Class 7 Science Chapter 3 Important Questions

Class 7 Science Chapter 3 Important Questions and Keywords of Fibre to Fabric updated for new academic session 2020-21. In Class 7 Science Chapter 3 Extra Questions, all the keywords are covered in the form of questions and explanation of 7th standard science.

Doing these questions along with NCERT Solutions of Chapter 3 of Class 7 Science, is provides an ample practice for the preparation of exams and school tests.

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Class 7 Science Chapter 3 Important Questions 2020-21

Class:7
Subject:Science
Contents:Important Questions & Keywords

Class 7 Science Chapter 3 Extra Questions for Exams

Class 7 Science Chapter 3 Important Questions are given below to use free for academic session 2020-21. This is just a collection of frequently asked questions in school exams and all important extra questions from NCERT Books of Class 7 Science Chapter 3 Fibre to Fabric. For any further suggestions, users are welcome.

7th Science Chapter 3 Important Questions Set – 1

Which part of the sheep have wool?

The sheep have fine and soft wool under the hair that grows close to the skin.

Write the name of some wool yielding animals? Mention some several breeds of sheep that are found in different parts of our country.

Wool comes from sheep, goat, yak and some other animals. These wool-yielding animals bear hair on their body.
Yak wool is common in Tibet and Ladakh. Angora wool is obtained from angora goats, found in hilly regions such as Jammu and Kashmir. Wool is also obtained from goat hair. The under fur of Kashmiri goat is soft. The fur (hair) on the body of camels is also used as wool.

“Sheep has two types of fibres that form its fleece” – Name them.

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. The fine hair provides the fibres for making wool.

Write any four names of the Indian breeds of sheep with their quality of wool.

Name of breed Quality of wool
Rampur bushair Brown fleece
Nali Carpet wool
Bakharwal For woollen shawls
Marwari Coarse wool

Rearing and Breeding of Sheep

Sheep are reared in many parts of our country for wool. Sheep are reared mainly for the wool. Sheep are herbivores and prefer grass and leaves. Apart from grazing sheep, rearers also feed them on a mixture of pulses, corn, jowar, oil cakes (material left after taking out oil from seeds) and minerals. In winter, sheep are kept indoors and fed on leaves, grain and dry fodder.
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. Once the reared sheep have developed a thick growth of hair, hair is shaved off for getting wool.

7th Science Chapter 3 Important Questions Set – 2

What is the importance of shearing process for getting wool?

Once the sheep have developed a thick growth of hair, hair is shaved off for getting wool. This process is called shearing. Machines similar to those used by barbers are used to shave off hair. Usually, hairs are removed during the hot weather.

Write down the occupational hazard which is related to the wool industry.

Wool industry is an important means of livelihood for many people in our country. But sorter’s job is risky as sometimes they get infected by a bacterium, anthrax, which causes a fatal blood disease called sorter’s disease. Such risks faced by workers in any industry are called occupational hazards.

What do you mean by SERICULTURE and SILKWORMS?

The rearing of silkworms for obtaining silk is called sericulture.
The female silk moth lays eggs, from which hatch larvae which are called caterpillars or silkworms. Silkworms spin the silk fibres.

Discuss the life stages of silkworms from “Pupa to Cocoon”.

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 (8).
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.

Scouring and Sorting

After the sheared skin of sheep with hair is thoroughly washed in tanks to remove grease, dust and dirt. This is called scouring. Nowadays scouring is done by machines.
After scouring, sorting is done. The hairy skin is sent to a factory where hair of different textures are separated or sorted.

7th Science Chapter 3 Important Questions Set – 3
How can we differentiate variety of silk? Name some types of silk.

The silk yarn (thread) is obtained from the cocoon of the silk moth. There is a variety of silk moths which look very different from one another and the silk yarn they yield is different in texture (coarse, smooth, shiny, etc.).
Thus, tassar silk, mooga silk, kosa silk, etc., are obtained from cocoons spun by different types of moths.

Name the most common silk moth found in India.

The most common silk moth is the mulberry silk moth. The silk fibre from the cocoon of this moth is soft, lustrous and elastic and can be dyed in beautiful colours.

From which substance natural silk is made?

When the caterpillar is ready to enter the next stage of its life history called pupa, it first weaves a net to hold itself. In this time, caterpillar secretes fibre made of a protein which hardens on exposure to air and becomes silk fibre.

Discuss the process of “rearing of silkworms” which is done by the farmers.

Rearing silkworms: For obtaining silk, moths are reared and their cocoons are collected to get silk threads.
A female silk moth lays hundreds of eggs at a time. The eggs are stored 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. The larvae, called caterpillars or silkworms, eat mulberry leaves day and night and increase enormously in size.

Discovery of Silk

The exact time of discovery of silk is perhaps unknown. According to an old Chinese legend, the empress Si-lung-Chi was asked by the emperor Huang-ti to find the cause of the damaged leaves of mulberry trees growing in their garden.
The empress found white worms eating up mulberry leaves. She also noticed that they were spinning shiny cocoons around them. Accidentally a cocoon dropped into her cup of tea and a tangle of delicate threads separated from the cocoon.
Silk industry began in China and was kept a closely guarded secret for hundreds of years. Later on, traders and travellers introduced silk to other countries. The route they travelled is still called the SILK ROUTE.
After 25 to 30 days, the caterpillars stop eating and move to a tiny chamber of bamboo in the tray to spin cocoons and small racks or twigs may be provided in the trays to which cocoons get attached.
The caterpillar or silk worm spins the cocoon inside which develops the silk moth. We get silk from these cocoons.

7th Science Chapter 3 Important Questions Set – 4
What will happen if cocoon is not boiled or exposed to steam?

If cocoon is not boiled then the silkworm will come out the fibres would not get enough long fibres to make the silk. Therefore, the cocoon is boiled to take out long fibres of silk.

Which types of food taken by the “mulberry silk moth”?

The larvae, called caterpillars or silkworms, eat a fresh leaves of mulberry trees day and night for growth.

Differentiate between Artificial silk and Pure silk.

Pure silk fibre is a natural fibre while artificial silk created by human. For getting pure silk, it can be rear in any sort of climate while artificial silk created in definite chemical and temperature.
Pure silk fibre made of protein while artificial made of chemical substances. Pure silk has high absorbing capacity whereas artificial does not hold this type of features.
Besides of these, burning of natural silk fabric gives a smell like burning of hair while artificial silk fabric gives a smell like burning of paper.

What do you mean by Reeling of silk?

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.

Processing of Silk

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 from cocoon and further it goes for the reeling process for getting silk fibres. The whole method from collecting cocoons to obtaining thread through reeling process, called processing of silk.

7th Science Chapter 3 Important Questions Set – 5
Write various steps for processing fibres into wool.

The various steps for processing fibres into wool are as follows:
Shearing: The first step is to remove fleece of the sheep along with thin layer of skin. This process is called shearing.
Scouring: In this step, the sheared hair is washed thoroughly to remove grease, dust and dirt.
Sorting: In this step, different textures of hair are separated or shorted.
Separating burrs: Burrs are small fluffy fibres which are picked out from the hair.
Dyeing: The fibres are dyed in various colours, as the original colour of fleece are usually black white or brown.
Rolling: In this process, the fibres are straightened, combed and rolled into yarn. And the fibres now as wool are ready to be oven.

In the rearing of silkworms, after how many days the caterpillar stop to eating the leaves of mulberry tree?

In the rearing of silkworms, after 25 to 30 days the caterpillar stops to eating the fresh leaves of mulberry tree and move to a tiny chamber of bamboo in the tray to spin cocoons.

What is meant by Rearing?

Rearing: It is raising and taking care of livestock (e.g. cows, buffaloes, goats etc.) for commercial purposes. These animals are fed, provided, shelters and are bred for better yield like milk, meat, wool etc. For example, sheep are reared mainly for the wool. They are mainly reared in areas with low rainfall. Reared sheep eat grass and leaves. They are also fed on a mixture of pulses, corn, jowar, oil cakes and minerals. In winter they are kept in indoors and fed on dry fodder, leaves and grains.

How does the hair of certain animals help in keeping their bodies warm?

Hair (or wool) of these animals trap a lot of air. Air is a poor conductor of heat. So, the air trapped in hair (or wool) of these animals prevents their body heat from being lost to cold surroundings and keeps them warm.

What is meant by Shearing?

Shearing: Once a sheep develops a thick coat of hair, it is shaved off to obtain wool. The process of cutting off the woollen fleece of sheep with a thin layer of skin is called shearing. It is done by the machine similarly, to those used by barbers to remove hairs.

Explain the phrase – “Unity is strength” on the basis of the making of fabric from fibre.

Fibres and fabric play a large role in everyday applications. A fibre is a hair-like strand of material. They are the smallest visible unit of a fabric and denoted by being extremely long in relation to their width. Fibres can be spun into yarn and made into fabric.
A single fibre is too weak to break but when some fibres together make a fabric, it is difficult to tear. Fabric needs more energy to tear apart as compared to a single fibre.

Sericulture

The breeding and management of silk worms for the production of silk is known as sericulture. Different types of silk (e.g. mulberry silk, tassar silk etc.) with different textures are obtained from different varieties of silk moths.

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