pH Testing Household Liquids Experiment
Make a pH indicator from red cabbage juice and test household liquids to discover which are acids and which are bases. Rainbow chemistry from your kitchen.
What You'll Need
- 1Red cabbage (quarter head)
- 2Water
- 3Pot for boiling (adult help)
- 4Strainer
- 56-8 clear cups
- 6Test liquids (lemon juice, vinegar, baking soda water, soap water, milk, soda, orange juice)
What You'll Need
Red cabbage (quarter head)
Water and a pot for boiling (adult help)
A strainer
6-8 clear cups
Test liquids: lemon juice, vinegar, baking soda water, soap water, milk, soda, orange juice
How to Play
Boil chopped cabbage in 2 cups water for 10 minutes. Strain — the purple liquid is your indicator.
Pour indicator into 6-8 cups.
Gather test liquids from around the kitchen.
Add a different test liquid to each cup. Watch the colors change!
Acids (lemon, vinegar) turn it pink/red. Bases (baking soda, soap) turn it green/blue.
Line cups from most acidic (red) to most basic (blue).
"You built a pH scale!"
The Science Behind It
Red cabbage contains anthocyanin, a pigment that changes color depending on pH. In acidic solutions (pH below 7), it turns pink or red. In neutral solutions (pH 7), it stays purple. In basic solutions (pH above 7), it turns blue, green, or even yellow. This is the same principle behind litmus paper, just using a natural indicator instead.
Tips
The cabbage juice should be a deep, saturated purple. Pale juice gives weak color changes.
Clear cups are essential so you can see the colors clearly. Glass works better than plastic.
Include a "neutral" reference: plain water keeps the indicator purple.
For dramatic effect, test bleach (adult-only handling) — it turns the indicator yellow/clear because it's a strong base.
Record the results with photos. Line up all the cups for a rainbow pH gradient.
Ask: "Our stomach is very acidic. Why? What does acid help our stomach do?" (Break down food.)
Frequently Asked Questions
How long does this activity take?
This activity takes about 30 min, with 15 min of preparation time beforehand.
What materials do I need?
You'll need: red cabbage (quarter head), water, pot for boiling (adult help), strainer, 6-8 clear cups, and 1 more item.
What age is this activity for?
This activity is designed for 8-12 years. You can adapt it for younger or older children by adjusting the complexity.
Can this be done indoors?
This activity is designed for indoor play, making it perfect for rainy days or when you're staying inside.
How difficult is this activity?
This activity has a moderate difficulty level. It may require some preparation or guidance, but is manageable for most families.
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