How to Create Your Own pH Indicator with Cabbage

Lena and Petya were always excited for the moment when they could do a new science experiment in the kitchen. They had already tried many different experiments, but today they decided to make something special – a pH indicator with cabbage.

— Have you ever heard that cabbage can be a pH indicator? — asked Lena, looking at the red cabbage they took from the kitchen.

Petya replied in surprise:

— No, I thought indicators were special liquids. How can cabbage change color depending on acidity?

— It’s very simple, — Lena said, showing Petya a book with explanations. — Cabbage juice contains natural pigments that change color depending on the pH of a solution. That means we can use it to determine if a solution is acidic or alkaline.

Petya said curiously:

— Cool! What do we need for the experiment?

Lena pointed to the ingredients on the table:

— We need a few leaves of red cabbage, a pot of water, a knife, a bowl, and several liquids with different acidities to test how the cabbage reacts to them. For example, vinegar, soda, lemon juice, and of course, regular water.

Lena began to chop the cabbage. She chose red cabbage because its pigments, anthocyanins, change color vividly at different pH levels. Once the cabbage was chopped, Lena put the pieces in a pot of boiling water to extract the pigments.

Petya stood by and watched every step carefully. He was amazed at how quickly the water turned purple.

— The water changes color immediately, — Petya said. — I didn’t know cabbage could be so interesting!

— This is the magic of chemistry! — replied Lena with a smile. — Now that the cabbage juice is ready, we need to strain it to separate the liquid from the cabbage leftovers. We now have a natural indicator that we can use to test different substances.

Petya eagerly helped Lena strain the liquid, and then they began preparing the solutions for the experiment. Lena filled several glasses with water and added a bit of vinegar to one, lemon juice to another, and soda to the third. They created solutions with different acidities and began testing how the cabbage juice would react to them.

— Look, — said Lena when they added the cabbage juice to the vinegar glass. — The solution turned red, which means it’s an acidic solution. Vinegar is an acid, so the cabbage juice became this bright color.

— And what happens with the other solutions? — asked Petya.

Lena added the cabbage juice to the lemon juice glass, and the solution turned red as well, confirming that lemon juice is also acidic. Then they added the cabbage juice to the soda glass, and the solution turned green, indicating that soda creates an alkaline solution.

— This is amazing! Cabbage juice really changes color depending on whether the solution is acidic or alkaline. We just created a pH indicator, — exclaimed Petya, amazed by the results of the experiment.

— Yes, and now we can use it to test other liquids and substances, — added Lena. — We can even do a whole series of tests to find out which solutions are more acidic and which are more alkaline.

After completing the main experiment, Lena and Petya decided to run a few more tests. They tested other substances in the kitchen — lemonade, vinegar, water with soda, and even milk. Every time, the cabbage indicator changed color, allowing them to accurately determine which solutions were acidic and which were alkaline.

— You know what’s the coolest part? We used really simple materials to create our own indicator. And it’s not only interesting, but also useful for learning chemistry! — said Petya as he gathered all the materials.

— Yes, it was fun and educational, — agreed Lena. — We can use the cabbage indicator to test any liquids and even check the pH of soil in the garden or yard!

Thus, the kids not only learned how a pH indicator works, but also developed an interest in chemical experiments. They realized that nature is full of amazing possibilities, and now they were ready to continue their scientific research, creating new exciting experiments at home.