Arizona Science Center: The Rainbow In A Bottle Reaction

Can you make your very own rainbow in a bottle?

You can with the magic of pH! pH is a measurement of how acidic or basic something is. Very acidic things have a pH of 0, while very basic things have a pH of 14. What’s in the middle? Neutral materials, like water, have a pH of around 7. Red grape juice naturally changes color base on pH, so we can use it as a pH indicator. Grape juice is mostly made out of the water and is fairly neutral, so its purple color indicates around pH 7. An acid with pH 0 would be a bright clear yellow. A base with a very high pH will have a green color. We can make a rainbow by first making an acid solution and then slowly lowering the pH until the solution is a base. We can make that happen slowly with a medicine called milk of magnesia, which can neutralize acids.


Chemistry
Early Childhood, K-6

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