( ( Energy ( and ( chemical ( reactions ( Chemical reactions ) ) ) ) ) ( ( require energy ) . ) )
(ROOT (S (NP (NNP Energy) (CC and) (JJ chemical) (JJ reactions) (NNP Chemical) (NNS reactions)) (VP (VBP require) (NP (NN energy))) (. .)))
Energy and chemical reactions Chemical reactions require energy.
(ROOT (S (NP (NP (DT The) (NN amount)) (PP (IN of) (NP (NP (NN energy)) (VP (VBN required) (S (VP (TO to) (VP (VB begin) (NP (DT a) (JJ chemical) (NN reaction))))))))) (VP (VBZ is) (VP (VBN known) (PP (IN as) (NP (DT the) (NN activation) (NN energy))))) (. .)))