Imagine you are holding an apple. Does this apple have energy? how do you know?

- - The apple has heat energy. If its temperature were Absolute Zero,

then the skin on my hand would freeze instantly and fall off.

- - The apple has potential energy, relative to the ground. If I were to

release it out of my hand, gravity would do work on it and pull it with

some speed to the ground, where it would have the kinetic energy to

break some blades of grass and dig a small crater in the soil.

- - The apple has chemical energy which, if I were to expose it to

human digestion and metabolism by eating it, would change to

glucose, soak into my muscles, and make itself available to me

whenever I need vim and vigor, mental alertness, visual acuity,

and the wherewithal to to escape any unexpected beast that might

in turn set upon me with the intention of converting MY entire person

into food energy for its own use.