Class Notes NCERT Solutions for CBSE Students
Question: Give uses of polyester and explain the reason for each use.
Answer: Uses of polyester:
- Polyester is used to make pants, shirts, suits and bedsheets either by itself or as a blend as it is strong, crease-resistant, light, elastic and absorb very little water.
- Its water-resistant property makes it ideal for garments and jackets that are to be used in wet or damp environments.
- It is used to make kackets and quilted garments.
- PET is a form of polyester used to make bottles, films, utensils, wire etc.
Question: These day clothes made out of mixture of synthetic fibres and natural fibres are more popular than those made purely out of synthetic fibres. Discuss the reasons for this.
Answer: This is because clothes made of synthetic fibres are not very comfortable to wear. They do not absorb water or sweat. In hot and humid weather these clothes stick to the body and make us feel uncomfortable. Synthetic fibres catches fire very readily, they melt on heating and stick to body of the person wearing them, causing severe burn injuries.
Question: Differentiate between thermoplastics and thermosetting plastics. Give two examples of each.
Answer: Difference between thermoplastic and thermosetting plastic is as follows:
Thermoplastic
Thermosetting plastic
1. The process of softening by heating and hardening on cooling can be repeated again and again to soften the plastic to get different shapes.
1. Thermosetting plastics can be softened by heating only once. Once they are put into mould and allowed to harden on cooling, they cannot be softened again on heating.
2. For example- Polythene, PVC
2. For example- Bakelite and Melamine
Question: Plastics are very useful materials. Why then is there concern today about their increasing use?
Answer: Today plastics have become a serious worldwide environmental and health concern. This is because of their non-biodegradable nature and wide spread use.
- Plastics are non-biodegradable, i.e., they cannot be decomposed by the microorganisms in the soil.
- Careless disposal of plastic bags chokes drains, chokes the soil and hinders the absorption of water by the soil.
- If eaten by animals such as cows, it can kill them.
- Plastic bags can also contaminate foodstuffs because of poisonous dyes getting absorbed into food.
- If burnt, they release poisonous fumes and pollute the air.
Question: List steps you can take to reduce the danger that plastics pose to the environment.
Answer: Steps to reduce the danger that plastics pose to the environment:
- Buy products with less plastic packaging.
- Shoppers should use their own bags or recycled paper bags.
- Support recycling schemes and promote support for one in your local area.
- Practise and promote proper disposal of plastics in your home. Never dispose off plastics in the sewage system.
- Pick up any plastic litter that you see in the vicinity and dispose it off in a proper place. Encourage others to do so.
- Never throw plastic litter in the streets, on the pavement or in drains.
- Always remember the 4R priciple- Refuse, Reduce, Reuse and Recycle.
