Question

What happens to the entropy of water when the ice cubes are made?
A. increases
B. decreases
C. does not change
D. may either increase or decrease which depends upon the process used.

Answer 1

Hint: The entropy function is defined as a numerical measure of the irreversibility of a given process. This means that it is a measure of disorderness of a system. During formation of ice cubes the molecules are getting arranged in a specific manner. These details will help you in solving the question.

Complete answer:
As we all know that the water is a liquid. A liquid is having a random arrangement of the molecules in it. Which means that the molecules are loosely packed in the liquid phase. When it is made into ice cubes, the phase of the water is changing from the liquid state to solid state. In a solid, generally the molecules are closely packed and well arranged. So when the water is changed from the liquid state to the solid state, the arrangement of the molecules is varying. Entropy is defined as the measure of the thermal energy of the system per unit temperature that is not available for doing useful work. This is because that the work has been measured from ordered molecular motion, the amount of entropy can be defined also as the measure of the molecular disorder otherwise called as randomness of a system. So as the disorderness decreases from liquid state to the solid state, the entropy is also decreasing.

So, the correct answer is “Option B”.

Note:
Water is having a higher entropy than the ice and so the entropy will prefer melting. But ice has a smaller energy than water and therefore the energy favours freezing. Therefore, as the surroundings are becoming hotter, they are gaining more energy and hence the entropy of the surroundings is also increasing.