Experience cohesion, hydrogen bonds, and the polarity of water molecules first hand with this hands-on science experiment
When you poke five, evenly-spaced wholes into the side of a bottle, they come out as five separate streams. That is, until you run your finger through the streams. Like magic, the five streams combine to form one! The principle at work is a force called cohesion, and the Water Twist is a great hands-on way to experience cohesion, polarity, and the properties of water.
- 1 liter bottle with cap.
- Adult supervision
- Fill a 1 liter bottle with water and screw on the cap.
- Using a thumbtack, make 5 evenly spaced holes on the side of the bottle, near the bottom.
- Loosen the cap to release the water.
- Run your finger along the streams of water that are coming from the bottle. What happens each time you run your fingers through the streams?
How Does It Work?
The force at work, when you run your finger through the streams of water, is called cohesion. Cohesion happens when molecules of a substance stick to each other. Water is a very cohesive substance because the molecules are polar. When you run your finger over the stream again, the bonds are broken and the streams resume their separate flows.
Water is the perfect substance to demonstrate cohesion because of the simplicity of a water molecule. Water molecules consist of one oxygen atom, possessing a weak negative charge, and a pair of hydrogen atoms that sport a slightly positive charge. The negative charge of the oxygen attracts the positive charge of the hydrogen atoms and hydrogen bonds are formed. These bonds are strong enough to create cohesion, but are easily broken.