Surface Tension Experiment

Demonstrate the effect of detergent on the surface tension of water in this easy surface tension experiment.

Water Surface Tension

Explain to your children that there are forces of attraction between molecules of water. These seem to make a 'stretchy skin' on the surface of the water. This 'skin' is called a meniscus. They might enjoy pronouncing that word!

Products like soaps and detergents weaken or break these forces of attraction and help other substances to mix with water more easily. This helps us with cleaning and washing things like dishes, clothing and our bodies.

You will need

a bowl of water
talcum powder or fine pepper
dishwashing liquid

Method

Sprinkle a little talcum powder over the bowl of water.
Observe how the talcum powder floats on the surface of the water.
Now add a drop of dishwashing liquid and observe what happens.

Result

The dishwashing liquid moves the talcum powder and spreads it out evenly towards the edges of the surface of the bowl of water, as it decreases the surface tension between the molecules. In plain language, it makes the meniscus more 'stretchy' than before.

Soap Bubbles

This is a winning science experiment for kids! Follow the recipe and instructions to make giant soap bubbles and let your kids discover more about surface tension.