1. Describe why some fibres are referred to as synthetic.
Ans. Some fibres are called synthetic because:
- They are artificially made from chemical substances such as petrochemicals.
- They are man-made fibres created with or without the use of natural raw materials derived from plants or animals.
- They are usually made up of a series of small units that are linked together to form a larger unit known as a polymer. Nylon, rayon, acrylic, and polyester are examples of synthetic fibres.
2. Circle the correct response.
Rayon differs from synthetic fibres in that it is a natural fibre.
- It resembles silk in appearance.
- It is made out of wood pulp.
- Its fibres can be knitted in the same way that natural fibres may be knitted.
Ans: (b) It is made out of wood pulp.
Rayon is created from wood pulp, which is a natural source, whereas most synthetic fibres are made without using any natural raw materials from plants or animals.
3. Use correct terms to fill in the blanks.
- Synthetic fibres are also known as or ……….
- Synthetic fibres are made from a raw material known as ……..
- Plastic, like synthetic fibres, is a ………
- Synthetic fibres are also known as artificial or man-made fibres.
- Synthetic fibres are made from a raw material known as petrochemicals.
- Plastic, like synthetic fibres, is a polymer.
4. Provide examples that demonstrate the strength of nylon fibres.
Solution: The examples below demonstrate the strength of nylon fibres.
- Nylon is used to make rock climbing parachutes and ropes.
- Seat belts, fishing nets, and tyre cords are all made of nylon.
- Nylon is used to make sporting equipment such as rackets.
5. Describe why plastic containers are preferred for food storage.
Solution: Plastic containers are preferred for food storage because plastic is non-reactive, it does not react with the ingredients in food.
6. Describe how thermoplastic and thermosetting polymers differ.
Solution: The distinctions between thermosetting and thermoplastic plastics are as follows:
- Thermosetting plastic is not bendable, they are hard and brittle
- It is not possible to soften thermosetting plastics by heating them. They cannot be remoulded.
- Thermoplastics are easily bendable, they are soft and less brittle.
- Thermoplastics soften when heated and may be easily moulded and reshaped.
7. Explain why thermosetting polymers are used in the following items:
(a) Handles for saucepans
(b) Plugs, switches, and plugboards
(a) Thermosetting polymers are used for making saucepan handles as they are poor conductors of heat. Hence, they do not get soft when heated.
(b) Bakelite is a thermosetting material. It is a poor conductor of heat and electricity, and is used to make items like electric plugs, switches, and plugboards because of this characteristic.
8. Rana wants to get some summer clothing. Is it better for him to buy cotton shirts or synthetic clothes? Give Rana your advice, explaining why.
For summers, Rana should buy a cotton shirt rather than a synthetic shirt because during the summer season we tend to sweat more. Cotton is a good water absorbent. It can absorb the sweat released from the body and help in the evaporation of sweat and keep our body cool.
9. Use examples to demonstrate that plastics are naturally non-corrosive.
Plastics are non-corrosive by nature and do not react even when exposed to harsh substances. Cleaning products, for example, are kept in plastic bottles rather than metal containers at home.
10. Should a toothbrush's handle and bristles be made of the same material? Explain your response.
A toothbrush's handle and bristle should not be made of the same material, as the handle should be hard and powerful while the bristle should be soft and flexible.
11. 'Avoid plastics to the greatest extent possible.' Please share your thoughts on this suggestion.
Plastics are non-biodegradable in nature, so we should avoid them as much as possible. When they are discharged into the environment, they cause harm to it. When plastic bags are burned, poisonous gases are generated, and when animals ingest them, their respiratory systems are strangled, resulting in death.
12. 'Manufacturing synthetic fibres aids forest conservation.' Comment.
Natural fibres involve the harvesting of raw materials from plants, which necessitates the falling of a huge number of trees, resulting in forest depletion. Synthetic fibres on the other hand are man-made and do not require cutting down of trees helping in forest conservation.
13. Describe an exercise that demonstrates how thermoplastic is a poor electrical conductor.
We shall build a circuit to demonstrate that thermoplastic is a poor conductor of electricity.
We would require:
- A light
- some cables
- A battery
- A piece of metal
- Plastic tubing (as shown in the figure below).
When you turn on the current, you'll see that in the first case, the bulb turns on. The bulb in the latter scenario does not light up. As a result, a thermoplastic plastic pipe is demonstrated to be a poor conductor of electricity.