The Color-Changing Sports Drink





Introduction: The Color-Changing Sports Drink

This blue drink turns purple then red/pink upon addition of a citric acid-boosted can of Sprite. It tastes good and has a similar chemical profile to a hypotonic sports drink (also see this homemade sports drink recipe). It's the kid-friendly version of the Color-Changing Martini - and it's much cheaper and more convenient than buying martini ingredients and dry ice. It's basically a classic chemistry demonstration you can drink.

Note: I published this instructable in 2010, but unpublished it while I developed it further as a submission to the American Chemical Society's  Journal of Chemical Education. The article has now appeared, so for those of you who happen to have electronic access to this journal (probably because you are connected through a university network), you can find the manuscript online here.

Step 1: Ingredients

You'll need: 

Sprite (or other clear carbonated beverage) ~ baking soda ~ red cabbage ~ citric acid ~ tap water

Step 2: Red Cabbage?

Yes - it has a pH-sensitive anthocyanin in it, which will act as an indicator. We're going to make the drink basic (alkaline) with baking soda (sodium bicarbonate, NaHCO3), then neutralise it with the acid (citric + carbonic) in the Sprite. The extra citric acid is not strictly necessary - the drink will change color to purple without it - but add it and the drink will turn out a bright pink color.
To get the indicator, you can chop up a cabbage leaf and microwave it in a small amount of water, or add boiling water, or blend and strain the cabbage leaf (thanks to groenert for this last tip). You should get a deep purple-colored liquid.

Step 3: Build

Add a few teaspoons of the cabbage juice to a glass, half-fill with water, and add very small amounts of baking soda until you get a nice bright blue color.
Add about 1/4 teaspoon of citric acid to a teaspoon or two of water, and stir until dissolved. Add it to a half-filled glass of Sprite (or similar).

Step 4: Serve!

Pour the blue solution into the adulterated Sprite. It will instantly turn bright pink, and bubble. Drink! It tastes quite good - a slightly sharp, slightly fizzy lemon/lime flavoured sports drink. The cabbage juice is not really detectable. See the video for the effect. If you don't add the citric acid, the colour will be more purple than pink.

Adding the clear Sprite to the blue solution works well, too, and if you watch closely you can see it transition through purple. Also, substituting sugary water for the Sprite works fine. Here's a video of these two together (sugar + citric acid + water added to cabbage juice + baking soda + water):

Pouring them in simultaneously from small glasses into a bigger one also looks good.

Step 5: That's a Good Cup of Joe

My son used this quote (courtesy of Stephen Colbert's POTUS from Monsters vs. Aliens) all the time after he saw the movie... 




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    Thanks for this. Did it as a science lesson with my kids. Trying it with calcium bicarbonate (Tums). The color change works well, but it does leave the liquid a bit cloudy/milky, trying to let the particulates settle a bit in the hopes I can pour off a nice blue liquid. The goal is to avoid that sodium flavor. Thanks again.

    Great! You need only a tiny bit of sodium carbonate to make it go blue - it's pretty hard to taste once you have the cabbage/sprite in there.

    I used the citric acid idk why it's kind of purple, might be the lighting?

    Cool, glad it worked. Still looks pretty purple tho - did you just use Sprite without the citric acid?

    Trying this

    Great stuff. I'm a chemist, and can mess with my non scientist family members with something they can see and taste, then hopefully understand. :-) Thank you!

    Cheers, you're welcome. Have fun!

    oh. Color is very good-looking.

    Will it still work if I add gin to it first? ;)