Question

When water freezes, its molecules take on a more structured order. Why doesn't this contradict the Second Law of Thermodynamics?

• A. Because the density of the water is decreasing
• B. Because the water is gaining entropy as it goes from liquid to solid state
• C. Because the waters internal energy is decreasing
• D. Because the surroundings are losing entropy
• E. Because the surroundings are gaining entropy

Answer 1

The correct option is E Because the surroundings are gaining entropy

The Second Law of Thermodynamics tells us that the total amount of disorder, or entropy, in the universe is increasing. The entropy in a particular system can decrease, as with water molecules when they turn to ice, but only if the entropy in the surroundings of that system increases to an equal or greater extent. The Second Law of Thermodynamics holds, but only because the surroundings are gaining entropy, so the correct answer is E . Answer D refers to the key part of the answer, but gives the wrong information about the change in entropy of the surroundings.
Answer C is not correct. This is an explanation for why the water does not lose heat when it freezes: it is, in fact, losing internal energy. This is an instance of the First Law of Thermodynamics, which states that the change in a systems internal energy is equal to the value of the heat transfer in the system minus the work done by the system.