Q. Explain why—if a highly pumped up bicycle tyre is left in the hot, it may burst.
A. All gases expand on heating. When a highly pumped up bicycle tyre is left in the hot, there occurs considerable increase in the volume of the air. As sufficient space for the expansion of the air is not available (because bicycle tyre is already highly pumped), it may result in bursting of the tyre.
Q. Why does a thermometer kept in boiling water show no change of temperature even when the water is continuously heated?
A. A liquid boils at a particular temperature called the boiling point of the liquid. Once the liquid starts boiling, the thermometer reading remains constant, because there is no further increase in temperature. The quantity of heat supplied is being utilised as latent heat in converting the liquid at boiling point into vapour at the same temperature. That is why a thermometer kept in boiling water shows no change of temperature even when the water is continuously heated.