Which of the following phase changes involves a decrease in entropy?

vaporization of liquid mercury

solid metal melting to form a liquid

condensation of water vapor to form dew

sublimation of dry ice into carbon dioxide gas

condensation of water vapor to form dew

Explanation:

Entropy is generally defined as degree of randomness. More the randomness in a system more its entropy.

If a system goes from a more random state to less random state then its entropy is said to be decreased.

In a physical process when the following leads to decrease in entropy

a) change from gas to liquid

b) change from gas to solid

c) change from liquid to solid

Increase in entropy:

a) change form solid to liquid

b) Change from solid to gas.

c) change from liquid to gas.

In the given examples condensation of water vapor to dew is is the change of gas to liquid thus the entropy will decrease.