Re: Is using an acid/base indicator a physical change or a chemical change?

Hi Becky! I think I have an easy answer for you:

The indicator represents a chemical change because it only works if the composition/characteristic of the surrounding liquid changes -> i.e. from an acid to a base. Food coloring doesn't really care what the rest of the material is doing, so normally doesn't change color with a change in pH -> i.e. represents a physical change.

You should also try our MAD Science Library's chemistry section. There are some links about acids and bases that explain indicators and pH in more detail.

Hope this explanation helps and have fun with your chemistry! ;)

Kieran