Task: Paraphrasing
Input (English): Question: A sealed, vacuum-insulated reaction flask approximates what condition, in which neither matter nor heat can be exchanged between system and surroundings? 
Answer: isolated system. 
Sentence: 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.
Output (English): When a scientist needs to make sure that energy and/or matter cannot be echanged between a system and the surroundings, they use a sealed, vacuum-insulated reaction flasks, to create an isolated system, which approximates these conditions..