Question: If a system does 150 J of work on the surroundings and absorbs 100 J of heat, what is the change in internal energy?
Options:
-50 J
50 J
100 J
250 J
Correct Answer: -50 J
Solution:
Using the first law, ΔU = Q - W = 100 J - 150 J = -50 J.
If a system does 150 J of work on the surroundings and absorbs 100 J of heat, wh
Practice Questions
Q1
If a system does 150 J of work on the surroundings and absorbs 100 J of heat, what is the change in internal energy?
-50 J
50 J
100 J
250 J
Questions & Step-by-Step Solutions
If a system does 150 J of work on the surroundings and absorbs 100 J of heat, what is the change in internal energy?
Step 1: Identify the work done by the system on the surroundings. In this case, it is 150 J.
Step 2: Identify the heat absorbed by the system. Here, it is 100 J.
Step 3: Recall the formula for the change in internal energy (ΔU) which is ΔU = Q - W.
Step 4: Substitute the values into the formula. Q (heat absorbed) is 100 J and W (work done) is 150 J.
Step 5: Calculate ΔU: ΔU = 100 J - 150 J.
Step 6: Perform the subtraction: 100 J - 150 J = -50 J.
Step 7: Conclude that the change in internal energy (ΔU) is -50 J.
First Law of Thermodynamics – The first law states that the change in internal energy (ΔU) of a system is equal to the heat added to the system (Q) minus the work done by the system on the surroundings (W).
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