🥬 CABBAGE pH INDICATOR
🧪 YOUR LAB CHECKLIST
Science buddy, grab a grown-up before you use the stove or handle hot liquid. Work on a stable counter with oven mitts ready. This comic explains why cabbage juice changes color.
- 🥬 Red cabbage: a few outer leaves or a quarter head, chopped small
- 💧 Water: enough to cover cabbage in a pot (about two cups)
- 🍋 Lemon juice or vinegar: acid test sample in a small cup
- 🧂 Baking soda mixed with water: base test sample in another cup
- 🥽 Clear cups, strainer, and tongs for pouring cool purple indicator safely
Time: about 40 min · Adult supervision required · One jar of purple indicator plus two color-change demos
PAGE 1 OF 5 · THE pH SCALE
ACID VS BASE
SOUR TO SOAPY
Scientists rank how acidic or basic a liquid is using the pH scale, usually from 0 to 14. Low numbers mean more acidic, like lemon juice and vinegar. Seven is neutral, close to plain water. High numbers mean more basic (also called alkaline), like baking soda in water. Acids donate hydrogen ions; bases soak them up. Many reactions, including the ones in your body, depend on keeping pH in a safe range. Cabbage juice can show that range with color.
pH!
ACID
🍋 Acids taste sour and rank below pH 7 on the scale.
BASE
🧂 Bases feel slippery in water and rank above pH 7.
PAGE 2 OF 5 · BREW PURPLE INDICATOR
CABBAGE SOUP SCIENCE
ANTHOCYANIN EXTRACT
Chop red cabbage into small pieces so hot water can reach more surface area. With adult help, simmer the pieces in water for about ten minutes until the liquid turns deep purple. That color comes from anthocyanins, natural pigments in many red and purple plants. Strain out the solids so you get smooth indicator juice. Let it cool before kids handle cups. The purple brew is neutral-ish on its own and ready to react when acids or bases join the party.
BREW!
CHOP
🔪 Smaller pieces release pigment faster in hot water.
STRAIN
🫙 Clear juice makes color changes easy to see.
COOL
❄️ Hot steam burns: wait until cups are safe to hold.
PAGE 3 OF 5 · ACID TURNS RED
LEMON TEST
PINK AND RED ALERT
Pour a few spoonfuls of cool cabbage indicator into a clear cup. Add lemon juice or vinegar drop by drop and stir gently. Watch the purple shift toward pink and bright red. Acid raises the concentration of hydrogen ions in the mix, which changes how anthocyanin molecules reflect light. The same pigment that makes cabbage purple is now shouting "acid here!" without needing fancy lab equipment. Try noting how many drops it takes to reach your favorite shade.
RED!
DROPS
💧 Small doses show gradual color steps on the pH journey.
STIR
🥄 Gentle stir spreads acid evenly for a uniform hue.
PAGE 4 OF 5 · BASE TURNS GREEN
BAKING SODA TEST
GREEN MEANS BASE
In a fresh cup of purple indicator, add a spoonful of baking soda dissolved in water. Stir and observe the color slide toward blue-green. Bases lower hydrogen ion levels, flipping anthocyanin into a different form that absorbs new colors of light. Place your acid cup beside your base cup and you have a homemade pH chart made from salad ingredients. Never mix strong cleaners for this demo: stick to kitchen-safe lemon and baking soda with adult permission.
GREEN!
COMPARE
🌈 Line up cups like a rainbow pH meter.
PIGMENT
🔬 Same molecule, new shape, new color you see.
SAFE
👩🍳 Stovetop steps stay with grown-ups every time.
PAGE 5 OF 5 · CLEANUP & WHAT YOU LEARNED
AFTER THE TESTS
COMPOST, RINSE, LABEL
Cooked cabbage solids can go in compost or trash. Rinse cups and jars with water. Leftover purple indicator keeps in the fridge a day or two in a labeled jar ("cabbage pH juice, not a drink"). You extracted a natural indicator and watched acid-base chemistry paint new colors. Gardeners even use cabbage tests on soil samples. Next upgrade: test clear soda vs soapy water, or compare lemon strength to vinegar. Always predict the color before you pour.
WOW!
FRIDGE
🏷️ Label jars so nobody thinks purple juice is punch.
REMEMBER
⚡ KEY FACTS
Anthocyanins in red cabbage change color with pH. Acids push toward red; bases push toward green. pH tells how acidic or basic a liquid is. Stovetop boiling needs a grown-up every time.
✅ Cool the juice before kid-led cup tests.
✅ Use fresh cups when comparing acid vs base.
✅ Predict first, then pour: that is real lab thinking.
✅ Use fresh cups when comparing acid vs base.
✅ Predict first, then pour: that is real lab thinking.
🧠 QUIZ TIME!
CABBAGE pH INDICATOR · 5 QUESTIONS
QUESTION 01
On the pH scale, numbers below 7 mean the liquid is…
QUESTION 02
The purple color in boiled cabbage juice comes mainly from…
QUESTION 03
When you add lemon juice to cabbage indicator, the color shifts toward…
QUESTION 04
Adding baking soda solution to the indicator pushes the color toward…
QUESTION 05
Most important safety step for this cabbage lab?
0/5
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