What to save from the recycling for junk modelling

Four to six cardboard tubes from kitchen roll and toilet roll are taped downhill across a large flat piece of cardboard, some cut lengthways into open troughs. A marble drops from one to the next into a cup. Steeper ramps make it go faster. An adult should help with cutting, and a marble is a choking hazard for under-threes.

A bit of everything goes into this one. A large box or clean tin becomes the body, smaller boxes, tubes and cans make the head, arms and legs, and bottle caps become eyes. Children practise planning a design from the parts to hand. Tape over any can rims, and keep small parts away from under-threes.

Save one cardboard box that fits over a child's head with room to spare. An adult cuts a large round face hole, then the box is covered in silver foil and decorated. It shows why real astronauts need a sealed helmet in space, where there is no air. The helmet must fit loosely and never cover the nose or mouth.

One cardboard egg box with 12 cups makes six bats. The cups are cut into joined pairs, painted black, given card wings and googly eyes, then taped along a string. Cutting matching wings from folded card is a simple lesson in symmetry. Allow 40 minutes. An adult may need to cut the cups apart, as the card can be tough.

Two clean, empty tins are joined by 5 to 10 metres of string, knotted inside a hole in each base. With the string pulled tight, one child talks quietly into a tin while the other listens. Sound travels along the string as vibrations. An adult must pierce the tins and tape sharp rims. Paper cups are safer for younger children.

Three to six clean tins, plastic tubs, pots and boxes of different sizes are turned upside down and set out in a curve. Tapped with wooden spoons, the big hollow ones sound deep and the small tight ones sound sharp. It suits ages 3 to 9. An adult should check for sharp edges and tape over any rough rims first.

A small plastic bottle, old newspaper and a cereal box all get used here. The newspaper is scrunched around the bottle and covered with card to make a mountain, then painted. Baking soda and vinegar in the bottle react to make a foam of carbon dioxide gas. Allow 40 minutes, and set it off on a tray or outdoors.

A clean glass jar with a wide mouth is lined with silver foil that an adult has pricked all over with a pin. With a battery tea light inside and the room dark, tiny beams dot the walls with stars, showing that light travels in straight lines. For ages 6 to 11. Never use a real flame in the jar.

An empty jam jar with its label soaked off gets covered in orange tissue squares and watery PVA glue, then given a black paper face. Lit by a battery tea light, the tissue glows while the face stays dark, which shows the difference between translucent and opaque materials. Check the jar for chips first, and keep the battery compartment closed.

An adult cuts the top third off a plastic bottle, which is turned upside down in a jar as a funnel. Layers of cotton wool, sand, small stones and gravel trap different sizes of dirt as dirty water trickles through. For ages 8 to 12. Never drink the filtered water, as filtering does not remove germs.