( ( ( the ( chemical energy ) ) ( released ( by ( this reaction ) ) ) ) ( ( is ( what ( powers ( the machine ) ) ) ) . ) )
(ROOT (S (NP (NP (DT the) (JJ chemical) (NN energy)) (VP (VBN released) (PP (IN by) (NP (DT this) (NN reaction))))) (VP (VBZ is) (SBAR (WHNP (WP what)) (S (VP (VBZ powers) (NP (DT the) (NN machine)))))) (. .)))
the chemical energy released by this reaction is what powers the machine.
(ROOT (S (NP (NP (DT The) (NN rate)) (SBAR (IN that) (S (NP (NN energy)) (VP (VBZ is) (VP (VBN released)))))) (VP (VBZ is) (VP (VBN known) (PP (IN as) (NP (NN power))))) (. .)))