Question

5ml of water was taken in a test tube and a china dish respectively. These samples were then kept under different conditions as below:
A) Both the samples are kept under a fan.
B) Both the samples are kept inside a cupboard.

Answer 1

Hint: Recall the basic definition about evaporation. Think how the rate of evaporation changes in terms of the surface area. Find out how the movement of air influences evaporation.

Complete Step-by-Step solution:
Vaporization is a process in which liquid changes its state by absorbing heat energy and acquiring its gaseous state. It is a change of state process. This happens only at its boiling point.
Evaporation is also a change of state process in which liquids absorb energy from their surroundings or from the atmosphere. This process happens at any temperature. It is a kind of vaporization that occurs only at the surface of the liquid.
It is a very slow process. There are four main factors that affect its rate – surface area, temperature, atmospheric pressure and air movement.
Let us consider the given case separately.

Case a: Here both have the same volume and mass. And they are kept under the same environmental conditions. But as we mentioned earlier the only factor that differs is the surface area of the water. As the surface area increases, the rate of evaporation also increases as there are more surface molecules per unit of volume that are potentially able to escape. So the water in the china dish evaporates faster than that of the water in the test tube.

Case b: Here also both the samples are kept under the same condition. Only the surface area is different. So again the water in the china dish will get evaporated faster compared to that in the test tube.
While comparing cases a and b, the water in the china dish kept under the fan evaporates faster since air is moving faster there compared to case b.

Note: Keep in mind that because evaporation is a very slow process, the water level does not reduce too much in the china dish. Since evaporation does not occur at a fixed temperature, we can see so many examples in our day to day life. For example, as we hang wet clothes they will dry out due to evaporation.