Know your rocks from your Roquefort

21st September 2007 at 01:00
Make the rock cycle more exciting by acting out how the layers were formed. All you need is a little imagination and a lot of cheese, says Helen Waddington

When I first started teaching the rock cycle as a graduate trainee, I groaned at the prospect, because it looked so dry and boring. But the lesson I am about to share with you which involves making cheese toasties is a winner.

Last year only one pupil out of 84 I did this practical with could not fully complete their rock cycle diagram at the end. The pupils love it; in fact they will nag you to know when it is coming if another class has already had a go.

Starter: the rock cycle song (sung to the tune of Row, Row, Row Your Boat, in a round). Pupils have learned this earlier in the topic and should now know the words, but it is helpful to have them displayed on the wall or projected on to the whiteboard:

Sedimentary rock has been formed in layers

Often found near water courses

With fossils from decayers.

Then there's igneous rock here since Earth was formed

Molten lava cooled and hardened

That's how it is formed.

These two types of rock can also be transformed

With pressure, heat and chemicals

Metamorphic they'll become.

Main lesson: you will need to organise pupils into four groups. Select one pupil from each group to assist you in the initial demonstration. Give each of them a job to do while the others watch.

* Person one: grates the red (igneous) cheese granite.

* Person two: grates the white (igneous) cheese basalt.

* Ask pupils what process they are performing on the rocks (the answer is weathering).

* Person three: is busily buttering the outsides of the slices of bread (the cheap stuff works the best).

* Person four: is monitoring the toastie machine raring to go. Once all the cheese is grated and the bread buttered they then get to play God and transform those rocks.

So, to making the rocks. The igneous rock has been weathered and is layered on a slice of bread. Add a layer of white, a layer of red and then a final layer of bread. It is now sedimentary rock you can squash it a bit to compact it here if you wish.

The completed toastie is placed into the machine and the lid closed, applying heat and pressure.

Once cooked it is removed, and the sedimentary rock has been transformed into a metamorphic toastie, which can be eaten once the pupil has completed their rock cycle diagram. Divide pupils back into groups and away they go.

Plenary: all pupils have a copy of the rock cycle diagram and have to complete this using their knowledge.

If time permits they can be peer marked or collected in

Helen Waddington teaches at Unity College in Burnley, Lancashire

Rock cycle recipe

Red cheese

White cheese

Cheese graters

Cheap white bread

Toasted sandwich makers

Paper towelspaper plates


Butter knife


Electric points


Pupils should be able to eat these toasties once they have completed the lesson. To do this safely all benches must be wiped down with antibacterial surface cleaner. Pupils must wash their hands before and after handling the food items.

Warn pupils that this is a one-off: eating in a lab is normally forbidden, but special precautions have been taken for this lesson.

Tips to cook up a fabulous lesson

If you cannot get four toastie makers, pupils can wrap their sandwich in a double layer of tin foil and toast it over a Bunsen flame. They must be extra careful and wear safety goggles for this and beware, they must keep an eye out if you attempt this, the toasties can burn quickly.

Ask questions along the way to check understanding: they will never forget this lesson.

Lactose intolerant pupils can still participate but need to use a special cheese, such as goat's this has only been an issue once and the pupil brought her own in.

What the lesson covers

QCA unit 8H key stage 3. The rock cycle.

National curriculum reference: Sc3. 2e About the formation of rock by geological changes.

Lesson Objectives

To enhance existing knowledge and recap learning of the rock cycle. Pupils should be able to complete a diagram of the rock cycle at the end. Most will be able to recite the rock cycle and answer questions.

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