This macromolecule is a source of short-term energy.

carbohydrates

Energy Content

As a result, your body tends to use fat to store energy over long periods of time and uses carbohydrates to store energy short-term.

Explanation:

before, trains worked using the steam engine. thus, it uses heat so it is crucial to apply heat balance. the steam engine absorbs energy during the stage of boiling water. so, this is the endothermic reaction. when the steam is used to work the piston, it has to release this energy through running the train. the excess energy is released as an exhaust to the chimney. this is the exothermic process because it releases energy to the surroundings.