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Reviewed CSCA Physics question · Easy

A gas in a cylinder absorbs 700 J of heat from its surroundings. During the process, the gas expands and does 250 J of work on the piston. What is the change in internal energy of the gas?

  1. 450 J
  2. 950 J
  3. -450 J
  4. 250 J
Show the answer and explanation

Correct answer

A. 450 J

Principle or equation

First law: ΔU = Q - W, where Q is heat added to the system and W is work done by the system.

Why this answer is correct

ΔU = 700 J - 250 J = 450 J.

Example

If Q = 500 J and W = 200 J, ΔU = 300 J.

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