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): Matter and heat can not be exchanged between a system and it's surroundings in an isolated system like a sealed and vacuum insulated reaction flask.