Is dry water possible

Experiment: dry water

Everything you need for this experiment:

  • 1 glass
  • ground pepper
  • 1 teaspoon
  • 1 jug of water
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That's how it works:

1. Fill the glass with water.

2. Carefully sprinkle 4 to 5 teaspoons of ground pepper on the surface of the water. Stop moving the glass.

3. Slowly dip a finger a little bit into the water and immediately pull it out again.

Water with skin

Water actually has a kind of elastic skin. It forms automatically on the border with other substances. The reason: The smallest water particles, the water molecules, attract each other. In technical language this is called "cohesion". In water, the force of attraction between the molecules works in all directions. But that's not possible on the surface. There the molecules are only drawn towards the water, but not upwards. This creates a wafer-thin, tense skin on the water. We call this phenomenon surface tension.

On this "water skin", insects like the water strider can whiz across a body of water without sinking. If you look closely, you can see that your feet are pressing the surface of the water very slightly. Leaves and bits of bark can also float on the water thanks to the surface tension. The surface tension always keeps the water surface as small as possible. That is why water droplets are spherical in the air!

What is happening:

The finger stays dry. Why? The pepper increases the surface tension of the water. Only with strong pressure will the "water skin" tear and your finger will get wet.

More information at: Klaus Gruber | dolphin photography

By the way, this experiment comes from the children's magazine Stafette.