Mai Lesson

Secret Agent Chemistry

Science · 30 min · Ages 9-11 · Upper elementary · You and your child together

This lesson turns everyday red cabbage into a secret spy tool, revealing hidden chemistry in your kitchen. Discover how liquids can change color based on their chemical properties, and use this knowledge to create invisible ink that only a family member can reveal! Needs 15 minutes of adult prep first: steep chopped red cabbage in hot water, then strain and cool it to make the indicator liquid.

What your child gets out of it

• Observe and describe chemical reactions using a natural pH indicator.
• Predict and test the acidity or basicity of common kitchen liquids.
• Apply knowledge of pH to create and reveal an invisible ink message.

What you need

• Red Cabbage — Steep in hot water 10-15 min, then strain and cool completely. Adult handling needed for hot water. (or Blueberries, Grape Juice)
• Water — Needed for making cabbage indicator and baking soda solutions.
• Heat-Safe Bowl — For steeping the red cabbage. (or Pitcher, Large Mug)
• Kettle — To heat water for steeping. (or Saucepan)
• Strainer — To separate cabbage pieces from the indicator liquid. (or Colander, Sieve)
• Clear Cups — Need at least 3 for testing different liquids. (or Small Bowls, Drinking Glasses)
• Lemon Juice — Used as an acid for pH testing. (or Vinegar)
• Baking Soda — Used as a base for pH testing and invisible ink.
• White Paper — For writing secret messages. (or Printer Paper)
• Cotton Swabs — For writing invisible ink messages.
• Paintbrush — For revealing invisible ink messages. (or Sponge, Cotton Ball)

How it runs

1. Introduction · 5 min
2. Explore & Plan · 9 min
3. Discussion · 6 min
4. Activity · 9 min
5. Summary · 1 min