Thermodynamics 1st Law First Law-Energy Conservation (1)Energy cannot be created or destroyed. (2)Total energy of the universe is constant Math representation △U=Q-W AU:(+) means increase of the Systems energy (means decrease of the Systems energy Q: (+)means the System absorbs heat, i.e. endothermic (means the Systems gives of heat, i.e. exothermic W: (+) means the System does work to the Surroundings (means the Surroundings does work to the System 9Thermodynamics 1st Law  First Law – Energy Conservation  (1) Energy cannot be created or destroyed. (2) Total energy of the universe is constant.  Math representation:  ΔU = Q – W  ΔU: (+) means increase of the System’s energy; (-) means decrease of the System’s energy.  Q: (+) means the System absorbs heat, i.e. endothermic; (-) means the Systems gives of heat, i.e. exothermic.  W: (+) means the System does work to the Surroundings; (-) means the Surroundings does work to the System. 9