What happens if you…? Kids' science questions answered

STOP: only on the screen. Together they make chlorine gas. It stings your eyes and hurts your lungs. In the game the room fills with yellow-green gas and you have to open the window. In real life, never mix them. If it ever happens, get out into fresh air and tell a grown-up.

STOP: only on the screen. The water turns to steam at once and throws the burning oil up in a ball of fire. If a pan catches fire, call a grown-up. They put a lid on it and turn off the heat. Never water.

In the game the oven is 180 °C for 20 minutes. Crayon melts into deep, shiny colour. The paper goes see-through where the wax soaked in. Secret lemon writing turns brown. The edges toast. Don't put real paper in a real oven: it can catch fire.

Everything wet freezes hard: puddles, paint, ketchup. Wet watercolour grows feathery ice patterns that stay after it thaws. Frozen paint is brittle, so the hammer shatters it. You can try freezing a wet watercolour painting for real, with a grown-up's OK.

It goes mouldy. Fuzzy spots grow: blue-green, white, black or orange. Fruit flies come too. Salt stops mould growing. Never eat or sniff mouldy food.

They don't mix. Oil is lighter, so it floats on top as a golden layer. Shake them and they go cloudy, then split again. Beat oil with egg yolk and it stays creamy: that's mayonnaise.

The salt melts little holes in the ice, one round each grain. Salt makes water freeze at a colder temperature. That's why people put salt on icy paths.

The colours fade. Reds fade most, blues least. But where something was lying on the paper, the colour stays bright. That's called a sun print.

The colours rush away from the soap and swirl around. Soap pulls on the milk's skin and its fat. It's called magic milk, and you can try it for real.

A fountain of cola shoots up! The gas in the cola escapes all at once on the bumpy mints. Do it for real only outside, with a grown-up, and step back.

The purple juice turns pink. On baking soda it turns blue-green. Red cabbage juice shows if something is an acid or an alkali.

STOP: only on the screen. In the game, dry paper burns into holes, but wet paper won't burn until the water boils off. A line of water stops the fire. Never play with fire for real.