( ( At ( higher temperatures ) ) ( it ( ( may ( become ( ( ( a liquid ) or ) ( a gas ) ) ) ) . ) ) )
(ROOT (S (PP (IN At) (NP (JJR higher) (NNS temperatures))) (NP (PRP it)) (VP (MD may) (VP (VB become) (NP (NP (DT a) (NN liquid)) (CC or) (NP (DT a) (NN gas))))) (. .)))
At higher temperatures it may become a liquid or a gas.
(ROOT (S (NP (NNS Gases) (CC and) (NNS liquids)) (VP (VBP become) (NP (NNS solids)) (PP (IN at) (NP (JJ low) (NNS temperatures)))) (. .)))
Gases and liquids become solids at low temperatures.