Surface tension

Surface Tension ~30 Minutes

Description: floating paperclips on water

Objective: investigate the surface tension of water

Outcomes:
-investigate the interactions of liquids and solids (grade 2)

Materials: Shallow plastic container (margarine tub etc...), paperclips, any type of liquid soap (dish soap, hand soap...)

Doing it: A1. Fill the container with water, try to get the paperclips to 'float' on the surface of the water. will bending them into a different shape make them easier to float?
A2. How many can you float at once?
A3. with some paperclips floating carefully add a drop of soap a few cm away from the clips. What happens? Why do you think this happens? (why do we use soap to wash with)

Fig 1.1 - 4 paperclips! notice the center clip has been bent.

Notes:

Explanation: All the water molecules in the cup are attracted to each other. On the surface, they are only attracted to the molecules beside and underneath them. This causes the attraction to be slightly stronger, and creates a skin on the surface of the water.

Extension: If you are having trouble getting the paperclips to stay up, you can put a small piece of paper towel down first and the paper clips on top. The towel will eventually sink and the paperclip should stay.
Different fluids?

Created by Brock Watson July 2007