Everyday substances

In the earlier post, you were showed how the universal indicator worked. The table here shows the pH values of some everyday substances.

(Please click on the image if it is not clear enough for viewing.)

As mentioned, acids have a pH value of less than 7 while akalis have a pH value of more than 7. This shows that items like milk, potatoes, tap water, soft drinks, lemons and grapefruit are acidic substances. Meanwhile, items like baking powder, soap, toothpaste, indigestion tablets, bleach and limewater are alkaline substances. Since neutral substances have a pH value of 7, we can therefore tell that distilled water is a neutral substance.

pH and universal indicator

A universal indicator is a mixture of a few other types of indicators. It may be used in the form of a solution or a paper. This indicator turns into different colours when added to different substances. Every colour will correspond to a pH value from 0 to 14. The only disadvantage of the universal indicator is that it can only give the approximate pH value of a solution.

The picture below shows how the indicator works. (Please click on the image if it is not clear enough.)


Acidic mixtures will have a pH value lesser than 7, while alkaline mixtures would have pH value of more than 7. Neutral mixtures will have a pH value of 7, meaning that they are neither alkali nor acid.

In order to get the accurate pH value of a substance, a pH meter can also be used. The electrode is dipped into the solution and the pH value is read directly from the meter.