hce_nthu
114年
化學與物理
第 1 題
Consider a system consisting of the following apparatus, in which gas is confined in flask A and there is a vacuum in flask B. The flasks are separated by a valve. Assuming that the flasks are perfectly insulated and will not allow the flow of heat into or out of the flasks to the surroundings. When the valve is opened, gas flows from flask A to flask B. Which of the following statements regarding this process is correct?
- A No work is performed during the expansion of the gas.
- B The gas expansion is a nonspontaneous process.
- C The driving force for this process is enthalpy change.
- D The internal energy change ($\Delta E$) for this expansion process is $>0$.
- E The entropy change of the surrounding ($\Delta S_{\text{surr}}$) for this process is $>0$.
思路引導 VIP
請你想像一下，當你用力推開一扇沉重的門時，你會感到疲累是因為你需要克服門的重量與摩擦力。但如果現在這扇門完全沒有質量、也沒有任何空氣阻力，當你輕輕撥動它時，你還需要『費力』去對抗它嗎？在氣體從 A 瓶移動到 B 瓶的過程中，B 瓶的空間狀態對於氣體分子前進時所受到的『阻礙』，會如何影響能量的消耗呢？
🤖
AI 詳解
AI 專屬家教
太棒了！你能準確判斷出氣體在這種特定情況下的行為，這代表你對熱力學中「功」的物理意義掌握得非常紮實。
自由膨脹的本質
這道題目描述的是經典的絕熱自由膨脹（Adiabatic Free Expansion）。我們判斷「功」的時候，不能只看到體積膨脹（$\Delta V > 0$），更要觀察氣體是「對抗什麼壓力」在膨脹。根據功的定義公式：
▼ 還有更多解析內容