Final answer:
In chemistry, a negative ∆H value means that a reaction releases heat (exothermic), and a negative ∆G value indicates a spontaneous reaction that releases free energy (exergonic). Positive values for these variables indicate heat absorption and non-spontaneous reactions, respectively.
Step-by-step explanation:
The ∆H value of a reaction represents the heat exchange that occurs with the reaction under specific conditions. When a reaction has a negative ∆H value, it indicates that heat is released by the system, making the reaction exothermic. Conversely, a positive ∆H value means heat is absorbed by the system, making the reaction endothermic.
The ∆G value, or Gibbs free energy change, indicates the spontaneity of a reaction. A negative ∆G value signifies that a reaction is spontaneous or exergonic, meaning it can proceed without any input of energy; the system releases free energy. On the other hand, a positive ∆G suggests that the reaction is non-spontaneous, or endergonic, and will not occur without an input of energy.
In summary, a negative sign in both ∆H and ∆G indicates energy release from the system. With a negative ∆H, the reaction releases heat (exothermic), and with a negative ∆G, the reaction releases free energy and proceeds spontaneously (exergonic).