( ( By ( lowering ( ( the ( activation energy ) ) ( of ( a ( chemical reaction ) ) ) ) ) ) . )
(ROOT (FRAG (PP (IN By) (S (VP (VBG lowering) (NP (NP (DT the) (NN activation) (NN energy)) (PP (IN of) (NP (DT a) (NN chemical) (NN reaction))))))) (. .)))
By lowering the activation energy of a chemical reaction.
(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))))) (. .)))