"Measured heat capacities of solids and liquids are almost always at constant pressure, not constant volume. To see why, estimate the pressure needed to keep V fixed as T increases, as follows. a)First imagine slightly increasing the temp of a material at constant pressure. Write the change in volume, dV1, in terms of dT and the thermal expansion coefficient Beta." There's more to it, but I'll start with just this for now. Beta=deltaV/(VdeltaT), PV=NkT, It says to write in terms of dT and Beta, but I am having a hard time trying to get rid of V when I rearrange as dV1=Beta*V*dT. I am missing something here, I just need a push in the right direction.