What comes to mind when you hear the word, "thermodynamics"? First law of thermodynamics: Energy conservation applied to the system and its surroundings. In other words, A(_ In equation form, for a closed system (i.e.,_ ) + A(_ ) = 0. where Q = energy due to heat W = energy due to work AU = change in internal energy - energy of molecules internal to a substance - translation, rotation, vibration - remember from Orgo? or PChem? If not, no worries. Q and W are for transfer TO the system FROM the surroundings. Intensive properties do NOT depend on quantity of material. Examples include: and the quantity of material. Examples include: Extensive properties depend on and