sentence2_structure: vacuum-insulated reaction flask<>approximates<>the condition of a isolated system$$$neither matter nor heat<>can be exchanged<>a isolated system
sentence1: The cryostat measures the heat flow through different insulation systems at various vacuum levels.
sentence2: 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.
question: A sealed, vacuum-insulated reaction flask approximates what condition, in which neither matter nor heat can be exchanged between system and surroundings?