Sorry i don't quite understand. I am not after a chemical equation answer. I am after one in words. I am only in grade 9 so we have not really done any chemical equations.
I just need to know what happens when the indicator contacts the base.
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Nobby: said twice
, pH indicators are large organic molecules, that are also weak acids themselves. When they're surrounded by strong acids, which give up H+ (by definition), the indicator molecule holds on to it's own H+. When surrounded by base, they give up their H+. This changes the molecules electron configuration, and it's color. That last part is pretty advanced chemistry, so you may want to read a basic chemistry textbook, until you understand acids, then read an advanced chemistry textbook, to understand electron configuration, multiple conjugates double bonds, and light adsorption. So you can write the best answer possible.