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, H being enthalpy. If the enthalpy, or total energy, of the products is greater than the energy of the reactants, then ΔH is positive and it is an endothermic reaction. If the energy of the products is less than the energy of the reactants, ΔH is negative and the reaction is exothermic.
Delta refers to the change between the final and the initial of value. When you have a negative delta H this is due to the fact that you have lost enthalpy, so it makes sense that the reaction would be exothermic (give off heat). The reverse is true for a reaction with positive delta H. It is an endothermic reaction.
This is how Dr. Lavelle explained it. Positive delta H signifies that it is endothermic which means energy is being put into the system. Negative delta H is exothermic which means energy is leaving the system. In this way, you can rationalize the positive and negative better as gain and loss of energy from the system.
H stands for enthalpy. So delta H represents the change in enthalpy during a reaction. If delta H is positive then the reaction requires energy and is endothermic. If delta H is negative then the reaction releases energy and is exothermic.
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