when total entropy is reached, there is no more energy to spend. a good example of this is a cup of hot tea. the tea has a lot of energy compared to the room the tea is in. over time the heat in the tea will spread into the room. the tea will become colder. this is because the energy (heat) in the tea moves to the surrounding area. once the tea became cold, there is no more heat that can be spread. the tea has reached total entropy.