Water striders using water surface tension whe...

Water striders using water surface tension when mating. (Photo credit: Wikipedia)

Pepper Scatter. Fun with Grandchildren.

This activity shows surface tension on water and how to break it.

Materials:

  • Bowl
  • Water
  • Pepper (freshly ground or powdered should both work)
  • Toothpick
  • Soap or dishwashing detergent

Instructions:

  • Put enough water in bowl to fill the bottom
  • Pour pepper gently across the surface of the water
  • Stick one end of a toothpick into the soap
  • Gently put the soapy end of the toothpick into the water near the pepper.

What Should Happen?

The pepper flakes should scatter anywhere you touch the water with the soapy toothpick.

Why is this happening?

The surface tension of the water, intact with the pepper floating on it, is disrupted when soap is introduced.

Water molecules hold together under water, with a stronger attachment at the surface because of the difference in attraction between water molecules to each other and to air.

This difference is shown by floating pepper on top of the water.

When you introduced soap, the surface tension was disrupted.

The pepper flew away from the soap, toward the surface of the water that still had a strong surface tension.

The detergent is not as attracted to the water molecules as they are to each other, so the water molecules move to be with other water molecules, taking the pepper on the surface with them.

Click here to read more about the chemical reaction of detergent to water.

Where Else Do We See Surface Tension?

Several types of bugs, like water striders, can walk on still water because of surface tension.

New research shows they also have microscopic hairs that trap air bubbles that help them float across water as a skater skims across ice.

The reason water beads into spheres on a waxy leaf is also because of surface tension, as the water does not stick well to the leaf and, instead, sticks together.

You may have been warned not to touch the side of a tent when it is raining outside.

This is because the surface tension of the wet tent holds the water, but if you touch it, you break the tension and the tent starts to leak.

You also have probably grown up with the idea that hot water cleans better.

This is because the surface tension of water goes down as the temperature goes up. Hot water cleans better because more water gets into the clothes to clean them and lift out the dirt.

Thanks to sciencesquad.questacon.edu.au for this activity.

Have you ever pointed out dragonflies and other flying insects along a creek to your grandchildren?

Did you know why you couldn’t touch a wet tent wall?

Have you ever wondered why water beads on a leaf?

To you and exploring the natural world with your grandchildren.

 

Carol Covin, Granny-Guru

Author, “Who Gets to Name Grandma? The Wisdom of Mothers and Grandmothers

Click here to order this blog on your Kindle.

http://newgrandmas.com

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