Resource 2: Some ways of eliciting your students’ ideas about energy and work

There are a several strategies – such as focused questioning, group discussions and poster presentations – that you might use in order to find out what prior ideas students have and the misunderstandings that students may hold.

Below are some other examples, with comments. The key point about using any of these strategies is to encourage students to share their ideas with you and with other students: the discussion that goes into producing a diagram is more important than having a neat or colourful diagram with impressive artwork!

Predict and explain

Give students a simple scenario and ask them to say what will happen next and why they think that. As an example, consider a ball on a U-shaped track (Figure R2.1).

Figure R2.1 A ball on a U-shaped track.

Predict what will happen when the ball is released. Explain your answer.

Comment

Many students will be able to make a correct prediction about what will happen to a ball on a U-shaped track, but fewer of them will be able to explain this prediction correctly in terms of energy conservation and transfer.

The ball should roll down the track and up the other side until it is at the same height as it was released from: the higher the ball is, the more potential energy it has, so the highest point it can climb to will have the same potential energy as it started with. The ball loses potential energy as it falls, but gains kinetic energy, so it is moving fastest (i.e. using the most kinetic energy) at the bottom of the curve, where it has the least potential energy.

The ball should continue rolling up and down the track indefinitely and reaching the same maximum height each time, if (and only if) there is no energy transferred to its surroundings due to air resistance or friction with the track. If energy is transferred to the surroundings, then each time the ball climbs up the track, it will climb to a slightly lower level than before. Its maximum potential energy will be less each time and it will eventually settle to a stop at the bottom of the curve.

It is important to ask for a prediction and an explanation. In an unfamiliar situation, students have to draw on their scientific understanding to make a prediction. But if you use a situation that students have met before, they may be able to make a correct prediction based on memory rather than understanding. Unless you ask for an explanation as well as a prediction, it may not be obvious that your students do not understand the underlying science.

Card sorts (‘True/false/unsure’ card sort)

Prepare a set of cards for a topic. Each card has a short statement on it such as ‘Using a lever saves you energy’. Students must decide if each statement is true or false, or if they are not sure. They should sort the cards into separate groups for each category. It is helpful to include pairs or groups of related statements in the set of cards you provide, to help pick out where the misconception may be. For example:

• ‘Using a lever makes it easier to lift something heavy because saves you energy.’
• ‘Using a lever makes it easier to lift something heavy because it lets you use a smaller force.’

Comment

Card sorts let you see very quickly what ideas students have as you walk round the classroom. They are also a ‘low threat’ activity, since there is no permanent record of choices.

‘Traffic Lights’

The ‘Traffic Lights’ game is similar to a true/false/unsure card sort. The activity still uses a set of statements and students must still decide if they agree or disagree with a statement, or if they are unsure about it. Instead of physically sorting statements into three groups on different parts of the table, students must respond to each statement that you read out or show them by holding up a response card. The ‘Traffic Lights’ are the three different cards they can hold up:

• green (true/agree)
• red (false/disagree)
• yellow or amber (not sure).

You can have all the statements written up on the blackboard for groups to discuss before you ask them to vote.

Comment

‘Traffic Lights’ let you see very quickly what ideas students have, and whether there are ideas that many or only a few find confusing. It is also a ‘low threat’ activity, since there is no permanent record of choices.

Concept cartoons

Two examples of concept cartoons are shown below. You could show Figure R2.2 to a class and ask, ‘What do you think?’

Figure R2.2 An example of a concept cartoon.

You could show Figure R2.3 to a class and read the following statements:

• Statement A: ‘It is easier to lift the load using a two-pulley system compared to just a single pulley. Pulleys save you energy!’
• Statement B: ‘The two-pulley system lets you lift the load with a smaller force, but it does not save you energy.’