Page 190 - ICSE Chemistry 8

2. Water present in oceans and seas is unfi t for consump on and other uses like washing, irriga on
and industrial purposes.

3. A crystal of alum is used for cleaning muddy water.
4. With decrease in pressure, the boiling point of water decreases.
5. With increase in pressure, the boiling point of water increases.

6. The survival of aqua c animals in cold regions is a ributed to anomalous expansion of water.
7. Water is used as a coolant in car engines, factories, nuclear reactors, etc.
8. Water is a universal solvent.

9. Hygroscopic substances are used as drying agents.
10. Permanent hardness of water cannot be removed by simple means such as boiling.

C. Answer in short.
1. What is groundwater?

2. What is potable water?
3. How can water be purifi ed at home?
4. What is anomalous expansion of water?
5. What is solubility?

6. What is tyndall eff ect?
7. What do you understand by the term ‘water of crystallisa on’?
8. What are hygroscopic substances? Give examples.

9. What happens when metals react with steam?
10. What are the disadvantages of hard water?

AT LENGTH

A. Diff eren ate between the following.

1. Sedimenta on and fi ltra on
2. Saturated solu on, unsaturated solu on and supersaturated solu on
3. True solu on, suspension and colloid

4. Hydrated salts and anhydrous salts
5. Hard water and so water

B. Read the following paragraph. Iden fy the incorrect parts.

To observe the forma on of scum in hard water and so water
• Pour 1 cup of tap water in a bo le and add a teaspoon of copper sulphate to it. Then add a few
drops of liquid detergent.
• Screw the bo le cap ghtly. Hold the bo le vigorously for 10 minutes.

• In the other bo le, pour 2 cups of tap water and add a few drops of liquid detergent in it.
• Screw the bo le cap ghtly and shake the bo le well for 10 minutes.

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