A chemical reaction which is associated with a release of energy and thus, is associated with a negative free energy change is said to be an exergonic reaction.
An exergonic reaction owing to the negative free energy change is a spontaneous reaction.
The energy that is released in the exergonic reaction is usually observed in the form of heat and light.
The energy is released due to the breaking of the chemical bonds.
Therefore, on burning of the firewood the bonds between the glucose molecules break up which leads to the release of energy in the form of heat and light and this is thus, an example of an exergonic reaction.
