Question

1. In a colorimetry, why is refrigerated water is better than tap water?

2. "The heat transfer of thermal energy to matter usually leads to an increase in temperature". Why not 'always' rather than 'usually'?

3. Several objects lying side by side on a table will not feel equally cool to touch even though they are at the same temperature. Explain.

Answer 1

1) Refrigirated water is at a lower temperature than water. So the temperature difference will be more and therefore the rate of heat transfer will also be more. So it will be easier to measure any quantities when the heat transfer rate is more.

2) Heat tranfer doesnot always mean increase in temperature because when a substance undergoes phase change, it will still require heat energy but the temperature will not change. For example, water turns to steam at 100^o C but for this we still need to heat the water.

3) Different objects at same temperature will not be felt equally cool because the rate of heat transfer from each substance is different. For example when you touch a metal at 50 ^oC you will feel it is very hot but if you touch a wooden piece at that same temperature it will feel cool or normal because wood doesnot conduct heat as fast as metal. That's why it is also difficult to heat wood than to heat a metal.