What you need:
A one-litre plastic bottle
Water
A drawing pin
What to do:
1. Fill the bottle with water. Screw on the cap.
2. Using the drawing pin, poke five evenly spaced holes in the side of the bottle, close to the bottom. The holes need to be close to each other though.
3. Loosen the cap so the water can start flowing out of the bottle through the holes.
4. Now pinch the five streams of water together with your finger and thumb.
What happens:
The five streams of water merge into one stream!
If you run your finger through the stream again, it splits once more.
Why?
The reason behind the joining of the streams is known as ‘cohesion. Cohesion means ‘stickiness and it happens when the molecules of a substance are attracted to each other. In water, this happens, because the water molecule is slightly uneven.
Each water molecule is made of two hydrogen atoms and one oxygen atom (remember the chemical formula, H20?). The oxygen atom has a weak negative charge and the hydrogen atoms have a weak positive charge. And because of the uneven number of oxygen and hydrogen atoms, these electrical charges are unbalanced. So, when two water molecules are close to each other, their opposite charges pull them to each other and they stick. But these bonds are weak and can be broken easily which is why the cohesion can be done away with by simply running your finger over the stream.
Picture Credit : Google
