Question

Explain each of the following observations:

(i) water bottles are kept under water during summer.

(ii) a bottle of liquid ammonia is cooled before opening the seal.

(iii) the size of weather balloon becomes larger and larger as it ascends into higher altitudes.

(iv) tyres of automobiles are inflated to lesser pressure in summer than in winter.

Answer 1

1. In summer, the solubility of the gas in water is likely to decrease because the rise in temperature decreases the solubility. Thus, in summer, more of gas will be present above the liquid surface in the glass bottle. To avoid this, the bottles are kept under water.
   
2. The vapour pressure of ammonia at room temperature is very high and hence the ammonia will evaporate unless the vapour pressure is decreased. Cooling decreases the vapour pressure so that the liquid remains in the same state. Hence, the bottle is cooled before opening.
   
3. The reason why the size of a weather balloon increases at higher altitudes is due to the decrease in atmospheric pressure. We know that atmospheric pressure decreases with height. So, pressure at higher altitudes is much lower than the pressure at sea level.
4. According to Gay Lussacs law, at constant volume, pressure of a fixed amount of a gas varies directly with the temperature As the temperature increases, the pressure also increases. In summer, due to the high temperature , the pressure inside the tyre also increases. and thus to prevent the bursting of the tyre, it is inflated to a slightly lesser pressure in summer.