Energy: its forms, and how it moves around
Energy is never made or destroyed — it only changes form or moves from one place to another. Once you can track it, you can explain almost any machine or process.
Energy is the ability to make things happen — to move, heat, light, or sound. You can't see it directly, but you can always track where it goes, and that's the skill this topic is really testing.
The forms energy comes in
| Store | Where you find it |
|---|---|
| Kinetic | Anything moving |
| Gravitational | Anything lifted up high |
| Chemical | Food, fuel, batteries |
| Thermal | Hot objects |
| Elastic | Stretched or squashed springs |
| Light & sound | Given out by lamps, speakers |
The one law that runs the whole topic
Energy cannot be created or destroyed. It can only be transferred from one store to another, or moved from place to place.
This is the law of conservation of energy, and it's the thread through every question. When something happens, energy doesn't appear or vanish — it changes form. Your job is to say which store it came from and which it went to.
Tracking a transfer
Follow the energy through a few everyday examples:
- A falling ball: gravitational store → kinetic store (it speeds up as it drops).
- A car braking: kinetic store → thermal store (the brakes get hot).
- A torch: chemical store (battery) → light and thermal stores.
Every one of these is the same idea: energy moving from one labelled box to another, with the total staying the same.
Wasted energy
In real machines, some energy always ends up somewhere useless — usually as heat from friction. It isn't destroyed (the law forbids that); it's just spread out into the surroundings where we can't use it. That's why no machine is ever efficient.
Name the start and end stores. For any "explain the energy changes" question, write it as an arrow: chemical → kinetic → thermal. Examiners give marks for naming the stores correctly, and the arrow keeps you from missing one.
Last revised 20 March 2025.