( ( Because ( ( ( the density ) ( of ( ( water changes ) ( as ( the temperature ) ) ) ) ) drops ) ) ( , ( ice ( floats . ) ) ) )
(ROOT (S (SBAR (IN Because) (S (NP (NP (DT the) (NN density)) (PP (IN of) (NP (NP (NN water) (NNS changes)) (PP (IN as) (NP (DT the) (NN temperature)))))) (VP (VBZ drops)))) (, ,) (NP (NN ice)) (VP (VBZ floats)) (. .)))
Because the density of water changes as the temperature drops, ice floats.
(ROOT (S (NP (NNP Density)) (VP (VBZ allows) (SBAR (S (NP (NN cut)) (VP (VBZ logs) (S (VP (TO to) (VP (VB float) (PP (IN on) (NP (NN water)))))))))) (. .)))