demonstrations:ph_indicator_easter_eggs
pH Indicator Easter Eggs
Materials: ★★☆ Available in most school laboratories or specialist stores
Difficulty: ★☆☆ Can be easily done by most teenagers
Safety: ★☆☆ Minimal safety procedures required
Categories: Acids and Bases, Special Occasions
Alternative titles: Color Changing Easter Eggs
Summary
Eggs are dyed with red cabbage extract, which contains the natural pH indicator anthocyanin. Applying acidic or basic solutions changes the color of the dye, allowing designs, messages, or patterns to be revealed on the eggs.
Procedure
- Boil red cabbage in water until the liquid turns deep purple, then strain out the cabbage.
- Hard-boil eggs and let them cool.
- Place the eggs in the cabbage water until they are dyed purple.
- Remove the eggs and dry them.
- Use a cotton swab dipped in vinegar to draw patterns or write messages (areas will turn pink/red).
- Use a cotton swab dipped in baking soda solution to draw patterns or write messages (areas will turn green/teal).
Links
Easter Egg Decorating - Cabage pH Indicator Experiment - Emily Calandrelli:
Variations
- Use lemon juice instead of vinegar for acidic patterns.
- Try washing soda or soap solution for stronger base effects.
- Use white or brown eggs to compare how the background shell color affects the final design.
Safety Precautions
- Adult supervision required when boiling water and handling hot eggs.
- Wear gloves to avoid staining hands with cabbage dye.
- Avoid contact with eyes when using vinegar or baking soda solutions.
Questions to Consider
- Why does red cabbage change color in acids and bases? (It contains anthocyanin, a pH-sensitive pigment.)
- What colors do you expect if you use something very acidic like lemon juice versus something strongly basic like washing soda?
- How could you use this experiment to test the pH of unknown household substances?