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DAV Class 7 Science Chapter 14 Question and Answer Fabric from Fibre
Something To Know
A. Fill in the blanks.
1. The hairy body coat of sheep and goats is called fleece.
2. Shaving off the body coat of sheep is called shearing.
3. Cleaning of fleece to remove dirt and grease is called scouring .
4. The process of separating hair, of different textures, from the fleece, is called sorting.
5. The rearing of silkworms to obtain silk is called sericulture.
6. Reeling is the process of separating silk fibres from cocoons.
7. The silk thread is made up of protein.
B. Write True or False for the following statements.
Ans:
| 1. Synthetic fibres are manufactured in factories. | Ans: (1) True |
| 2. Air is a good conductor of heat. | (2) False |
| 3. Scouring is the process of removal of fleece of sheep. | (3) False |
| 4. The process, of twisting of raw and dyed fibre, is known as sorting. | (4) False |
| 5. Silkworm’s feed on mulberry leaves. | (5) True |
| 6. The larvae secrete very fine filaments made of protein. | (6) True |
| 7. Reeling is the process of getting silk fibres from cocoons. | (7) True |
C. Tick the correct option.
1. The process, of removing fleece along with a very thin layer of dead skin of sheep, is called
Ans 1: Shearing
2. Which of the following animals does not yield wool?
Ans 2: buffaloe
3. The caterpillars of silkworms feed on
Ans 3: mulberry leaves
4. The egg of a silk moth hatches into a
Ans 4: caterpillar
5. The process of taking out silk threads from the cocoon is called
Ans 5: reeling
D. Answer the following questions in brief.
1. Name three animals whose fleece is used for making woollen fibres.
Ans 1: sheep, goat and camel
2. Name three common varieties of wool.
Ans 2: angora, pashmina & shahtoosh
3. Give the meaning of the term: ‘sorting:
Ans 3: The process of separating the hair of different textures from the fleece.
4. Define the term: ‘sericulture.
Ans 4: the process of rearing of silkworms for obtaining silk.
5. How is silk fibre obtained from cocoons?
Ans 5: silk fibre is obtained from cocoons by the process of reeling, in which cocoons are exposed to steam and then silk fibres are separated out.
6. Name two countries in which silk is produced on a large scale.
Ans 6: China and India.
E. Answer the following questions.
1. How do woollen clothes keep us warm in winter?
Ans 1: Woollen clothes basically trap air between them and the air is a poor conductor of heat. So the heat which is radiated from the body also gets trapped due to the air between the woollen clothes fabrics and thus it keeps us warm during winter.
2. Describe the purpose of ‘scouring’ in the production of wool?
Ans 2: The Purpose of scouring is to remove dirt and grease present in the sheared fleece by washing it in hot water and detergent.
3. State the practical uses of the (a) long (b) short yarn threads, obtained during the making of wool.
Ans 3: The longer threads are usually knitted to make sweaters, mufflers, caps, gloves, socks, etc.
The shorter threads are woven to make woollen fabrics which are used for making coats, trousers, jackets and shawls, etc.
4. Write a short note on ‘rearing of silkworms’.
Ans 4: A female silk moth lays hundreds of eggs which are stored at a suitable temperature. These eggs produce silkworms which feed on fresh mulberry leaves for 25-30 days and grow in size.
They secrete a liquid that hardens on coming in contact with air and changes into a fine thread called silk which is made up of a protein. The caterpillar covers itself completely with these fine fibres. This covering is called a cocoon. The silkworm develops into a silk moth inside the cocoon.
5. Describe the different stages in the life cycle of a silk moth.
Ans 5: Different stages in the life cycle of a silk moth are
Stage 1: Eggs: – An egg is the first stage of the life cycle of the silkworm. A female moth lays eggs.
Stage 2: silkworms: – Silkworm arises from the eggs. They feed on mulberry leaves for 25 – 30 days.
Stage 3: cocoon: – Silkworms secrete a liquid that hardens on coming in contact with air and changes into a fine thread called silk. Silkworms covers themselves with these threads change into a silk moth inside it.
Stage 4: moth: –The female moth lays eggs and thus the life cycle of the silkworm begins again.