Energy is none of these. Elements, compounds and mixtures are all forms of matter. Energy isn't matter, as it doesn't have mass or occupy space.
Energy is defined as the ability to do work or change something. Work is done when a force applied to an object causes the object to move in the direction of the force. Some common forms of energy are:
- Electrical energy - the energy of moving electrons
- Chemical energy - the energy stored in compounds
- Gravitational potential energy - the energy an object has due to its height, for example a rock falling from a greater height has more energy than a rock falling from a lower height.
- Kinetic energy - the energy of motion
- Thermal energy - heat
- Radiant energy - light
Energy can be changed from one form to another, for example when fuel burns its stored chemical energy is transformed to thermal and radiant energies (heat and light.)
The Law of Conservation of Energy states that energy is neither created nor destroyed. This is also known as The First Law of Thermodynamics.