Thursday , July 7 2022
NCERT 7th Class (CBSE) Science: Fibre to Fabric – Quiz

NCERT 7th Class (CBSE) Science: Fibre to Fabric

Question: Give reasons why does shearing cause no pain to the sheep?

Answer: Shearing does not cause any pain to the sheep because the uppermost thin layer of their skin is dead.

Question: What kind of feed be given to a sheep for good growth of curly and shiny hair?

Answer: Protein rich food such as mixture of corn, pulses, jowar and oil cakes should be given to the sheep for good growth of curly and shiny hair.

Question: What happens when the silk caterpillar stops feeding?

Answer: When the silk caterpillar stops feeding its salivary gland starts secreting a sticky fluid, a protein called fibroin. This fluid hardens on exposure to air and forms a long thread of silk. This thread gets wrapped around its body to form a ball like structure called cocoon.

Question: Give the rearing process of silk worm in brief.

Answer: The moth is kept under controlled temperature. A female moth lay eggs that hatch into caterpillar (silk worm). The silk worm feeds on fresh mulberry leaves and their size increase 50 to 70 times in four weeks. Racks or twigs are placed on tray, where silk worms spin cocoon. The cocoon are obtained before the larva matures by putting them in hot water.

Question: What kind of animals in different regions are reared for obtaining wool?

Answer: Various kinds of animals are:

  1. Yak: Yak wool is common in Tibet and Ladakh.
  2. Angora goat: They are used to obtain Angora wool. They are found in hilly regions such as Jammu and Kashmir.
  3. Cashmere goats: They are used to obtain fur.
  4. Camel: It also provide fur.
  5. Llama and Alpacea: They are found in South America. They also yield wool.

Question: Compare the result when wool and silk are burnt.

Answer: Comparison is as follows:

Features
Wool
Silk
Approaching flame
Becomes curly by the flame
Becomes curly by the flame
In flame
Burns slowly
Burns slowly and sputters in flame
Removed from flame
Stops burning when removed from flame.
Stops burning when removed from flame.
Odour
like burning hair.
like burning hair.
Residue
Small black beads brittle, crushable
Small black beads brittle, crushable

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5 comments

  1. Not useful

  2. It was very useful to me!

  3. Mam issi chapter k iss qies ka answer bta dijis Q– write in brief process of obtaing silk