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Equilibria involving gaseous carbon dioxide in solution gives details of an excellent practical activity using fizzy (carbonated) water. Methyl red indicator added to the water in a syringe, turns from red to yellow as the solution is degassed, showing the solution has become less acidic as the equilibria shifts.

Understanding equilibria provides a useful overview of some of the difficulties students experience with chemical equilibria together with supporting ideas and activities for the classroom. The cobalt equilibrium practical activity is of particular interest – a key point being the change in equilibrium position produced by temperature change.

The Gridlocks game of pH and pOH provides an interactive and printable game, with an added walkthrough. The puzzle involve matching boxes to their corresponding values of pH or pOH and H⁺ ion or OH^– ion concentrations to complete the grid. An added benefit is the convenient numbers used, which allow the use of 'estimating logs' without the necessity for a calculator.

Further gridlocks games can be found for pH on Learn Chemistry and they are listed in the subsequent Additional resources and activities section.