What is evaporation? Explain four factors which affect the rate of evaporation.
VerifiedHint: When molecules of some liquid present near the surface absorb enough heat energy they will cross the vapour pressure barrier and change into a gaseous state.
Complete Step By Step Answer:
Evaporation is a type of vaporization that occurs on the surface of the liquid when it changes from its liquid state to gaseous state. For this to occur the gas surrounding the liquid should not be in saturation with the evaporating substance. When the liquid molecules collide with each other, they transfer energy from one to another depending on how they collide with each other. Any molecule will enter the gas phase and escape if it absorbs energy enough to overcome the vapour pressure.
In short, evaporation is the process where any substance gets converted from liquid to gaseous state by the use of heat energy.
Since heat is absorbed during evaporation, it is an endothermic process.
Some examples of evaporation are: salt production, crystallization, drying of clothes, water evaporates into water vapour, etc.
-Any changes in the state of a substance occur due to either increase or decrease in temperature, due to which the molecules either speed up or slow down. In solids, the molecules vibrate against each other since they are widely packed, in liquids they move freely and in gases they move around widely in great spaces.
-Now we will talk about factors affecting evaporation. They are:
(1) Temperature: With an increase in temperature, the rate of evaporation also increases. This means that the rate of evaporation is proportional to temperature.
$\text{Rate of evaporation} \propto Temperature$
(2) Humidity: With an increase in humidity, the rate of evaporation will decrease since there is a capacity of the environment to hold moisture. This means that the rate of evaporation is inversely proportional to humidity.
$\text{Rate of evaporation} \propto \dfrac{1}{{Humidity}} $ .
(3) Surface area: With an increase in surface area, the evaporation rate will also increase since there are more molecules available at a time for evaporation. This means they are proportional to each other.
$\text{Rate of evaporation} \propto \text{Surface area}.$
(4) Wind speed: With an increase in wind speed, evaporation also increases. Hence they are also proportional to each other.
$\text{Rate of evaporation} \propto \text{Wind speed}.$
Note:
Evaporation along with condensation and precipitation is an important step in earth’s water cycle. 90% of the moisture present in the earth’s atmosphere is due to evaporation, while the rest 10% is due to transpiration. Since 70% of the earth’s surface is covered by oceans, they are the main source of water in the atmosphere and evaporation of this ocean water is important for freshwater production.
