Smash hit

What do I do? Fill the cup to about two-thirds full with cereal, and with the spoon or pestle crush the cereal into a fine powder. It is worth spending a lot of time on this stage – the finer the powder, the better. Put the crushed cereal into the sandwich bag and add hot water. Leave the mixture for about 15 to 20 minutes. Now gently tilt the bag forward so that the cereal collects on one side, and place the magnet along the outside of the bag near the cereal, running it over the bottom, because the iron tends to sink. Tilt the bag back so that the cereal runs away from the magnet. You can also lay the bag flat on the table and stroke it with the magnet towards one corner.

Alternatively, if you are using a blender, put the cereal straight into the blender and add hot water until the cereal is submerged. Wait for about 15 to 20 minutes until the cereal is soft, then blend it all together. While the blender is whirring, place the magnet on the outside of the blender near the mixture, and keep it there as you turn the blender off.

What will I see? The magnet will attract a black fuzz of iron. Move the magnet over the surface of the bag or blender and the tiny pieces of iron will follow it.

What’s going on? The black stuff really is iron in your cereal – the same stuff that is found in nails and trains and motorbikes. And it’s quite heavy, which is why you need to make sure you run your magnet along the bottom of the cup. The iron is added to the mix when the cereals are being made and you really do eat it when you devour your cornflakes.

The reason it is added in a form that you can extract is that iron ions (iron that would more easily combine with other molecules in the cereal) increase the spoilage rate of the food. Using iron in its pure metal form gives the cereal a longer shelf-life. The hydrochloric acid and other chemicals in your stomach dissolve some of this iron and it is absorbed through your digestive tract, although much of it remains untouched and is excreted.

PS: Humans need iron for many important bodily functions. Red blood cells carry haemoglobin, of which iron is a key constituent. Haemoglobin transports oxygen through the blood to the rest of the body by binding oxygen to its iron atom and carrying it through the bloodstream. As our red blood cells are being replaced constantly, iron is an essential part of our diet.

For more experiments go to www.newscientist.com/hamster

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