is an indicators reaction in acids and bases a chemical or physical change how can you tell?

Question

Science

Answer 1

Chemical change. Let the indicator molecule be X or X-OH. Then:

H+ + X(one color) ===> HX+(other color)

OH- + X-OH(one color) ===> X-O-(other color)

Always a chemical change, never a physical one. Indicators are acids and bases themselves. Acids of one color react with OH- to produce the conjugate base of the other color. Bases of one color react with H+ to produce the conjugate acid of another color.

Answer 2

Chemical. There is a physical change but that is a result of the chemical change.