Simple Test on Cohesion

Cohesion or cohesive force, which is a physical property of a material, is the intermolecular force of attraction between like molecules. For example, there is a force of attraction between the molecules of water which causes them to stick together. This science fair project idea is to prove that cohesion exist between water molecules through a simple test.


To prove that cohesion exist between water molecules.

Materials Required
  1. a paper cup or a Styrofoam (not less than 6 oz)
  2. a pencil
  1. Using the pencil punch four holes in the cup such that the holes are close to each other as possible in a straight line at the base of the cup.
  2. Make the cup to stand on the side of a sink such that the holes are on the sink side.
  3. Now fill the cup with water.
  4. Pinch the four streams of water together with your thumb and forefinger
 Science Fair Projects Hub Cohesion
When you pinch the streams, the streams get united. Water pours out through the four holes on it and if the holes are close enough, it results in the formation of one stream. If not, then two streams will be formed.
Why is it so?
Water molecules attract each other. As a result one water molecule has an attraction for another water molecule. Actually these molecules pull each other and get stick together.