After the samples have been prepared, test each one with chemical indicators. This gives an indication of the colour of the indicators at different pH levels. Repeat as above, starting with a 0.1 M NaOH solution. Test a variety of solutions with chemical indicators. Determine whether the solutions are acidic, basic, or neutral.
Students can determine the approximate pH of each unknown solution with indicators.
The serial dilutions prepared previously can be used as standards for comparison. Try to react each of the unknown samples with a small strip of magnesium ribbon. Record the results and look for a correlation between the pH and the reactivity with magnesium for each substance. Once the standard and unknown solutions have been tested, a variety of household materials can be tested. Place a few drops of phenolphthalein indicator into a beaker of water.