What is energy's form what form does it make?

Answer 1

Energy is not an easy thing to define, but it can be described as the capability to do work. When energy is used, work results. Work in the scientific sense means the result of a movement against a force. Thus in the SI system of units, work is in Joules, and a Joule is defined as a movement of 1 meter against a force of 1 Newton. Imagine a piston in a cylinder with a push-rod which is connected to an object which exerts a force of 1 Newton towards the piston. If the cylinder is filled with gas at pressure, it contains energy because work had to be done to pressurise the gas. Now if the piston is allowed to move against the force of 1 Newton by a distance of 1 meter, it does work of 1 Joule, and that work has resulted from the energy stored in the gas in the cylinder. Actually 1 Joule is a small quantity, but the example illustrates the process.

Energy can be thermal as well as mechanical, in this case the unit is the Calorie or BTU