Lets go back to the basics of chemistry. Delta G is change in energy (or “Gibbs free energy”). If ΔG is positive, you need to add energy to make a reaction happen. Look at this flowering plant. Through photosynthesis, this plant is converting energy from the sun, and carbon dioxide, into chemical energy that the plant can use (in the form of carbohydrates). This process is “positive ΔG”– sunlight is needed for photosynthesis to occur.
Say you walk into your office’s break room at 4:30 PM and find some cake sitting on the table. This cake is full of fat and sugar, and if you eat it, your body will digest it. Through biochemical reactions, the cake’s energy will be stored as fat (adipose tissue). Adipose provides an enormous storage capacity of energy in the form of triglycerides. If you eat cake frequently, you will be in a stage of positive ΔG, and you will gain weight. Eventually, you may develop diabetes, like 26 million Americans.
But if you exercise, you burn that stored energy. Negative ΔG is good for our bodies!
Now think about the combustion of fossil fuels and the release of greenhouse gasses (negative ΔG). Human activities are filling up Earth’s atmosphere with carbon dioxide, leading to global warming.
It all comes down to ΔG.