Question

Different liquids have different evaporating rates.explain with reference to ether and alcohol

Answer 1

In order to turn into a gas the molecules held together inside the liquid have to break free to get into the air. This means the hydrogen bonds holding the molecules together need to be broken. Thus, molecules that are able to form lots of hydrogen bonds among themselves are much harder to turn into a gas and have a higher heat of evaporation. This also affects the boiling temperature of a liquid. Molecules that attract one another very strongly start to boil at higher temperatures compared with those that have weak attractions. A lower boiling point generally means a liquid will evaporate more quickly. Water, for example, with one oxygen and two hydrogen atoms, can form two hydrogen bonds per molecule. Its heat of evaporation is 2,260 joules per gram, or 541 calories per gram, and it starts boiling at 100 degrees Celsius (212 degrees Fahrenheit).

Your body makes use of the evaporative process when sweating. Sweat, which consists of 90 percent water, starts to evaporate. The necessary heat of evaporation is extracted from the sweat itself, which leads to a heat transfer from the liquid into the gaseous state. This results in a cooling effect (called evaporative cooling) that helps to maintain body temperature and cools the body down when it gets too hot. The degree of cooling is dependent on the evaporation rate and heat of evaporation. In this activity you will find out which liquid has a greater cooling power: rubbing alcohol or water.