Question Answers For All Chapters – General Science Class 8
Exercise
1. Try to find it.
(a) Plastic shows plasticity property, hence it can be molded into any shape.
(b) Motor cars are coated with Teflon.
(c) Thermocol melts at 100°C.
(d) Alkali silicate glass dissolves in water.
2. Who is my partner?
| Column A | Column B |
|---|---|
| a. Lead glass | iii. Electric bulb |
| b. Bakelite | iv. Electric switch |
| c. Thermocol | i. Plates |
| d. Optic glass | v. Lens |
| e. Polypropylene | ii. Mattresses |
3. Answer the following:
(a) Thermocol is produced from which material?
- Thermocol is made from polystyrene, a type of plastic that becomes soft when heated and hard when cooled.
(b) Write uses of PVC.
- PVC (Polyvinyl Chloride) is used in pipes, raincoats, handbags, shoes, electric wire insulation, furniture, and toys.
(c) Write the natural or man-made raw material of the following items:
| Item | Material Type |
|---|---|
| Mattress | Man-made (Polyurethane) |
| Glass vessel | Man-made (Silica-based) |
| Bangle | Man-made (Glass, Plastic, or Metal) |
| Chair | Natural or Man-made (Wood or Plastic) |
| Gunny bag | Natural (Jute fiber) |
| Broom | Natural (Grass or Coconut fibers) |
| Knife | Man-made (Steel or Plastic) |
| Pen | Man-made (Plastic or Metal) |
(d) Which are the main ingredients of glass?
- The main ingredients of glass are sand (silica), soda (sodium carbonate), lime (calcium carbonate), and small amounts of magnesium oxide.
(e) How is plastic produced?
- Plastic is made from petroleum and natural gas through a chemical process called polymerization, which links small molecules (monomers) into long chains (polymers).
4. Distinguish between:
(a) Man-made materials and Natural materials
| Man-made Material | Natural Material |
|---|---|
| Materials made by humans from natural resources. | Found naturally in the environment. |
| Examples: Plastic, Glass, Thermocol | Examples: Wood, Cotton, Water |
(b) Thermoplastic and Thermosetting Plastic
| Thermoplastic | Thermosetting Plastic |
|---|---|
| Can be reshaped when heated. | Cannot be reshaped once molded. |
| Example: PVC, Polythene | Example: Bakelite, Melamine |
5. Answer the following in your own words.
(a) Explain the effect and remedial plans of the following materials on the environment and human health.
Plastic
- Effect: Plastic is non-biodegradable and causes pollution, harming wildlife and blocking drainage systems.
- Solution: Use biodegradable alternatives, recycle plastic, and reduce its usage.
Glass
- Effect: Glass takes a long time to degrade and can cause injuries if broken pieces are left in the environment.
- Solution: Recycle and reuse glass items to reduce waste.
Thermocol
- Effect: Thermocol releases toxic gases when burned and is harmful to health and the environment.
- Solution: Avoid using thermocol for packaging and replace it with eco-friendly materials.
(b) Which measures will you take to minimize environmental problems due to non-degradable plastic?
- Use cloth or jute bags instead of plastic bags.
- Recycle and reuse plastic items.
- Encourage the use of biodegradable materials.
- Avoid using plastic cups, plates, and straws.
6. Write short notes:
(a) Glass production
- Glass is made by heating sand (silica), soda, and lime at 850°C – 1500°C.
- The molten glass is cooled quickly to form a transparent, non-crystalline solid.
(b) Optic glass
- Optic glass is pure glass used in making lenses, microscopes, and cameras.
- It is produced from silica, soda, lime, barium oxide, and boron.
(c) Uses of plastic
- Plastic is used in household items, furniture, toys, medical equipment, automobile parts, packaging, and pipes.
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