The first law of thermodynamics may be expressed as shown: ∆U=Q+W Where ∆U is the change of internal energy, Q is the heating of the system, W is the work done on the system. A fixed mass of ideal gas at high pressure is contained in a balloon. The balloon suddenly bursts, causing the gas to expand and cool. In this situation, which row describes the values of ∆U, Q and W?
Correct answer: B. B
- A. A
- B. B
- C. C
- D. D
Explanation
As the gas expands, W is negative, also ∆U decreases and gas expand. There is no heat supplied to the system. The cooling occurs because of expansion.
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About First Law of Thermodynamics
The first law relates heat supplied, work done and the change in internal energy through energy conservation. Problems use sign conventions and apply the law to isothermal, adiabatic, isobaric and isochoric processes. Internal energy is a state function, while heat and work depend on the path followed.
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