Why does cabbage juice work as an indicator?

Cabbage juice acts as an indicator because it contains a pigment called anthocyanin. Anthocyanins are a type of flavonoid that changes color depending on the pH of the solution it's in.

Here's how it works:

* Acidic Solutions: In acidic solutions, the anthocyanin molecules in cabbage juice become protonated (gain a hydrogen ion). This causes them to have a reddish or pink color.

* Basic Solutions: In basic solutions, the anthocyanin molecules deprotonate (lose a hydrogen ion). This causes them to have a bluish or greenish color.

Therefore, cabbage juice can be used to test the pH of solutions. For example:

* Vinegar (acidic): The cabbage juice will turn pink or red.

* Baking soda solution (basic): The cabbage juice will turn blue or green.

* Water (neutral): The cabbage juice will remain a purple color.

The exact color change can vary depending on the concentration of anthocyanin in the cabbage juice and the strength of the acid or base. But generally, the color shift provides a visual indication of the pH level.