Question

9.
Which of the following substances sublime on heating?
(a) sodium chloride
(b) ammonium chloride
(c) sugar
(d) sand
A gas can be best liquefied:
(a) by increasing the temperature (b) by lowering the pressure
(c) by increasing the pressure and lowering the temperature
(d) none of the above is correct
If the external pressure decreases, boiling point of water:
(a) increases
(b) decreases
(c) may increase or decrease
(d) does not change
Water solidifies to ice, then heat is:
(a) absorbed
(b) evolved
(c) no change take place
(d) heat may be evolved or absorbed
In the determination of boiling of water, it is advised to put the bulb of the thermometer above the
water rather than in water. Why?
6.
Explain why naphthalene balls kept in stored clothes in our homes disappear over a period of time
Explain why, there is no rise in temperature of a substance when it undergoes a change of sta
though heat is supplied continuously.
8. Define 'melting point of a substance ? What is the melting point of ice?
Define 'boiling point of a substance? What is the boiling point of water?
10. Why should we wear cotton clothes in summer?
11. (a) Why do we see water droplets on the outer surface of a glass containing ice-cold water?
(b) Which contains more heat: 1 kg of water at 100°C or 1 kg of steam at 100°C? Give a reason
your answer.
12. (a) State the differences between evaporation and boiling,
(b) Explain why:
(1) When the humidity of air is low, then the rate of evaporation is high.
(ii) The rate of evaporation of liquid increases with increasing wind speed.
3. Describe an activity to show that air contains water vapours.
4. (a) Explain briefly interconversion of states of matter on the basis of kinetic theory of gases wit
help of a diagram
(b) The freezing point of a substance is the same as the melting point of its solid state. Justif
statement with the help of a suitable example.
Which one of the following sett of phenomena would increase on raising the temperature ?
(a) Diffusion, evaporation, compression of gases
(b) Evaporation, compression of gases, solubility
(c) Evaporation, diffusion, expansion of gases
(d) Evaporation, solubility, diffusion, compression of gases
Seema visited a Natural Gas Compressing Unit and found that the gas can be liquefied unders
conditions of temperature and pressure. While sharing her experience with friends she got co
Help her to identify the correct set of conditions:​

Answer 1

Answer:

• very very wrong question I think it is not to first one

Answer 2

1 . b. ammonium chloride

2. C. by increasing pressure and lowering temperature

3. b. decreases

4. b. evolved