Here's why:
* Copper sulfate is acidic. When copper sulfate dissolves in water, it forms hydrated copper ions (Cu²⁺) and sulfate ions (SO₄²⁻). These ions react with water molecules, releasing hydrogen ions (H⁺) and making the solution acidic.
* Universal indicator changes color based on pH. Universal indicator is a mixture of dyes that changes color depending on the acidity or alkalinity of a solution. In an acidic solution, it turns red.
Therefore, when you add copper sulfate to water and dip universal indicator paper into the solution, the paper will turn red.
