Capillary Tubes

A simple capillary tubes demonstration visually highlights the principles of capillary action, where liquids flow against gravity in narrow spaces due to the forces of adhesion (liquid to tube) and cohesion (liquid molecules to each other).

The liquid rises because the adhesive forces between the water and the glass are stronger than the cohesive forces of the water itself. The height (h) to which the liquid rises is mathematically inversely proportional to the inner radius (r) of the tube, described by Jurin's Law

h=(2yCOS(∅))/(pgr))

y is the liquid-air surface tension

∅ is the contact angle

p is the density of the liquid

g is the acceleration due to gravity

r is the radius of the tube

The Thinner the Tube, the Higher the Rise: The narrowest tube will show the highest column of liquid, while the wider tubes will have shorter columns