What is pH | Acid and base experiment at home | Red and blue litmus paper experiment | pH Paper Test

                  Define pH

What is pH?

pH is a scale used in chemistry to represent acidic, basic or neutral nature of solutions. pH can be measured with acid base indicators, pH paper strips,  automatic pH measuring instrument or pH meter etc.

Definition of pH

pH is negative logarithm of hydrogen ion concentration.

pH = -log10[H+]
pH scale is from 0 to 14
1. Acids have pH below 7.
2. Bases have pH above 7.
3. Neutral solutions have pH of 7.


Red and Blue Litmus Paper Experiment

Acid and base experiment with litmus paper is the most common tests for acids, bases and neutral solutions or chemicals. These tests can be even performed at home. Litmus paper tests are also known as red and blue litmus paper test. The litmus papers are the chemical indicators used to test the nature of the solution. 

Dip one end of litmus paper in the chemical solution, litmus paper changes its colour as per pH of the solution. Red litmus papers are used to identify basic solution. While, blue litmus papers are used to identify acidic solution.

pH Paper Test

Another most common test for acid and bases is pH paper test. PH papers are used to identify the pH of the chemical substance using pH paper. 

Dip one end of PH paper in the chemical solution, PH paper changes its colour as per pH of the solution.  After 2-3 seconds, remove the paper and compare the colour of the pH paper with the colour chart provided with pH paper kit.


=> in Acid - Blue litmus paper turns Red 
=> in Neutral Solution - No Change in Color 
=> in Base - Red litmus paper turns Blue

pH is a numerical scale to represent acid, base or neutral solution on scale of 0 to 14. Measurement of pH is very important in so many fields like chemistry, biology, medicine, agriculture, food and many more...... In your school college days you surely see litmus paper to test pH of chemicals. 

Formula for pH Calculation-


Previous Post Next Post