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CBSE Sample Paper Class 7 Science Fibre to Fabric
Chapter – 3
Fibre to Fabric
Multiple choice questions: (marks:1×3)
1.) Sorter’s disease is a fatal :
A.) Blood disease
B.) Skin disease
C.) Autoimmune disease
Ans: blood disease.
2. Which country leads the world in silk production:
3. There are………steps of processing fibres into wool.
Fill in the blanks: (marks:1×3)
1. Wool is obtained from …………………of sheep or yak.
2. Silk fibres obtained from……………of the silk moth.
3. Silk industry began in……………
Answer the following questions: (marks:1×9)
1. From which animal wool is derived?
Ans: From sheep,goat,yak and some other animals wool is derived.
2. What is called shearing?
Ans: During the production of wool the fleece of the sheep along with a thin layer of skin is removed from its body. This process is called shearing.
3. What is called sericulture?
Ans: The rearing of silkworms for obtaining silk is called sericulture.
4. Which is the most common silk moth?
Ans: The mulberry silk moth is the most common silk moth.
5. Which route is called the ‘silk route’?
Ans: The route by which the traders and travellers introduced silk to other countries is called the silk route.
6. Which bacteria causes sorter’s disease?
Ans: Anthrax bacteria causes sorter’s disease.
7. Which process is called reeling the silk?
Ans: The process of taking out threads from the cocoon for use as silk is called reeling the silk.
8. What are caterpillars or silkworms?
Ans: The female silk moth lays eggs, from which hatch larvae which are called caterpillars or silkworms.
9. What is called scouring?
Ans: During the production of wool the fleece of the sheep along with a thin layer of skin is removed from its body. Then the sheared skin with hair is thoroughly washed in tanks to remove grease, dust and dirt. This is called scouring.
Answer the following questions: (marks:2×5)
1. What is termed as selective breeding?
Ans: Wool comes from sheep, goat, yak and some other animals. These wool-yield in ganimals bear hair on their body. The hairy skin of the sheep has two types of fibres that formits fleece: (a) the coarse beard hair, and (b)the fine soft under-hair close to the skin. The fine hair provides the fibres for making wool. Some breeds of sheep possess only fine under-hair. Their parents are specially chosen to give birth to sheep which have only soft under hair. This process of selecting parents for obtaining special characters in their offspring, such as soft under hair in sheep, is termed selective breeding.
2. What are the two types of hairy skin sheep have?
Ans: The hairy skin of the sheep has two types of fibres that form its fleece: (i) the coarse beard hair, and (ii) the fine soft under-hair close to the skin.
3. Write down the names of some Indian breeds of sheep and where it is found?
Ans: The Indian breeds of sheep are:
A. Lohi: Found in Rajasthan, Punjab. B. Rampur bushair: Found in Uttar Pradesh,Himachal Pradesh. C. Nali: Found in Rajasthan, Haryana, Punjab. D. Bakharwal: Seen in Jammu and Kashmir. E. Marwari: Found in Gujarat. F. Patanwadi: Found in Gujarat.
4. What are occupational hazards?
Ans: Risks faced by workers in any industry are called occupational hazards. Example: The Wool industry is an important means of livelihood for many people in our country. But a sorter’s job is risky as sometimes they get infected by a bacterium, anthrax, which causes a fatal blood disease called sorter’s disease.
5.) How do cocoons form?
Ans: The female silk moth lays eggs, from which hatch larvae which are called
caterpillars or silkworms. They grow in size and when the caterpillar is ready to enter the next stage of its life history called pupa, it first weaves a net to hold itself. Then it swings its head from side to side in the form of the figure of eight. During these movements of the head, the caterpillar secretes fibre made of a protein which hardens on exposure to air and becomes silk fibre. Soon the caterpillar completely covers itself by silk fibres and turns into pupa. This covering is known as cocoon. The further development of the pupa into moths continues inside the cocoon.
Answer the following questions: (marks:5×2)
1. Discuss briefly about the processing fibres into wool?
Ans: The wool which is used for knitting sweaters or for weaving shawls is the finished product of a long process, which involves the following steps:
- Step I: The fleece of the sheep along with a thin layer of skin is removed fromits body. This process is called shearing. Machines similar to those used by barbers are used to shave off hair. Usually, hair are removed during the hot weather. This enables sheep to survive without their protective coat of hair. The hair provides woollen fibres. Woollen fibresare then processed to obtain woollen yarn. Shearing does not hurt the sheep because the uppermost layer of the skin is dead. Also, the hair of sheep grows again just like human hair does.
- Step II: The sheared skin with hair is thoroughly washed in tanks to remove grease, dust
and dirt. This is called scouring. Nowadays scouring is done by machines.
- Step III: After scouring, sorting is done the hairy skin is sent to a factory where hair of
different textures are separated or sorted.
- Step IV: The small fluffy fibres, called burrs, are picked out from the hair. These arethesame burrs which sometimes appear on your sweaters. The fibres are scoured againanddried. This is the wool ready to be drawn into fibres.
- Step V: The fibres can be dyed in various colours, as the natural fleece of sheep and goats is black, brown or white.
- Step VI: The fibres are straightened, combed and rolled into yarn. The longer fibres are made into wool for sweaters and the shorter fibres are spun and woven into woollencloth.
2. Write down the process of transformation of cocoon to silk?
Ans: For obtaining silk, moths are reared and their cocoons are collected to get silk threads.
Rearing silkworms: A female silk moth lays hundreds of eggs at a time. The eggs are stored carefully on strips of cloth or paper and sold to silkworm farmers. The farmers keep eggs under hygienic conditions and under suitable conditions of temperature and humidity. The eggs are warmed to a suitable temperature for the larvae to hatch from eggs. This is done when mulberry trees bear a fresh crop of leaves. The larvae, called caterpillars or silkworms, eat day and night and increase enormously in size The larvae are kept in clean bamboo trays along with freshly chopped mulberry leaves. After 25 to 30 days, the caterpillars stop eating and move to a tiny chamber of bamboo in the tray to spin cocoons. Small racks or twigs may be provided in the trays to which cocoons get attached. The caterpillar or silkworm spins the cocoon inside which develops the silk moth.
Processing silk: A pile of cocoons is used for obtaining silk fibres. The cocoons are kept under the sun or boiled or exposed to steam. The silk fibres separate out. The process of taking out threads from the cocoon for use as silk is called reeling the silk. Reeling is done in special machines, which unwind the threads or fibres of silk from the cocoon. Silk fibres are then spun into silk threads, which are woven into silk clothby weavers