Water Tension

 Water tension experiment:

supplies:

plate of water

pepper

dish soap

Put water in a shallow bowl or plate.

Sprinkle pepper on top of the water.

Use your finger or tool, drop one drop of dish soap into the plate.

What happens to the pepper?  Why?

This happens because the liquid dish soap changes the surface tension of water. 

The surface tension of a liquid is the tendency of liquid surfaces to resist an external force due to the cohesive nature of its molecules. The pepper flakes are so light, it floats on the water surface due to surface tension. The addition of soap broke the surface tension of water, but the water molecules want to keep the surface tension intact. So they pull away from the soap along with the pepper flakes. This pushes the pepper or “germs” away from your soap covered finger. This is why soap is such a great cleaning agent and so effective in cleaning dishes and taking all the grease and dirt away. 

This pepper and soap experiment also shows how germs are removed from hands with soap. The pepper flakes or “germs” were not chased away until you added soap to the bowl.