of Neon Cl^– ion resembles noble gas configuration of Argon.
(f) Electronic configuration of Mg²⁺ is 2, 8. and Electronic configuration of Cl^– is 2, 8, 8.

Question 5.
What is covalent bond?
Answer:
Bond which is formed between atoms by the mutual sharing of electrons is known as a covalent bond.

Question 6.
Name of the following:
(a) An element which obtains the noble gas configuration of neon by losing three electrons.
(b) An element which gains two electrons to obtain the noble gas configuration of Neon.
Answer:
(a) Aluminium (Al → Al³⁺ + 3e^–)
(b) Oxygen atom (O + 2e^– → 0^2-)

Question 7.
Identify the following reactions as oxidation/reduction/redox reaction.
(a) Zn + CuSO₄ → Cu + ZnSO₄
(b) CuO+H₂ → Cu+H₂O
(c) 2Mg +O₂  → 2MgO
Answer:
(a) Redox reaction
(b) Reduction
(e) Oxidation

Question 8.
What are oxidising agents? Give an example.
Answer:
Substances which have the ability to oxidise other substances are called oxidizing agents. These are also called electron acceptors because they remove electrons from other substances. ’
Example:

Question 9.
What are reducing agents? Give examples.
Answer:
Substances which have the ability to reduce other substances are called reducing agents. These are also called electron donors because they donate electrons to other substances.
Example: NaBH₄, LiAlH₄ and metals like Palladium, Platinum.

Question 10.
What are redox reactions? Give examples.
Answer:
Both the oxidation and reduction occurs in the same reaction simultaneously is known as a redox reaction. If one reactant gets oxidised, the other gets reduced. Such reactions are called oxidation-reduction reactions or redox reactions.
Ex. 1 : 2 PbO + C → 2 Pb + CO₂
Ex. 2 : Zn + CuSO₄  → Cu + ZnSO₄

Question 11.
Define (a) oxidation (b) reduction reactions : Give examples.
Answer:

Question 12.
What is rancidity?
Answer:
The oxidation reaction in food materials that were left open for a long period is responsible for spoiling of food. This is called rancidity.

Question 13.
Define oxidation number.
Answer:
Oxidation number of an element is defined as the formal charge which an atom of that element appears to have when electrons are counted.

Question 14.
Identify the type of bond in \(\mathrm{NH}_{4}^{+}\)

Answer:

VII. To interpret:

Question 1.
Ionic bond is also called electrostatic bond.
Answer:
In ionic bond formation the bond is formed between the oppositely charged ions and these ions come closer to each other due to electrostatic force of attraction. So ionic bond is also called an electrostatic bond.

Question 2.
Ionic compounds are crystalline solids at room temperature.
Answer:
Ionic compounds are formed because of the strong electrostatic force between cations and anions which are arranged in a well-defined geometrical pattern. Thus ionic compounds are crystalline solids at room temperature.

Question 3.
Covalent compounds have a low melting point.
Answer:
In covalent compounds, atoms are held by a weak force of attraction. When heat is applied, the molecules are readily pulled out and get free movement.

VIII. Assertion and Reason type questions :

Question 1.
Statement (A) : Ionic compounds do not conduct electricity in a solid-state.
Reason (B) : The ions in ionic compounds are tightly held together by a strong electrostatic force of attraction and they can not move freely.
(a) B explains A
(b) B does not explain A
(c) B is wrong A
(d) A is right B is wrong
Answer:
(a) B explains A

Question 2.
Statement (A) : Covalent compounds are bad conductors of electricity.
Reason (B) : Covalent compounds contain charged particles (ions)
a) B explains A
b) B does not explain A
c) Both A & B are right
d) Both A & B are wrong
Answer:
(b) B does not explain A
Reason: Since covalent compounds do not have charged particles (ions), they are bad conductors of electricity.

IX. Find the oxidation number of the elements in the following compounds.

(1) Zn in ZnSO₄
(2) Ca in CaH₂
(3) Mg in MgO
(4) N in NH₃
(5) A1 in AlCl₃
Answer:
(1) ZnSO₄
1(Zn) + 1 (S) + 4 (0) = 0
x + 1(+6) + 4(-2) = 0
x + 6 – 8 = 0
x = + 2
Oxidation number of Zn in ZnSO₄ is +2

(2) CaH₂
1(Ca) + 2 (H) = 0
x + 2 (-1) = 0
x -2 = 0
x = + 2
Oxidation number of Ca in CaH₂ is +2

(3) MgO
1(Mg) + 1 (O) = 0
x + 1 (-2) = 0
x -2 = 0
x = + 2
Oxidation number of Mg in MgO is +2

(4) NH₃
1(N) + 3 (H) = 0
x + 3 (-1) = 0
x – 3 = 0
x = +3
Oxidation number of N in NH₃ is +3
(5) AlCl₃
1(Al) + 3(Cl) = 0
x + 3 (-1) = 0
x – 3 = 0
x = + 3
Oxidation number of Al in AlCl₃ is +3

X. Complete the following table:

Question 1.

Atoms	Atomic number	Electron distribution
a) O	8	–
b) N	–	–
c) –	17	–
d) –	–	2,8,2

Answer:

Atoms	Atomic number	Electron distribution
a) O	8	2,6
b) N	7	2,5
c) Cl	17	2,8,7
d) Mg	12	2,8,2

Question 2.

a) Dativebond	–
b) CaH2 → Ca+H2	–
c) –	Reduction
d) –	Redox reaction

Answer:

a) Dativebond	Co-ordinate covalent bond
b) CaH2 → Ca+H2	Oxidation
c) Fe3+ + e– →Fe2+	Reduction
d) both Oxidation of Reduction takes place simultaneously	Redox reaction

XI. To Match:

Name of compound	Type of compound
a) Sodium chloride	?
b) ?	co-ordinate covalent compound
c) Methane	?
d) Fluorine molecule	?

Answer:

Name of compound	Type of compound
a) Sodium chloride	Ionic compound
b) NH3 → BF3	co-ordinate covalent compound
c) Methane	Covalent compound
d) Fluorine molecule	Covalent compound

XII. Answer in detail :

Question 1.
Explain the ionic bond formation in sodium chloride with electron distribution diagram.
Answer:
Formation of Sodium Chloride (NaCl)

(i) The atomic number of Sodium is 11 and its electronic configuration is 2, 8, 1. It has one electron excess to the nearest stable electronic configuration of a noble gas – Neon.

(ii) So sodium has a tendency to lose one electron from its outermost shell and acquire a stable electronic configuration forming sodium cation (Na⁺).

(iii) The atomic number of chlorine is 17 and its electronic configuration is 2, 8, 7. It has one electron less to The nearest stable electronic configuration of a noble gas – Argon.

(iv) So chlorine has a tendency to gain one electron to acquire a stable electronic
configuration forming chloride anion (Cl^–)

(v) When an atom of sodium combines with an atom of chlorine, an electron is transferred from the sodium atom to chlorine atom forming sodium chloride molecule. Thus both the atoms achieve stable octet electronic configuration.

Question 2.
Explain the covalent bond formation in the following molecules.
(a) Chlorine
(b) Nitrogen
(c) Hydrogen
(d) Oxygen
Answer:
(a) Chlorine
Chlorine molecule is formed by two chlorine atoms. Each chlorine atom has seven valence electrons (2,8,7). These two atoms achieve a stable completely filled electronic configuration (octet) by sharing a pair of electrons.

(b) Nitrogen
Nitrogen molecule is formed by two nitrogen atoms. Each nitrogen atom has five valence electrons (2, 5). These two atoms achieve a stable completely filled electronic configuration (octet) by sharing three pair of electrons. Hence a triple bond is formed in between the two atoms.

(c)Hydrogen
Hydrogen molecule is formed by two hydrogen atoms. Both hydrogen atoms contributes one electron each to the shared pair and both atoms acquire stable completely filled electronic configuration.

(d) Oxygen
Oxygen molecule is formed by two oxygen atoms. Each oxygen atom has six valence electrons (2,6). These two atoms achieve a stable electronic configuration (octet) by sharing two pair of electrons. Hence a double bond is formed in between
the two atoms.

Question 3.
Explain the co-ordinate covalent bond formation in between NH₃ → BF₃ molecules.
Answer:
The ammonia molecule gives a lone pair of electrons to boron trifluoride (BF₃) molecule which is electron deficient. Thus a coordinate covalent bond is formed between NH₃ (donor molecule) and BF₃ (acceptor molecule) and is represented by

Question 4.
Write notes on the characteristics of covalent compounds.
Answer:
a. Physical state: Depending on the force of attraction between covalent molecules the bond may be weaker or stronger. Thus covalent compounds exist in gaseous, liquid, and solid forms. Eg. Oxygen-gas; Water-liquid: Diamond-solid.

b. Electrical conductivity: Covalent compounds do not contain charged particles (ions), so they are bad conductors of electricity.

c. Melting point: Except few covalent compounds (Diamond, Silicon carbide), they have relatively low melting points compared to Ionic compounds.

d. Solubility: Covalent compounds are readily soluble in non-polar solvents like benzene (C₆H₆), carbon tetrachloride (CCl₄). They are insoluble in polar solvents like water.

e. Hardness and brittleness: Covalent compounds are neither hard nor brittle. But they are soft and waxy.

f. Reactions: Covalent compounds undergo molecular reactions in solutions and these reactions are slow.

Question 5.
Write notes on the characteristics of ionic compounds.
Answer:
a. Physical state: These compounds are formed because of the strong electrostatic force between cations and anions which are arranged in a well-defined geometrical pattern. Thus ionic compounds are crystalline solids at room temperature.

b. Electrical conductivity: Ionic compounds are crystalline solids and so their ions are tightly held together. The ions, therefore, cannot move freely, so they do not conduct electricity in a solid-state. However, in a molten state and their aqueous solutions conduct electricity.

c. Melting point: the strong electrostatic force between the cations and anions hold the ions tightly together, so very high energy is required to separate them. Hence ionic compounds have high melting and boiling points.

d. Solubility: Ionic compounds are soluble in polar solvents like water. They are insoluble in non-polar solvents like benzene (C₆H₆), carbon tetrachloride (CCl₄).

e. Density, hardness, and brittleness: Ionic compounds have high density and they are quite hard because of the strong electrostatic force between the ions. But they are highly brittle.

f. Reactions: Ionic compounds undergo ionic reactions which are practically rapid and instantaneous.

Tamilnadu State Board New Syllabus Samacheer Kalvi 9th Science Guide Pdf Chapter 12 Periodic Classification of Elements Text Book Back Questions and Answers, Notes.

Samacheer Kalvi 9th Science Solutions Chapter 12 Periodic Classification of Elements

9th Science Guide Periodic Classification of Elements Text Book Back Questions and Answers

I. Choose the correct answer :
Question 1.
If Dobereiner is related with ‘law of triads’, then Newlands is related with
(a) Modem periodic law
(b) Hund’s rule
(c) Law of octaves
(d) Pauli’s Exclusion principle
Answer:
(c) law of octaves

Question 2.
Modern periodic law states that the physical and chemical properties of elements are the periodic functions of their ……………
(a) atomic numbers
(b) atomic masses
(c) similarities
(d) anomalies
Answer:
(a) atomic numbers

Question 3.
Elements in the modern periodic table are arranged in …………. groups and ………….. periods .
(a) 7, 18
(b) 18,7
(c) 17,8
(d) 8, 17
Answer:
(b) 18, 7

Fill in the blanks:

1. In Dobereiner’s triads, the atomic weight of the middle element is the __________ of the atomic masses of 1 and 3rd elements.
Answer:
average

2. Noble gases belong to ___________ group of the periodic table.
Answer:
18th

3. The basis of the classifications proposed by Dobereiner, Newlands and Mendeleev was ……………….
Answer:
atomic mass

4. Example for liquid metal is ______________ .
Answer:
mercury

III. Match the following:
Question

Triads	Newlands
Alkali metal	Calcium
Law of octaves	Henry Moseley
Alkaline earth metal	Sodium
Modern Periodic Law	Dobereiner

Answer:

Triads	Dobereiner
Alkali metal	Sodium
Law of octaves	Newlands
Alkaline earth metal	Calcium
Modern Periodic Law	Henry Moseley

IV. State whether true or false. If false, correct the statement:

Question 1.
Newlands’ periodic table is based on atomic masses of elements and modem periodic table is based on atomic number of elements.
Answer:
True.

Question 2.
Metals can gain electrons.
Answer:
False.
Correct statement: Metals tend to lose electrons.

Question 3.
Alloys bear the characteristics of both metals and nonmetals.
Answer:
False.
Correct statement: Metalloids bear the characteristics of both metals and nonmetals.

Question 4.
Lanthanides and actinides are kept at the bottom of the periodic table because they resemble each other but they do not resemble with any other group elements.
Answer:
True.

Question 5.
Group 17 elements are named as Halogens.
Answer:
True.

V. Assertion and Reason :

Question
Statement : Elements in a group generally possess similar properties but elements along a period have different properties.
Reason : The difference in electronic configuration makes the element differ in their chemical properties along a period.
a) Statement is true and reason explains the statement.
b) Statement is false but the reason is correct.
Answer:
(a) Statement is true and reason explains the statement

VI. Answer the following :

Question 1.
State modern periodic law.
Answer:
The modem periodic law states that:
“The Chemical and Physical properties of elements are periodic functions of their atomic numbers”.

Question 2.
What are groups and periods in the modern periodic table?
Answer:

•  The horizontal rows in the periodic table are called periods.
• Vertical columns in the periodic table starting from top to bottom are called groups.

Question 3.
What are the limitations of Mendeleev’s periodic table?
Answer:

• Elements with large differences in properties were included in the same group. Eg: Hard metals like copper (Cu) and silver (Ag) were included along with soft metals like sodium (Na) and potassium (K).
• No proper position could be given to the element hydrogen. Non-metallic hydrogen was placed along with metals like lithium (Li), sodium (Na) and potassium (K).
• The increasing order of atomic mass was not strictly followed throughout. Eg. Co & Ni, Te &I.
• No place for isotopes in the periodic table.

Question 4.
State any five features of the modern periodic table.
Answer:

• All the elements are arranged in the increasing order of their atomic number.
• The horizontal rows are called periods. There are seven periods in the periodic table.
• The elements are placed in periods based on the number of shells in their atoms.
• Vertical columns in the periodic table starting from top to bottom are called groups. There are 18 groups in the periodic table.
• Based on the physical and chemical properties of elements, they are grouped into various families.

Intext Activities

ACTIVITY -1

Find the pair of elements having similar properties by applying Newlands’ law of Octaves
(Example: Mg & Ca):
Set I : F, Mg, C, O,B
Set II: Al, Si, S, Cl, Ca
Answer:

1. F-Cl
2. Mg-Ca
3. C-Si
4. O-S
5. B-Al

9th Science Guide Periodic Classification of Elements Additional Important Questions and Answers

Choose the correct answer:

Question 1.
Noble gases are placed in the _______ group in the modern periodic table.
(a) 13th
(b) 18th
(c) 17th
(d) 2nd
Answer:
(b) l8th

Question 2.
Group 16 elements are collectively called as _______ .
(a) chalcogen family
(b) carbon family
(e) halogens
(d) nitrogen family
Answer:
(a) chalcogen family

Question 3.
The maximum number of electrons that can be accommodated in s, p ,d, and f subshells are _________ .
(a) 14, 10, 6, 2
(b) 6, 10, 2, 14
(c) 2, 6, 10, 14
(d) 6, 2, 14, 10
Answer:
c) 2, 6, 10, 14

Question 4.
d-block elements are otherwise known as _________ .
(a) transition elements
(b) inner transition elements
(c) halogens
(d) alkali metals
Answer:
(a) transition elements

Question 5.
Which block of the periodic table contains metals, non-metals and metalloids?
(a) s
(b) p
(c) d
(d) f
Answer:
(b) p

Question 6.
Which of the following non-metals can form alloys with metals?
(a) Boron
(b) Carbon
(c) Silicon
(d) All the above
Answer:
(d) all the above

Question 7.
Which of the following metals have low melting and boiling point?
(a) Sodium :
(b) Potassium
(e) Iroñ
(d) Both a & b
Answer:
(d) Both a & b

Question 8.
Which of the following metal (s) do not react with water?
(a) Gold
(b) Silver
(c) Copper
(d) All the above
Answer:
(d) All the above

Question 9.
If the electronic configuration of an element is 1s² 2s² 2p⁶ 3s² 3p¹’then it will
occupy ……………… block of the periodic table.
(a) s
(b) p
(c) d
(d) f
Answer:
(b) p

II. Fill in the blanks :

1. ……………… group elements are called alkaline earth metals.
Answer:
Second

2. The elements that follow lanthanum are called ……………..
Answer:
Lanthanides

3. f-block elements are also known as …………………..
Answer:
inner transition elements

4. …………… block element is placed at the bottom of the periodic table.
Answer:
f-

5. The mixture of metal with mercury is called …………………..
Answer:
amalgam

6. Elements are placed in periods based on the number of ……………… in their atoms.
Answer:
shells

III. Spot the error :

Question 1.
The elements of group 13 are called the carbon family.
Answer:
The elements of group 13 are called boron family
(or)
The elements of group 14 are called the carbon family.

Question 2.
There are 5 periods and 17 groups in the modern periodic table.
Answer:
There are 7 periods and 18 groups in the modem periodic table.

IV. Pick the odd one out and write the reason:

Question 1.
Copper, brass, gold ornament, bronze.
Answer:
Copper.
Copper is metal whereas the other three are alloys.

Question 2.
Bromine, carbon, hydrogen, aluminium.
Answer:
Aluminium.
Aluminium is metal whereas the other three are non-metals.

V. To match :

Group in the modern periodic table	Families
a) 1	?
b) ?	Transition metals
c) ?	Boron family
d) 15	?
e) 17	?

Answer:
a) alkali metals
b) 3 to 12
c) 13
d) Nitrogen family
e) halogens

VI. Answer in brief :

Question 1.
What are the s-block elements?
Answer:
Elements whose valence electron is filled in s subshell is known as s-block elements.

Question 2.
What are the p-block elements?
Answer:
The last electron in these elements is filled in p subshells and hence these elements are called p block elements. These elements are in group 13 to 18 in the periodic table.

Question 3.
What are alloys?
Answer:
Alloys are mixtures of two or more metals and are formed by mixing molten metals thoroughly. Rarely nonmetals are also mixed with metals to produce alloys.

Question 4.
What are metalloids? Give examples.
Answer:
Elements which have the properties of both metals and non-metals are called as metalloids, (eg) Boron, Arsenic.

Question 5.
State Mendeleev’s Law of Periodicity.
Answer:
The physical and chemical properties of elements are the periodic functions of their atomic masses.

Question 6.
State Newlands’ Law of Octaves.
Answer:
Every eighth element had properties similar to those of the first element like the eighth note in an octave of music is similar to the first.

Question 7.
An element has atomic number 12.
a) Write the electric configuration.
b)To which group and period do it belong.
Answer:
a) K = 2, L = 8, M = 2
b) Group No . 2, Period No. 3

Question 8.
Relate the names of the following scientists with the statements given below. (Mendeleev, Newlands, Dobereiner).
a) Arranged elements into groups containing three elements each.
b) Arranged elements in a group of seven with increasing atomic masses and eighth elements with similar properties kept below the first like eight note in an act of music.
c) Arranged elements in the increasing order of atomic mass
Answer:
a) Dobereiner
b) Newlands
c) Mendeleev

Question 9.
Complete the following triads by inserting the missing elements.
a) Cl, ………., I
b) Li, ………, K
c) Ca, …………, Ba
Answer:
a) Br
b) Na
c) Sr

Question 10.
How are elements grouped into various families in the periodic table?
Answer:
Based on the physical and chemical properties of elements, they are grouped into various families.

VII. To interpret:

Question 1.
Group 1 (except hydrogen) elements are called alkali metals.
Answer:
The elements of group 1 (except hydrogen) are metals. They react with water to form solutions that change the colour of a vegetable dye from red to blue. These solutions are said to be highly alkaline or basic. Hence they are called alkali metals.

Question 2.
d-block elements are called transition elements.
Answer:
d-block elements are found in the centre of the periodic table. Their properties are intermediate to that of s block and p block elements and so they are called transition elements.

Question 3.
Group 3-12 elements in the modern periodic table are called d block elements.
Answer:
The elements of group 3 to 12 have their valence electrons in their outermost d subshells. These elements are called d block elements.

VIII. Complete the following table :

Question

Symbol	Atomic No.	Electronic Configuration
1) He	2	?
2) Ne	?	2,8
3) Ar	?	2, 8,8
4) Na	11	?

Answer:
1) 2
2) 10
3) 18
4) 2,8,1

IX. Assertion and Reason :

Question 1.
Assertion (A): Group 2 elements in the modem periodic table are called alkaline earth metals.
Reason (R): The oxides of group 2 elements produce alkaline solutions when they are dissolved in water.
(a) A is right R is wrong
(b) R explains A
(c) R does not explain A
(d) R is right A is wrong
Answer:
(b) R explains A

Question 2.
(A) : Noble gases are chemically inert in nature.
Reason (R) : Noble gases have stable electronic structures.
(a) Both A & R are right
(b) Both A & R are wrong
(c) A is right R is wrong
(d) A is wrong R is right
Answer:
(a) Both A & R are right]

Question 3.
Assertion (A): Non-metals are electronegative.
Reason (R) : Non-metal losë electrons to form cation.
(a) Both A & R are right
(b) Both A & R are wrong
(c) A is right R is wrong
(d) A is the wrong R is right
Answer:
(c) A is right R is wrong

X. Long answer type questions:

Question 1.
List the advantages of alloys.
Answer:

• Alloys do not get corroded or get corroded to a very less extent.
• They are harder and str9ner than pure metals (Example: Gold is mixed with copper and it is harder than pure gold)
• They have less conductance than pure metals (Example: Copper is a good conductor of heat and electricity whereas brass and bronze are not good conductors)
• Some alloys have lower melting point than pure metals (Example: Solder is an alloy of lead and tin which has a lower melting point thàn each of the metals)
• When metal is alloyed with mercury, it is called amalgam.

Question 2.
Write the advantages of the Modern Periodic Table.
Answer:

• The table is based on a more fundamental property i.e., atomic number.
• It correlates the position of the element with its electronic configuration more clearly.
• The completion of each peçiod is more logical. In a period, as the atomic number increases, the energy shells are gradually filled up until an inert gas configuration is reached.
• It is easy to remember and reproduce.
• Each group is an independent group and the idea of subgroups has been discarded.
• One position for all isotopes of an element is justified since the isotopes have the same atomic number.
• The position of the eighth group (in Mendeleev’s table) is also justified in this table. All transition elements have been brought in the middle as the properties of transition elements are intermediate between the left portion and right portion elements of the periodic table.
• The table completely separates metals from nonmetals. The nonmetals are present in the upper right corners of the periodic table.
• The positions of certain elements which were earlier misfit (interchanged) in Mendeleev’s periodic table are now justified because it is based on an atomic number of the elements.
• Justification has been offered for placing lanthanides and actinides at the bottom of the periodic table.

Question 3.
Explain the position of hydrogen in the periodic table.
Answer:
Hydrogen is the lightest, smallest and first element of the periodic table. Its electronic configuration (1s¹) is the simplest of all the elements. It occupies a unique position in the periodic table. It behaves like alkali metals as well as halogens in its properties. In the periodic table, it is placed at the top of the alkali metals.

• Hydrogen can lose its one electron to form a hydrogen ion (H⁺) like alkali metals.
• It can also gain one electron to form the hydride ion (H^–) like halogens.
• Alkali metals are solids while hydrogen is a gas.
  Hence the position of hydrogen in the modem periodic table is still under debate
  as the properties of hydrogen are unique.

Question 4.
List the features of Mendeleev’s Periodic Table.
Answer:
1. It has eight vertical columns called ‘groups’ and seven horizontal rows called ‘period’.

2. Each group has two subgroups ‘A’ and ‘B’. All the elements appearing in a group were found to have similar properties.

3. For the first time,-elements were comprehensively classified in such a way that elements of similar properties were placed in the same group.

4. It was noticed that certain elements could not be placed in their proper groups in this manner. The reason for this was wrongly determined atomic masses, and consequently those wrong atomic masses were corrected. Eg: The atomic mass of beryllium was known to be 14. Mendeleev reassessed it as 9 and assigned beryllium a proper place;

5. Columns were left vacant for elements which were not known at that time and their properties also were predicted. This gave me the motivation to experiment in Chemistry. Eg: Mendeleev gave the names Eka Aluminium and Eka Silicon to those elements which were to be placed below aluminium and silicon respectively in the periodic table and predicted their properties. The discovery of Germanium later on, during his lifetime, proved him correct.

Properties of Germanium:

Property	Mendeleev’s prediction (1871)	Actual property (1886)
Atomic Mass	About 72	72.59
Specific Gravity	5.5	5.47
Colour	Dark grey	Dark grey
Formula of oxide	EsO2	GeO2
Nature of chloride	ESCl4	GeCl4

 

Tamilnadu State Board New Syllabus Samacheer Kalvi 9th Science Guide Pdf Chapter 9 Universe Text Book Back Questions and Answers, Notes.

Tamilnadu Samacheer Kalvi 9th Science Solutions Chapter 9 Universe

9th Science Guide Universe Text Book Back Questions and Answers

I. Choose the correct answer:

Question 1.
Who proposed the heliocentric model of the universe?
(a) Tycho Brahe
(b) Nicolaus Copernicus
(c) Ptolemy
(d) Archimedes
Answer:
(b) Nicolaus Copernicus

Question 2.
Which of the following is not a part of outer solar system?
(a) Mercury
(b) Saturn
(c) Uranus
(d) Neptune
Answer:
(a) Mercury

Question 3.
Ceres is a …………….
(a) Meteor
(b) Star
(e) Planet
(d) Asteroid
Answer:
(d) Asteroid

Question 4.
The period of revolution of planet A around the Sun is 8 times that of planet B. How many times is the distance of planet A as great as that of planet B?
(a) 4
(b) 5
(e) 2
(d) 3
Answer:
(a) 4

Question 5.
The Big Bang occurred _____ years ago.
(a) 13.7 billion
(b) 15 million
(e) 15 billion
(d) 20 million
Answer:
(a) 13.7 billion

II. Fill in the blanks :

1. The speed of Sun in km/s is ………………
Answer:
250 km/s

2. The rotational period of the Sun near its poles is ………………
Answer:
36 days

3. India’s first satellite is ……………..
Answer:
Aryabhatta

4. The third law of Kepler is also known as the Law of ……………….
Answer:
Harmonics

5. The number of planets in our Solar System is …………………
Answer:
8

III. State whether true or false. If false, correct the statement:

1. ISS is a proof for international cooperation.
Answer:
True.

2. Halley’s comet appears after hearly 67 hours.
Answer:
False.
Correct statement: Halley’s comet appears after nearly 76 years.

3. Satellites nearer to the Earth should have lesser orbital velocity.
Answer:
False.
Correct statement: Satellites nearer to the Earth should have faster orbital velocity.

4. Mars is called the red planet.
Answer:
True.

IV. Answer briefly :

Question 1.
What is the solar system?
Answer:
The Sun and celestial bodies which revolve around it form the solar system. It consists of a large number of bodies such as planets, comets, asteroids, and meteors.

Question 2.
Define orbital velocity.
Answer:
The horizontal velocity that has to be imparted to a satellite at the determined height so that it makes a circular orbit around the planet is called “orbital velocity”.

Question 3.
Define time period of a satellite.
Answer:
Time taken by the satellite to complete one revolution around the Earth is called the time period.
Time period, T = Distance covered/Orbital velocity
T = 2πr/v

Question 4.
What is the satellite? What are the two types of satellites?
Answer:
A body moving in orbit around a planet is called a satellite.
The two types of Satellites are

1.  Natural satellites,
2.  Man-made satellites.

Question 5.
Write a note on the inner planets.
Answer:
The planets are spaced unevenly. The first four planets are relatively close together and close to the Sun. They form the inner solar system. The four planets grouped together in the inner solar system are Mercury, Venus, Earth, and Mars. They are called inner planets. They have a surface of solid rock crust and so are called terrestrial or rocky planets. Their insides, surfaces, and atmospheres are formed in a similar way and form a similar pattern. Our planet, Earth can be taken as a model of the other three planets.

Question 6.
Write about comets.
Answer:

• Comets are lumps of dust and ice that revolve around the Sim in highly elliptical orbits.
• Their period of revolution is very long.
• Comet vapourises and forms a head and tail on approaching the sun.
• Tail of the biggest comet may be around 160 million km.
• There are period comets (e:g) Halley’s comet which appears after every 76 years.

Question 7.
State Kepler’s laws.
Answer:
In the early 1600s, Johannes Kepler proposed three laws of planetary motion.
First Law – The Law of Ellipses
The path of the planets about the Sun is elliptical in shape, with the center of the Sun being located at one of the foci.

Second Law – The Law of Equal Areas
An imaginary line drawn from the center of the Sun to the center of the planet will sweep out equal areas in equal intervals of time.

Third Law – The Law of Harmonies
The ratio of the squares of the periods of any two planets is equal to the ratio of the cubes of their semi-major axis from the Sun.

Question 8.
What factors have made life on Earth possible?
Answer:
Factors responsible for life on Earth.

1. Right distance from the Sun.
2. Right temperature.
3. Presence of water.
4. Suitable atmosphere.
5. Blanket of ozone.

V. Answer in detail:

Question 1.
Give an account of all the planets in the solar system.
Answer:

The planets are spaced unevenly. The first four planets are relatively close together and close to the Sun. They form the inner solar system. Farther from the Sun is the outer solar system, where the planets are much more spread out. Thus the distance between Saturn and Uranus is much greater (about 20 times) than between the Earth and Mars.

The four planets grouped together in the inner solar system are Mercury, Venus, Earth, and Mars. They are called inner planets. They have a surface of solid rock crust and so are called terrestrial or rocky planets. Their insides, surfaces, and atmospheres are formed in a similar way and form a similar pattern. Our planet, Earth can be taken as a model of the other three planets.

The four large planets Jupiter, Saturn, Uranus and Neptune spread out in the outer solar system that slowly orbits the Sun are called outer planets. They are made of hydrogen, helium and other gases in huge amounts and have very dense atmosphere. They are known as gas giants and are called gaseous planets. The four outer planets Jupiter, Saturn, Uranus and Neptune have rings whereas the four inner planets do not have any rings. The rings are actually tiny pieces of rock covered with ice.

Question 2.
Discuss the benefits of ISS.
Answer:

1. Water purification efforts :
The water recovery system (WRS) and the oxygen generation system (OGS) techniques developed by ISS provides advanced water Alteration and purification to water scarcity areas

2. Eye-tracking technology :
Eye-tracking technology can be used in many laser surgeries which tracks eye’s position very accurately and helps the disabled people with limited movement and speech.

3. Robotic arms and Surgeries :
Robotic arms provide significant help to surgeons in removing inoperable tumours and taking biopsies with great accuracies.

4. Apart from the above, there are many other applications such as the development of improved vaccines, breast cancer detection and treatment, and so on.

Question 3.
Write a note on orbital velocity.
Answer:
Nowadays many artificial satellites are launched into the Earth’s orbit. The first artificial satellite Sputnik was launched in 1956. India launched its first satellite Aryabhatta on April 19, 1975. Artificial satellites are made to revolve in an orbit at a height of a few hundred kilometres. At this altitude, the friction due to air is negligible. The satellite is carried by rocket to the desired height and released horizontally with a high velocity so that it remains moving in a nearly circular orbit. The horizontal velocity that has to be imparted to a satellite at the determined height so that it makes a circular orbit around the planet is called orbital velocity.

The orbital velocity of the satellite depends on its altitude above Earth. The nearer the object to the Earth, the faster is the required orbital velocity. At an altitude of 200 kilometres, the required orbital velocity is a little more than 27,400 kph. That orbital speed and distance permit the satellite to make one revolution in 24 hours. Since Earth also rotates once in 24 hours, a satellite stays in a fixed position relative to a point on Earth’s surface. Because the satellite stays over the same spot all the time, this kind of orbit is called ‘geostationary’.

Orbital velocity can be calculated using the following formula.
v = \(\sqrt{\frac{\mathrm{GM}}{(\mathrm{R}+\mathrm{h})}}\)
where; G = Gravitational constant (6.673 × 10^{– 11}Nm²kg^{– 2})
M = Mass of the Earth (5.972 × 10²⁴kg)
R = Radius of the Earth (6371 km)
h = Height of the satellite from the surface of the Earth.

VI. Conceptual Questions

Question 1.
Why do some stars appear blue and some red?
Answer:

1. Stars appear in different colours depending on their temperatures.
2. Hot stars are white or blue in colour.
3. Cooler stars are orange or red in colour.

Question 2.
How is a satellite maintained in nearly circular orbit?
Answer:
Artificial satellites are made to revolve in an orbit at a height of a few hundred kilometres. At this altitude, the friction due to air is negligible. The satellite is carried by rocket to the desired height and released horizontally with a high velocity so that it remains moving in a nearly circular orbit.

Question 3.
Why are some satellites called geostationary?
Answer:
The Earth rotates once in 24 hours, a satellite stays in a fixed position.
Because the satellite stays over the same spot all the time, this kind of orbit is called . “geostationary”.

Question 4.
A man weighing 60 kg on the Earth will weigh 1680 kg in the Sun. Why?
Answer:
Mass of the man = 60Kg
w = m × g
m = 60Kg, g = 274.13m/s²
The sun’s gravitational acceleration is 30 times more than that of the earth. So the person would weigh 16,447N on the surface of the sun.

VII. Numerical Problems

Question 1.
Calculate the speed with which a satellite moves if it is at a height of 36,000 km from the Earth’s surface and has an orbital period of 24 hr (Take R = 6370 km).
[Hint: Convert hr into seconds before doing the calculation)

Solution:
Given:
Height of the satellite, h = 36,000 km = (36,000) ×10³m
Radius of the Earth, R = 6370 km = (6370) × 10³m
We know: Gravitational constant, G = 6.673 10^-11Nm²kg^-2
Mass of the Earth, M = 5.972 × 10²⁴kg.

Orbital velocity, v = 3.067×10 ³ m/s (or) 3067m/s (or) 3.067 km/s.

Question 2.
At an orbital height of 400 km, find the orbital period of the satellite.
Solution : Given : Orbital height, h = 400 km = 400 × 10³m
We know : Gravitational constant, G = 6.673 × 10^-11Nm²kg^-2
Mass of the earth, M =5.972 ×10²⁴kg
Radius of the Earth, R = 6371 km = 6371 × 10^-3m.

Intext Activities

ACTIVITY – 1

Form a team of three to four students. Prepare a poster about the astronomers

ACTIVITY – 2

Observe the sky keenly during night. Can you see group of stars? Can you figure out any shape? Discuss with your teachers and find out their name.
Aim : To observe the group of stars in the night sky.

Procedure :

1. Observe the night sky keenly.
2. Observe the movements of stars
3. Imagine the shapes

Observation :
By discussing with the teachers following groups are identified.

Group of Star	shape
1. Orion	Hunter
2. pisces	Fish
3. Gemini	Twins table
4. Leo	Lion
5. Cancer	Crab
6. Capricornus	Sea goat

ACTIVITY – 3

Watch the sky in the early morning. Do you see any planet? What is its name? Find out with the help of your teachers.
Aim :
1. Most of the planets cannot be seen in normal sky.
2. Few planets can be seen during some specific period in the night sky.
3. Mercury, closest to the sun can be seen from the earth.
4. Venus is also seen few days in a year.
5. Uranus may be also seen on odd days in October.

ACTIVITY – 4

Prepare a list of Indian satellites from Aryabhatta to the latest along with their purposes.
S.No. Name of satellite Year Purpose
s

9th Science Guide Universe Additional Important Questions and Answers

I. Choose the correct answer :

Question 1.
The Geocentric model of universe was proposed by ……………
(a) Tyago Brane
(b) Kepler
(c ) Ptolemy
(d) Copernicus
Answer:
ptolemy

Question 2.
The total area of observable universe is about light-years.
(a) 9.3 billion
(b) 93 billion
(c) 93 million
(d) 9.3 million
Answer:
93 billion

Question 3.
All the atoms together only make up ______ percent of universe.
(a) 3
(b) 4
(c) 5
(d) 2
Answer:
(b) 4

Question 4.
The milky way galaxy is ………………in shape.
(a) Elliptical
(b) Circular
(e) Spiral
(d) Irregular
Answer:
(c) spiral

Question 5.
Stars are built by ____ gases.
(a) Hydrogen
(b) Helium
(e) Nitrogen
(d) Oxygen
Answer:
(a) Hydrogen

Question 6.
The process that takes place in the Sun is ………………
(a) Nuclear Fission
(b) Spallation
(c) Nuclear Fusion
(d) None of these
Answer:(c)
Nuclear Fusion
Question 7.
The energy of the sun is radiated in the form of_____ Rays.
(a) Ultraviolet
(b) Infrared
(e) neutron radiation
(d) X-rays
Answer:
(b) Infrared

Question 8.
The ____ colour is the most intense colour in solar radiation.
(a) blue
(b) red
c) violet
(d) yellow
Answer:
(d) yellow

Question 9.
Athe distance of the planet from the sun increases, the period of revolution ………………..
(a) increases
b) decreases
(c) remains the same
(d) a & b
Answer:
(a) increases

Question 10.
Which among the planets has less length of a day?
(a) Mercury
(b) Uranus
(c) Jupiter
(d) Saturn
Answer:
(c) Jupiter

Question 11.
The hottest planet on the solar system is ……………….
(a) Venus
(b) Mercury
(c) Mars
(d) Earth
Answer:
(a) Venus

Question 12.
Which planet is known as Red Planet?
(a) Venus
(b) Saturn
(c) Mars
(d) Neptune
Answer:
(c) Mars

Question 13.
The number of moons present in Saturn is ………………..
(a) 20
(b) 30
(c) 50
(d) 60
Answer:
(d) 60

Question 14.
The planet having the longest summers and winters is ………………….
(a) Saturn
(b) Neptune
(c) Uranus
(d) Jupiter
Answer:
(c) Uranus

Question 15.
Windiest planet in the solar system ………………..
(a) Neptune
(b) Uranus
(c) Saturn
(d) Jupiter
Answer:
a) Neptune

Question 16.
Which among the planets does not have a moon?
(a) Mars
(b) Earth
(c) Uranus
(d) Mercury
Answer :
(d) Mercury

Question 17.
The orbital velocity of the satellite depends on its ……………………
(a) Shape of orbit
(b) altitude
(c) distance
(d) All of these
Answer:
(b) altitude

Question 18.
Which among the following statements is correct?
(i) Meteors are attracted by the gravitational at force of earth.
(ii) Meteors are travelling in low speeds.
(iii) Most of Meteors are burnt by the heat generated by friction in atmosphere.
(a) (i) & (ii)
(b) (ii) & (iii)
(c) (i) & (iii)
(d) All of these
Answer:
(c) (i) & (iii)

Question 19.
The first part of the ISS was launched by
(a) Russian Soyuz
(b) Russian Zarya
(c) Russian Orbital
(d) American Sputnik
Answer:
(b) Russian Zarya

Question 20.
The time is taken by the sun to complete one revolution around the milky way
(a) 250 million years
(b) 200 million years
(c) 225 million years
(d) 240 million years
Answer:
(c) 225 million years

Question 21.
Which of the following statements is correct?
A. There are eight planets in our Solar System.
B. Except Mars, all other planets revolve around the Sun in elliptical orbits.
(a) A only
(b) B only
(c) Both A and
(d) None
Answer:
(a) A only

II. Fill in the blanks :

1. Sun is the star present in the galaxy called ………………
Answer:
milky way

2. The universe began with the start of a massive explosion called ……………..
Answer:
Big Bang

3. Scientists believe that there are ……………… galaxies in the observable universe.
Answer:
one hundred billion (10¹¹)

4. Our closest neighbouring galaxy is ……………
Answer:
Andromeda

5.We can see nearly _______ stars with the naked eye in the dark night
Answer:
3000

6. The brightness of stars depends on their _______ and _____ from the earth.
Answer:
Intensity and distance

7. The Greek name for the Sun is …………………
Answer:
Helios

8. The sun is believed to be more than ______ years ago
Answer:
4.6 billion

9. The inner planets are also known as __________
Answer:
Rocky planets

10. The outer planets are also called as _____
Answer:
Gaseous planets

11. ______ is the brightest heavenly body in our night sky.
Answer :
Venus

12. ______ is called as giant planet
Answer :
Jupiter

13. ________ is the only moon iñ the solar system with clouds.
Answer :
Titan

14. Uranus is a ______ giant
Answer:
cold gas

15. Pluto crosses the orbit of Neptune in every ______
Answer :
248 years

16. The biggest asteroid is …………………
Answer :
Ceres

17. Satellites move around the planets due to ………….. and ……………… force.
Answer :
gravitý, the centripetal

18. The ratio of____ of the periods of any two planets is equal to the ratio of their semi-major axis from the Sun.
Answer :
squares, cubes

19. The temperature of the star is determined by ______
Answer :
Colour

20. ……………… is the only moon in the solar system that moves in the opposite direction to
the direction in which its planet spins.
Answer:
Triton

III. Match the following:

(I)

1.Mercury	a) Hottest planet
2.Saturn	b) Greenish star
3.Neptune	c) Rocky planet
4.Venus	d) Lightest planet

Answer:
1-c,2-d,3-b,4-a

(II)

1.Mars	a) Bluish-green planet
2.Jupiter	b) Cold gas giant
3. Earth	c) Giand planet
4. Uranus	d) Red planet

Answer:
1-d,2-c,3-a,4-b

(III)

1. Ganymede	a) Neptune
2. Triton	b) Jupiter
3. Titan	c) Mars
4. Phobas	d) Saturn

Answer:
1-b,2-a,3-d,4-c,
(IV)

1. Jupiter	a)17.2 hours
2. Mercury	b)10.7 hours
3. Venus	c) 87.97 days
4. Saturn	d) 9 hours 55 min
5. Mars	e) 243 days
	f) 87.97 days
	g) 24 hours 37 min

Answer:
1-d,2-c,3-e,4-b,5-g

IV. State whether true or false. If false, correct the statement:

1. The basic constituent of the universe is the luminous matter.
Answer:
True.

2. The important thing about universe is that it is currently shrinking.
Answer:
False.
Correct statement: The important thing about the universe is that it is currently expanding.

3. All the matter in the universe is made up of hydrogen and helium.
Answer:
True.

4. Stars also appear to be in different colours depending on their composition of Gases.
Answer:
False.
Correct statement: Stars also appear to be in different colours depending on their temperature.

5. The planets are revolving around the sun because of the gravitational force of attraction between them.
Answer:
True.

6. The rotation of the sun near the poles takes around 25.4 days.
Answer: False.
Correct statement: The rotation of the Sun near the poles takes around 36 days.

7. Mercury is a special planet from the Sun, almost the same size as Earth.
Answer:
False.
Correct statement: Venus is a special planet from the Sun, almost the same size as Earth.

8. The axis of rotation of the Earth is perpendicular to the plane of its orbit.
Answer:
False.
Correct statement: The axis of rotation of the Earth is not perpendicular to the plane of its orbit.

9. Pole star is not visible from the southern hemisphere.
Answer:
True.

10. Comets revolve around the Sun in highly spiral orbits.
Answer:
False.
Correct statement: Comets revolve around the Sun in highly elliptical orbits.

11. The distance between Saturn and Uranus is about 10 times that between Earth and Mars.
Answer:
False.
Correct statement: The distance between Saturn and Uranus is about 20 times that between Earth and Mars.

V. Assertion and Reason type questions :

Mark the correct choice as :
(a) If both assertion and reason are true and Reason is the correct explanation of Assertion.
(b) If both assertion and reason are true but reason is not the correct explanation of assertion. ,
(c) If assertion is true but reason is false.
(d) If assertion is false but reason is true.

Question 1.
Assertion: Earth appears bluish-green.
Reason: This is due to the reflection of light from water and land mass on its surface.
Answer:
(a) If both assertion and reason are true and Reason is the correct explanation of Assertion.

Question 2.
Assertion: Sun is a medium-sized star.
Reason: Sun is situated at the centre of the solar system.
Answer:
(b) Both assertion and reason are true but the reason is not the correct explanation of the assertion

Question 3.
Assertion : The outer planets are called as Terrestial Planets.
Reason : Outer planets are made up of hydrogen, helium and other gases in huge amounts and have very dense atmospheres.
Answer:
(d) Assertion is false but reason is true
Assertion : The outer planets are called as Gas giants.

Question 4.
Assertion : The period of revolution of a satellite around a planet is directly proportional to the radius of the orbit of the satellite.
Reason : Artificial satellites do not follow Kepler’s Laws of motion.
Answer:
(c) Assertion is true but reason is false
Reason : Artificial satellites follow Kepler’s laws of motion.

Question 5.
Assertion : At the pole, the value of acceleration due to gravity (g) is greater than equator.
Reason : Earth rotates on its axis in addition to revolving around the sun.
Answer:
(a) Both Assertion and Reason are true and Reason is the correct explanation of Assertion

VI. Very Short Answer questions :

Question 1.
What is the universe?
Answer:
The collection of all the things that exist in space is known as the universe.

Question 2.
What is a galaxy?
Answer:
A galaxy is a massive collection of gas, dust and billions of stars and their solar systems.

Question 3.
How are galaxies classified?
Answer:
Depending on their appearance, galaxies are classified as

• Spiral,
• Elliptical, (or)
• Irregular.

Question 4.
Why is our galaxy called Milky way?
Answer:
Our galaxy is called milky way galaxy, because it appears as a Milky band of light in the sky.

Question 5.
What is an orbit?
Answer:
A definite curved path in which a planet revolves around the sun is called an orbit.

Question 6.
Define Period of rotation.
Answer:
The time taken by a planet to complete one rotation is called its period of rotation.

Question 7.
Give a reason for changes of seasons on Earth.
Answer:

• Earth is not perpendicular to the plane of its orbit.
• This tilt is responsible for the change of seasons on earth.

Question 8.
Mention the factors responsible for motion of satellite.
Answer:

• Gravity and
• The centripetal force are the factors responsible for motion of satellite

Question 9.
What is a geostationary orbit?
Answer:
A satellite stays in a fixed position relative to a point on Earth’s surface. That is, the satellite stays over the same spot all the time. This kind of orbit is called “Geostationary Orbit”.

Question 10.
How is eye-tracking technology helpful?
Answer:
Eye-tracking technology is helping disabled people with limited movement and speech.

Question 11.
What is a cosmic year?
Answer:
The sun travelling at a speed of 250 km per second (9 lakhs km/h) takes about 225 million years to complete one revolution around the Milky Way. This period is called a cosmic year.

Question 12.
Why are we able to see the Moon even though it is not a luminous body?
Answer:
are able to see the moon, because it reflects the light of the Sun

VII. Answer briefly :

Question 1.
Write notes on the Milky Way.
Answer:

1. Milky Way galaxy is spiral in shape.
2. It is made up of approximately 100 billion stars.
3. Its diameter is 1,00,000 light years.
4. Our solar system is 25,000 light-years away from the centre of our galaxy.

Question 2.
How does a planet differ from a star?
Answer:

Star	Planet
1. Star is luminous body (emit their own light).	Planet is a non-luminous body, (does not emit light). table
2. It revolves in the galaxy-without any centre.	Planet revolves around the star.

Question 3.
Briefly explain (i) brightness (ii) colour of star.
Answer:
Brightness of star:
The brightness of a star depends upon their intensity and distance from the earth. Colour of star:

1. The colour of the stars depends on their temperature.
2. Hot stars are white or blue.
3. Cooler stars are orange or red in colour.

Question 4.
What is a constellation?
Answer:

1. A group of stars forming an imaginary outline or meaningful pattern on the space is called a constellation.
2. They represent an animal, mythological person or creature or an object.
3. 

Question 5.
How is life on earth supported?
Answer:

1. Life on earth is supported by Sun.
2. Solar energy from the Sim has supported and sustained terrestial existence on Earth since the beginning of time.

Question 6.
Write short notes on Asteroids.
Answer:

1. 1. Half a million pieces of rocks that were left over when the planets were formed are called Asteroids.
2. Asteroids revolve around the Sun.
3. Asteroids can only be seen through large telescope.
4. The biggest asteriod is Ceres.

Question 7.
Differentiate Meteors and Meteorites?
Answer:

Meteors	Meteorites
Small pieces of rocks that are burnt up by the heat generated due to friction in the Earth’s atmosphere.	Bigger pieces of rocks that are not completely burnt by heat and fall on the surface of the Earth.

Question 8.
Write down the formula of orbital velocity.
Answer:
v = \(v=\sqrt{\frac{\mathrm{GM}}{(\mathrm{R}+h)}}\)
where v = Orbital velocity.
G = Gravitational constant. (6.673 × 10^-11Nm ²kg^-2
M = Mass of the Earth (5.972 × 10²⁴kg)
R = Radius of Earth (6371 km)
h = Height of thé satellite from the surface of the Earth.

Question 9.
Write short notes on Halley’s comet.
Answer:

1. Halley’s comet is a periodical comet.
2. It appears after nearly everý 76 years.
3. It was last seen in 1986 and will next be seen in 2062

Question 10.
Mention the uses of Robotic arms.
Answer:
Robotic arms

1. Helps in removing inoperable tumours.
2. Takes biopsies with great accuracy.
3. Helpful in breast cancer detection and treatment.
4. Helpful in the development of improved vaccines.

VIII. Answer In detail:

Question 1.
Explain the salient features of the Big Bang Theory.
Answer:
According to the Big Bang Theory,

1. The universe was a hot dense matter.
2. 13.7 billion years ago, an explosion occurred.
3. All the matter is ejected in all directions in the form of galaxies.
4. The galaxies consist of stars which are held together by gravity.
5. The stars explode and planets are liberated throughout the Universe.

Question 2.
How is Sun formed according to Big Bang theory?
Answer:
According to the Big Bang theory.

1. Hydrogen gas condensed to form huge clouds.
2. Some of the hydrogen gas was left free and started floating around. in our galax
3. The free-floating hydrogen gas concentrated and paved way for the formation Sun and solar system.
4. The Sun and solar system turned into a slowly spinning molecular cloud, composed of hydrogen and Helium molecules.
5. The clouds undergo compression due to gravity.
6. The excessive and high-speed spinning of cloud results in flattening into a giant disc.

Question 3.
Give a comparative account of satellites and rings of planets.
Answer:

IX. Numerical problems :

Question 1.
The Earth’s distance from the Sun is 149.6 × 10⁶km and the period of Earth’s revolution is 1 year. Calculate the ratio of the squares of the periods to cubes of the major axis.
Solution :
Semi major axis from sun, R = 149.6 × 10⁶ km.
Period of Earth, T = 1 year.
The ratio = \(\frac{T^{2}}{R^{3}}=\frac{(1)^{2}}{\left(149.6 \times 10^{6}\right)^{3}}\) = 2.98 ×10^-25 year² / km ³.

Question 2.
The mean distance of Earth from the Sun is 149.6 × 10⁶ km and the mean distance of mercury from the sun is 57.9× 10⁶km. The period of Earth’s revolution is 1 year. What is the period of Mercury’s revolution? .
Solution: Given
1. Mean distance of Earth from Sun, r1 = 149.6 × 10 ⁶
2. Mean distance of Mercury from sun, r2 = 57.9 × 10⁶
3. The period of Earth’s revolution, T1 = 1 year
4. The period of Mercury’s revolution, T2 = ?
According to Keplar’s Third Law


Question 3.
Calculate the speed and period of revolution of satellite orbiting at a height 700 km above the Earth’s surface.
Solution:
Given: 1. Height of th Satellite, h = 700 km = 700 x 103 m
We Know: 2. Gravitational constant G = 6.673 × 0^-11 Nm2 kg^-2
3. Mass of the Earth, M = 5.972 × 1024 kg
4. Radius of Earth, R = 6371 km = 6371 × 10³ m
Formula (R + h) = (6371 + 700)km = 7071 km
= 7071 × 10³m=0.7071 × 10⁷m

Period of Revolution T = 5.9 15 × 10³ s
= 5915 sec. (or) 98 min 35 sec.

Tamilnadu State Board New Syllabus Samacheer Kalvi 9th Science Guide Pdf Chapter 11 Atomic Structure Text Book Back Questions and Answers, Notes.

Tamilnadu Samacheer Kalvi 9th Science Solutions Chapter 11 Atomic Structure

9th Science Guide Atomic Structure Text Book Back Questions and Answers

I. Choose the correct answer :

Question 1.
Among the following the odd pair is

Answer:

Question 2.
Change in the number of neutrons in an atom changes it to
(a) an ion.
(b) an isotope.
(c) an isobar.
(d) another element.
Answer:
(b) an isotope

Question 3.
The term nucleons refer to
(a) protons and electrons
(b) only neutrons
(c) electrons and neutrons
(d) protons and neutrons
Answer::
(d) protons and neutrons

Question 4.
The number of protons, neutrons and electrons present respectively in \({ }_{35}^{80} \mathrm{Br}\) are
(a) 80,80,35
(b) 35,55,80
(c) 35,35,80
(d) 35,45,35
Answer:
(d) 35,45,35

Question 5.
The correct electronic configuration of potassium is
(a) 2,8,9
(b) 2,8,1
(c) 2, 8, 8, 1
(d) 2, 8, 8, 3
Answer:
(c) 2, 8, 8,1

II. State whether true or false. If false, correct the statement:

1. In an atom, electrons revolve around the nucleus in fixed orbits.
Answer:
True.

2. Isotopes of an element have different atomic numbers.
Answer:
False.
Correct statement: Same atomic numbers but different mass numbers.

3. Electrons have negligible mass and charge.
Answer:
True.

4. Smaller the size of the orbit, lower is the energy of the orbit.
Answer:
True.

5. The maximum number of electron in L Shell is 10.
Answer:
False.
Correct statement :The maximum number of electrons in L Shell is 8.

III. Fill in the Blanks :

1. Calcium and Argon are examples of a pair of ………….
Answer:
isobars

2. Total number of electrons that can be accommodated in an orbit is given by …………..
Answer:
the formula 2n²

3. ………….isotope is used in the nuclear reactors.
Answer:
Uranium-235

4. The number of neutrons present in \({ }_{3}^{7} \mathrm{Li}\) is ………….
Answer:
4

5. The valency of Argon is ………………
Answer:
Zero

IV. Match the following :

a) Dalton	1. Hydrogen atom model
b) Chadwick	2. Discovery of nucleus
c) Rutherford	3. First atomic theory
d) Neils Bohr	4. Plum pudding model
	5. Discovery of neutrons

Answer:
a – 3, b – 5, c – 2, d – 1.

V. Complete the following table :

Answer:

VI. Answer very briefly :

Question 1.
Name an element which has the same number of electrons in its first and second shell.
Answer:
Beryllium. Atomic number – 4 (K-shell-2, L-shell-2)

Question 2.
Write the electronic configuration of K and Cl
Answer:

Question 3.
Write down the names of the particles represented by the following symbols and explain the meaning of superscript and subscript numbers attached. ₁H¹, ₀n¹, _-1C⁰
Answer:
₁H¹ – hydrogen atom mass number 1. Atom number 1.
₀n¹– neutron change 0. Mass 1 amu.
_-1C⁰ – electron change -1. Mass negligible.

Question 4.
For an atom ‘X’, K, L, and M shells are completely filled. How many electrons will be present in it?
Answer:
K – 2, L – 8, M – 18, 28 electrons – Nickel

Question 5.
What is the same about the electron structures of:
a. Lithium, Sodium and Potassium.
b. Beryllium, Magnesium and Calcium.
Answer:
a. Lithium, sodium & potassium have 1 electron in their outermost shell.
b. Beryllium, magnesium and calcium have 2 electrons in their outermost shell.

VII. Answer briefly :

Question 1.
How was it shown that atom has empty space?
Answer:
Rutherford performed an experiment of bombarding a thin gold foil with very small positively charged particles called a particles. He observed that most of the alpha particles passed straight through the foil. He infered by thin experiment that most of the space in the atom is empty.

Question 2.
Why do \({ }_{17}^{35} \mathrm{Cl}\) and \({ }_{17}^{37} \mathrm{Cl}\) have the same chemical properties? In what respect do these atoms differ?
Answer:
\({ }_{17}^{35} \mathrm{Cl}\) and \({ }_{17}^{37} \mathrm{Cl}\) have same chemical properties because they have same number of electrons but their atoms differ in the number of neutrons.

Question 3.
Draw the structure of oxygen and sulphur atoms.
Answer:

Question 4.
Calculate the number of neutrons, protons and electrons :
(i) atomic number 3 and mass number 7
(ii) atomic number 92 and mass number 238.
Answer:
(i) atomic number 3 and mass number 7
∴ No. of electrons (or) No. of protons = 3
Mass number = No. of protons + No. of neutrons
∴ No. of neutrons = 7-3=4

(ii) atomic number 92 and mass number 238
Atomic number = 92
∴ No. of electrons = 92
No. of protons = 92
No. of neutrons = 238-92 = 146

Question 5.
What are nucleons? How many nucleons are present in Phosphorous? Draw its structure.
Answer:

The number of protons and neutrons present in the nucleus are called nucleons. The number of nucleons present is phosphorus is 31.

VIII. Answer in detail :

Question 1.
What conclusions were made from the observations of Gold foil experiment?
Answer:

In Rutherford’s Alpha ray scattering experiment, the following conclusions were made from the observations.

• Atom has a very small nucleus at the centre.
• There is a large empty space around the nucleus.
• The entire mass of an atom is concentrated in a very small positively charged region, which is called Nucleus.
• The electrons are distributed in the vacant space around the nucleus.
• The electrons move in circular paths around the nucleus.

Question 2.
Explain the postulates of Bohr’s atomic model.
Answer:
The main postulates are:

• In atoms, electrons revolve around the nucleus in stationary circular paths called orbits or shells or energy levels.
• While revolving in orbits the electrons do not radiate energy.
• The circular orbits are numbered as 1,2,3,4,… or designated as K, L, M, N, shells. These numbers are referred to as principal quantum numbers (n).
• K shell (n=l) is closest to the nucleus and is associated with lowest energy.
• The energy of each orbit or shell is a fixed quantity and the energy is quantized.

Question 3.
State Gay Lussac’s law of combining volumes, explain with an illustration.
Answer:
Whenever gases react together, the volumes of the reacting gases as well as the products, if they are gases, bear a simple whole number ratio, provided all the volumes are measured under similar conditions of temperature and pressure.
Example:
Step 1: Hydrogen combines with oxygen to form water (word equation) Hydrogen + Oxygen → Water.

i. e. Two volumes of hydrogen reacts with one volume of oxygen to form two volumes of water vapour, i.e. the ratio by volume which gases bears is 2:1:2 which is a simple whole number ratio.
It follows that at a given temperature and pressure, the volumes of all gaseous reactants and products bear a simple whole number ratio to each other.

Intext Activities

ACTIVITY – 1

Symbolically represent the following atoms using the atomic number and mass number, a) Carbon b) Oxygen c) Silicon d) Beryllium
Answer:

ACTIVITY – 2

Assign the valency for Phosphorus, Chlorine, Silicon and Argon
Answer:
Phosphorus – P – 3, 5
Chlorine – Cl – 1
Silicon – Si – 4
Argon – Ar – 0

ACTIVITY – 4

Draw the structures of the isotopes of oxygen O¹⁶ and O¹⁸
Atomic number of oxygen = 8.
Answer:

ACTIVITY – 5

Draw the model of the following pairs of isotones:
(i) Fluorine & Neon (ii) Sodium & Magnesium (iii) Aluminum and Silicon.
Answer:

ACTIVITY – 6

Nitrogen combines with hydrogen to form ammonia (NH3). Illustrate Gay Lussac’s law using this example.
Answer:

1 volume of nitrogen reacts with 3 volumes of hydrogen to form 2 volumes of ammonia gas. The ratio by volume which gases bear is 1 : 3 : 2. Which is a simple while number ratio.

Test Yourself :

Question 1.
Calculate the number of neutrons in the following atoms:

Answer:
Number of neutrons (n) = Mass number (A) – Atomic number (z)
a) \(\frac{27}{13} \mathrm{Al}\) ⇒ Number of neutrons (n) = 27 – 13 = 14
b) \(\frac{31}{15} \mathrm{P}\) ⇒ Number of neutrons (n) = 31-15 = 16
c) \(\frac{190}{76} \mathrm{Os}\) ⇒ Number of neutrons (n) = 190 – 76 = 114
d) \(\frac{54}{24} \mathrm{Cr}\) ⇒ Number of neutrons (n) = 54 – 24 = 30

9th Science Guide Atomic Structure Additional Important Questions and Answers

I. Choose the correct answer :

Question 1.
Hydrogen atom does not have …………………..
(a) Proton
(b) Neutron
(c) Electron
(d) Proton and electron
Answer:
(b) Neutron

Question 2.
An electron has ……………………
(a) Mass 1/1837^th of proton and positively charged
(b) Mass equal to proton and positively charged.
(c) Mass 1 / 1837^th of proton and negatively charged.
(d) Mass equal to proton and negatively charged.
Answer:
(c) Mass 1/1837^thof proton and negatively charged

Question 3.
Which statement is not correct about isotopes of an element?
(a) Their chemical properties are same.
(b) Their atomic number is same.
(c) Number of electrons are different.
(d) Number of neutrons are different.
Answer:
(c) Number of electrons are different

Question 4.
Co-60 is used in the treatment of …………………..
(a) Cancer
(b) Thyroid disorders
(c) Leukemia
(d) Blockage of arteries.
Answer:
(a) Cancer

Question 5.
Every atom has an equal number of protons and electrons. The nature of the atom is …………………..
(a) Positive
(b) Neutral
(c) Negative
(d) None of the above
Answer:
(b) Neutral

Question 6.
Gold foil alpha particle scattering experiment was performed by …………………..
(a) Dalton
(b) Goldstein
(c) Thomson
(d) Rutherford
Answer:
(d) Rutherford

Question 7.
Which subatomic particles have no charge …………………..
(a) Proton
(b) Neutron
(c) Electron
(d) Proton and electron
Answer:
(b) Neutron

Question 8.
The outermost shell of an atom cannot accommodate electrons more than
(a) 2
(b) 8
(c) 18
(d) 32
Answer:
(b)8

Question 9.
The ratio of masses of oxygen in CO and C02 for fixed mass of carbon is 1 : 2. The above is the law of ……………………
(a) Law of multiple proportions
(b) Law of reciprocal proportions
(c) Gay Lussac’s Law of combining volumes
(d) None of the above
Ans:
(a) Law of multiple proportions

Question 10.
………………….. is a radioactive isotope present in our bodv.
(a) Cobalt 60
(b) Uranium 235
(c) Iodine 131
(d) Potassium 40
Answer:
(d) Pottassium 40

Question 11.
Proton was discovered by ………………….
(a) Rutherford
(b) Goldstein
(c) Chadwick
(d) J.J. Thomson
Answer:
(a) Rutherford

Question 12.
Electron was discovered by …………………..
(a) J.J. Thomson
(b) Rutherford
(c) Goldstein
(d) Chadwick
Answer:
(a) J.J. Thomson

Question 13.
α – particles are …………………..
(a) Negative charged particles
(b) Positive charged particles
(c) Beam of Neutrons
(d) gamma radiation
Answer:
(a) Negative charged particles

Question 14.
An α – particle is …………………..
(a) hydrogen Nucleus
(b) a Helium Nucleus
(c) a Proton
(d) an electron
Answer:
(b) a He Nucleus

Question 15.
The electronic configuration of an atom is 2,8,3. The valency of the atom is ……………………
(a) 13
(b) 10
(c) 3
(d) 8
Answer:
(c) 3

Question 16.
The No. of electrons in the outermost shell of the atom of an inert gas ……………………
(a) 0
(b) 1
(c) 2
(d) 8
Answer:
(d) 8

Question 17.
Which one of the following will have the maximum charge / mass ratio?
(a) Electron
(b) Proton
(c) Neutron
(d) a – Particle
Answer:
(a) Electron

Question 18.
The maximum No. of electrons that can be accommodated in M shell is ……………………
(a) 2
(b) 8
(c) 18
(d) 32
Answer:
(c) 18

Question 19.
Elements with valency 1 are ……………………
(a) always metals
(b) always metaloids
(c) either metals (or) non-metals
(d) always non – metals
Answer:
(a) always metals

Question 20.
The electronic configuration of ‘Cl’ is ……………………
(a) 2,7
(b) 2,8,8,7
(c) 2,8,7
(d) 2,7,8
Answer:
(c) 2, 8, 7

Question 21.
The isotope used to remove the brain tumour and treatment of Cancer is ……………………
(a) Cobalt 60
(b) Uranium 235
(c) Iodine 131
(d) Na – 24
Answer:
(a) Cobalt 60

II. Fill in the Blanks :

1. ………………….. are the building blocks of matter.
Answer:
Atoms

2. The combination of different elements to form a compound is governed by certain basic rules called …………………..
Answer:
Laws of chemical combination

3. Volume of the nucleus of an atom is ………………….. compared to the volume of the extranuclear part of the atom.
Answer:
very small

4. the Atomic number of an element is 20. It has………………….. valence electrons.
Answer:
2

5. Atoms are so tiny their mass number cannot be expressed in grams but expressed in…………………..
Answer:
atomic mass unit (amu)

6. Elements having completely filled outermost shell, show………………….. valency.
Answer:
Zero

7. A ………………….. number describes a specific aspect of an electron.
Answer:
quantum

8. When an atom gives electrons from its outermost shell, it becomes ………………….. charged.
Answer:
positively

9. The elementary particles such as protons and neutrons are collectively called as…………………..
Answer:
nucleons

10. In two isotopic species number of protons is same but the number of………………….. is different.
Answer:
Neutrons

11. The combination of different elements form a…………………..
Answer:
Compound

12. A compound is governed by basic rules are known as ……………………
Answer:
Laws of chemical combination

13. The ratio of masses of H and O in H₂O is…………….
Answer:
1 : 8

14. α, β, γ rays are during the ratio active decay of an atom.
Answer:
emitted

15. Beryllium + α – rays → Carbon +……………….
Answer:
Neutron

16. …………… = No. of protons = No. of the electrons.
Answer:
Atomic No.

17. ‘A’ is denoted by …………………
Answer:
Mass No

18. ‘Z’ is denoted by . …………………
Answer:
Atomic No

19. Mass No =………………… + No. of Neutrons
Answer:
No. of protons

20. The Mass No. of 27 is for the element…………………….
Answer:
Aluminium

21. U-235 Isotope is used as ………………….
Answer:
Fuel in nuclear reactors

22. The symbol of phosphorus is ……………………….
Answer:
P

23. Na – →……………….. Na⁺.
Answer:
e-

24. Elements with 4 to 7 in their valence shells are …………………
Answer:
non -metals

25. Valency of the elements having ……………..is 1, 2, 3 respectively.
Answer:
Valence electrons 1, 2, 3

26. Atomic orbitals allow atoms to make…………………….. bonds
Answer:
Co-valent

27. The symbol of Azimuthal quantum number is……………………..
Answer:
l

28. The symbol of the Principal quantum number is……………………..
Answer:
n

29. Valency is the combining capacity of ……………………..
Answer:
an atom

III. State whether true or false. If false, correct the statement:

1. In Rutherford’s experiment, bouncing of alpha particles suggests that nucleus of an atom is negatively charged.
Answer:
False
Correct statement: Nucleus of an atom is positively charged.

2. Electrons revolve around the nucleus in definite open shells.
Answer:
False
Correct statement: Electrons revolve around the nucleus in definite closed shells.

3. K and L shell can accommodate a maximum 2 and 8 electrons respectively.
Answer:
True

4. Radio activity of Carbon 14 is considered to determine the age of object, especially of archeological importance.
Answer:
True

5. In a neutral atom number of protons is equal to the number of neutrons.
Answer:
Correct statement: In a neutral atom number of protons is equal to the number of
electrons.

6. If an atom has 6 electrons in its outermost shell, it is inert.
Answer:
Correct statement: If an atom has 8 electrons in its outermost shell, it is inert.

7. The valency of Chlorine is 7.
Answer:
Correct statement: The valency is 1.

8. Smaller the size of the orbit, the smaller the energy of the orbit.
Answer:
True

9. The stability of the nucleus is determined by the Neutron – Proton ratio.
Answer:
True

10. Isotopes of elements have the same chemical properties.
Answer:
True

IV. Match the following :

1.

Column A	Column B
1) Prinicipal quantum number	a) Orientation of orbitals
2) Azimuthal quantum number	b) Spin of the electron
3) Magnetic quantum number	c) Main energy level
4) Spin quantum number of orbital	d) Sub shell/shape of orbital

Answer:
1) – c, 2) – d, 3) – a, 4) – b

2.

Column A	Column B
1. K shell	a) 8
2. L shell	b) 32
3. M shell	c) 2
4. N shell	d) 18

Answer:
1) – c, 2) – a, 3) – d, 4) – b

3.

Column A	Column B
a) Mass of proton	1. +1
b) Mass of electron	2. -1
c) Charge of electron	3. 9.31 x 10-28g
d) Charge of proton	4. 1.67 x 10-24g

Answer:

a) 4
b) 3
c) 2
d) 1

V. Answer very briefly :

Question 1.
If and element M has mass number 24 and atomic number 12, how many neutrons does its atom contain?
Answer:
Mass number = No. of protons + neutrons
Atomic number = No. of protons
No. of neutrons = 24 – 12 = 12.

Question 2.
Atomic number of A and B are 18 and 19 respectively. What is the electronic configuration of A and B?
Answer:
Electronic configuration of A = 2, 8, 8
Electronic configuration of B = 2, 8, 8, 1.

Question 3.
How will you define the term ‘electronic configuration’?
Answer:
The systematic arrangement of electrons in various shells or orbits in an atom is called the electronic configuration.

Question 4.
Why do the chemical properties of an element are determined by valence electrons?
Answer:
Because they are the one which takes part in the chemical reaction.

Question 5.
What are the elements which have valence electrons 1 or 2 or 3 are called and what are the elements with valence Electrons 4 to 7 in their valence shells?
Answer:
Elements with valence electrons 1 or 2 or 3 are metals and valence electrons with 4 to 7 are non – metals.

Question 6.
How is an atom of the element represented? Give an example.
Answer:
If ‘X’ is the element, atomic mass at the upper left side and atomic number at the lower left side of the symbol of the element.
Example : \({ }_{11}^{23} \mathrm{Na}\) ⇒ 23 →Atomic Mass, 11 →Atomic number.

Question 7.
Why an atom is considered neutral?
Answer:
An atom of an element contains equal number of positively charged protons and negatively charged electrons and so it is neutral.

Question 8.
Name the scientist and his experiment to prove that nucleus of an atom is positively charged.
Answer:
Name of the scientist – Earnest Rutherford
Name of the experiment – Gold foil alpha particle scattering experiment.

Question 9.
Name the particles which determine the mass of an atom?
Answer:
The mass of an atom is determined by protons and neutrons.
Atomic mass = No. of protons + No. of neutrons.

Question 10.
What are the shells?
Answer:
Different energy levels outside the nucleus are called as shells. They are designated as K, L, M, N and numbered as 1, 2, 3…..

Question 11.
Rutherford’s model of an atom has a very small ………….. at the center.
Answer:
Nucleus.

Question 12.
Niels Bohr was Born on …………
Answer:
October 7, 1885.

Question 13.
When an electron returns from high energy level to lower energy level it gives …………
Answer:
It gives off energy.

Question 14.
In \({ }_{\mathrm{Z}}^{\mathrm{A}} \mathrm{X}\)what are the letters A, Z, X stand for?
Answer:
X → symbol of element
Z →Atomic No.
A → Mass No.

VI. Answer briefly :

Question 1.
State the law of reciprocal proportion.
Answer:
If two different elements combine separately with the same weight of a third element, the ratios of the masses in which they do so are either the same or a simple multiple of the mass ratio in which they combine.

Question 2.
Why proton is considered to be the fingerprint of an atom?
Answer:
An atom of an element has its own characteristic number of protons in its nucleus, which distinguishes it from the atoms of other elements. Hence proton is considered to be the fingerprint of an atom.
This characteristic number (Number of protons) is called the atomic number of the element. The atomic number is denoted by Z.

Question 3.
How can an element be identified on the Periodic Table? What makes an element different from another element?
Answer:
An element can be identified by its atomic number which is a representation of the number of protons contained in the nucleus of a particular element. The amount of protons of an element never changes.

Question 4.
Because atoms are so small, what do scientists do?
Answer:
Since atoms are so small, scientists create models to describe them. A model may be a diagram, mental picture, a mathematical statement or an object that helps explain ideas about the natural world.

Question 5.
What are isotopes?
Answer:
Atoms of the same element with the same number of protons and a different number of neutrons – the number of protons will never change! Ex.: Carbon 12, Carbon 13 and Carbon 14 are isotopes of the element carbon.

Question 6.
Draw the diagram of laws of chemical combination.
Answer:
Laws of chemical combination

Question 7.
Define Isobars.
Answer:
Isobars are the atoms of the different elements of same mass number but different atomic number.

Question 8.
What is a combination reaction?
Answer:
A combination reaction is a reaction where two or more substances combine to form a single substance.
The combination of different elements to form a compound is governed by certain basic rules. These rules are known as Laws of chemical combination.

Question 9.
What are the salient features of Rutherford’s model of an atom?
Answer:
RUTHERFORD’S MODEL OF AN ATOM- Salient features

• Atom has a very small nucleus at the center.
• There is large empty space around the nucleus.
• Entire mass of an atom is concentrated in a very small positively charged region which is called the nucleus.
• Electrons are distributed in the vacant space around the nucleus.
• The electrons move in circular paths around the nucleus.

Question 10.
What are the Limitations of Bohr’s Model?
Answer:
Limitations of Bohr’s model:

• One main limitation was that his model was applicable only to Hydrogen.
• It could not be extended to multi-electron atoms.
• Hence more research and deeper study of atoms became necessary.

Question 11.
Explain the Composition of the Nucleus.
Answer:
COMPOSITION OF NUCLEUS

• Electrons have a negligible mass; hence the mass of the atom mainly depends on the mass of the nucleus. Nucleus of an atom consists of two components, they are protons and neutrons.
• Protons are positively charged. Protons repel each other because of their like charges. Hence more than one proton cannot be packed in a small volume to form a stable nucleus, unless neutrons are present.
• Neutrons reduce the repulsive force between the positively charged protons and contribute to the force that holds the particles in the nucleus together.

Question 12.
Define the Nucleons.
Answer:
Nucleons: The elementary particles such as protons and neutrons are collectively called as Nucleons.

Question 13.
What are the relation between mass no. & atomic no?
Answer:
Relationship between Mass Number and Atomic Number:
Mass Number (A) = Number of Protons + Number of Neutrons(n)
Atomic Number (Z) = Number of Protons or Number of Electrons
Mass Number = Atomic Number (Z) + Number of neutrons (n)
A = Z + n.

Question 14.
What are the types of Quantum Number?
Answer:

Question 15.
Draw the atomic structure of Mg (At. No. 12, Mass No. 24)
Answer:

Question 16.
Compare the charge and mass of protons and electrons.
Answer:

Question 17.
Ca²⁺ has completely filled outer shell. Justify your answer.
Answer:
The atomic number of Calcium is 20. It has K = 2, L = 8, M = 8, N = 2.
If we remove the last 2 electrons, that is from N shell, Ca2+ and we will be having 8 in the outermost shell (M shell). So we have completely filled outer shell. (The maximum 8 electrons in a shell is a completely filled shell).

Question 18.
State the law of multiple proportion. .
Answer:
When two elements A and B combine together to form more than one compound, then masses of A which separately combines with a fixed mass of B are in simple ratio.

Question 19.
List the uses of isotopes.
Answer:
Uranium 235 – Used as fuel in nuclear reactors
Cobalt 60 – Used in the treatment of cancer
Iodine 131 – Used in the treatment of goitre.
Carbon 14 – To find the age of plants and animals.

Question 20.
What is isotone? Give an example.
Answer:
Atoms of different elements with different atomic numbers and different mass numbers, but with the same number of neutrons are called isotones.
Example: Pair of elements Boron and Carbon has the same number of neutrons but
different number of protons and hence different atomic numbers.

VII. Answer in detail :

Question 1.
Prove that in the following example, Sulphur and Oxygen combine using the law of reciprocal proportions.
Answer:
Oxygen and sulfur react with copper to give copper oxide and copper sulfide, respectively. Sulphur and oxygen also react with each other to form S02. Therefore,

in CuS ⇒ Cu : S = 63.5 : 32
in CuO ⇒ Cu : O = 63.5 : 16
S : 0 = 32 : 16 ⇒ S:0= 2:1
Now in SO₂:
S : 0 = 32 : 32 ⇒ S: 0 = 1:1
Thus the ratio between the two ratios is 2 : 1
This is a simple multiple ratio.

Question 2.
Explain about radioactive decay and radioactive isotopes.
Answer:
When the nucleus of an atom possesses either too many or too few neutrons compared to the number of protons it becomes unstable. These are called radioactive isotopes. Unstable nuclei split up in a process called radioactive decay and emit radioactive radiation.

Many elements have isotopes of which some of them are radioactive isotopes. There is a lot of low-level natural radioactivity around us. For example, our bodies contain radioisotopes, such as Potassium – 40, which continuously emit radiation, but because the amount is very low this does not harm us. Carbon -14 is a radioactive isotope used to date organic material.

Question 3.
Describe the limitations in Rutherford’s model.
Answer:

• According to electromagnetic theory, a moving electron, accelerate and continuously lose energy.
• Due to the loss of energy, path of the electron may reduce and finally the electron fall into the nucleus.
• If it happens so, atom becomes unstable. But atom are stable. Thus Rutherford’s model failed to explain the stability of an atom.

Question 4.
Explain the electronic configuration of atoms with an illustration.
Ans. Electronic configuration of atoms:

• Electrons occupy different energy levels called orbits or shells.
• The distribution of electrons in these orbits of an atom is governed by certain rules or conditions. These are known as Bohr and Bury Rules of electronic configuration.
• Bohr and Bury simultaneously proposed the following rules for the distribution of electrons in different shells.

Rule 1: The maximum number of electrons that can be accommodated in a shell is equal to 2n² where ‘n’ is the quantum number of the shell (i.e., the serial number of the shell from the nucleus).
Shell Value of (n) Maximum number of electrons (2n2)

Shell	Value of (n)	Maximum number of electrons (2n2)
K	1	2 x 12 = 2
L	2	2 x 22 = 8
M	3	2 x 32 = 18
N	4	2 x 42 = 32

Rule 2: Shells are filled in a stepwise manner in the increasing order of energy.
Rule 3: The outermost shell of an atom cannot have more than 8 electrons even if it has the capacity to accommodate more electrons. For example Electronic configuration in Ca

Illustration:

Question 5.
Explain the valence electron and valency with an illustration.
Answer:

Valence elect runs
How many electrons are in the outermost shell of nitrogen? 5 The outermost shell of an atorh is called its valence shell and the electrons present in the valence shell are known as valence electrons.

The chemical properties of elements are decided by these valance electrons, since they are the ones that take part in chemical reaction.

The elements with same number of electrons in the valence shell show similar properties and those with a different number of valence electrons show different chemical properties. Elements, which have valence electrons 1 ‘ or 2 or 3 (except Hydrogen) are metals.

These elements can lose electrons to form ions which are positive charged and are called cations.

Elements with 4 to 7 electrons in their valence shells are non-metals.
These elements can gain electrons to form ions which are negatively charged and are called anions

VALENCY:

Valency of the element is the combining capacity of the element with other elements and is equal to the number of electrons that take part in a chemical reaction. The valency of the elements having valence electrons 1, 2, 3 is 1, 2, 3 respectively.
While valency of element with 4, 5, 6 & 7 valence electron is 4, 3, 2 and 1 (8 – valence electrons) respectively. Elements having completely filled the outermost shell show Zero valency.

For example The electronic configuration of Neon is 2,8 (completely filled). So valency is 0

Illustration:
Assign the valency of Magnesium & Sulphur.
Electronic configuration of magnesium is 2, 8, 2. So valency is 2.
The electronic configuration of sulphur is 2, 8, 6. So valency is 2 i.e. (8 – 6).