Screen-free things to do when they say "I'm bored"

Four or five raisins dropped into a tall glass of freshly opened fizzy lemonade rise and sink again and again. Bubbles cling to the rough raisins and lift them, then pop at the top so they drop. It takes about 15 minutes and three things from the kitchen. This is one for watching, so nobody drinks the glass afterwards.

Two cups of cornflour and about one cup of water make a mixture that feels solid when punched fast and drips like liquid from a slow handful. For ages 3 to 6, it shows how materials can surprise. Expect mess: use a wipeable mat, wipe up slippery spills at once and bin the leftovers, as gloop can block drains.

Small waterproof toys are frozen into a tub of water, which takes a few hours or overnight, so this suits a tub made ahead. The rescue is about 15 minutes of dripping warm water, sprinkling salt and tapping with a lolly stick. Children see what speeds up melting. Keep the water warm, not hot.

A blob of runny paint on paper is blown through a straw into branching, spidery shapes, and turning the paper sends the branches in new directions. Children see moving air push the paint about. Thicker paper holds up best. Remind them to blow out and never suck in, and cover clothes and the table against splatters.

Thin paper laid over a leaf and rubbed with the long side of a peeled wax crayon brings up the pattern of veins. The same paper held against a tree captures the ridges of the bark. It works from age 3 and takes about 20 minutes. Only pick leaves from plants that are recognised, and wash hands afterwards.

Setting up takes around 15 minutes: line a clear jar with damp kitchen roll or cotton wool and tuck a dried broad bean or runner bean against the glass. Over about a week on a light windowsill, roots grow down and a green shoot grows up in full view. The beans are for growing, not eating.

A pencil or straight stick pushed through the centre of a paper plate makes a sundial. Left in a spot that stays sunny all day, its shadow is marked on the hour and the time written beside it. For ages 6 to 12, it shows that shadows move as the sun crosses the sky. Never look straight at the sun.

Banana, frozen mixed berries, yoghurt and milk or juice are measured into a blender and blended for about 30 seconds, then poured into two tall glasses. At around 10 minutes it is the quickest thing here. Children see separate ingredients mix into something new. An adult operates the blender with the lid firmly on. Check for allergies first.

A firm pear laid on a plate becomes a hedgehog, with halved grapes, strawberry quarters and pineapple on cocktail sticks for spines and raisins for eyes. Arranging the fruit by colour is sorting and pattern-making. An adult cuts the pear so it sits flat and halves the grapes. Count the cocktail sticks in and out, and remove them before eating.

Icing sugar, food-grade citric acid and bicarbonate of soda are stirred together in a completely dry bowl. A small taste on a damp finger fizzes and pops on the tongue, because the dry powders only react when they meet the wet. For ages 5 to 10. Go easy, as too much citric acid can sting. Use clean hands and bowls.

About ten thumb-sized ghosts are cut from a single thin layer of tissue paper and laid on a dark tray. A balloon rubbed on a woolly jumper or dry hair for 20 seconds builds up static electricity that lifts them off the tray to dance. An adult should blow up the balloon. It works best on a dry day.

A cotton bud dipped in lemon juice writes a secret message on plain white paper, which vanishes as it dries. Gentle warmth near a radiator or warm lamp brings the writing back in brown, because lemon juice browns faster than the paper. Around 20 minutes for ages 5 to 10. An adult must do the warming step.