How to Make Red Cabbage PH Indicator?

The Red Cabbage Indicator is a super colorful household science experiment with the domestic materials. Adding different materials like baking soda, vinegar can change its color.

Ages: 3+        Est. Time: < 1 hour

 Safety 

1. Adult supervision.
2. Be careful with sharp scissors.
3. Wear gloves and goggles.
4. Be careful when heating.

 Materials List 

• Red cabbage
• Baking soda
• Water
• Vinegar
• Scissors
• Heater
• Pot
• Wine glass (transparent container)

 Instruction 

Step 1/5 – Cut some red cabbage leaves about 100g.

Step 2/5 – Cook the red cabbage in 500ml water and then let it cool down for about 30mins.

Step 3/5 – Pour out the juice to a container.

Step 4/5 – Add about 16g of vinegar, stir it up, and the cabbage juice will turn to red.

Step 5/5 – Add about 10g of baking soda powder. A lot of bubbles will be generated and, in the meantime, the red color will turn back to purple.

 Troubleshooting 

Why does my red cabbage fail to turn its color?

– Make sure the red cabbage is fresh enough.

 Scientific Description 

Red cabbage contains lots of water-soluble pigment, anthocyanins. It may appear red, purple, blue, or even black in different PH. The anthocyanins can also be found in many plants. Like apple, plums, cornflowers, and grapes. Cook the red cabbage in water making the anthocyanins solve into the water. anthocyanins can turn into different colors when in different PH. When the vinegar is added, the PH is below 7 and the red cabbage juice will turn to red. Then add baking soda which reacts with vinegar producing carbon dioxide which releases from liquid and causes lots of bubbles. The backing soda uses up the vinegar and the PH turns back so the color of the liquid turns back to purple.

 Extensions 

1. Your kids can draw a cabbage juice painting and turn its color with just a spray of baking soda solution or vinegar.
2. You can let your kids guess which color of the red cabbage juice will become before you pour different liquids into the cabbage juice.

 Disposal 

The used material can be treated as domestic waste. And, do not forget to wash what you have used.