Red Cabbage Anthocyanin pH Spectrophotometry
An engaging, screen-free learning activity that builds real-world creativity and critical thinking for kids aged 7 to 9.
Materials Needed
- • Boiled red cabbage indicator broth (cooled) (2 cups)
- • Clear glass tumblers or test tubes (6 units)
- • Household test liquids (lemon juice, vinegar, baking soda, soap) (1 tablespoon each)
- • Liquid pipettes or medicine droppers (2 units)
Pro Tips
- → Boil chopped red cabbage in water beforehand (or steep shredded leaves in warm water) until a deep purple broth forms.
- → Arrange the glasses in a straight line against a sheet of white paper to highlight subtle color transitions.
- → Prompt your child to predict the pH category (acid or alkaline) before introducing the purple indicator.
Safety First
Wear safety goggles or glasses; ensure child does not taste any test solutions.
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Step-by-Step Instructions
Step 1
Line up 6 clear glasses on a white surface and add 2 tablespoons of warm purple cabbage juice to each.
Step 2
Add 1 teaspoon of lemon juice to glass 1 and white vinegar to glass 2; observe the deep magenta and bright red acidic shifts.
Step 3
Leave glass 3 as pure water for the neutral violet baseline; add baking soda solution to glass 4 and liquid hand soap to glass 5 to reveal turquoise and emerald green alkaline shifts.
Step 4
Slowly drip acidic lemon juice into the green alkaline glass to neutralize the solution back toward purple in real time.