Question

When steam condenses it becomes liquid water. When liquid water solidifies it becomes ice. What happens to the temperature of steam while it is condensing, and what happens to the temperature of water while it is solidifying?
A. Temperature of steam while it is condensing - decreases, temperature of water while it is solidifying – decreases
B. Temperature of steam while it is condensing - decreases, the temperature of water while it is solidifying - stays the same
C. Temperature of steam while it is condensing - stays the same, temperature of water while it is solidifying – decreases
D. Temperature of steam while it is condensing - stays the same, temperature of water while it is solidifying - stays the same

Answer 1

Hint: We are asked to state what happens to the temperature of steam when it is undergoing the process of condensation, and solidification. We can start to answer this by defining both processes. This will lead us to our required solution.

Complete answer:
Let us start to answer this question by defining condensation and solidification.
Condensation: It is the process by which the vapours of water become liquid. This is the reverse of the process of evaporation. This happens mainly because of two reasons. Either the vapours cannot hold more water molecules or the air is cooled to its dew point.

Solidification: It is the process by which a liquid becomes solid. Here, the liquid is water.During the process of fusion or condensation, the heat released comes from the increase in the interaction of molecules of water, and not from the cooling of the molecules.This explains that the temperature during phase change remains constant.

Therefore, the correct answer is option D.

Note: The temperature at which liquid turns to solid is called the freezing point of the liquid. Likewise, vapours condense to form liquid at a particular temperature as well. This temperature is known as the condensation point. This point is the same as the boiling point of the liquid. Phase transition from vapours to liquid (condensation) and the phase transition from liquid to vapor (boiling) happens at the same temperature.