Scaredy Pepper
Word of the day: surface
“These pepper bits are scared of soap. Watch what happens when soap comes near.”
Grab
- a plate with a little water
- ground pepper
- dish soap
- a cotton swab or a fingertip
Do
- Shake pepper over the water so it floats.
- Touch the middle with a clean finger. Nothing much.
- Put a drop of soap on the finger and touch the middle again. The pepper rushes to the edges.
- Try a paper clip laid gently on clean water (a fork helps). It floats. Add soap and it sinks.
The big moment
Soapy finger in, pepper runs for the edges.
Ask (guess first, then try)
- Why did the pepper run away?
- How can a metal paper clip float?
What's going on (for you)
The top of water acts like a thin stretchy skin (surface tension) because water bits hold hands with each other. Soap breaks that grip where it lands, and the skin everywhere else pulls away, dragging the pepper with it. The same skin is what lets bugs walk on ponds.
If they want more
Count how many drops of water fit on a penny before it spills. It's more than you'd think.