What happens to energy once it has been used?

No it has not been destroyed. It is years since I did physics, but it was clear that energy cannot be created or destroyed, it is just there. The heat is absorbed by objects as is light. This energy is stored in these objects. Think about when you boil a kettle. You have the electrical energy being used by the kettle. What happens to this electrical energy? It is converted to heat energy. Then what happens to this heat energy? It is absorbed by the water. What happens to the heat energy in the water? It is then absorbed by cooler things like the surrounding atmosphere. I think these absorbtions are called "potential energy" as it is possible to retrieve the energy from them. When you throw a rock into the air you use kinetic energy to force it into the air. As it rises in the air against gravity it is building up potential energy. Once the kinetic energy you gave the rock is used up, it reaches the highest point and starts to fall back down. Finally it will hit the ground. Energy will be given out here as sound, kinetic (vibrations from the rock hitting the ground), heat (the vibrations will cause tiny amounts of heat). Note that the rock will also have friction with the air going both up and down and this will release heat and possibly sound energy. It is a bit if a ramble, but hope some of it made sense.

Electrical energy can go to movement, heat light etc. energy. This energy then usually goes to heat.

Your teacher is right, energy cannot be destroyed. It should be pointed out that heat energy or light energy is not 'used', it is transferred or changed to a different kind of energy. I think this is is the part you're stuck on. For example, when your warm hand touches an ice cream cone, heat energy moves from your hand to the ice cream because of heat equilibrium, which a fancy way to say heat balancing. That's an example of heat energy moving as heat energy to another object. But there's also changing energy, for example light energy to heat energy. An example of this is a camp fire. You see the flames and feel the heat coming from the fire. The fire is bright and a source of light. This is the light energy. The heat that you feel is the same light energy that's been transformed into heat energy. I hope that makes sense.

When energy is "used" it is converted wholly or partly to another form of energy or and/or work. For example, heat can be used to vaporize water to steam. This means that the internal energy of water is increased. Now this increased energy of water can be used to turn the blades of dynamo (mechanical energy) which in turn causes the generation of electricity. The electricity then is used to run various electric appliances, machines, etc. Here, energy transformation takes place: heat, internal energy, mechanical energy, electrical energy, light, sound, radiant energy, etc. If we take this to the extreme, we know from Einstein theory of relativity that energy and matter under proper conditions can be converted into each other. This is what his famous equation means: E = mc^2 Under this situation, mass is considered as another form of energy. It is called mass energy. Hence, we have what we called the Conservation of Mass/Energy. Hope this helps. teddy boy

Energy is just a flow and your teacher is right. If you burn a paper it produce heat energy and light energy. The heat energy will then remains as heat energy. light energy will remains as light energy.

I suppose everything must go through physical or chemical change somethings can be reversed while others cannot, they are simply changed into other matter, hence chemical change.

instead of the energy being destroyed in a matter of speaking all it does is it changes into a different form of energy, such as light to heat, and heat to light and so on. it is a never ending cycle

Energy can neither be produced nor destroyed. Therefore, it converts to other forms of energy after its utilization.

It hasn't been destroyed because energy can not be destroyed. There is a set amount of energy in the universe. Whenever someone moves, whenever a light is switched on, energy is used up in the form of light, kinetic, heat, etc. Eventually in trillions of years, there will be no energy left in the universe!!