Module 5 Intro

Module 5—Acids and Bases

Lesson Summary

In this lesson you explored the following essential questions:

• What are acid-base indicators?
• How are acid-base indicators used to predict the pH of a solution?
  

Acid-base indicators are weak acids and bases that can have multiple forms, and each form is associated with a colour. The colour change of one or more indicators can be used to estimate the pH of a solution.

At the beginning of the lesson you made a red cabbage indicator solution that was tested with vinegar and baking soda. When mixed with the vinegar, the solution turned red; when mixed with baking soda, the solution turned a blue-green. The loss of a hydrogen ion by the indicator to the basic hydrogen carbonate ion is responsible for the colour change you observed.

Lesson Glossary

acid-base indicator: a substance that changes colour in solution when the acidity of the solution changes