1. The problem statement, all variables and given/known data I am not necessarily having a problem with a particular homework problem. It is more of a conceptual issue. I have been reading about Carnot engines and refrigerators. In trying to understand the topic better, I did a little more digging and looked up how a refrigerator actually works. There is one aspect that I am not really understanding, and that is how does the compressor of a refrigerator in compressing the gas form of the refrigerant cause the temperature of the compressed gas to increase? Also, how does pressurizing the gas allow it to condense into a liquid as it starts releasing heat into the environment outside the refrigerator even though the temperature it ends up at after releasing heat is still way above its boiling point? 2. Relevant equations 3. The attempt at a solution My best guess is that the compressor does work on the refrigerant by decreasing the volume that the gas occupies and pressurizing it, which adds to the internal energy of the refrigerant and this causes the temperature to increase. As for my second question, my guess is that since the molecules have been forced into this small volume and heat is being released, the molecules being compacted into this tight space start to bond with each other forming a liquid.