Hands on examination which examines the pH of 6 acidic solutions of hydrochloric acid. Each solution is 10% of the previous one. The pH is measured using sensitive pH strips, sensitive to 0.5pH units, and recorded.
The results are analyzed and a conclusion drawn which relates the strength of the acid solution and the pH.
The Chemistry of the pH change is shown to be related to the hydrogen ions produced by each dilution. The stronger the acid, the greater the number of hydrogen ions and the smaller is the pH number.