Make amazing patterns using milk and surface tension.
Time: about 2 minutes.
- A plate
- food coloring – any color(s)
- paper clip (bend a portion straight for dipping into the soap)
- pour a thin layer of milk onto a flat plate
- carefully add a drop of food coloring in the middle of the milk
- dip a bent paper clip into dish soap
- now, touch the milk with the paper clip
Observation and Results:
- What did you observe?
- What do you think is happening?
Liquids such as water and milk have a property called surface tension. Surface tension is like a tighter skin on the edge of the liquid than inside the liquid. Another way of imagining this is that the water (or milk) molecules really like each other. In fact, they want to be surrounded on all sides by other water molecules. This makes them happy. The water molecules on the edge are not surrounded by other water molecules so they are trying to get back into the middle and surrounded. This ‘desire’ to be surrounded is what causes the surface tension. Soap has a property that gets in between water molecules thus counter-acting the surface tension.
Surface Tension Experiment Pictures
- water drops on a penny (before and after soap)
- scatter pepper on a plate of water