Answer: Acid change the blue litmus paper to red.
Step-by-step explanation:
Litmus paper is defined as paper which is used to detect the acidity and basicity of the solution. It acts as an indicator. There are 2 types of litmus paper.
- Red litmus paper: This paper changes its color to blue when dipped in basic solution and remains as such when dipped in acidic solution.
- Blue litmus paper: This paper changes its color to red when dipped in acidic solution and remains as such when dipped in basic solution.
Hence, to detect an acid, blue litmus paper will change its color to red.