( ( For atoms ) ( , ( ( ( the change ) ( of ( kinetic energy ) ) ) ( ( changes ( ( ( their size ) and ) ( ( the ( inter ( atomic distance ) ) ) ( in molecules ) ) ) ) . ) ) ) )
(ROOT (S (PP (IN For) (NP (NNS atoms))) (, ,) (NP (NP (DT the) (NN change)) (PP (IN of) (NP (JJ kinetic) (NN energy)))) (VP (VBZ changes) (NP (NP (PRP$ their) (NN size)) (CC and) (NP (NP (DT the) (JJ inter) (JJ atomic) (NN distance)) (PP (IN in) (NP (NNS molecules)))))) (. .)))
For atoms, the change of kinetic energy changes their size and the inter atomic distance in molecules.
(ROOT (S (NP (NP (DT The) (NN sum)) (PP (IN of) (NP (NP (DT the) (JJ kinetic) (CC and) (JJ potential) (NNS energies)) (PP (IN of) (NP (NP (DT a) (NN system) (POS 's)) (NNS atoms) (CC and) (NNS molecules)))))) (VP (VBZ is) (VP (VBN called) (NP (JJ internal) (NN energy)))) (. .)))