Acid/Base Indicator

by Alaa Yahya

Indicator Used

An indicator is a substance that changes color when added to another product, due to presence of an acid or base. The indicator we used in this experiment was a red cabbage juice.

Why is red cabbage a good indicator?

Red cabbage is a good indicator because it contains a pigment or coloring agent called Anthocyanin. Acid and bases are compounds that release hydrogen ions, however, Anthocyanin are complex molecules that can add and subtract hydroxide ions. Now, if you put anthocyanin in acidic solution, OH- will pop of the anthocyanin molecules. In basic solution, OH- in the water will hop into the anthocyanin molecules. Moreover, what makes anthocyanin an indicator, is that each form of the compound reacts with light differently, so that each form is a different color. All acid-base indicators, in fact, change color because they change their structure in some way( Posted by: Sue Klemmer, Secondary School Teacher science)

My Experiment

Acid/Base indicator


A base has a pH greater than 7. Therefore, when we add our indicator, the color must change to yellow, green or blue.


An acid has a pH less than 7. So, to identify an acid, we should add our indicator and the color must change to red, pink or purple.


A neutral solution has a pH of 7, which means that the color won't change because it's neither acid nor base

Proof of my experiment

Make your OWN pH Indicator from Red Cabbage!
This indicator is one of a kind, and its very easy to make at home. It is very helpful for teachers to identify what kind of solution they're using. Not only that! But students also are able to use it because the indicator we use is made from natural resources and not toxic!!