( ( ( ( Note ( that ( ( all ( of them ) ) ( are ( ( ( ( soft ( -LRB- ( ( cut ( with ( a ( butter knife ) ) ) ) -RRB- ) ) ) , ) ( low density ) ) ( -LRB- ( ( Li ( ( ( floats ( on oil ) ) , ) ( ( ( Na and ) K ) ( float ( on water ) ) ) ) ) -RRB- ) ) ) ) ) ) ) , ) ( ( very reactive ) metals ) ) . )
(ROOT (S (VP (VP (VB Note) (SBAR (IN that) (S (NP (NP (DT all)) (PP (IN of) (NP (PRP them)))) (VP (VBP are) (ADJP (ADJP (JJ soft)) (PRN (-LRB- -LRB-) (VP (VBN cut) (PP (IN with) (NP (DT a) (NN butter) (NN knife)))) (-RRB- -RRB-)) (, ,) (ADJP (RB low) (JJ density)) (PRN (-LRB- -LRB-) (S (NP (NNP Li)) (VP (VBZ floats) (PP (IN on) (NP (NN oil))) (, ,) (S (NP (NNP Na) (CC and) (NNP K)) (VP (VB float) (PP (IN on) (NP (NN water))))))) (-RRB- -RRB-))))))) (, ,) (NP (ADJP (RB very) (JJ reactive)) (NNS metals))) (. .)))
Note that all of them are soft (cut with a butter knife), low density (Li floats on oil, Na and K float on water), very reactive metals.
(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)))))))))) (. .)))