This is to help me understand a problem in the book, I don't want to state the question I'm attempting to solve though I would rather just get a nudge in the right direction conceptually. (I am analyzing an isotherm and adiabatic curve at the same point.) My book states that for an ideal gas, an adiabatic curve at any point is always steeper than an isotherm passing through the same point: why is this? Also, the question I'm given does not explicitly state that I'm dealing with an ideal gas, is the ratio of heat capacities still valid for a van der waals gas (which is the only other type of gas that I know how to deal with)? What about the rule i stated above concerning the slopes at a particular point?