Education Technology

Diffusion and Equilibrium

Activity Overview

Students will observe how equilibrium is reached when salt is added to water.

Before the Activity

Students should have access to either the TI-83 or TI-84 family of calculators. NOTE: This activity does not contain attachments.

During the Activity

Students will be shown a long container filled with water (I use a plastic shoebox type storage container) with two salinity probes (one on each end).
Students will be asked to graph their prediction of what will happen when salt is added to one end. After making their predictions, students will observe the graph (using a view screen) as it progresses after the addition of the salt. This is a great way to really drive home the concept of equilibrium.
The probe on the side of the addition of salt registers a high initial reading while the other probe registers close to zero. In a few minutes, as the salt dissolves and diffuses, the graphs meet in the middle. One pitfall to this is that you must calibrate the probes together to get the two lines to actually meet. This is a great classroom conversation starter for this particular content.

After the Activity

Review student results:

  • As a class, discuss questions that appeared to be more challenging
  • Re-teach concepts as necessary