Energy Models In Teaching and Assessment

Why are there two different energy models? 

Why are there two types of language used to talk about energy? 

In science, we often use models to describe and explore complex concepts. We use models because they are simplified, containing only the details that are relevant to understanding the concept. There are two main models that are used to describe energy transfers; the transform model and the transfer model. 

The transform model of energy

The transform model is the older way of describing energy transfers. The idea behind it is that there are different ‘types’ of energy (which is not true – energy is energy): electrical, light, sound, elastic, kinetic, gravitational, nuclear, magnetic, chemical, and thermal or heat energy, and that these energy types can be ‘transformed’ or ‘converted’ into different types or forms of energy.

The transfer model of energy

The transfer model is the newer way of describing energy transfers. The idea behind it is that objects store energy in energy stores; these are elastic potential, kinetic, gravitational potential, nuclear, magnetic, chemical, electrostatic and thermal stores. Energy can be transferred from store to store via transfer pathways: electrically, mechanically, by heating or by radiation. 

Why was the energy model changed?

Educational experts all over the world were noticing that students were accumulating lots of misconceptions in their understanding of science. This was a problem because it made it much harder for students to unlearn and relearn concepts at all levels of education. And if left unaddressed, those misconceptions negatively impact their ability to make informed decisions about science-related issues throughout their lives (for example, medicine and healthcare, the environment, nutrition, transport, energy, the list goes on…).

A group of international experts in science education had a big conference in 2009 in which they compiled a list of the 14 Big Ideas of Science that they felt every student needed to be taught in order to ‘enable them to understand the scientific aspects of the world around them and make informed decisions about the applications of science’. Energy is one of these Big Ideas.

In England, a new National Curriculum (2014) was developed to raise standards of education, which was followed by a new exam structure (grades 9–1) and an increase in the difficulty of GCSE subjects. The language of the new National Curriculum for Science reflected the language used in the Big Ideas of Science and the transfer model for energy recommended by the Head of Education at the Institute of Physics.

The issues with the transform model are that it treats energy as an actual substance (which it is not), and that tracking the energy ‘conversions’ throughout a process doesn’t actually tell us anything useful. With the transform model, the description of energy is only used as an introduction to calculations, and the emphasis is shifted towards the more useful aspects of knowing how much energy is required to do something, or how efficient the process is. So, with the subsequent release of new exam board specifications for GCSE and then IGCSE, the focus of the energy questions shifted.

Why is the language so confusing?

The problem with the change in energy terminology was that until a few years’ worth of exam papers were released, nobody could be sure of the exact way the questions would be asked, or the exact wording that would be awarded marks. This was a confusing time to be learning or teaching about energy! Over the years, we, as teachers and content writers, have learnt how it works. But there are still many textbooks that either use the older transform language or use the language of both models interchangeably. And unfortunately, the A Level specifications are generally yet to make the swap, so you may learn about energy stores in GCSE and then energy types at A Level, or more likely you will meet a blended version of the two.

In my experience, it is not the change in language that is the difficult bit, it's changing the way you think about energy that is hard. I was lucky; I did my undergraduate teaching degree at the time these changes were taking place, so I learnt to teach using the transfer model. All the already established teachers had to unlearn and relearn how they thought about and taught about energy, which was a difficult thing to do.

What do you need to know to ace your energy exam questions?

Exam specifications are not the most exciting reads, but I would advise you to read the section on energy so that you know the exact terminology to use. You don’t see too many questions now on describing energy transfers, but if you do get one, there are lots of examples in our Energy Transfers Revision Notes.

There are two main ways to describe energy transfers using the transfer model:

1. Energy is transferred from the …………. store to the …………. store.

2. Energy in the …………. store decreases as energy in the …………… store increases.

The vast majority of exam questions now will focus on energy calculations and efficiency. Work done is a force applied over a distance, but work done is also equal to the amount of energy transferred, so you will often see this used as a mathematical link between the topics of forces and energy in exam questions.

If you see the language of ‘types’ of energy, or names of energy such as ‘sound energy’ or ‘electrical energy’, those are from the old transform model. If energy that gets ‘transformed’ or ‘converted’, you guessed it, that’s from the transform model. 

A bit of advice from me

Try not to get hung up over the language. Stick with what your specification uses for the exam. But embrace the transform model in the way you think about energy. I always tell my students that energy is like the currency of the universe. It can be stored for a time in different stores in an object (like you store money in your bank account), but it will inevitably be transferred (like when you buy something, or pay a bill). Whenever changes happen, large or small, energy is transferred. Some changes cost energy; energy needs to be transferred into the system, like melting ice to liquid water. Some changes pay out energy; energy is transferred away from the system, like freezing water into ice. But the most amazing thing about energy (so amazing that it made it onto the Big Ideas list) is that the total amount of energy in the universe is constant. That means it can never be created or destroyed; it is transferred around the universe from store to store, from object to object, making possible all the wonderful changes and events that occur in the whole universe, from an excited electron jumping to a new energy level, to a massive star exploding in a supernova. 

My hope is that by understanding why and how the way we think about energy has changed, you will be able to successfully navigate the terminology, avoid the misconceptions, and achieve that fully rounded understanding of science that we, as educators, aim to provide.