Can pupils guess what this substance is? It is found in the earth’s crust, where it is the fourth most common element. It is essential for the body.

It is often found in meteorites. It is used to make steel. It makes blood red and poo brown. It is magnetic and conducts electricity. It is used to make pipes, cars, radiators, and many other things.

Iron is essential for the body, but how many of us would eat a lump of it? However, small pieces of iron are added to breakfast cereal. It reacts with the acid in the intestine and is absorbed by the body.

Pupils can explore the amount of iron that is used in breakfast cereal.

There are several ways to do this, but the most important items are the cereal itself and a magnet. It is useful to paint the magnet white, or to buy a white one, as it is then easier to see the iron filings from the cereal.

Attach your magnet to a spoon and cover with cling film. Use the spoon to break up the cereal, and stir it for 10 minutes. When you remove the spoon the iron filings will be stuck to the magnet. You can take the cling film off the spoon and weigh the amount of iron that you removed from the cereal, and then compare it with the weight of cereal used. Compare the result with the chart on the side of the cereal packet that explains how much iron has been added.

Alternatively, mash up the cereal with twice the volume of warm water. Mix it for at least 20 minutes. Now take the cling-film-covered spoon and magnet and stir the mixture for 10 minutes. How do the results compare with the first experiment? What is the best way of to get the iron filings to separate from the cereal? Try different cereals, and work out the best way to get accurate results.

Sophie Duncan is project manager for sci ence at the BBCwww.bbc.co.ukscience