What exactly is energy? Is it defined as the motion of molecules?
One way to define energy as the ability to do some amount of work, and the amount depends on how much energy you have. The energy of molecular motion is also known as heat, and is a form of kinetic energy. Other forms energy include (but are not limited to): 1) photons (electromagnetic energy) 2) kinetic energy as in the case of a mass that has some relative velocity to you. 3) potential energy (think of a large mass suspended on a cable… if the mass falls it gains kinetic energy and loses potential energy) 4) Nuclear energy … energy in the form of mass. E = mc^2 – I’m sure you’ve seen that formula! 5) Excited atom state energy where one or more of an atom’s electrons are occupying “orbits” outside of its ground state. When an excited atom returns to a lower energy state, it gives off energy in the form of photons. So this is really a type of potential energy.
