You should explore at least one of these resources before continuing. The amount of change in each of these functions depends only on the beginning and the final states, not on the path followed during the change. Their value depends on the path by which a system gets from the initial state to the final state. D U is positive. This would be an endergonic reaction.
D U is negative.
This would be an exergonic reaction. J Again, the negative value indicates work was done by the system. Enthalpy equals internal energy plus the product of pressure and volume. In an exothermic reaction the products have less enthalpy than the reactants. In an endothermic reaction the products have more enthalpy than the reactants.