( ( When ( ( the pressure ) ( is decreased ) ) ) ( , ( ( the volume ) ( increases . ) ) ) )
(ROOT (S (SBAR (WHADVP (WRB When)) (S (NP (DT the) (NN pressure)) (VP (VBZ is) (VP (VBN decreased))))) (, ,) (NP (DT the) (NN volume)) (VP (VBZ increases)) (. .)))
When the pressure is decreased, the volume increases.
(ROOT (S (S (VP (VP (VBG Decreasing) (NP (NP (DT the) (NN volume)) (PP (IN of) (NP (DT a) (NN gas))))) (CC and) (VP (VBG keeping) (NP (NP (NN everything)) (NP (RB else) (DT the) (JJ same)))))) (VP (MD will) (VP (VB cause) (NP (PRP$ its) (NN pressure) (S (VP (TO to) (VP (VB increase))))))) (. .)))