Let's go down the garden to grow some worms

For young children, it is best to foster enthusiasm for the subject through practical examples before worrying about whether they've got 'the head' for it

1 Making a rainbow

This is Adam Hart-Davis's favourite experiment.

You need: a plastic bowl half full of water, a shaving mirror that can be angled, three torches, three pieces of cellophane coloured red, green and blue, and tape.

In 1666, Isaac Newton proved that white light was made up of a range of different colours by separating them through a glass prism. Water droplets also split light into individual colours which are red, orange, yellow, green, blue, indigo and violet. Previously, people had believed that colours were added to white sunlight.

Make a room dark by drawing the curtains, leaving only a tiny slit. Place your bowl so that a sliver of sunlight falls on the water. Put the shaving mirror in the water angled so the sunlight hits it and bounces on to the wall, creating a rainbow.

Join the colours back together again with the three torches. Over the end of the torches tape a piece of coloured cellophane. The light from the torches will be the colour of the cellophane: by shining them on a wall and overlapping them, you can create different colours. When all three torches are shone on one spot, the light should turn white.

This principle is used in television. If you sit close to the TV screen, you can see dots arranged in rows of red, green and blue. Light behind the screen illuminates these dots: the combination of dots that are lit creates different colours. When all the dots in one area are lit, this section of the screen will be white.

2 Making a car

You need: two matchbox covers, one matchbox drawer, scissors, a drinking straw, paper, four identical buttons with loops, and glue.

Cut a notch either side of one end of the matchbox cover. Cut halfway down the top of both matchbox covers and fold the flaps over. Slide both covers on to the matchbox drawer. Wrap a piece of paper around it, sticking the ends so they meet the edge of the matchbox drawer in the middle. The matchboxes will slide like a sledge.

Cut the straw into two lengths so they are slightly wider than the matchbox. Slide them into the notches to form the wheel axles. Stick buttons on the end of the straws. Let your child find a toy or model person to drive the car.

Moving wheels helps cars move around on roads. But on slippery roads, which are wet or covered in ice, the tread on rubber tyres increases the 'friction' and helps to prevent the car from skidding. The model car's wheels are like a sledge skidding on a slippery surface.

3 Making paper

You need: three sheets of newspaper or other paper, a cup of water, bowl, stiff mesh or embroidery canvas, J-Cloth, rolling pin, hand whisk and tea towel.

Tear the paper into small pieces and put in the bowl. Add a cup of water. Leave for at least two hours. Mash the torn paper into a pulp with your hands or using a fork, whisk, or blender. Smooth pulp evenly on to the mesh. Place the J-Cloth over it. Roll it to squeeze out excess water. Turn it over and remove mesh, leaving the pulp on the J-Cloth. When it's dry, peel the cloth from the paper and trim the edges.

Try using different coloured paper, and adding dried flowers and glitter to the pulp.

Newspaper is made from finely ground-down wood chips and water. Tough fibres inside the wood, called cellulose, make the newspaper soak up water. As the fibres unravel, the newspaper turns into a pulp. When it dries, the cellulose tangles together again to make paper.

You can see the fibres in paper with a magnifying glass. Try comparing different sorts of paper, for instance, hand-made paper compared to printer paper. You could also look at an old wasp's nest. Wasps bite off bits of wood and chew them into a pulp with their jaws to create the tough paper of which their nests are made.

4 Making a worm farm

You need: a bowl, soil, fallen leaves, fine sand and, of course, earthworms.

Fill the bowl with alternate layers of soil and sand. Put the leaves on top. Add the worms. Keep the farm cool, moist and dark. Soon the worms will start making tunnels and pulling leaves from the surface down into the soil. Eventually the soil will be completely mixed. Please put the worms back in the garden when you've finished looking at them.

Worms keep soil full of air by tunnelling and chewing up dead matter like leaves. They have no bones, only muscle segments and one long muscle running down the middle. They move by contracting the muscle segments one after another. They're covered in tiny bristles that help them grip the soil. They carry eggs in the thick saddle region. There are about 1,800 species of worm. One kind, which lives in Australia, grows to 3.3m long. S O'C