Class Notes NCERT Solutions for CBSE Students
Question: Write a short note on acrylic.
Answer: Acrylic resembles wool and hence is also called synthetic wool. It is cheaper and more durable than wool, and is easier to wash and maintain. Acrylic is less expensive, easily available, easy to wash and is easy to maintain.
Question: What is the difference between nylon and rayon?
Answer: Nylon and Rayon:
Question: What are the reasons for popularity of plastic?
Answer: Following are the reasons for popularity of plastic:
- Thermal conductivity: Plastic are poor conductor of heat (‘thermal’ means ‘heat’). Therefore, they are used to make handles of cooking utensils, and as insulating wool used in refrigerators to prevent heat from outside to enter inside it.
- Electrical conductivity: Plastics are poor conductors of electricity. This is the reason why electric wires, cords of electrical appliances and cables have a plastic coating.
- Solubility in water: Plastics are insoluble in water, that is why buckets to store water and glasses to drink water are made from plastics.
- Effect of flame: Plastics are inflammable, that is, they burn easily. This explains why a polythene bag burns so easily.
- Reactivity: Plastics have no reaction with and air. They are non-reactive and do not corrode easily. That is why they are used to store chemicals and other materials.
Question: Give examples which indicate that nylon fibres are very strong.
Answer: Nylon is used for making parachutes. A parachute needs to strong as it has to withstand high speed wind and huge amount of air pressure. Nylon ropes are used by mountaineers. A mountaineer’s life highly depends on the strength of ropes he is using. These examples show that nylon fibres are very strong.
Question: Explain why plastic containers are favoured for storing food.
Answer: Plastic does not react with most of the substances. Hence, food kept in plastic container remains fresh for longer duration. Due to this, plastic containers are preferred for storing food.
