January 2019 Chemistry Regent
During which phase change does the entropy of a sample of H2O increase?
(1) H2O(g) → H2O(l)
(2) H2O(g) → H2O(s)
(3) H2O(l) → H2O(g)
(4) H2O(l) → H2O(s)
Answer and Explanation:
Entropy represents disorder in chemistry. Universe wants to be as disordered as possible and therefore increasing disorder, or entropy, is favorable. Now, lets lookout phases to figure out what is more disordered. Between solid, liquid, and gas, solid is the lease disordered phase and gas is the most disordered phases.
Now, let's look at the answer choices. The first choice is g to l, or gas to liquid. This should result in a decreases of entropy since liquid is less disordered than gas. The second choice is also a decreases in entropy since solid is less disordered than gas. The third choice goes from liquid to gas. This choice results in an increase of entropy and is therefore the correct answer choice.
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