1. The problem statement, all variables and given/known data 400. g of oxygen has a volume of .25 m3 and a pressure of 125,000 Pa. What is the internal energy of the gas? What would the internal energy of the gas be if it were compressed to .10 m3 while the pressure was held constant? 2. Relevant equations U = 3/2 PV 3. The attempt at a solution I got U = 3/2(125,000)(.25) = 46,875 J and when it is compressed it is 3/2(125,000)(.10) = 18,750 J. This seemed too easy and I did a quick web search and found that when it is compressing, the internal energy should increase. My solution shows a decrease in energy after the compression. So I'm not sure what I'm supposed to do beyond just switching my value for volume (or why that wouldn't work)... can anyone help me out?