Glass water hammer, after Donny

The attractive force between water molecules (cohesion) is strongly increased by removal of the air that is normally solved in water. This is done by prolonged heating. This V-shaped glass contains such boiled water. Two effects can be demonstrated with this tube. First, the water behaves more coherent than ‘normal’ water. When it is put in motion, it bumps against the glass wall as if a solid block hits the wall (hence the name of ‘water hammer’). A second effect appears when the apparatus is softly tapped on a table. Gradually the sound will become duller. When the tube is then turned, the water will adhere to the wall as one block. Because of the tapping the molecules have become so attached to each other, that the cohesion forces overcome the gravitational force.