PHY_10_14_V2_DM_Surface tension.Wetting,capillary phenomena

Instructions for teachers

Group1: Surface tension

Pipette, coin, water, soap

The students drip water on a coin using a pipette and then count the number of water drops on a coin just before the water flows over the edge of the coin. They add a few drops of liquid soap to the water and the drip the mixture on the coin while counting the drops. The blob of water on the coin fell apart. Why?

Group 2: The capillary

Three test tubes, sand of different grains, water, 20 cm of gauze (cotton mesh)

The students add sand containing different grains to the three test tubes. The level of sand in the test tubes should be the same. They wet the gauze and squeeze it to humidify the sand in the test tubes. Why does the level of wet sand change? Explain the process.

Group 3: Surface tension

Glass, paper clips, water

The students pour water into a glass and gradually add paper clips. They count the clips as they add them. The water does not overflow. Why? Explain the process.