St. Patrick's Day Science: Making Green Soda Pop

It’s always fun to have themed learning for a holiday. Even as the kids get older, they enjoy a change from the routine. And, to be honest, so do I. So the younger girls and I cooked up some kitchen science this weekend and made green soda pop in honor of St. Patrick’s Day.

As a cultural note, we rarely use the word “soda” in the South to mean anything you drink. And we never use the word “pop” to refer to a drink. In the South we drink coke. It’s a generic word that may mean any number of sugary, carbonated beverages. So when I told the kids we were going to make green soda pop, my third- wild child- told me never to use those words again. But, somehow, I didn’t think most of the world would understand my post if I had titled it Making Green Coke.

St Patrick's Day science experiment

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So…we messed around with acids and bases, learning about some chemical reactions, all while attempting to make a drinkable, green soda pop creation. Here’s what we did and the science behind it.

The Ingredients

Plastic cups- at least three and possibly more if you want to mess around with different variations
Baking soda
Citric acid- This was very difficult to find. Stores- if they carry it- will keep it near the canning supplies. I looked in several stores, and I couldn’t find it. I ended up using a powder used to keep fruit fresh in canning. It contained mostly citric acid. Our results probably weren’t as bubbly as they could have been. (Later I found that Amazon does carry citric acid, so I’ll plan ahead next time.)
Green food coloring
Measuring cups and spoons

St Patrick's Day science experiment

The Process

In each of three cups, we placed 1/4 tsp of citric acid. 
Then we placed 1/16 tsp of baking soda, 1/4 tsp of baking soda, and 1 tsp of baking soda in different cups, labeling the cups so that we knew which was which.

St Patrick's Day science experiment

We added 1/4 cup of water to each cup, one at a time. Each time, the girls mixed and stirred and then observed the liquid. They also tasted it, although I admit the taste was pretty minute. It isn’t a harmful mixture, but it isn’t especially tasty either.

St Patrick's Day science experiment

With each mixture we were observing a few specific things.
  • Does this mixture make bubbles? How many?
  • Does the mixture feel smooth or gritty in your mouth?
  • Does the mixture have a taste? What does it taste like?
St Patrick's Day science experiment

St Patrick's Day science experiment

As we answered these questions, we talked about which form of the mixture might be better for making a soda. The 1/4 tsp of baking soda was the winner because it had more bubbles than the 1/16 tsp baking soda mixture but was definitely not as gritty as the 1 tsp baking soda mixture.

Once we had determined this, we made a new mixture with the original 1/4 tsp citric acid, 1/4 tsp baking soda and water. Then we began adding sugar to achieve a mixture that was actually drinkable. We began with 1/8 tsp and continued adding 1/8 tsp until we had reached 1/2 tsp. With this mixture our “soda” actually had an okay, sugary taste.

At this point, we added green food coloring to make our soda pop mixture nice and festive.

St Patrick's Day science experiment

Then we decided to experiment a little more. I happened to have some lemon juice in the fridge, and lemon juice is very high in citric acid. We repeated the mixture, using 1/4 tsp lemon juice instead of the citric acid. We didn’t get nearly as many bubbles, but the result- with 1/4 tsp baking soda, 1/2 tsp sugar, and 1/4 cup water- was a little more tasty.

St Patrick's Day science experiment

St Patrick's Day science experiment

The Science

So what does soda pop have to do with science? Quite a bit actually.

Soda is made with sugar and carbonated water (and maybe a little artificial flavoring). The carbonation in the water is what makes it all bubbly. But what makes the carbonated water?

Carbonated water is water with carbon dioxide( CO2) dissolved in it. The CO2 gets into the water under high pressure. That’s why, when you open a soft drink, you’re immediately releasing pressure (and why the drink will sometimes fizz over).

In our experiment, we were mixing citric acid with baking soda. This mixture causes a chemical reaction that releases…you guessed it…CO2. That’s how our soda pop became bubbly.

Now that you know the basic process and the science behind it, you can create your own green soda pop for St. Patrick’s Day and try out other variables like the amount of baking soda, other substances that contain citric acid, or the amount of citric acid.

St. Patrick's Day science experiment

If you’re looking for more St. Patrick’s Day fun, you need to check out the St. Patrick’s Day Online Unit Study from Techie Homeschool Mom. You’ll find this activity and more in this study. If you haven’t had the opportunity to check out the Online Unit Studies yet, you can read my review of one here.

Some cool things about these studies…

  • Everything is online, all gathered in one place for you.
  • Everything is already prepared. There is very little required for you to get together.
  • The Online Unit Studies can be used with multiple ages.
  • Along with the theme of the study, kids will also learn new tech skills while they’re doing the study.
The St. Patrick’s Day study is a mini study that will teach kids the history of the holiday, guide them through a science experiment- this one!-, allow kids to create a watercolor, and teach kids how to create a digital illustration.

How are you going to celebrate St. Patrick’s Day with your kids?

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