A phenomenon where an energetically unfavorable reaction (endergonic) is driven by a favorable one (exergonic), allowing the overall process to occur.
A chemical reaction that requires energy input; like needing courage to get on that scary roller coaster.
A chemical reaction that releases energy; similar to your friend's excitement about the roller coaster.
The energy in a system available for work; think of it as the combined courage and excitement between you and your friend which allows you both to enjoy the ride!