Thermodynamics!! Need help for AP test in 40 minutes! Lets say that you have a gas that starts at an initial pressure P, volume V, and temperate T. Then it undergoes an isothermal expansion, during with pressure decreases and volume increases. What is the work done BY the gas during the transition? What is the work done ON the gas during the transition? Now, if I want to do this with integrals (i.e. area under the curve), for work done BY the gas, would it be the POSITIVE AREA under the curve?