Question

can someone anwser this question please. in graphing enthalpy entropy and state changes which two variables are included ? A. volume and temperature B. amount of heat added and temperture C. pressure and volume D. amount of heat added and pressure

Answer 1

Probably b but not sure tho

Answer 2

B. Although, due to the PV=NkT relationship I could also see C being a viable option. It is dependent on what you are looking at (dS/dP, dS/dT...).

Answer 3

Generally you'll be looking at heat added and how that affects the temperature. To help illustrate, lets look at a system, a simple ice cube. So we can control the amount of energy we put into the ice cube by increasing the heat by putting the ice cube on the stove. At first the ice cube will stay solid and start raising in temperature until eventually it will reach 0 degrees Celsius.

At this point, you will keep adding energy into it by heat, but this will not change temperature! Instead, that energy will be used to change the state from solid to liquid. From there you'll heat up your liquid from cold water to hot water until you eventually get to 100 degrees Celsius and do an almost identical thing. You will add heat and the temperature will not rise, instead it will take in that extra heat and use it to change states from liquid to a gas!

This is generally why we look at heat vs temperature, because we can look at the areas where temperature does not increase when we add heat and see how much energy it takes to change between states of matter!