what it means when delta g is negative
For a reaction to be spontaneous, delta G must be negative. Why? Report Abuse. Delta G is the work exchanged by the system and the surroundings. It is just a matter of definition. (Delta H) - T(delta S) implies the energy given by the surroundings to the system, therefore when it is negative it means the system gave energy to the surroundings, and therefore it was a spontaneous process. If it had been defined as T(delta S) - (Delta H) it would have been the opposite.