Final answer:
Gibbs free energy represents the potential work excluding volume expansion that can be performed by a system undergoing a spontaneous process. A negative ΔG during methane combustion suggests the release of free energy that could, in theory, be converted to work such as electrical work, despite most energy being liberated as heat.
Step-by-step explanation:
Understanding Gibbs Free Energy and Spontaneity
The Gibbs free energy (G) is a thermodynamic potential that is a measure of the maximum amount of non-expansion work that a system can perform at constant temperature and pressure as it reaches equilibrium.
When considering a spontaneous process, such as the combustion of methane, a negative ΔG indicates that the process can release free energy which can be harnessed to do work.
It is important to note that the 'work' here refers to work other than volume expansion against external pressure, such as electrical work or osmotic work.
While it may not be immediately obvious how a spontaneous combustion reaction like methane's can perform work, the release of free energy during such a process could, in theory, be coupled with a mechanical or electrical device to convert some of that energy into useful work.
In practice, however, most of the energy is released as heat. The key point is that a negative Gibbs free energy symbolizes the possibility of doing work, even if it is not always utilized or converted into work in every scenario.
Moreover, Gibbs free energy is not a conserved quantity, which means that while it always decreases in a spontaneous process, this does not imply there is a compensatory increase in energy elsewhere.
It signifies a redistribution of energy, aligning with the second law of thermodynamics, which stipulates that the entropy of the universe increases with spontaneous processes.
Thus, we see that ΔG is closely related to the entropy change of the world and reflects the energy that can be 'freed' to do work, excluding energy lost as heat and contributing to increased entropy.