Blue Litmus Paper in Acid and Base:
Blue litmus paper is commonly used to test for the presence of acids and bases. The color change of blue litmus paper in acidic and basic solutions is a simple and effective way to determine the nature of a substance.

Blue Litmus Paper in Acid:
- When blue litmus paper is dipped into an acidic solution, it will turn red.
- This color change occurs because acids have a low pH, which means they have high concentrations of hydrogen ions (H+).
- The blue litmus paper reacts with the hydrogen ions in the acid, causing a chemical change that results in the paper turning red.
- This color change is a reliable indicator that the solution is acidic.

Blue Litmus Paper in Base:
- In contrast, when blue litmus paper is placed in a basic solution, it will remain blue.
- Bases have a high pH, meaning they have low concentrations of hydrogen ions and high concentrations of hydroxide ions (OH-).
- The blue litmus paper does not react with the hydroxide ions in the base, so it retains its blue color.
- The lack of color change in the blue litmus paper indicates that the solution is basic.
In conclusion, blue litmus paper is a useful tool for distinguishing between acidic and basic solutions based on the color change it undergoes. By observing whether the paper turns red or remains blue, one can quickly determine the nature of the substance being tested.