St. Patrick’s Day Science: Brew up Some Green Soda Pop!
Have you ever wanted to make your own soda pop? Even if you haven’t, maybe as a treat on a relaxing afternoon you like to open a can of your favorite carbonated beverage and take a deep drink. The bubbles in the soda tickle your tongue’s taste buds and propel the ingredients to your palate and nose so that you get a kick of flavor. But how do the bubbles, fizz and taste get into the water? In this tasty science activity, you will work with baking soda, citric acid and sugar to create your own soda pop! After you develop your recipe, add a few drops of green food coloring and you’ve got a festive drink you could share with friends and family to celebrate St. Patrick’s Day together!
This activity is not appropriate for use as a science fair project. Good science fair projects have a stronger focus on controlling variables, taking accurate measurements, and analyzing data. To find a science fair project that is just right for you, browse our library of over 1,200 Science Fair Project Ideas or use the Topic Selection Wizard to get a personalized project recommendation.
Soda pop is essentially carbonated water with sugar added. Carbonated water is water into which a gas called carbon dioxide has been dissolved under high pressure. When you open a can or bottle of soda, the pressure is released and the carbon dioxide starts to come out of the solution. The escaping carbon dioxide is what causes the bubbles in the beverage. Carbonation also occurs in nature, when water underground comes in contact with a source of carbon, such as limestone. The reaction between the water, limestone and the high pressure of the earth creates carbon dioxide that becomes dissolved into the water. When the water eventually rises to Earth’s surface, the pressure is released and bubbly water is the result.
In this science activity, you’ll use baking soda (also called sodium bicarbonate), citric acid and sugar to develop your own recipe for soda pop. When you mix baking soda and citric acid together with water, a chemical reaction takes place that creates carbon dioxide, along with sodium citrate. Sodium citrate, like the others you’ll be using in this activity, is a harmless substance that’s safe to eat or drink.
Extra: Ask your friends and family to taste the final recipe that you developed. Do they enjoy the beverage as much as you do? Collect their feedback and see if you can develop a recipe that everyone enjoys. You could even try adding flavorings, such as vanilla, cinnamon or a little bit of crushed fruit.
Extra: Do this activity again but test a wider variety of baking soda and citric acid recipes (such as including 1/8 tsp. and ½ tsp. baking soda recipes). Then try to numerically rank (such as on a scale of 1 to 5) how gritty and bubbly each combination is. Which recipe makes the bubbliest soda pop? What about the least gritty one? Overall, which recipe is best?
Extra: Some fruits contain citric acid. Try recreating your soda recipe using fruit juice from a fruit that contains citric acid, instead of using food-grade citric acid. How does the amount of fruit juice compare to the quantity of food-grade citric acid in your ideal flavor combination?
Observations and Results
Was the recipe that used ¼ tsp. baking soda and ½ tsp. sugar the best, tasting the most like a normal soda pop?
In this activity, when you mixed together baking soda and citric acid (with water), the chemical reaction should have made fizzy carbon dioxide bubbles, making all of the recipes you tested produce at least some bubbles. The recipe with the least amount of baking soda added (1/16 tsp.) should have made the fewest, shortest-lived bubbles, while the recipe with the most baking soda (1 tsp.) should have been clearly the fizziest. This is because there is more baking soda available to react with the citric acid, making carbon dioxide bubbles. However, the recipe with 1 tsp. baking soda was likely rather gritty and bitter, due to the large amount of baking soda. This probably made the recipe using ¼ tsp. baking soda the ideal recipe in terms of bubbliness, flavor and texture. You may also have found that adding ½ tsp. of sugar was the ideal amount, but this can vary based on personal preference.
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Teisha Rowland, PhD, Science Buddies
Science Buddies |
Chemistry, chemical reactions, carbonation, sugar
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