( and ( ( in gases ) ( ( the ( ( atoms and ) molecules ) ) ( ( are ( free ( to ( ( ( move independently ) , ) ( colliding frequently ) ) ) ) ) . ) ) ) )
(ROOT (S (CC and) (PP (IN in) (NP (NNS gases))) (NP (DT the) (NNS atoms) (CC and) (NNS molecules)) (VP (VBP are) (ADJP (JJ free) (S (VP (TO to) (VP (VB move) (ADVP (RB independently)) (, ,) (S (VP (VBG colliding) (ADVP (RB frequently))))))))) (. .)))
and in gases the atoms and molecules are free to move independently, colliding frequently.
(ROOT (S (PP (IN Within) (NP (DT a) (NN substance))) (, ,) (NP (NP (NNS atoms)) (SBAR (WHNP (WDT that)) (S (VP (VP (VBP collide) (ADVP (RB frequently))) (CC and) (VP (VBP move) (ADVP (RB independently)) (PP (IN of) (NP (CD one) (DT another)))))))) (VP (VBP are) (ADJP (ADJP (RBS most) (JJ likely)) (PP (IN in) (NP (DT a) (NN gas)))))))