FIBRE TO FABRIC class 7 important questions
Q.1. What are natural fibres?
Ans. The fibres which we get from the nature are called natural fibres. Two types of natural fibres are animal fibre and plant fibre. Fibres such as cotton, jute and flax are obtained from plants and are called plant fibres and fibres such as wool and silk are obtained from animals and are called animal fibres.
Q.2. Name some animals which are a source of wool.
Ans. Some animals which are a source of wool are sheep, goat, camel, yak, Llama, alpaca and vicuna etc.
Note: Yak reared in Tibet and Ladakh.
Angora goats and sheep reared in Kashmir.
Camels, reared in Rajasthan.
Llama, alpaca and vicuna reared in South America.
Q.3. Why do some animals have thick coat of hair?
Ans. Some animals have thick coat of hair because hair trap a lot of air. Air being a poor conductor of heat, acts as an insulator and does not allow the heat energy of their bodies to escape. So, the thick coat of hair keeps these animals warm.
Q.4. What do you mean by the term ‘breeding of sheep’?
Ans. The sheep having thick coat of hair in their body in large quantity are multiplied to get more number of sheep, so that good quality of wool will be obtained. This is called breeding of sheep.
Q.5. The different steps involved in the processing of fleece to wool are
a) Shearing: The fleece of the sheep along with a thin layer of skin is removed from its body. This process of removing fleece from the body of the sheep is known as shearing. Machines similar to those used by barbers are used to shear off fleece from the body of the sheep.
b) Scouring: The sheared skin with hair is thoroughly washed in tanks to remove grease, dust and dirt. This process of removing grease, dust and dirt from the sheared skin is known as scouring. In the old days it is done manually, but now a day it is done by machines.
c) Sorting: After scouring, sorting is done. The hairy skin is sent to factory where hair of different textures are separated or sorted. This process of separation of wool is known as sorting.
d) Dyeing: The natural fleece of sheep and goats being black, brown or white, the fibres are dyed in various colours. This process is known as dyeing.
e) Rolling: The process by which fibres are straightened, combed and rolled into yarn is called Rolling. .The longer fibres are made into wool for sweaters and the shorter fibres are spun and woven into woolen clothes.
Q.6. What is sericulture?
Ans. The rearing of silkworms for obtaining silk is called sericulture. In this process farmers take care of the silkworms, keep their eggs under hygienic conditions and suitable condition of temperature and humidity. It is a very old occupation in India.
Q.7. Explain the life history of silk moth ?
Ans. The life history of silk moth passes through four different stages. They are egg, larva pupa and adult moth.
Egg: The female silk moth is larger than the male silk moth. It lays hundreds of eggs on the underside of the fresh mulberry leaves which stick to it because of some gummy material.
Larva: In due course of time these eggs hatch to form white larva, commonly known as silk worm or caterpillar. They eat mulberry leaves day and night for 4 to 6 weeks and grow in size.
Pupa: The third stage in the life cycle of silk moth is pupa. The grown up silk worm or larva stops eating and secrets a sticky fluid, a protein called fibroin from its salivary gland which hardens on exposure to air and becomes silk fibre.. This silk fibre is wrapped around its body to form a ball-like structure called cocoon. At this stage, the larva becomes a pupa.
Adult: Further development of pupa stage takes place within the cocoon. It develops into adult silk moth. At this stage the silk moth cuts the cocoon around it and emerges out to start a new life cycle.
Q.8. Explain about the processing of silk from cocoon.
Ans. The two main process involved are:-
a) Rearing of the silk worms
b) Processing of the silkworms.
a) Rearing of the silk worms: A female silk moth lays hundreds of eggs at a time. The eggs are stored carefully on strips of clothes or paper and sold to silkworm farmers. The eggs are kept under hygienic conditions and suitable conditions of temperature and humidity. Then the larvae hatch out from the eggs. Then they eat mulberry leaves and forms into a pupa. The outer covering of the pupa is known as cocoon. Then when it is fully developed into a silk moth, it comes out and leaves the cocoon.
b) Processing silk: A pile of cocoons is taken. They are kept under sun or boiled or exposed to steam. The silk fibres are separated out. The process of taking out threads from the cocoon is known as reeling the silk. It is done in special machines which unwind the threads or fibres of silk from the cocoons. Silk fibres are then spun into silk threads, which are woven into silk cloth by weavers.
