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## Homework Statement

Imagine some helium in a cylinder with an initial volume of 1 liter and an initial pressure of 1 atm. Somehow the helium is made to expand to a final volume of 3 liters, in such a way that its pressure rises in direct proportion to its volume.

(b) calculate the work done on the gas during the process, assuming no other types of work being done.

(c) calculate the change in the helium's energy content during this process.

(d) calculate the amount of head added to or removed from the helium during this process.

## Homework Equations

W = - integral PdV

delta U = Q + W

## The Attempt at a Solution

I know that the final pressure will be 3 atm since the pressure is directly proportional to the volume.

So I found the work done in going from the initial state (1 atm, 1 L) to the final state (3 atm, 3 L) by doing the integral above. This works out to be -4 J.

But I have no idea how to find the change in the internal energy. I figure you need to know the heat added or removed from the system and I don't know how to do that either. I guess once I can understand part c, then I can get part d, or vice versa.

Any ideas?

Thanks a lot for any help.