The trouble with most “kitchen science” lists is that half the experiments do not work, and the ones that do come with no explanation — so the child sees a trick, not an idea.
These five work every time. Each one takes under ten minutes, and each has a why your child can actually hold on to.
1. The bag that will not leak
You need: a zip-lock freezer bag, water, several sharpened pencils.
Fill the bag two-thirds with water and seal it. Hold it over the sink — this is the moment everyone flinches — and push a sharp pencil straight through, in one side and out the other.
Almost no water escapes. Add four or five more pencils.
Why: the bag is made of long, flexible polymer chains. The pencil pushes between them rather than cutting them, and the chains close back around the wood, gripping it tightly. Pull a pencil out and then you get a leak — the hole has nothing filling it any more.
Do it over the sink anyway.
2. Pepper that runs away
You need: a shallow bowl of water, ground pepper, washing-up liquid.
Scatter pepper over the water until the surface is freckled. Dip one clean fingertip in — nothing much happens. Now put a single drop of washing-up liquid on your fingertip and touch the centre again.
The pepper flees to the edges instantly.
Why: water molecules pull on each other, and at the surface that pull acts like a tight skin — surface tension — which the pepper is resting on. Soap breaks the pull where you touched. The skin is still tight everywhere else, so it drags outward and takes the pepper with it. This is exactly why soap cleans: it lets water get in among things it otherwise skates over.
3. The raisin lift
You need: a clear glass, fizzy water or lemonade, a few raisins.
Drop the raisins in. Wait. Within a minute they begin to rise, hover, and sink again — over and over, sometimes for ten minutes.
Why: raisins are denser than the drink, so they sink. But their wrinkled surface catches carbon dioxide bubbles, and enough bubbles make the raisin-plus-bubbles bundle less dense than the liquid, so up it goes. At the surface the bubbles pop, the raisin is heavy again, and it sinks. That is buoyancy, running on a loop you can watch.
4. Walking water
You need: three glasses, water, food colouring, two strips of kitchen roll.
Fill the outer two glasses with water and colour one blue and one yellow. Leave the middle glass empty. Drape a rolled strip of kitchen roll from each coloured glass into the empty one.
Come back in an hour: water has climbed up the paper and down into the middle glass, which is turning green.
Why: kitchen roll is a mesh of fibres with tiny gaps. Water is drawn along those gaps because it clings to the fibres more strongly than it clings to itself — capillary action. It is the same force that carries water from a tree’s roots to leaves thirty metres up, with no pump anywhere.
5. The unpoppable balloon
You need: two balloons, a bamboo skewer, a little cooking oil.
Blow one balloon up fully and push the skewer in — bang, as expected. Now inflate the second only two-thirds and tie it. Oil the skewer and push it slowly through the thick rubber at the very bottom (opposite the knot), then out through the thick patch beside the knot.
It survives, skewered.
Why: the rubber is stretched thinnest around the balloon’s middle, and stretched rubber tears the instant it is punctured. At the top and bottom the polymer is still relaxed and thick, so it stretches around the skewer instead of splitting. Going slowly matters; so does the oil.
Getting the most out of them
Before each one, ask: what do you think will happen? Then do it. Then ask: were you right?
That sequence — guess, test, compare — is the whole of science, and it works just as well on a raisin as it does in a laboratory. A wrong guess is not a failure; it is the most interesting result you can get.
More of these, with proper record sheets, in Awesome Science Experiments You Can Do at Home — and there is a free experiment log you can print right now.