( ( A ( chemical substance ) ) ( ( is ( burned ( in ( air ( in ( a ( confined vessel ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT A) (NN chemical) (NN substance)) (VP (VBZ is) (VP (VBN burned) (PP (IN in) (NP (NP (NN air)) (PP (IN in) (NP (DT a) (JJ confined) (NN vessel))))))) (. .)))
A chemical substance is burned in air in a confined vessel.
(ROOT (S (NP (NP (DT The) (NN action)) (PP (IN of) (S (VP (VBG burning) (NP (NP (DT a) (NN piece)) (PP (IN of) (NP (NN wood)))))))) (VP (VBZ forms) (NP (DT a) (JJ different) (NN chemical) (NN substance))) (. .)))