Indicators for Acid and Alkali

 Topic: Indicators for Acid and Alkali.

Objectives: by the end of the lesson,  you will be bale to;

1. use simulation to find the pH of different solution.

  

Indicator: the materials such as litmus paper, pH paper, methyl orange, etc, are called indicators because they are used to test the presence of acids and bases in certain specific materials.

pH: Power of hydrogen. It is the concentration of hydrogen ion. Greater the concentration of hydrogen ions, stronger the acid.

There is a simulation link given below, which will help you understand the pH of various solution without any experimental materials. 

Procedure: 

• Click on the link ‪pH Scale‬ (colorado.edu)

• Click on “Macro”

• There is a list of solutions on the top. You can choose any solution and click on the dropper to fill the beaker.

• On the left hand side there is pH scale and you can drag the pH reader into the solution to test the solution.

Some commonly used acid-base indicators and their color change are given below.

Acid-base indicators	Colour changes
	In acid	In base
Litmus paper	Blue to red	Red to blue
phenolphthalein	Remain colourless	Colourless to pink
Methyl orange	Orange to pink	Orange to yellow