( ( Internal energy ) ( ( is ( ( ( ( the ( total energy ) ) ( of ( ( all ( the molecules ) ) ( within ( a substance ) ) ) ) ) ; ) ( ( the sum ) ( of ( ( ( ( ( their ( average ( translational kinetic ) ) ) , ) ( rotational kinetic ) ) and ) ( potential energies ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNP Internal) (NN energy)) (VP (VBZ is) (NP (NP (NP (DT the) (JJ total) (NN energy)) (PP (IN of) (NP (NP (PDT all) (DT the) (NNS molecules)) (PP (IN within) (NP (DT a) (NN substance)))))) (: ;) (NP (NP (DT the) (NN sum)) (PP (IN of) (NP (NP (PRP$ their) (JJ average) (JJ translational) (NN kinetic)) (, ,) (NP (JJ rotational) (NN kinetic)) (CC and) (NP (JJ potential) (NNS energies))))))) (. .)))
Internal energy is the total energy of all the molecules within a substance; the sum of their average translational kinetic, rotational kinetic and potential energies.
(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)))) (. .)))