( ( As ( ( the volume ) ( is constant ) ) ) ( , ( ( ( the increase ) ( in ( ( the temperature ) ( of ( the gas ) ) ) ) ) ( ( causes ( ( a rise ) ( in ( its pressure ) ) ) ) . ) ) ) )
(ROOT (S (SBAR (IN As) (S (NP (DT the) (NN volume)) (VP (VBZ is) (ADJP (JJ constant))))) (, ,) (NP (NP (DT the) (NN increase)) (PP (IN in) (NP (NP (DT the) (NN temperature)) (PP (IN of) (NP (DT the) (NN gas)))))) (VP (VBZ causes) (NP (NP (DT a) (NN rise)) (PP (IN in) (NP (PRP$ its) (NN pressure))))) (. .)))
As the volume is constant, the increase in the temperature of the gas causes a rise in its pressure.
(ROOT (S (SBAR (WHADVP (WRB When)) (S (NP (NP (NN temperature) (NNS increases)) (PP (CC but) (NP (NP (NN amount)) (PP (IN of) (NP (NP (NN gas)) (CC and) (NP (PRP$ its) (NN pressure))))))) (VP (VBP are) (ADJP (JJ constantvolume))))) (NP (NNS increases)) (VP (VBZ happens) (PP (TO to) (NP (NP (DT the) (NN volume)) (PP (IN of) (NP (DT the) (NN gas)))))) (. .)))