Grandparents and Little Ones · Experiment 2 of 3
Atoms have parts — and those parts can be pushed around
What to do — make paper jump
You will need: a plastic comb · a sheet of printer paper · your own hair
- Tear the paper into tiny pieces — about the size of your fingernail — and pile them on the table.
- Comb your hair hard and fast, about ten times. Dry hair works best — and our Highveld winter air is perfect for this!
- Hold the comb close to the paper bits without touching them. Watch them jump up and stick!
- Bonus: hold the charged comb (charged from combing your hair) near a thin trickle of water from the tap. Watch carefully — the water should bend towards the comb, but only for a second or two. The charge escapes into the water quickly, so be ready!
For grandparents to explain
In Experiment 1 we learned that everything is made of molecules, and that molecules are always moving. Now we go one step further. Those molecules are themselves made of even tinier things called atoms — so small they can never be seen, even under a microscope. And inside every atom there are smaller parts still. Some of those parts carry a positive charge, and some carry a negative charge. Normally every atom has equal numbers of each, perfectly balanced, sitting quietly.
Think of it like a seesaw with one child on each side — perfectly balanced, going nowhere. That is a happy, neutral atom. But if an extra child jumps onto one side, it tips. That tipping — that imbalance — is what makes static electricity.
When you rub the plastic comb through your hair, the rubbing is like a tiny tug-of-war between the comb and the hair. Some of the negative parts get pulled off your hair and onto the comb. Now the comb has too many negatives — it is unbalanced and very eager to sort itself out.
Here is the important rule: opposites attract. Negative pulls towards positive, just like the two ends of a magnet snap together. The paper bits are still balanced, but the comb’s extra negative charge pulls the positive parts of the paper molecules towards it — and up the paper jumps.
On our dry Highveld winter, the air holds almost no moisture, so the extra charges stay on the comb long enough to do their work. In humid air, water molecules in the air, carry the charge away before it can build up — which is why the water tap trick only lasts a second or two. Water is very good at stealing charge.
Those flashes you sometimes see when pulling off a polar fleece blanket in the dark? Exactly the same thing — the fleece fibres rub together; charge builds up and then crack! — it jumps as a tiny spark. It looks dramatic but it is just atoms sorting out their seesaw again. Completely harmless.
You have felt this before! That little zap on a lift button or sliding-door handle? Static electricity built up as you walked across a carpet. The charge that built up on the comb jumped to the paper. The charge that built up on you jumped to the metal handle. Same process — the atoms were just using a finger instead of a piece of paper to rebalance their seesaw.
Next: Experiment 3 — The volcano in a glass · When atoms swap partners and become something completely new.