Question

Explain how water’s entropy can decrease when it freezes without violating the second law of thermodynamics. Specifically, explain what happens to the entropy of its surroundings.

Short answer

The second law of thermodynamics is not violated in this situation because water increases the entropy of the surroundings.

Step-by-step solution

Describe how water’s entropy decreases when it freezes.

The particles are loosely arranged in the water. So, the particle will be in random motion and the entropy will be high. Because entropy is the measure of randomness. When water freezes, the particles will come closer together and motion will be restricted. As a result, entropy decreases.

Describe how the entropy changes as the gas liquify.

According to the second law of thermodynamics, entropy won’t decrease in a process, but it can increase or remain constant in a process that occurs in the universe. So, entropy in the system and surroundings has to be considered. Even though entropy decreases as the water freezes, it doesn’t mean that the total entropy of the universe has decreased.

Only the entropy of the system decreased in this case, and as water freezes, it emits energy into the surrounding environment. The particles in the surrounding environment gains energy and move in random motion, resulting in an increase in entropy in the surrounding. So, the entropy will remain constant or increase in this case.

Thus, when water freezes, it gives more energy to the environment and reduces entropy without violating the second law of thermodynamics.