How Things Work 2-minute video · ages 4-8 · free coloring page
How does soap get the dirt off my hands?
My hands are dirty. I rinse them with water, but they still feel greasy. Then I add soap, and they come out clean! How does soap get the dirt off?
2 min
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Free coloring page
The scene from the video as a coloring page, plus the three-sentence answer, the experiment, and a QR code back to this page. One sheet, US Letter, black and white.
The answer in three parts
Why?
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Dirt and germs get stuck in the oil on your skin.
Your skin always has a thin layer of oil on it, and dirt sticks in it like crumbs stuck in butter. Water alone can't help. Water and oil do not mix, so the water just rolls over the oil and runs away.
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Every tiny bit of soap has two ends.
One end loves water. The other end loves oil. When you rub soap on your hands, the oil-loving ends dive right into the oil and hold on tight.
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Soap wraps the oil into tiny balls.
More and more soap bits crowd around a drop of oil, with the dirt and germs trapped inside. The outside of the ball is covered with water-loving ends, so when you rinse, the water carries the balls down the drain. Bye bye, germs!
For grown-ups: Soap works because one end of each soap bit grabs the oil and the other end grabs the water, so together they wash the dirt away. But soap needs time to do its job: scrub for about twenty seconds, and scrub everywhere, because germs love to hide between the fingers and under the nails.
Scrub everywhere!
- Backs of your hands
- Between your fingers
- Your thumbs
- Under your nails
A tiny experiment
Try it!
Oil, water and soap
You need: a clear jar with a lid, water, a spoon of cooking oil, a squirt of dish soap, and a grown-up
- Ask a grown-up for a clear jar with a lid. Put in some water and a spoon of cooking oil, close it, and shake.
- Wait a minute. The oil floats back to the top.
- Now add a squirt of dish soap and shake again. This time, do they stay mixed?
What happened? The oil-loving ends of the soap grab the oil, and the water-loving ends grab the water. So the oil and water stay mixed.
Did you know?
Scrub for about twenty seconds. That is as long as singing Happy Birthday two times.
Your guide in this video
I'm Sudsy, a little soap bubble. Today we will solve a slippery mystery!
Sudsy is a little rainbow soap bubble. The tadpole-shaped soap bits in the video each have a water-loving end and an oil-loving end.
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