Write down the approximate pH value and set the cup aside. Dip an unused, clean strip of pH paper into the water cup for about 2 seconds and immediately compare with the color chart. Write down the approximate pH value. Vinegar is an acid, and in this experiment it will display a pH of about 4. Ammonia is a base and in this experiment it will display a pH of about 12.
Bases turn most pH indicators blue.
PURE distilled water would have tested neutral, but pure distilled water is not easily obtained because carbon dioxide in the air around us mixes, or dissolves, in the water, making it somewhat acidic. The pH of distilled water is between 5.6 and 7. If the water is still acidic, repeat the process until pH 7 is reached.