( Then ( , ( ( at ( ( 100 degrees ) C ) ) ( , ( ( the water ) ( ( becomes ( ( an ( invisible gas ) ) ( in ( ( ( the air ) , ) ( called ( water vapor ) ) ) ) ) ) . ) ) ) ) ) )
(ROOT (S (ADVP (RB Then)) (, ,) (PP (IN at) (NP (NP (CD 100) (NNS degrees)) (NP (NNP C)))) (, ,) (NP (DT the) (NN water)) (VP (VBZ becomes) (NP (NP (DT an) (JJ invisible) (NN gas)) (PP (IN in) (NP (NP (DT the) (NN air)) (, ,) (VP (VBN called) (NP (NN water) (NN vapor))))))) (. .)))
Then, at 100 degrees C, the water becomes an invisible gas in the air, called water vapor.
(ROOT (S (NP (NNP Water) (NN vapor)) (VP (VBZ exists) (PP (IN in) (NP (NP (DT the) (NN atmosphere)) (PP (IN as) (NP (DT an) (JJ invisible) (NN gas))))))))
Water vapor exists in the atmosphere as an invisible gas