Fizzy Drink Science

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.

Concocting ‘fizz powder’

What You Need

Fizzy drink ingredients

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.

Adding water to our fizz powder

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.

Fizzy drink flavourings (if your’e feeling brave)

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.

Taste testing our fizzy drinks

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:

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.

Taste testing our fizz powder

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

BBC GCSE Science

How to make sherbet

***

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.