More Deep Purple Magic

More Deep Purple Magic

Students are fooled by an acid-base colour-changing reaction, and learn how chemistry can explain this magical result.

Introduction

Phenolphthalein is an indicator — a chemical which changes colour depending on whether it meets an acid or a base. It turns purple if it meets something basic, such as ammonia; it stays colourless if it meets an acid like vinegar or a neutral substance like water.
In this magic trick, the phenolphthalein in beakers 1 and 3 will turn purple when you mix it with the ammonia in beakers 2 and 4. When you pour the two purple solutions into the large beaker, the acidic vinegar neutralizes the basic ammonia. The phenolphthalein becomes colourless.

Objectives

Students will be able to:

• Explain the importance of observation when doing science.
• Explain the chemistry behind a simple acid-base reaction.

Entire Activity

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Other Resources

Full Lesson & other activities - Magic

Science World School Programs: Chemistry

Illusions Gallery at TELUS World of Science