Sentence:  A <WSD>liquid</WSD> can freeze to become a solid or evaporate into a gas. 
Meaning of the word marked with <WSD> tags:  A substance that is flowing, and keeping no shape, such as water; a substance of which the molecules, while not tending to separate from one another like those of a gas, readily change their relative position, and which therefore retains no definite shape, except that determined by the containing receptacle; an inelastic fluid.