a) Enumerate the change that takes place in a liquid during evaporation.
b) How is rate of evaporation affected by change in the following? Justify your answer.
i) Temperature ii) Wind speed iii)Humidity
Answers
Answer:
a) The change of liquid into vapour without reaching its boiling point is called Evaporation. The kinetic energy of molecules at the surface of the liquid increases when exposed to some temperature. Due to the increased kinetic energy the molecules overcome the force of attraction between the particles of the liquid
b) evaporation is directly proportional to temperature and wind speed . inversely proportional to humidity because in atmosphere there is more amount of water .
The rate of evaporation is affected by wind, temperature, area of exposed surface and humidity is as follows:
1) Wind - When water evaporates, the air surrounding it gets saturated by it. Wind increases the rate of evaporation by quickly removing the saturated air thereby allowing more evaporation to occur.
2) Temperature - As temperature increases, rate of evaporation also increases.
3) Area of exposed surface - Evaporation is a surface phenomenon. Only the water of exposed surface changes from liquid state to gaseous state, thus as the area exposed increases, rate of evaporation also increases.
4) Humidity - It is the measure of amount of water vapour present in air. Evaporation increases with a decrease in humidity If the temperature increases and the wind speed and humidity stay constant, then the rate of evaporation will increase since warmer air can hold more water vapor than colder air.