( ( A gas ) ( is ( ( ( a state ) ( of matter ) ) ( ( in which ) ( the matter ) ) ) ) )
(ROOT (S (NP (DT A) (NN gas)) (VP (VBZ is) (NP (NP (DT a) (NN state)) (PP (IN of) (NP (NN matter))) (SBAR (WHPP (IN in) (WHNP (WDT which))) (S (NP (DT the)) (VP (VBP matter))))))))
A gas is a state of matter in which the matter
(ROOT (S (NP (NNS Gases)) (VP (VBP have) (NP (DT the) (JJS lowest) (NN density))) (. .)))