( ( A liquid ) ( ( ( becomes ( a gas ) ) ( if ( ( its temperature ) ( is increased ) ) ) ) . ) )
(ROOT (S (NP (DT A) (NN liquid)) (VP (VBZ becomes) (NP (DT a) (NN gas)) (SBAR (IN if) (S (NP (PRP$ its) (NN temperature)) (VP (VBZ is) (VP (VBN increased)))))) (. .)))
A liquid becomes a gas if its temperature is increased.
(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.