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In a thermodynamic process, a gas does 150 J of work on the surroundings while absorbing 350 J of heat. Calculate the change in internal energy of the gas using the first law of thermodynamics and state the sign conventions used.
Model answer
What a good answer should say
- Using the first law of thermodynamics, the change in internal energy (ΔU) is calculated as ΔU = Q - W.
- Here, Q = 350 J (heat absorbed) and W = 150 J (work done by the gas).
- Thus, ΔU = 350 J - 150 J = 200 J.
- The sign convention used is that heat added to the system is positive and work done by the system is positive.
Explanation
Why this works
This answer effectively demonstrates the application of the first law of thermodynamics with correct sign conventions. It tests the ability to analyze energy transfers in thermodynamic processes.
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