1 Some common misunderstandings about energy

When students try to make sense of a new situation, they draw on everyday experience and on ideas that have worked well for them before. Teachers may recognise some of these ideas as ‘not scientific’ or ‘not the accepted explanation’. But as long as these ideas are able to predict what will happen, then students will use them.

These ‘misunderstandings’ are not like equations or definitions that have been learnt incorrectly. Misunderstandings can be the result of explanations that students have been given by other people (sometimes a much-loved and respected relative or teacher). Sometimes they are explanations that the student has constructed for themselves. Alternatively, these explanations were appropriate for earlier classes but are no longer relevant for more complex ideas and topics.

There is often a lot of ‘common sense’ appeal about these ideas, but the problem is that using them is going to be unhelpful in work in secondary school science. These ideas can act as a barrier to understanding the accepted models of science.

For example, many people think that insulation ‘makes things warm’ because they have observed that wearing thick clothing on a cool evening makes them feel warmer. This could lead to an incorrect prediction as in this situation:

Figure 1 A thin glove and a thick glove. Which is warmer on the outside surface?
  • Incorrect prediction: The sensor placed on the outside of the thick glove (see Figure 1) will show a higher temperature than the one on the thin glove because a thick glove will make the hand warmer. Thick gloves are warmer so the surface of the glove will be at a higher temperature.
  • Correct prediction: The sensor placed on the thick glove will show a lower temperature because the thick glove slows down the transfer of energy from the warm hand to the cold surroundings more than the thin one does. The outside of the thick glove will still be relatively cool.

Case Study 1: Misunderstandings about energy

Mr Gupta attended a training session at the local DIET. Instead of sitting and listening to the trainer, the group members were asked to take part in a number of activities.

Last week I attended a training session about common misunderstandings in science. The trainer started by asking us to work in groups of three, where one of us was a physics specialist, one a chemistry specialist, and another a biology specialist. The trainer gave us three questions to consider, one about each subject. We had to think about each question on our own and then share our ideas, with the subject specialist listening to the others before offering their ideas.

The physics question we had to think about was: ‘A spacecraft is going to be sent out on a long voyage beyond our solar system. It has a powerful rocket engine with large fuel tanks. Why does it need a lot of fuel and what will happen when the fuel is used up?’ I’m a biology specialist, and it was interesting (and a bit scary) to share ideas about this! I said that you would need fuel to get away from Earth and propel the spacecraft over the huge distance it would need to travel. Once the fuel was used up, the spacecraft would slow down and stop, so if there wasn’t enough fuel it might be stranded in the middle of space.

My physics colleague explained that the large fuel tanks were needed for the launch stage to break away from the Earth, and that some relatively small motors are needed for the main part of the voyage. In deep space there is no air resistance or strong gravitational pull to overcome, so a spacecraft does not need fuel to keep it at a steady chosen velocity – only to change speed or direction.

I felt a bit embarrassed when I realised my misunderstanding, but the trainer told us that lots of people have the same idea as I had. It was a relief when she told us this and also when the physics teacher had difficulty with the biology question about plants, food and photosynthesis. Neither of us was stupid; it was just that we were trying to explain something unfamiliar using models based on everyday experiences, and we needed to use accepted models of science to correctly explain what happened.

Pause for thought

  • What answer would you have given to the ‘spacecraft’ question, and why?
  • Can you think of any misunderstandings that you have noticed your students have shown in the ‘energy and work’ topic?

You can find some more examples of common misunderstandings about energy in Resource 1.

Everyone has misunderstandings of science topics, or understandings that are different to the scientific models in the curriculum. You may find it surprising that teachers can have misunderstandings about their own specialist subject, too! They often only realise this when they see a question about something that they haven’t studied or taught before, or if an idea is presented in an unusual, unfamiliar context.

Although this can seem embarrassing, a good teacher will appreciate that they have learnt something important and improved their own understanding. It will also help them to be aware of the potential problem for students, and plan to identify and deal with it.

Activity 1: Common misunderstandings in your students’ work

This activity will help you to plan for teaching about work and energy. You will need Resource 1 for this activity, plus a set of sticky note labels.

Read through the list of common misunderstandings in Resource 1. Which of these have you met before in your students’ work on this topic?

Now read through the Class IX textbook chapter on work and energy. As you read, look for any misunderstandings in Resource 1 that might be relevant to the chapter. Every time you identify a possible misconception, write it down on a sticky label and put it next to the relevant section of the textbook. You may find that some possible misunderstandings are relevant several times, while others don’t seem so likely to be relevant. Do not worry about finding a match for every section or for every misunderstanding! The purpose of this activity is to alert you to some of the common misunderstandings, so you can be ready to notice them when they occur. It is much easier to recognise something when you know what you are looking for!

In the next section you will learn about ways of probing your students’ understanding. The techniques described here work for any topic area. The key resource ‘Assessing progress and performance [Tip: hold Ctrl and click a link to open it in a new tab. (Hide tip)] ’ will also be helpful.

Why this approach is important

2 Finding out about your students’ understanding of work and energy