Capillary Action

When colored water is placed in a capillary tube apparatus, the water is carried up the thin tubes by capillary action. It can be seen that the water rises higher in the smaller tubes. 

Curriculum Notes 

This demo would be appropriate for a class discussing physical properties of a liquid such as cohesion, adhesion, and surface tension. This demo also shows the properties of water due to hydrogen bonding. Projection is recommended.

Lead Time 
One day of lead time is required for this project.
Discussion 

Capillary action occurs when intermolecular adhesive forces between a liquid and another substance are stronger than the cohesive forces between liquid molecules. Water is adhesive to the glass capillary tubes due to hydrogen bonding. The adhesion of the water to the glass causes the water to climb up the sides of the tube, forming a concave meniscus. Due to the strong surface tension of water, the entire liquid is carried up the capillary tube. The water rises to higher levels in a smaller tube.

Materials 
  • Capillary tube apparatus attached to ring stand
  • Water with dark food coloring
Procedure 

Pour the water containing the dark food dye into the capillary tube apparatus. The water rises up the thin capillary tubes to demonstrate capillary action.

Safety Precautions 

As in any other demonstration, standard safety measures should be used and goggles should be worn.

Prep. Notes 

Capillary test tube apparatus is available from the physics demo room

© Copyright 2012 Email: Randy Sullivan, University of Oregon Chemistry Department and UO Libraries Interactive Media Group