Indicators are special substances that change color when the acidity or basicity of a solution changes. They help us see how acidic or basic something is by changing colors.

Here's how they work:

• They have two forms: acidic and basic.
• Their balance between these forms helps them indicate pH levels, which is a measure of acidity or basicity.

Color Changes Based on pH:

Indicators change color at certain pH levels. Usually, this happens between pH 4.0 and pH 10.0. This means that they can show us different pH levels just by changing color.

Common Indicators and Their pH Ranges:

• Litmus:

  • pH 4.5 - 8.3
  • Goes from Red in acid to Blue in a base.

• Phenolphthalein:

  • pH 8.2 - 10.0
  • Is Colorless in acid and turns Pink in a base.

• Methyl Orange:

  • pH 3.1 - 4.4
  • Shows Red in acid and Yellow in a base.

Using these indicators, scientists can track chemical reactions, especially acid-base reactions. This helps them get important information about how these reactions are going, often measuring changes in pH to a precision of just 0.1 units.