Glass capillary tubes demonstrate the attraction that exists between certain fluids and the walls of a narrow glass tube. This causes the column of fluid, usually water, to rise up the tube until the weight of the water equals the pull of gravity. The narrower the capillary the less the volume of water and the higher it will rise. The same phenomenon causes sap to rise from the roots to the top of a plant.
Method: place the tubes in a container of water so they can be compared. Note the heights reached.
This set of 5 20 cm long tubes have 0.5, 1.0, 1.5, 2.0 & 3.0 mm diameters.