Introduction: The Color-Changing Sports Drink

Picture of 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Note: I published this instructable in 2010, but unpublished it while I developed it further as a submission to the American Chemical Society's  Journal of Chemical Education.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

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You'll need: 

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

Step 2: Red Cabbage?

Picture of 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

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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!

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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

Picture of 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... 

  

Comments

klixtopher (author)2015-03-01

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.

makendo (author)klixtopher2015-03-01

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.

Indestructibility Man (author)2014-01-26

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

Indestructibility Man (author)2014-01-25

Amazing!!!!
Worked so good!! Freaked my younger siblings out

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

gluvit (author)2014-01-07

Trying this

hotfarts (author)2014-01-03

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!

makendo (author)hotfarts2014-01-04

Cheers, you're welcome. Have fun!

Jane Oreo (author)2014-01-03

oh. Color is very good-looking.

Ohnanka (author)2013-09-06

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

makendo (author)Ohnanka2013-09-06

Oh yes

cmanuel1 (author)2011-03-31

Well as jaegerschlager said in the comments of The Morphing Martini (https://www.instructables.com/id/The-Morphing-Martini/step4/Present/), you can also use blueberry.

But will the colour-change be as fast?

makendo (author)cmanuel12011-04-05

Yes, the colour change will be as fast, because the reaction is very rapid. However, exactly what the colour change is will be dependent on the exact identity of the anthocyanins, so it may be less dramatic. However, I just don't know - I may try it next time I have both dry ice and blueberries in the house...

aidylgs (author)2011-01-12

Anyone tried dryice instead of vitamin C for the color change or is it a bad idea?

makendo (author)aidylgs2011-01-12

Dry ice works well, see https://www.instructables.com/id/The-Morphing-Martini/
but the color change is less dramatic (carbonic acid is pretty weak).

aidyl (author)makendo2011-01-16

Thanks for your reply. My students enjoyed it but you are correct about a VERY SLOW color change.

makendo (author)aidyl2011-01-16

The speed of the color change will likely depend on how much baking soda you add at the start, because you need to neutralize all of it. In the video I posted for the martini, the color-change is essentially complete in about 15 seconds, but I just used a small pinch of baking soda. I'm interested to hear what was "very slow" for you (several minutes?). I agree that the change does need to be reasonably quick for best effect.

aidyl (author)makendo2011-01-17

The color change time was a little over a minute. I did use about a tsp of baking soda.

Rocky122797 (author)2010-08-25

i tryed it

makendo (author)Rocky1227972010-08-25

Good stuff. Did it go red, pink or purple?

Rocky122797 (author)makendo2010-08-25

Kind of purple-pink

makendo (author)Rocky1227972010-08-25

OK, that makes sense - it's a weaker acid than citric. Hope it was drinkable as well as healthy!

AngryRedhead (author)2010-01-02
Your son takes it over the top!  SOOO CUTE!

If you didn't have citric acid, could you use a crushed up Vitamin C tablet (the chewable kind)?
 
makendo (author)AngryRedhead2010-01-02

He's a character, all right.
A vitamin C tablet is a really good idea, even though ascorbic acid is weaker than citric - I think an effervescent vitamin C tablet would be neat (provided it was one of the crystal clear types, and didn't have any coloring), because you could drop it in the blue solution and it would bubble and change color slowly (which is always neater somehow than the rapid changes). Whether it would go pink or only purple, I don't know - I hope someone tries it. 

Rocky122797 (author)makendo2010-08-25

i did

winterfresh (author)2010-01-17

Eye-candy + tongue candy = really sweet instructable!

Really sweet instructable = I click Favorite.

makendo (author)winterfresh2010-01-18

Thanks - glad you enjoyed it.

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Bio: Analog maker dabbling in digital manufacture
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