Implication of heat content

[kenhung123]

So when the change in heat content of reactants and products is negative/positive, could we say there is a net loss (negative) or net gain (positive) of energy in the chemical reaction? (assuming the enclosed system is not part of the chemical reaction?)

[Mao]

You mean if the change in enthalpy of the system (reactants and products) is negative, the surroundings must have gained energy, and vice versa.

[kenhung123]

Umm yea, but alternatively could you say the chemical reaction results in a net production of heat in an exothermic?

[Martoman]

if its negative think of the thing as losing heat, and if it loses heat then it must give it off in some way. This is always exothermic.

Obviously the converse holds. If there is a net gain of heat then the product has gained heat. This must mean it absorbed it from somewhere, usually in the solvent it is reacting in (think of the ice packs the afl use to treat injuries the "snap" ones, they are endothermic as they absorb heat).