CBSE Class 7 Science Fibre to fabric Set B

Question. How many weeks are required for the eggs of silk moth to hatch?
(a) One
(b) two
(c) three
(d) four

Answer : B

Question. silk worms mainly feed on som leaves.
(a) Mulberry
(b) tassar
(c) eri
(d) moonga

Answer : D

Question. Which of the following is not a natural fibre?
(a) Cotton
(b) rayon
(c) silk
(d) wool

Answer : B

FILL IN THE BLANKS :

Question. Silk is obtained from cocoons of ____

Answer : Silkworm

Question. The _____ the burrs, the better is the wool.

Answer : Fewer

Question. ____ and ____ fibres are obtained from animals.

Answer : Wool, silk

Question. During the spinning of cocoon, a silkworm is transformed Into _____

Answer : Pupa

Question. Natural fibres are obtained from and _____

Answer : Plant, animal

DEFINE :

3. Sericulture - the rearing of silkworms for obtaining silk is called sericulture.

1. Selective breeding - it is also known as artificial selection, it is a process used by humans to develop new organisms with desirable characteristics.

5. Scouring - the process of washing the fleece of sheep to remove dirt, dust, sweat, grease, etc, is called scouring.

2. Rearing - it is the process to look after the animals by giving them proper food, shelter, and health care.

4. Shearing - the process of removing hair from the body of sheep is called shearing.

VERY SHORT ANSWER TYPE QUESTIONS :

Question. Name the sheep that is found In Gujarat whose wool is used in hosiery.
Answer : Patanwadi

Question. What is the process of removing the burrs from fleece called?
Answer : The process of removing the burrs from fleece is called combing.

Question. Which country leads in silk production?
Answer : China is the leading country in silk production.

Question. Name an two breed of sheep found In India.
Answer : Lohi and Nali

Question. What is the process of taking out thread from the cocoon is called?
Answer : The process of taking out thread from the cocoon is called realing.

SHORT ANSWER TYPE QUESTIONS :

Question. What is cocoon?
Answer : A cocoon is a shell made of silk by silkworm and most kinds of moth caterpillars and other insect larvae.

Question. What are raw silk and spun silk?
Answer : The fibres of the cocoon are too fine and delicate to handle. So, many of them are reeled together to yield stronger thread called raw silk. The inferior quality silk produced by damaged or waste cocoons is called spun silk.

Question. Why does shearing not hurt the sheep?
Answer : Shearing does not hurt the sheep because the uppermost layer of the skin of the sheep is dead

Question. What is sorter's disease? Why this disease is called occupational disease?
Answer : In wool industry there is an important role of sorters, who separates the fleece of sheep into fibres of different qualities. The job of sorters is very risky because sometime they get infected by the bacteria called 'Bacillus anthracis' that causes deadly blood disease called sorter's disease. This is also called occupational disease because the person catches this disease while working in the industry due to the nature of his work.

Question. What is meant by selective breeding? What is its purpose?
Answer : it is a process used by humans to develop new organisms with desirable characteristics for any industry. By this process high yield breeds of animals is produced. So that production should be increased. For example- such sheep breed can be produced which give good quality and thick coat of hair on their body.

LONG ANSWER TYPE QUESTIONS :

Question. Describe the process of wool production?
Answer : Step 1: Shearing: It is a process of removing the fleece of the sheep along with a thin layer of its skin.
Step 2: Scouring: It is a process of removing dirt, grease and dust from the hair removed from the sheep. It is generally done with the help of machines.
Step 3: Sorting: It is the process of separating the hair of the sheep according to their textures.
Step 4: Removing of burrs: In this step, the burrs or small fibres present on the hair are picked out. Then the hair is cleaned and dried out. The product so obtained is the wool that can now be converted into fibres.
Step 5: Colouring of wool fibres: In this step, the fibres are dyed in different colours. 
Step 6: Rolling of wool: In the last step, the fibres for wool so obtained is straightened out combed and then rolled into a yarn.

ACTIVITY 
Cut out/draw pictures of the stages of the life cycle of silkworm. Paste them on an A4 sheet. Label and explain it.

Question. Write the various steps involved in the production of silk cloth from silk moth.
Answer : • Rearing: the silkworm farmers raise the eggs of the Silkmoth.
• These eggs are generally large in numbers as a single silk moth can lay about 100 eggs at a time.
• These eggs are stored in an environment having an appropriate temperature, humidity and hygienic conditions.
• In order to hatch the larvae out of the eggs are heated.
• They are then kept in a bamboo tray.
• This process is conducted generally when the fresh leaves appear on the Mulberry trees so that the Caterpillar can get enough feed.
• The Caterpillar feeds for around 25 to 30 days and then moves into a chamber in the tray to build a cocoon.
• The cocoon when spun gets attached to the rocks present in the Bamboo tray.

Processing of Silk
• Firstly, as the cocoons are acquired they are kept under the sun or boiled so that the Silk fibres can separate out from them.
• Then, the reeling of the silk takes place. It is a process in which the cocoon's threads are processed to be used as silk.
• The silk fibres thus obtained are drawn and rolled into threads.
• Thrown silk is then dyed for making coloured threads.