Moving or stored?

Students classify energy as kinetic (activity: movement, heat, sound, light, electrical) or potential (stored: chemical, gravitational, elastic), with examples, and see the two change into each other (AC9S8U05, nodes 1 and 2). About 22 minutes.

Open the teacher guide: answers, solutions, slides and a worksheet.

Students will be able to

• I can sort energy into kinetic and potential.
• I can give examples of chemical, gravitational and elastic potential energy.
• I can say what decides how much energy is stored.

Before class

A concept tutorial for introducing or revising the idea. Set the width with ?width=minimum, typical (default) or wider. It opens Year 8 Physics.

Neither node is a hinge, but they organise everything after: students arrive with energy forms learned one at a time (sound, heat, light, electricity) and think energy means movement. The book prediction targets that.

The classification follows the progression: kinetic for energy of activity (movement, heat, sound, light, electrical) and potential for stored energy (chemical, gravitational, elastic). Some textbooks list stores and transfers differently; the idea that matters is "active" versus "stored".

Board notes: the coaster has no friction here, so its energy only changes between gravitational potential and kinetic and the total is constant. It is given a small push at the start. Heights and masses are typical of a real coaster.

Running the lesson

1. Engage: tally the predictions. 'No, it isn't moving' is the idea to work on.
2. Explore: ask where the orange bar was tallest, and where the blue bar was.
3. Explain: the sort is the success criterion; the fastest-point question links the bars to the ride.
4. In your own words: two columns of examples and the labelled coaster.

The hard part (on purpose)

Heat, sound and light as kinetic. When a student puts heat under potential, ask what the particles are doing in something hot.

When students get stuck

• A student says a still object has no energy. Ask: If it fell, would it speed up? Where would that energy come from? Fix: From the energy stored by its height: gravitational potential energy.
• A student puts food under kinetic because it gives you energy to move. Ask: Is the energy active while the food sits in the box? Fix: No: it is stored, chemical potential energy, until your body releases it.
• A student thinks the coaster loses energy at the bottom. Ask: Did the total line on the board move? Fix: No. The stored energy became kinetic energy; the total stayed the same.

Stretch and support

Stretch: Why can't the car (without friction) ever get higher than its starting point? (It would need more potential energy than it started with, and the total can't grow.)

Support: Give the two family headings with picture cues: a moving ball, a speaker, a torch (kinetic); a battery, a book on a shelf, a stretched spring (potential).

Where it leads

Next: Transfer or transformation? (nodes 3 and 4).

In class: drop a ball from different heights onto sand; stretch a rubber band different amounts and measure how far it flies.

What each step is for

• Engage: the book on the shelf: Students link energy only to movement; a still book with stored energy is the case that needs the idea of potential energy.
• Explore: ride the coaster: Watching two bars trade places as the car goes down and up makes 'stored' and 'moving' energy two forms of one thing.
• Explain: two families: Sorting familiar energy forms into kinetic and potential, then naming what decides how much is stored, organises years of separate ideas into one framework.
• Elaborate: a higher hill: Starting higher shows stored energy depends on height, and that a bigger store means more kinetic energy later.
• Elaborate: trampolines and bows: Elastic potential energy completes the potential family and shows energy changing back and forth.