“Something with a lot of energy will kill you.”
This has stayed with me from my PGCE course at Swansea University, many years ago. It was said by Frank Banks, the course tutor, in response to the question “What’s the simplest way to describe energy?”
And as pithy descriptions of energy go, it’s not half-bad. A small stone, dropped from the top of a skyscraper: lots of energy before it hits the ground — it could kill you. A grand piano, dropped from six feet above your head: lots of energy — it could kill you. Licking your fingers and touching the bare live and neutral wires in a socket: the conduction electrons in your body suddenly acquire a lot of energy — and yes, they could kill you. (With alternating current, of course, the electrons that will kill you are already inside your body — freaky!)
This attention-grabbing definition of energy seems to lead naturally to a more formal definition of “Energy is the capacity to do work“. This still leaves the problem of defining work, of course, but as R. A. Lafferty once said, that’s another and much more unpleasant story.
As I mentioned in an earlier post, I have been writing the Energy scheme of work for GCSE Science. As part of that brief, I wrote a short summary for my science colleagues of the IoP’s new approach to energy. I present it below without much amendment (or even a proper spellcheck) in the hope that someone, somewhere, at some time — may find it useful 🙂
The problem with teaching energy
One reason for the difficulty in deciding what to say about energy at school level is that the scientific idea of energy is very abstract. It is, for example, impossible to say in simple language what energy is, or means. Another problem is that the word ‘energy’ has entered everyday discourse, with a meaning that is related to, but very different from, the scientific one. [ . . .]
This ‘forms of energy’ approach has, however, been the subject of much debate. One criticism is that pupils just learn a set of labels, which adds little to their understanding. For example, one current textbook uses the example of a battery powered golf buggy. It asks pupils to think of this in the following terms:
Chemical energy in the battery is transformed into electrical energy which is carried by the wires to the motor. The motor then transforms this into kinetic energy as the buggy moves.
This, however, adds nothing to the following explanation, which does not use energy ideas:
The battery supplies an electric current which makes the motor turn. This then makes the buggy move.
A good general rule when explaining anything is that you should use the smallest number of ideas needed to provide an explanation, and not introduce any that are unnecessary
Energy – a new hope (!)
The new approach to the teaching of energy developed by the Institute of Physics (IoP) suggests that we limit our consideration of energy to situations where we might want to do calculations (at KS4, KS5 or beyond).
We should talk of energy being stored and shifted. The emphasis should be on the start and end of the process with minimal attention being given to any intermediate stages.
Consider the following examples:
- lifting an object. Chemical potential energy store is emptied, and gravitational potential energy store is filled (note that we are not interested in intermediate motion as it doesn’t affect the final energy store).
- rolling an object down a slope to the bottom. Gravitational potential energy store is emptied and thermal energy stores (of slope, of pen) increased.
- Boiling water in kettle. Chemical store (from coal/gas power station) is emptied. Thermal store of water increased, thermal store of air increased, thermal store of kettle increased.
[Examples taken from http://scientistshavesaid.blogspot.co.uk/2013/02/teaching-energy.html]
The new approach has been adopted by all UK exam boards for their new specs and is used in the AQA approved textbooks.
The following energy stores are considered: kinetic energy store, gravitational potential energy store, elastic potential energy store, thermal energy store, chemical potential energy store, nuclear energy store, vibrational energy store, electromagnetic energy store (note: the last is limited to situations involving static electric charges and static magnetic poles in magnetic fields).[NB Items in bold are those required for GCSE Combined Science.]
One major difference is that electric current and light are no longer considered as forms of energy. Rather, these are now regarded as means of transferring energy.
Rise of the Enojis
[Image from http://www.supportingphysicsteaching.net/En02PN.html]
I suggest these energy icons should be called enojis (by analogy with emojis).
Probably the biggest adjustment for most teachers will be to avoid referring to light and sound as forms of energy and to treat them as pathways for transferring energy instead.
“Energy is the new orange” and summary
More (much more!) on the IoP’s “energy as an orange liquid” model can be found at http://www.supportingphysicsteaching.net/En02TL.html and http://www.supportingphysicsteaching.net/En02PN.html.