Words used to describe energy
The topic of energy needs to be visited many times with a gradual increase in the sophistication and depth of the teaching. As there is no convenient definition of energy for beginners, the concept needs to develop slowly until students can write about energy without making mistakes; putting the right words into the right places. It benefits from a spiral approach to teaching.
As a first introduction you can show some interesting demonstrations concerned with energy transfer, which will prepare the ground for a fuller discussion. (See the experiments Jobs needing food or fuel, Moving energy from one thing to another 1 and Moving energy from one thing to another 2.)
Energy should not get a reputation among students as a magic word that will answer any question about why things happen. Students know a lot about food and what it does for them. They are interested in climbing hills, hauling up loads, shoving things along and in engines and what they will do. An informal approach to energy can be made by linking students’ natural knowledge of food and fuels with their interest in those activities.
To keep the language simple at the start, you might wish to use the following vocabulary:
- ‘Spring’s energy’ or ‘elastic energy’ instead of the more formal 'elastic strain energy', for the energy held in a stretched spring.
- ‘Uphill energy’ rather than the more formal 'gravitational potential energy', for the energy transferred to a raised brick.
- ‘Light energy’ rather than 'radiation' for the energy transmitted by a lamp, as the word radiation may mean very little to students. Light energy refers not only to the visible parts of the electromagnetic spectrum but also to the invisible parts.
- 'Motion energy’ for a moving object rather than the more formal 'kinetic energy'.
- ‘Spin energy’ for the motion of spinning things rather than the more formal 'rotational kinetic energy'.
- ‘Electrical energy’ for the energy stored in the space around electrical charges which will later be extended to electromagnetic energy.
- `Chemical energy' for energy released from fuels and food. This could also be called 'molecular energy'.
- `Molecular' energy for the energy stored in intermolecular bonds which changes when melting occurs.
- `Nuclear energy' (‘atomic energy’) which is stored deep inside every atom and is released in nuclear reactions, e.g. the decay of radioactive atoms.
As students progress then these simple descriptors will generalize into two labels: stored or potential energy and moving or kinetic energy.
'Electrical energy' is better avoided when it refers to the energy transferred by an electric current. Here it is simply a method of energy transfer; just like 'work' is the energy transferred when potential energy is transferred to kinetic energy.
Energy transfers are often more important than energy itself. If we haul bricks to the top of a building then the useful thing is that we have raised the bricks higher up. That was done by transferring energy from chemical energy stored in a fuel to the uphill energy stored in the raised bricks.
Indeed, machines built during Britain's industrial revolution to transfer the energy released by burning fossil fuels more and more efficiently, continue to change newly ‘industrialized’ societies for ever. This is most evident currently with economic growth in India and China.