MODEL NOTES ON SCIENCE

1. While heating a liquid, it has to be stirred properly. This is to let:

• the dust particles not settle at the bottom
• the liquid get uniform temperature throughout

2.The boiling point of water at the atmospheric pressure is

• 373 K
• 273 K

3. In the determination of boiling point of water, it is advised to put the bulb of the thermometer above the water rather than in water, it is to:

• reduce the error due to atmospheric pressure
• make sure that boiling point is accurate even when water sample contains non-volatile impurities dissolved

4. To find the melting point of ice what should be taken in the beaker?

• Salt + ice
• Ice cubes
• Crushed ice

5. At 0°C or 273 K, the physical state of water is observed as:

• solid
• liquid
• vapour
• both solid and liquid

6.Water in a container is heated uniformly from 0°C to 100°C. The volume

• increases continuously
• decreases continuously
• decreases upto 4°C and increases further

7.At room temperature a student sets up an apparatus to determine the melting point of ice. He takes a beaker half filled with crushed ice and dips a mercury thermometer in it. After this he would observe that:

• mercury in the thermometer keeps on falling till it reads – 1 °C, it remains constant thereafter
• temperature falls, reaches 0°C and remains constant only as long as both ice and water are present in it

8. What will be boiling point of water at hill stations?

• 100° C
• < 100° C

9. When some common salt is added to water, the boiling point of water

• decreases
• increases

10. When water boils, its temperature

• remains constant
• first increases then decreases