Class 7 chemistry important questions with answers are provided here for Chapter 3 – Fibre to Fabric. These important questions are based on the CBSE board curriculum and correspond to the most recent Class 7 chemistry syllabus. By practising these Class 7 important questions, students will be able to quickly review all of the ideas covered in the chapter and prepare for the Class 7 annual examinations.
Download Class 7 Chemistry Chapter 3 – Fibre to Fabric Important Questions with Answers PDF by clicking on the button below.
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Multiple Choice Type Questions
Q1. Which of the following is performed on looms?
(a) Spinning
(b) Weaving
(c) Reeling
(d) All of the above
Answer: (b) Weaving
Explanation: Weaving is the method of interlacing yarn (thread) to obtain fabric (cloth). It is performed on looms.
Q2. Which of the following countries is the leading producer of silk?
(a) Los Vegas
(b) China
(c) India
(d) The United States of America
Answer: (b) China
Explanation: China is the leading producer of silk, followed by India. It is also known as a silk country. In 2005 China accounted for 74% of international silk production.
Q3. Which of the following is a variety of silk?
(a) Tussar silk
(b) Mulberry silk
(c) Muga silk
(d) All of the above
Answer: (d) All of the above
True or False Type Questions
Q1. Wool is obtained only from sheep.
Answer: False
Explanation: Sheep are not the only source of wool. We can yield wool from animals like llamas, yak, alpacas and angora. Thus, the above statement is false.
Q2. Wool traps more air in it as compared to cotton.
Answer: True
Explanation: Wool traps more air because of the air spaces present in its fibres. Thus, the above statement is true.
Q3. Silk fibre is made of proteins.
Answer: True
Explanation: Silk fibre is typically made of fibroin and sericin. They are composed of different amino acids (proteins). Sericin is a binding liquid that binds the fibroin’s solid fibre. Thus, silk fibre is made of proteins.
Q4. The insect in the cocoon is killed before reeling the silk.
Answer: True
Explanation: Silkworms are killed to maintain silk grade, yarn length, and worth as they chew their route out of the cocoon and degrade it. Thus, the insect in the cocoon is killed before reeling the silk.
Q5. Rearing of goats, camels, etc., is called sericulture.
Answer: False
Explanation: The rearing of silkworms on a commercial scale to manufacture silk is known as sericulture. Thus, the above statement is false.
Fill in the blanks Type Questions
Q1. The thread obtained during reeling is known as ______.
Answer:
Raw silk
Q2. ______ and _____ produce the best wool.
Answer:
Australia and New Zealand
Q3. Silk is obtained from _______ of silkworms.
Answer:
Cocoons
Q4. ______ is secreted by the larva from its salivary glands.
Answer:
Protein
Q5. ______ and ______ are obtained from animals.
Answer:
Silk and wool
Q6. _______ and _______ are obtained from plants.
Answer:
Cotton and Jute
Q7. ______ is the world’s second-largest producer of silk after ______.
Answer:
India, China
Match the following Type Questions
Q1. Match the items of column A with those of column B.
| Column A | Column B |
| Alpaca and Llama | Finest wool-yielding animal |
| Angora goat | Food of silkworms |
| Merino sheep | Mohair wool |
| Mulberry leaves | Wool yielding animal |
| Cocoon | Cleaning of sheared skin |
| Scouring | Camel family wool-yielding animals |
| Yak | Yields silk fibre |
Answer:
| Column A | Column B |
| Alpaca and Llama | Camel family wool-yielding animals |
| Angora goat | Mohair wool |
| Merino sheep | Finest wool-yielding animal |
| Mulberry leaves | Food of silkworms |
| Cocoon | Yields silk fibre |
| Scouring | Cleaning of sheared skin |
| Yak | Wool yielding animal |
Q2. Match the items of column A with those of column B.
| Column A | Column B |
| Sericulture | Fur |
| Kashmiri goat | Wool |
| Camel | Pashmina |
| Sheep | Rearing of silkworm to get silk |
Answer:
| Column A | Column B |
| Sericulture | Rearing of silkworm to get silk |
| Kashmiri goat | Pashmina |
| Camel | Fur |
| Sheep | Wool |
Very Short Answer Type Questions
Q1. What are the sources of fibre?
Answer:
Plants and animals are the sources of fibre.
Q2. Which body part of sheep yields wool?
Answer:
Fleece (hairs) of sheep yields wool.
Q3. Name the four stages of a silk moth.
Answer:
Egg, larva, pupa and adult are the four stages of a silk moth.
Q4. What can the maximum length of continuous silk thread be obtained from a cocoon?
Answer:
We can get more than 1000 feet of constant silk thread from a cocoon.
Q5. Which bacterium is found in wool processing work?
Answer:
Bacillus anthracis is found in wool processing work.
Q6. Name the disease caused by bacillus anthracis.
Answer:
Sorter’s disease or anthrax, is caused by bacillus anthracis.
Q7. Name the fibre obtained from the Angora goat.
Answer:
Mohair fibre is obtained from the Angora goat.
Q8. Name any two animal fibres.
Answer: Silk and wool are animal fibres.
Q9. Name any three plant fibres.
Answer:
Cotton, coir and jute are plant fibres.
Q10. How many silkworms are required to produce 1 kg of silk?
Answer:
Around 5500 silkworms are required to make 1 kg of silk.
Short Answer Type Questions
Q1. Why do we get hair burnt odour while burning wool?
Answer:
We get a scent of hair burn while burning wool because it is obtained from the fleece (hairs) of goats, sheep, yak, etc.
Q2. What is rearing?
Answer:
The process of keeping, feeding, breeding, and taking medical care of animals is known as rearing.
Q3. What is shearing?
Answer:
The process of removing the fleece (hairs) of the sheep along with a thin layer of skin from its body by a razor, clipper or shearing machine is known as shearing.
Q4. What do you mean by the term reeling of silk?
Answer:
The process of obtaining silk fibre from the cocoons is known as the reeling of silk. It is also known as the filature of silk.
Q5. What is sorter’s disease? How does it spread?
Answer:
Sorter’s disease is another name for anthrax. The bacteria Bacillus anthracis causes it via animals to humans.
Q6. Name the four countries which are the leading producer of wool. Which country produces the best wool in the world?
Answer:
Australia is the leading producer of wool, followed by China, Russia, and New Zealand.
Australia produces the best wool in the world.
Q7. Name three health hazards associated with sericulture.
Answer:
The three health hazards associated with sericulture are mentioned below.
1. Sorter’s disease, or Anthrax
2. Asthma
3. Bronchitis
Q8. What is sericulture? Name some diseases associated with it.
Answer:
The rearing of silkworms on a commercial scale to manufacture silk is known as sericulture. Bronchitis, asthma, and sorter’s disease (anthrax) are associated with sericulture.
Q9. Why does the caterpillar of a silk moth feed constantly?
Answer:
The caterpillar of a silk moth is fed constantly as they have a brief life span. If there is insufficient food for the caterpillars, they will not grow properly and will not produce silk.
Q10. Why should we kill the silkworm after the pupa stage?
Answer:
We should kill the silkworm after the pupa stage because the silkworm chews its route out of the cocoon and degrades the silk quality. Therefore, silkworms are killed after the pupa stage to maintain the silk grade and yarn length.
Long Answer Type Questions
Q1. Describe with a labelled diagram the life cycle of a silk moth.
Answer:
There are four phases in the silk moth lifecycle.
1. Egg
2. Larva
3. Cocoon
4. Adult worm
Stage 1: Egg: The life cycle of a silk moth begins when a female silk moth lays eggs. The eggs hatch into black worm-like larvae. The larvae of a silk moth are known as a caterpillar or silkworm.
Stage 2: Larva: The caterpillar or silkworm constantly feeds on mulberry leaves, giving rise to pupa. During this time, it sheds its skin four times. The process of shedding skin to grow a new one is known as moulting.
Stage 3: Cocoon: The silkworms spin a shielding cocoon around themselves. The cocoon is composed of a single silk yarn (thread) and is of a cotton ball size.
Stage 4: Adult: When the worm matures into an adult moth, it secretes a fluid that dissolves the cocoon’s silk fibres so that it can emerge out of it. The female moth lays eggs during this stage, and the life cycle begins again.
Q2. Describe the processing of fibres into wool in detail.
Answer:
The following steps are carried out to process the hair or fleece obtained from the animals into the wool.
1. Shearing
2. Scouring
3. Sorting
4. Separating burrs
5. Dyeing
6. Rolling
Step 1: Shearing: In this process, the thick growth of hairs and a thin layer of sheep’s skin is removed by a razor, clipper, pair of scissors or shearing machine. It is carried out in summer so that hair grows back in the winter.
Step 2: Scouring: In this step, the sheared wool is washed with the detergent in large tanks to remove dirt, grease and sweat. The cleaned wool is treated with an acid and dried by low heating. In large factories, machines are used for scouring.
Step 3: Sorting: In this process, the clean wool is graded according to its texture.
Step 4: Separating burrs: Burrs are the tiny fluffy fibres present in the fleece of sheep. It can also be seen on some of the sweaters we wear.
In this process, the burs are separated, and the process of scouring is repeated. The hairs are then twisted into fibres.
Step 5: Dyeing: The fleece of sheep and goats is naturally black, brown or white in colour. It is dyed into different colours according to requirement.
Step 6: Rolling: In this process, fibres are straightened, combed and rolled into yarn. This method will produce two kinds of yarns. The longer yarns are knitted into sweaters, shawls, etc. In contrast, the shorter yarns are woven into blankets, carpets, etc.
Q3. What is scouring? Why is it essential during the processing of fibres into wool?
Answer:
Scouring refers to cleaning sheared wool with detergent to remove dirt, grease and sweat. It is a critically important step in wool processing. During the growth of the wool fibre, it becomes coated with oil (called wool wax), sweat salts (or suint) and contaminated with dirt, dust, dung and vegetable matter of various kinds. Scouring enables the cleaning of the fleece of sheep. Thus, it is critical.
Q4. Answer the following questions.
(a) Are silkworms and silk moths the same?
(b) Why do caterpillars shed their skin?
(c) Why do people of animal protection oppose sericulture?
Answer:
(a) No, silkworms and silk moths are different. A silkworm is an earlier or previous stage of a silkmoth. A silkmoth is an insect that lays eggs to reproduce silkworms which spin silk. In contrast, a silkworm is the larvae caterpillar of a silk moth in the form of a cocoon to produce silk.
(b) Caterpillars shed their skin while growing. This process is known as moulting.
(c) Sericulture is opposed by the people working for animal protection because, in sericulture, silkworms are killed by placing the cocoon in hot water. Hence, the people working for animal protection stand against it.
Q5. Answer the following questions.
(a) Why do we wear wool in the winter?
(b) Differentiate between silk and wool.
(c) Why is the silkworm killed after the pupa stage?
Answer:
(a) Wool is a soft, light and wrinkle-resistant fibre. It is highly porous and traps air between the spaces of the fibre. Thus, it acts as an insulator of heat and does not allow body heat to escape. Therefore, it is used in winter as winter clothing.
(b) Silkworms produce silk. It is used to make shiny clothes. In contrast, wool is produced by the fleece of cold region animals. It is used to make winter clothes.
(c) Silkworm is killed after the pupa stage because silkworm chews their route out of the cocoon and degrades the silk quality. Therefore, the silkworm is killed after the pupa stage to maintain the silk grade and yarn length.
Read Also:
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- Chemistry Worksheets Class 7 on Chapter 3 Fibre to Fabric with Answers – Set 1
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- Chemistry Worksheets Class 7 on Chapter 3 Fibre to Fabric with Answers – Set 3
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