- New cellulose kitchen sponge
- Bowl of water
- Petroleum jelly
- Something to spread the jelly with – if you’re not into using your fingers… :)
- Cut one-inch strip of sponge for use with experiment.
- Cut a section from the one-inch strip so that about half of the sponge is half as thick.
- Rinse sponge strip and squeeze out. Let it dry thoroughly.
Once the sponge is dry, we’re ready to begin! Press the dry sponge with your fingers, making it as flat as possible.
Thoroughly cover the surface of the thinner section of the sponge with petroleum jelly.
Use your finger to drop 2-3 water drops onto the petroleum jelly-covered section of the sponge. The drops will sit like a round ball on top of the sponge.
Drop 2-3 water drops onto the uncoated section of the sponge.
The sponge will pucker up where the water falls.
Now try dripping 2-3 water drops onto your arm or the back of your hand. Does it look like the petroleum jelly-coated area or the uncoated area of the sponge?
Your skin secretes oil (sebum), which makes your skin water-resistant. However, your toes and fingers have thicker skin without the oil layer, so that skin soaks up water and puckers up faster when you are in the water for a long time.
Now play! Esmé made water handprints on the paper towel, emptied the bowl of water, and then covered her arms with petroleum jelly…
Inspired by Janice VanCleave’s Play and Find Out about the Human Body: Easy Experiments for Young Children.