How can we control viscosity?

Investigating ionic molecules, surfactants and micelles.

14 16 Lesson2 Large

In this lesson

In this lesson students explore how surfactants (the active compounds in detergents) can be made to have different viscosities or thickness, depending on use.

Students learn how surfactant molecules can form ‘micelles’, small spherical groups of surfactant molecules. They add salt solution to change the ionic concentration of a sample solution and discover how the salt concentration changes how closely together these micelles can pack together.

Students then test the viscosity of their solutions, recording results and plotting their 'salt curve' on a graph.

To complete this experiment, you will need to order a free surfactant concentrate from SUOS. Each school is entitled to a 1L container of concentrate which is enough to make 10L of solution. This will be enough to complete the experiment three times with a class of 30 students. The finished diluted surfactant must not be used, kept in the classroom or taken home by the students after the experiment. Please dispose of in a sink with plenty of water.

Details for how to order your solution are in the teacher notes.