Question

Give reasons for the following :
(i)- Air is dense at sea level
(ii)- Evaporation causes cooling
(iii)- Alcohol evaporates faster than air​

Answer 1

( i ) When water molecules are added to a given volume of air, the dry air molecules must decrease by the same number, to keep the pressure or temperature from increasing. Hence the density decreases.

( ii ) Evaporation causes cooling because the process requires heat energy. The energy is taken away by the molecules when they convert from liquid into gas, and this causes cooling on the original surface.

( iii ) As alcohol evaporates at a much faster rate compared with water due to its lower boiling temperature (82 compared to 100 degrees C), it is able to carry away more heat from the skin. This means for a given amount of time much more alcohol evaporates than water.

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