( That ( ( is ( ( the energy ) ( producing ( chemical reaction ) ) ) ) . ) )
(ROOT (S (NP (DT That)) (VP (VBZ is) (NP (NP (DT the) (NN energy)) (VP (VBG producing) (NP (NN chemical) (NN reaction))))) (. .)))
That is the energy producing 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))))) (. .)))