CBSE Class 7 Science Fiber To Fabric Worksheet

I. DEFINE THE FOLLOWING:

Question 1. Selectivebreeding:
Answer: Selective breeding is the process of selecting parent animals with desired special characteristics (such as soft underhair) to breed and produce offspring that also possess these desired traits.
In simple words: Choosing special parent animals to produce babies with desired qualities like good wool.

Exam Tip: Always mention the parent selection and desired traits for full marks.

Question 2. Shearing:
Answer: The process of removing the fleece of a sheep along with a thin layer of dead skin from its body is called shearing.
In simple words: Shaving off the wool coat from a sheep's body.

Exam Tip: Mention that shearing does not hurt the sheep because the uppermost layer of skin is dead.

Question 3. Scouring:
Answer: The process of thoroughly washing sheared skin and hair in tanks to remove dust, dirt, sweat, and grease is called scouring.
In simple words: Washing sheared wool with soap and water to clean dirt and grease.

Exam Tip: Scouring removes dust, dirt, and grease; nowadays it is done using machines.

Question 4. Sorting:
Answer: The process of separating hairy skin of different textures from each other after scouring is called sorting.
In simple words: Separating wool hair based on texture, quality, and length.

Exam Tip: Link sorting directly to the classification of wool based on quality after scouring.

Question 5. Sericulture:
Answer: The rearing of silkworms for the commercial production of silk is called sericulture.
In simple words: Farming silkworms to produce silk.

Exam Tip: Sericulture is an important agricultural and cottage industry question often asked in exams.

Question 6. Reelingofsilk:
Answer: The process of taking out threads from the cocoon for use as silk is called reeling of silk.
In simple words: Unwinding silk threads from cocoons.

Exam Tip: Reeling is done by special machines that unwind the continuous silk filament from cocoons.

Question 7. Rearing:
Answer: The process of raising, feeding, taking care of, and breeding animals (like sheep, goats, or silkworms) for commercial use is called rearing.
In simple words: Feeding and taking care of useful animals.

Exam Tip: Use keywords like feeding, shelter, and medical care in your definition.

II. ANSWER THE FOLLOWING:

Question 1. Wool yielding animals have a thick layer of hair. Why?
Answer: Wool-yielding animals have a thick layer of hair because hair traps a lot of air. Since air is a poor conductor of heat, it keeps these animals warm in cold weather and protects them from harsh winter climates.
In simple words: Thick hair traps air, which acts as a blanket and keeps the animals warm.

Exam Tip: Emphasize the role of trapped air as a thermal insulator.

Question 2. Does shearing hurt the sheep? Why?
Answer: No, shearing does not hurt the sheep. This is because the uppermost layer of the sheep's skin is dead skin cells, which has no nerves or sensation, similar to how it does not hurt when you get a haircut or trim your nails.
In simple words: It does not hurt because the outer skin layer is dead tissue.

Exam Tip: State clearly that the topmost layer of skin is dead.

Question 3. Usually hair of sheep is removed during the hot weather. Why?
Answer: The hair of sheep is removed during hot weather so that they can survive without their protective thick coat when the weather is warm. Without wool, they do not need their heavy winter insulation and can stay comfortable.
In simple words: Shaving in summer helps sheep stay cool when they no longer need their heavy winter wool.

Exam Tip: Mention survival comfort during hot summer months.

Question 4. What is sorters' disease?
Answer: Sorters' disease is a fatal blood infection caused by a bacterium named *Bacillus anthracis* (Anthrax). It affects wool sorters who handle infected wool fibers, catching the infection through cuts or inhalation.
In simple words: A dangerous disease caught by workers who sort infected wool.

Exam Tip: Mention the causative organism (*Bacillus anthracis*) for full credit.

Question 5. The silk obtained from mulberry silk moth is most popular. Why?
Answer: The silk obtained from the mulberry silk moth is most popular because its fibers are soft, lustrous, elastic, and durable, and can be dyed in attractive bright colors easily.
In simple words: Mulberry silk is very soft, shiny, strong, and easy to dye.

Exam Tip: Keywords to include: soft, lustrous (shiny), and elastic.

Question 6. How silk worms are reared?
Answer: Female silk moths lay hundreds of eggs at a time. These eggs are stored on clean cloth or paper and sold to silkworm farmers. The farmers keep eggs under hygienic conditions at suitable temperature and humidity. The eggs hatch into larvae (caterpillars or silkworms), which are kept in clean bamboo trays and fed fresh chopped mulberry leaves day and night until they spin cocoons.
In simple words: Farmers keep silkworm eggs warm, hatch them into caterpillars, and feed them fresh mulberry leaves until they form cocoons.

Exam Tip: Outline the stages: eggs, warming/hatching, feeding on mulberry leaves, and spinning cocoons.

Question 7. Briefly explain the life history of silk moth.
Answer: 1. Female silk moth lays eggs on mulberry leaves.
2. Eggs hatch into larvae called caterpillars or silkworms.
3. The caterpillar feeds on mulberry leaves and grows in size.
4. When ready to enter the next stage (pupa), it spins a net to hold itself, swings its head from side to side, and secretes fiber made of protein that hardens on exposure to air, forming a cocoon.
5. Inside the cocoon, the caterpillar develops into a pupa, which eventually transforms into an adult silk moth.
In simple words: Egg hatches into caterpillar, caterpillar eats leaves and spins a cocoon around itself, becomes a pupa, and finally emerges as a moth.

Exam Tip: Mention the sequence: Egg -> Caterpillar (Larva) -> Pupa (Cocoon) -> Adult Moth.

Question 8. Briefly explain the processing of silk.
Answer: 1. Rearing: Silkworms are reared and cocoons are collected.
2. Pulping/Killing Pupa: Cocoons are kept in the sun, boiled, or exposed to steam to kill the developing moth inside.
3. Reeling: The process of taking out threads from the cocoon for use as silk is called reeling.
4. Spinning: Silk fibres are spun into silk threads.
5. Weaving: Silk threads are woven into silk cloth on looms.
In simple words: Collecting cocoons, boiling them, reeling the threads, spinning, and weaving into fabric.

Exam Tip: Mention boiling of cocoons and reeling as essential steps.

Question 9. Explain the various steps involved in the processing of wool.
Answer: 1. Shearing: Removal of fleece along with thin skin layer.
2. Scouring: Washing sheared skin and hair thoroughly to remove grease, dust, and dirt.
3. Sorting: Separating hair of different textures.
4. Cleaning burrs: Small fluffy fibres called burrs are picked out from the hair.
5. Dyeing: Fibres are dyed in various required colours.
6. Rolling/Spinning: Fibres are straightened, combed, and rolled into yarn.
In simple words: Shearing -> Scouring -> Sorting -> Removing burrs -> Dyeing -> Making yarn.

Exam Tip: Remember the 6 steps in correct chronological order: Shearing, Scouring, Sorting, Burrs removal, Dyeing, Spinning.

Question 10. How can you test the purity of silk and wool?
Answer: The purity of silk and wool can be tested by the burning test. When a pure silk or wool fibre is burned, it smells like burning hair or feathers, whereas artificial synthetic fibers smell like burning plastic and form hard beads.
In simple words: Burn a small thread; if it smells like burning hair, it is pure silk or wool.

Exam Tip: Note that protein-based natural fibres (silk/wool) smell like burning hair when burned.

Question 11. What is the scientific name of mulberry tree?
Answer: The scientific name of the mulberry tree is *Morus alba*.
In simple words: The biological name of the mulberry tree is Morus alba.

Exam Tip: Underline genus and species names separately or italicize them in print.

Question 12. Name the different varieties of silk available in the market.
Answer: The different varieties of silk available in the market include Mulberry silk, Tassar silk, Eri silk, and Muga silk.
In simple words: Common varieties are Mulberry, Tassar, Eri, and Muga silk.

Exam Tip: List at least three major varieties for full marks.

Question 13. From which animal, wool for Pashmina shawls is obtained?
Answer: Wool for Pashmina shawls is obtained from the under-fur of Kashmiri goats (*Capra hircus*).
In simple words: Pashmina wool comes from special mountain goats found in Kashmir.

Exam Tip: Mention Kashmiri goat / Pashmina goat.

Question 14. What are burrs?
Answer: Burrs are small, fuzzy, stray burrs or knots of fibers found entangled in the hair of sheep, which are picked out during wool processing.
In simple words: Little fuzzy knots found stuck in sheep hair.

Exam Tip: Burrs are picked out prior to dyeing and spinning.