( ( ( The condition ) ( that ( ( the system ) ( is ( mechanically isolated ) ) ) ) ) ( ( ( is necessary ) ( ( in order ) ( to ( ensure ( it ( ( does not ) ( ( exchange energy ) ( with ( ( any ( external object ) ) ( besides ( the ( heat bath ) ) ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (DT The) (NN condition)) (SBAR (IN that) (S (NP (DT the) (NN system)) (VP (VBZ is) (ADJP (RB mechanically) (VBN isolated)))))) (VP (VBZ is) (ADJP (JJ necessary)) (SBAR (IN in) (NN order) (S (VP (TO to) (VP (VB ensure) (SBAR (S (NP (PRP it)) (VP (VBZ does) (RB not) (VP (VB exchange) (NP (NN energy)) (PP (IN with) (NP (NP (DT any) (JJ external) (NN object)) (PP (IN besides) (NP (DT the) (NN heat) (NN bath)))))))))))))) (. .)))
The condition that the system is mechanically isolated is necessary in order to ensure it does not exchange energy with any external object besides the heat bath.
(ROOT (S (NP (DT A) (JJ sealed) (, ,) (JJ vacuum-insulated) (NN reaction) (NN flask)) (VP (VBZ approximates) (NP (NP (DT the) (NN condition)) (PP (IN of) (NP (NP (DT a) (VBN isolated) (NN system)) (, ,) (SBAR (WHPP (IN in) (WHNP (WDT which))) (S (NP (CC neither) (NP (NN matter)) (CC nor) (NP (NN heat))) (VP (MD can) (VP (VB be) (VP (VBN exchanged) (PP (IN between) (NP (NN system) (CC and) (NNS surroundings)))))))))))) (. .)))
A sealed, vacuum-insulated reaction flask approximates the condition of a isolated system, in which neither matter nor heat can be exchanged between system and surroundings.