Acids and bases differ in the way they behave in aqueous solution. Their properties depend not only on concentration, but also on the extent to which the acid or base ionises in water.
This interactive PhET simulation allows you to explore strong and weak acids and bases, compare the particles present in their solutions, measure pH and investigate electrical conductivity.
Experiment with the model rather than simply observing it. Compare strong and weak solutions, change their concentrations and predict what will happen to the pH and the ions present before using the simulation to check your ideas.
Acid–Base Solutions is provided by PhET Interactive Simulations, University of Colorado Boulder, and is used under the CC BY-NC 4.0 licence.
1. Compare a strong and weak acid
Choose a strong acid and a weak acid at the same concentration. Compare their pH values and the particles present in solution. What does this tell you about the extent of ionisation?
2. Compare a strong and weak base
Repeat the comparison using a strong base and a weak base. How do the concentrations of ions in solution differ?
3. Change the concentration
Select one acid and gradually decrease its concentration. Predict what will happen to the pH before checking the result.
4. Strength is not the same as concentration
Try to create a concentrated weak acid and a dilute strong acid. Which has the lower pH? What does this show about the difference between strength and concentration?
5. Investigate conductivity
Compare the electrical conductivity of strong and weak acids or bases at similar concentrations. Explain the result in terms of the number of mobile ions present.
6. Examine the particles
Use the particle view to compare a strong acid with a weak acid. Which species are most abundant in each case? How does this microscopic picture explain the measured pH?
7. Predict before measuring
Choose several different solutions. Before using the pH meter, predict whether each solution will have a very low, moderately low, neutral, moderately high or very high pH.
Keep asking:
What determines the concentration of H⁺ or OH⁻ ions present in the solution?
That question connects acid or base strength, concentration, ionisation, pH and conductivity.