( ( ( ( ( ( Water vapor ) ( is ( an ( invisible gas ) ) ) ) , ) but ) ( ( ( the clouds ) ( of ( condensed ( water droplets ) ) ) ) ( ( ( ( ( refract and ) disperse ) ( the ( sun light ) ) ) and ) ( so ( are visible ) ) ) ) ) . )
(ROOT (S (S (NP (NNP Water) (NN vapor)) (VP (VBZ is) (NP (DT an) (JJ invisible) (NN gas)))) (, ,) (CC but) (S (NP (NP (DT the) (NNS clouds)) (PP (IN of) (NP (JJ condensed) (NN water) (NNS droplets)))) (VP (VP (VBP refract) (CC and) (VBP disperse) (NP (DT the) (NN sun) (NN light))) (CC and) (VP (ADVP (RB so)) (VBP are) (ADJP (JJ visible))))) (. .)))
Water vapor is an invisible gas, but the clouds of condensed water droplets refract and disperse the sun light and so are visible.
(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