Acidification of Water

We use a drinking straw, some water and universal indicator to show that breathing out creates acid. Universal indicator is added to the water to show its pH value. When we blow into the water the indicator changes colour showing that the pH has decreased and is acidic. Chemistry - Reactions - Learning Points. Acids have a pH of 0 to <7.Alkalis have a pH of >7 to 14. Water is neutral or pH 7. Chemical indicators change colour to indicate pH. Carbon dioxide and water produce carbonic acid, a weak acid.Weak acids and alkalis partially dissociate in solution. Strong acids and alkalis completely dissociate in solution. A Twig Experiment Film. Let students experience real experiments in lab conditions anywhere, from setup, method all the way through to analysis and real-world application.