Question

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

liquid water freezing into ice
vaporization of liquid mercury
solid metal melting to form a liquid
sublimation of dry ice into carbon dioxide gas

Answer 1

which of these represents a state of matter where the average distance between molecules decreases?

Answer 2

a change in state of matter*

Answer 3

Is she lost?

Answer 4

since entropy is degree of randomness or disorder in the system, it means that the more chaotic a system becomes the more is the entropy. Imagine the molecules as crazy cows running around everywhere (LOL!) now to control them you have to confine them.
another hint is that decrease in the regularity of the structure would mean increase in entropy. for example, a crystalline solid state is the state of lowest entropy and gaseous state is the state of highest entropy :D
therefore, by understanding this concept, LIQUID WATER FREEZING INTO ICE involves decrease in the entropy.

Answer 5

Thank you guys!!