How to Break Surface Tension
- Place the first glass of water in the center of the pie plate.
- Slowly, pour some water from the second glass into the first glass until it is very full and the water forms a dome above the rim of the first glass. Set the second glass of water aside.
- Carfully stick your finger straight down through the dome of the water in the full glass. Watch what happens, then remove your finger.
- Add a small drop of dish soap on the tip of your finger and repeat step 3. What happens this time?
What Happened to the Water?
Before we begin, let's define molecule. A molecule is two or more atoms bonded together. An atom is the smallest piece of a chemical element that is still that element.
In this activity, the water molecules are attracted to each other and stick together. At the top of the water, the molecules stick together very closely to make a force called surface tension. Surface tension is what caused the water to rise up above the rim of the glass in the experiment and form a dome instead of spilling over the side.
What happened when you put your soapy finger into the water? The soap broke the water's surface tension and some of the water molecules stopped sticking to each other causing them to be pushed out of the glass.
The force of surface tension also created bubbles. In plain water, the surface tension is strong and the water might make some bubbles but they will be small and won't last for very long because the other molecules in the water will pull on the bubbles and flatten them. When you made bubbles, you added soap to the wter. This made the water become flexible and appear elastic. This allowed the bubbles to hold their shape when you blew into your bubble wand.
