Close your eyes and imagine taking a long sip of your favourite soda. How does it taste? Now imagine drinking a different type of soda – Sprite, or Pepsi, maybe. What taste do the different fizzy drinks have in common? Are they salty? Acidic? Something else?
In this fun Science Buddies lab we discovered how sodas get their fizz, then we experimented to find our personal favourite soda recipes.
What You Need
Baking soda (bicarbonate of soda)
Citric acid (food grade)
Measuring spoons (1/8 tsp, 1/4 tsp, 1/2 tsp, tsp)
1/4 cup measure
Clear plastic cups or glasses
Wooden stirrers or spoons
Sugar or sweetener
Digital timer
Chart to record results (optional – click link for printable)
Flavourings (optional)
What You Do
1. Mix 1/16 tsp baking soda with 1/4 tsp citric acid in an empty cup.
2. Add 1/4 cup of cold water and quickly stir, then taste. (You’ll probably want to have somewhere to spit out, too, especially for the first few mixtures.) Observe the reaction between the chemicals in the water, and start your timer for 1 minute.
3. Discuss (and, if you wish, record) your observations. How bubbly is the mixture, on a scale of 1-5? How ‘gritty’ is it?
4. Observe and taste again after 1 minute. Has the taste changed? Is the drink more or less bubbly? Discard any remaining liquid.
5. Repeat in a clean cup, increasing the amount of baking soda to 1/8 tsp. (The amount of citric acid stays the same throughout.) Repeat again using 1/4, then 1/2 and finally 1 tsp of baking soda.
6. Make a note of the formula that tasted best. Did everyone like the same?
7. Experiment by adding different amounts of sweetener to your preferred base recipe, beginning with 1/4, 1/2 then 1 tsp.
See Science Buddies for more detailed instructions.
What happens
What do you see?
Nothing happens when you add the two white powders (citric acid and baking soda) together. But when you add water, bubbles are produced. More bubbles are produced when you increase the proportion of baking soda, and the reaction lasts longer.
How does it taste?
Depending on the amounts of baking soda used, our drinks ranged from fairly disgusting to reasonably palatable. J(10) hated every single unsweetened beverage, confirming our suspicion that he has only persuaded himself to endure fizzy drinks because of their ton of added sugar.
We also tried adding a few flavourings. J(10) had run away to clean his teeth by this point, but C(11) was keen to try chocolate flavour soda. I suspected that if that combination worked we’d already know about it. I was right.
Vanilla soda wasn’t much better, but lemon juice worked nicely (of course, adding lemon juice also increases the ratio of citric acid to baking soda). Finally, we taste-tested our fizzy drinks against shop-bought lemonade, and decided our formula stood up pretty well against Schweppes.
Edit: All Things Beautiful tried some appealing flavourings when they made their own cola recipes.
The scientific explanation
Making fizzy drinks is a great demonstration how an acid and a carbonate react in the presence of water to form carbon dioxide, a salt and water.
Citric acid + Bicarbonate of soda ——> Sodium citrate (a salt)+ Carbon dioxide + Water
If you want to talk ions: acids ionise in water. This means they lose electrons, producing positively charged hydrogen ions. Meanwhile, a carbonate is a mild alkali. Alkalis in water generate negative ions, which combine with the positive ions from the acid in a neutralisation reaction.
(See BBC GCSE Bitesize Science – Acids, Bases & Salts for a more detailed explanation.)
The Cartoon Guide to Chemistry:
More fizzy fun – Making sherbet
You can also make a batch of ‘fizz powder’ by mixing citric acid, baking soda and icing (powdered) sugar. This time the reaction happens on your tongue!
We followed Science on the Shelves’ recipe. Mix 6 tsp citric acid, 3 tbsp bicarbonate of soda and 2 tbsp icing sugar, then crush with a spoon to make a fine powder.
My husband and I found the fizz powder charmingly reminiscent of the sherbet dib-dabs we’d buy with our pocket money as children, but – as you can see from the photo – our kids weren’t convinced.
More fizzy drink science
Try testing the acidity of your home-made sodas with indicator paper or a home-made indicator.
Remind your kids not to drink too many sodas by showing them the effect on their teeth – see Ticia’s What soda does to teeth.
If you’re mathematically inclined, you could graph your results – see Science Buddies’ experimental procedure.
More fun chemistry for older kids
Make hydrogen and oxygen from water using electrolysis
Resources
Shimmy, shimmy soda pop: Develop your own soda pop recipe
***
We don’t have fizzy drinks at home but when we were in Spain C(11) and I sometimes treated ourselves to a coke at the beach cafe. J(10) has never liked anything fizzy, but while we were away he decided to overcome his aversion. The 1-minute video below shows how that turned out.
This lab appealed to us because we had been speculating, in the light of J(10)’s distaste for all fizzy drinks, what they must all contain, apart from bubbles. And I thought it would be fun to watch J(10)’s face as he taste-tested the various recipes {mwah ha ha}.
Look out for J(10)’s taste-bud theory about why C(11) and I can drink fizzy drinks, and his verdict on alcohol, which I shall be reminding him of on his 18th birthday. 😉
I’m appreciatively linking up here:
Science Sunday at All Things Beautiful
Weekly Wrap-Up at Weird Unsocialized Homeschoolers
We’ve made some mildly fizzy drinks using dry ice, but it doesn’t work super well.
I wish it was easy to get dry ice over here. It’s really expensive and you can only buy it in huge quantities. There are so many things I’d like us to do with it. But maybe not make fizzy drinks, by the sound of it.
Great post! Thank you for the step-by-step directions. You’ve really done a lot of cool science experiments with your kids.
Hi Julie, It’s lovely to hear from you! Thanks for your lovely comment.
Their facial expressions at the taste-testing session are priceless. J(10)’s theory is ground-breaking! 🙂 Here’s an anomaly to his theory: I used to love fizzy drinks as a child, but can’t drink it anymore as an adult because they make me burp uncontrollably (which is terribly not-funny when you’re an adult), so maybe that part of my taste bud that had burnt off from early exposure to fizzy drinks eventually grew back upon reaching adulthood in order to save me from social embarrassment? 😉 Thank goodness for the wonders of nature’s design!
I’ve returned to add congratulations to C(11) for achieving the Bronze Arts Award. What an achievement! I heard the news from the public grapevine. 🙂
Thank you from C, Hwee! The Arts Award was a learning experience for us both. C has always enjoyed art, but doing the award gave her a much greater ‘appreciation’ (ahem) for what’s required to pass external exams. It was certainly a worthwhile experience, though.
Love your extension of J’s theory, Hwee! We’re in Greece at the moment so we’ve all been doing some further experimentation. All in the name of science, of course.? (This topic reminds me of the BFG, which always makes me giggle.) I think my fizz-buds must have changed again, actually. I’m finding myself preferring delicious cold tea drinks instead of fizzy ones. You should’ve seen J’s face when he tried my iced green lemon tea just now, and assured him I preferred it to his Fanta!? Thank you for reading & watching, Hwee!
So you’re the one contributing to the sudden spike in my blog’s readership from Greece! I did wonder… 🙂 Enjoy your time there! And thanks for sharing the story of your extended experimentations, and of J’s reactions. Boys are so funny and are such good fun to tease!
Lol yes I’m your mystery ‘Greek’reader! ?
I have never done any of these activities! They would work well with our soda studies though… http://homeschooljournal-bergblog.blogspot.com/2008/03/our-in-home-scientists-made-their-own.html
Brilliant – thanks for that link, Phyllis. Your children look so cute in those pics!
So hi, I found your blog today and have been all over it. I just love it. And seeing as how my lunch break ended at least 40 mituens ago, I should get out of here, but I don’t know if I can. There is still so much left for me to read 🙂 Just thought I’d give you a little shout out, and if it’s okay with you, I will be back soon! Thanks for the great read!
Hello There,
I am trying to make my own fizzy drink. So far I have experimented with .6g citric acid combined with .6g grams of baking soda added to 6 ounces of water. While the initial reaction is very bubbly and active, it quickly loses its fizz. I want to make something comporable to the fizz of Emergen-C. Any tips?