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There are many different modelling simulations available freely online to support teachers and students of chemistry and science across a range of topics. However, it is worth exploring a particular simulation yourself in advance, to ensure that it actually shows what you want it to show for a particular lesson, and is not simply a flashy, new, attractive graphic that may even confuse your students.

One example of a simulation for strong and weak acids and alkalis is the acid-base solutions from PhET University of Colorado.

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Have a look through the introduction to familiarise yourself with the options: view strong or weak, acid or base, or the water equilibrium with its small numbers of ions on the bar chart. Explore the available options. Consider which aspects, in particular, might you use with students.

The pH meter or electrical conductivity probe can be selected. Drag and drop the probe into solution. Why do the strong acid/alkali solutions conduct very well, yet not so well for the weak solutions?

The greater numbers of ions, carry the charge, allowing better conductivity in solution. Does it help to see this visual representation?

Selecting the 'My solution' tab, compare what happens to the pH when a strong or weak acid is diluted. What happens to the relative numbers of particles when an acid is diluted?

This can be viewed as a bar chart on the simulation by clicking the 'Graph' option, and then adjusting the concentration to show more dilute or more concentrated.