1.    Since man-made fibres are obtained by the synthesis of petrochemicals, they are called synthetic fibres.

2.    (b) it is obtained from wood pulp.

3.    Fill in the blanks with appropriate words.

(d) Synthetic fibres are also called artificial or man-made

(e) Synthetic fibres are synthesized from raw material called polymer.

(f) Like synthetic fibres, plastic is also a petrochemicals.

4.    They are used to make parachutes and ropes for rock climbing.

5.    The main advantage of using plastic for storing food are-

a. Plastic has light weight.

b. Good strength.

c. Easy to handle.

6.    Thermoplastic

(i) These are the plastics which get deformed easily on heating and can be easily bent.

(ii) These are used for making toys, combs and various types of containers.

(iii) Ex- polythene, PVC.

Thermosetting Plastics

(i) These are the plastics which when molded once cannot be softened by heating.

(ii) Used for making electrical switches and handles of various utensils.

(iii) Ex-Bakelite, melamine etc.

7.    (a) As Bakelite is a bad conductor of heat, therefore, saucepan handles are made up of it.

(b) Bakelite is also a bad conductor of electricity, so these electrical appliances are made up of it.

8.    Can be recycled                                Cannot be recycled

Telephone instruments                  Cooker handles

Plastic toys                                        Carry bags

Ball point pens                                 Plastic covering of electrical wires

Plastic bowels                                   Plastic chairs.

9.    I will advise Rana to wear cotton clothes. Cotton clothes, which are natural fibres, do not retain heat, instead they reflect out heat. They also provide aeration. So, during summer, we prefer cotton clothes and not the synthetic clothes.

10.  The plastic are non-corrosive, that is, they do not react or do not have chemical reaction with the material contained in it. Many containers like bucket, mug, water bottles, and food containers are made up of plastics.

11.   Yes, because both should be made of the material which is light in weight and have good strength as well as hygiene.

12.   Since, plastics takes several years to decompose, it is not environment friendly and causes environmental pollution. On combustion, plastic do not burn completely and produce lots of carbon monoxide gas along with residual particles into the atmosphere. These gases cause air pollution and green-house effect that may leads to global warming.

13.   Match the following

Column A        Column B

(i)                    (d)

(ii)                   (c)

(iii)                  (a)

(iv)                   (b)

14.   The synthetic fibers are made up of petrochemical. So, the manufacture of synthetic fibres does not depend upon plants and trees. These synthetic fibres cater the need of people up to great extent. Thus the forests are not destroyed to manufacture clothes and other items. So, indirectly, we can come to a conclusion that manufacturing synthetic fibres is actually helping conservation of forests.

15.   If we make an experiment set up using copper wire, a thermoplastic object, a bulb and a cell, as shown in the figure below, the bulb does not glow.

However, if the thermoplastic object is removed from the circuit, the bulb glows up. This shows that thermoplastic objects are bad conductor of electricity.