PH indicators?

Question

1. For example, there's a substance that has color on it, and you would want to know or to determine the pH of that substance, how will you do it? - I mean, would you just look at the color sample and match your pH answer there? What's really the right way?

2. How come the color of indicators change? GIve causes.

Thanks.

Answer 1

use a pH paper to know the pH

it changes color due to reactions

Answer 2

1.  You can not tell the pH of a substance by its color, if that is what you mean.  Are you refering to pH test strips?  Dip the strip into the solution, and match the color of the strip to the color on the chart to get pH.  For this to work, you need to dissolve the substance into solution, but then you get the pH of the solution with te substance in it, not the substance itself.

Essentially, pH is meaningless unless the substance is in some kind of liquid which can donate or accept protons, since this is what pH measures.

2.  pH Indicators change color when they accept or give up a proton or a hydroxide ion.  This changes the energy level of the molecule, causing it to absorb different frequencies of light which your eye registers as a different color.

Answer 3

To determine the ph of a substance you would simply just  dab som indicator in the required amounts (indicated by commercial qunatities) and wait for the reaction. You'd then compare the colour to your ph scale.

How this works is  because ph solutions are usually weak acids or bases. They can bind with hydrogen ions to to configurate electrons to give a different colour.