Viscosity

One large, stoppered, test tube contains glycerine, the other contains water. Each contains a small metal ball. When the tubes are inverted, the balls fall to the bottom (and a couple of inadvertantly trapped air bubbles rise to the top). The ball falls (and the bubbles rise) much more slowly in the glycerine than in the water. 

Curriculum Notes 

This straightforward demonstration should be used when viscosity is being discussed. This demo takes about five minutes and is greatly enhanced by video projection.

Lead Time 
Two days of lead time is required for this project.
Discussion 

Viscosity is related to the strength of the intermolecular forces, but the bulkiness of longer chain molecules seems to contribute more to viscosity than it does to other intermolecular force dependent properties. Thus alcohol, though it has a lower boiling point than water, has a slightly higher viscosity. 

Materials 
  • Two large, stoppered, test tubes containing a small metal ball. One should be filled with glycerine, the other with water.
  • A contrasting background.
Procedure 

Simply invert the tubes, either one at a time or simultaneously. 

Prep. Notes 

We borrow these tubes from the physics demo prep room. They have them already prepared.

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