Ncert solutions science class 8 Solutions for Chapter 3 synthetic fibres and plastic

Explain why some fibres are called synthetic.

Pick the synthetic fibre out of the following?

(a) Cotton

(b) Nylon

(c) Jute

(d) Wool

Q1) Explain why some fibres are called synthetic.

Mark the correct answer.

Rayon is different from synthetic fibres because

(a) it has a silk-like appearance.

(b) it is obtained from wood pulp.

(c) its fibres can also be woven like those of natural fibres.

Which of the following is a source of rayon?

(a) Wool

(b) PET

(c) Wood pulp

(d) Silk

Q2) Mark (✓) the correct answer.

Rayon is different from synthetic fibres because

(a) it has a silk-like appearance.

(b) it is obtained from wood pulp.

(c) its fibres can also be woven like those of natural fibres.

Fill in the blanks with appropriate words.

(a) Synthetic fibres are also called __________ or __________ fibres.

(b) Synthetic fibres are synthesised from raw material called __________.

(c) Like synthetic fibres, plastic is also a __________

Polycot is obtained by mixing

(a) nylon and wool

(b) polyester and wool

(c) nylon and cotton

(d) polyester and cotton

Q3) Fill in the blanks with appropriate words.

(a) Synthetic fibres are also called __________ or __________ fibres.

(b) Synthetic fibres are synthesised from raw material called __________ .

(c) Like synthetic fibres, plastic is also a __________ .

Which is a thermosetting plastic?

(a) Melamine

(b) Polythene

(c) PVC

(d) Nylon

Q4) Give examples which indicate that nylon fibres are very strong.

Give examples which indicate that nylon fibres are very strong.

Explain why plastic containers are favored for storing food.

Q5) Explain why plastic containers are favoured for storing food.

The material similar to silk in appearance is

(a) Nylon

(b) Rayon

(c) Polyester

(d) Terylene

The most suitable material for the preparation of handles of cooking utensils is

(a) Polythene

(b) PVC

(c) Nylon

(d) Bakelite

Q6) Explain the difference between thermoplastic and thermosetting plastics.

Explain the difference between thermoplastic and thermosetting plastics.

Explain why the following are made of thermosetting plastics.

(a) Saucepan handles

(b) Electric plugs/switches/plug boards

Q7) Explain why the following are made of thermosetting plastics.

(a) Saucepan handles

(b) Electric plugs/switches/plug boards

Which of the following is not a common property of plastics?

(a) Non-reactive

(b) Light in weight

(c) Durable

(d) Good conductor of electricity

Which of the following represents the correct match for items in Column A with those in Column B.

Column A Column B

I. Nylon (i) Thermoplastic

II. PVC (ii) Thermosetting plastic

III. Bakelite (iii) Fibre

(a) I-(ii), II-(iii), III-(i)

(b) I-(iii), II-(i), III-(ii)

(c) I-(ii), II-(i), III-(iii)

(d) I-(iii), II-(ii), III-(i)

Categorise the materials of the following products into ‘can be recycled’ and ‘cannot be recycled’.

Telephone instruments, plastic toys, cooker handles, carry bags, ball point pens, plastic bowls, plastic covering on electrical wires, plastic chairs, electrical switches.

Q8) Categorise the materials of the following products into ‘can be recycled’

and ‘cannot be recycled’.

Telephone instruments, plastic toys, cooker handles, carry bags, ball point

pens, plastic bowls, plastic covering on electrical wires, plastic chairs,

electrical switches.

Q9) Rana wants to buy shirts for summer. Should he buy cotton shirts or shirts made from synthetic material? Advise Rana, giving your reason.

Rana wants to buy shirts for summer. Should he buy cotton shirts or shirts made from synthetic material? Advise Rana, giving your reason.

Which of the following groups contain all synthetic substances?

(a) Nylon, Terylene, Wool

(b) Cotton, Polycot, Rayon

(c) PVC, Polythene, Bakelite

(d) Acrylic, Silk, Wool

Q10) Give examples to show that plastics are noncorrosive in nature.

The material which is commonly used for making kitchen containers is

(a) PVC

(b) Acrylic

(c) Teflon

(d) PET

Give examples to show that plastics are noncorrosive in nature.

Q11) Should the handle and bristles of a tooth brush be made of the same material? Explain your answer.

Cotton is a natural polymer. What is its chemical name?

Should the handle and bristles of a tooth brush be made of the same material? Explain your answer

A synthetic fiber which looks like silk is obtained by chemical treatment of wood pulp. It is, therefore, known as artificial silk. What is its common name?

Q12) ‘Avoid plastics as far as possible’. Comment on this advice.

Avoid plastics as far as possible’. Comment on this advice.

Terrycot is made by mixing two types of fibres. Write the names of the fibres.

Match the terms of column A correctly with the phrases given in column B

Q13) Match the terms of column A correctly with the phrases given in column B.

Q14) ‘Manufacturing synthetic fibres is actually helping conservation of forests’. Comment

Plastic articles are available in all possible shapes and sizes. Can you tell why?

‘Manufacturing synthetic fibres is actually helping conservation of forests’. Comment.

Plastic is used for making a large variety of articles of daily use and these articles are very attractive. But it is advised to avoid the use of plastic as far as possible. Why?

Describe an activity to show that thermoplastic is a poor conductor of electricity

Q15) Describe an activity to show that thermoplastic is a poor conductor of electricity.

Why is it not advisable to burn plastic and synthetic fabrics?

Select the articles from the following list which are biodegradable.

(a) paper

(b) woolen clothes

(c) wood

(d) aluminium can

(e) plastic bag

(f) peels of vegetables

A bucket made of plastic does not rust like a bucket made of iron. Why?

A lady went to the market to buy a blanket. The shopkeeper showed her blankets made of acrylic fibres as well as made of wool. She preferred to buy an acrylic blanket. Can you guess why?

PVC (polyvinyl chloride) is a thermoplastic and is used for making toys, chappals, etc. Bakelite is a thermosetting plastic and is used for making electrical switches, handles of various utensils, etc. Can you write the major difference between these two types of plastics?

Fill in the blanks.

(i) A polymer is a chain of many small units joined together which are called ______.

(ii) The synthetic fibres are also known as ______ fibres.

(iii) The first fully synthetic fibre was ______.

(iv) A fibre similar to wool is ______.

(v) A plastic used for making crockery is ______.

Match items in List A with the items of list B.

List A List B

(a) nylon (i) non-stick coating

(b) PET (ii) electric switches

(c) rayon (iii) parachutes

(d) thermosetting plastics (iv) polyester

(e) teflon (v) artificial silk

Unscramble the jumbled words given below, related to synthetic materials.

(a) anory

(b) lopmery

(c) relyteen

(d) laspict

(e) yespolter

(f) felton

Indicate whether the following statements are True or False. Also write the false statements in their correct form.

(i) The fabric terywool is obtained by mixing terylene and wool.

(ii) Synthetic fibres do not melt on heating.

(iii) It is risky to wear synthetic clothes while working in the kitchen.

(iv) Most of the plastics are biodegradable.

Write the importance of synthetic polymers in our life.

Despite being very useful it is advised to restrict the use of plastic. Why is it so? Can you suggest some methods to limit its consumption?

Write an activity to show that synthetic fibres are stronger than the cotton fibres.

Complete the crossword given below with the help of clues