As a substance changes from a liquid to a gas, the average distance between molecules...?

Question

1) decreases
2) increases
3) remains the same

and why? Thanks :)

Answer 1

Increases (and considerably too). The conversion from liquid to gas requires energy, which allows the molecules to "spread out". However, the density change is about the order of 1000, which means that the average distance is about 10 times more in a gas than in a liquid.