Above: Image © Anettelinnea, iStockphoto.com

Don’t you just love it? That shhhhhhhhh sound of the fizz when you open a can of soda; the bubbles rising and popping… it sure is fascinating! All this magic is locked up, just waiting to escape from a can of Coca-Cola, or Coke, as some of us like to call it.

This carbonated soft drink was invented in Columbus, Georgia, by John S. Pemberton in 1884.

According to Wikipedia, the free encyclopedia, “The beverage was named Coca-Cola because originally, the stimulant mixed in the beverage was coca leaves from South America. In addition, the drink was flavoured using kola (Cola) nuts, the beverage's source of caffeine.”

“It’s amazing that a drink made from coca leaves and carbonated water could be so successful, making billions of dollars,” says Alex Wilson, a first year Chemistry student of the University of Toronto at Scarborough, who once studied the history of the drink.

Interestingly, “it was initially sold as a patent medicine thanks to a belief that carbonated water was good for the health,” says Wikipedia. “Pemberton claimed Coca-Cola cured a myriad of diseases, including morphine addiction, dyspepsia, neurasthenia, headache, and impotence”.

But, let’s get back to that wonderful fizz we associate so well with Coke because there is actually some pretty cool science behind it! Fizz, or more properly known as carbonation, is actually a chemical process!

Carbonation occurs when carbon dioxide (CO2) is dissolved in water (H2O) or an aqueous solution. This process is generally represented by the reaction H2O + CO2 «-» H2CO3, where water and gaseous carbon dioxide react to form a dilute solution of carbonic acid (H2CO3). Notice this reaction is reversible: the acid can be converted back to water and carbon dioxide under the right conditions. For Coke and other sodas, the defining condition is pressure. At any given moment these three compounds exist in a happy equilibrium.

Through this chemical process, the fizz is created. When a can of Coke is sealed, high pressure inside the can forces the chemical equation to the right, and towards the formation of H2CO3. But, once a can is opened the pressure is released; This shifts the chemical equation to the left, allowing some of the CO2 gas to come out of solution, thus forming those characteristic bubbles. The chemical equation is re-established and a new equilibrium is reached.

But did you know that the fizzy taste is caused by the dilute carbonic acid inducing a slight burning sensation on your tongue, and is not caused by the presence of bubbles? It is also the reason why “flat” Coke lacks excitement.

When soda is left out in the open, CO2 gas is continually escaping away into the atmosphere, which brings us back to that chemical equation above. As CO2 bubbles away from the soda, the chemical reaction is continually pushed to the left, in an attempt to replace the lost gas. As that happens, the concentration of carbonic acid in the soda gets less and less. As the amount of H2CO3 in the beverage goes down, so does the soda’s ability to bring about that tingling sensation on your tongue.

Now, that you know the science of fizz, how about making yourself a glass of the magic potion? Wikipedia assures us that it is not so easy, “the Coca-Cola formula is The Coca-Cola Company's secret recipe for Coca-Cola. The formula is one of the most closely held trade secrets in modern business that only a few employees know or have access to.”

According to CBC Television archives, the ingredient list is such a secret that it is stored in an Atlanta bank vault! (CBC Television, 1985).

But we do have a general idea about the production of Coke:

Step one begins with the mixing of H2O with refined sugar, until the mixture becomes syrupy. The next step is to add Coca-Cola’s “secret formula” to this syrupy mixture. Many have tried to figure out the formula, but it has remained a secret since its invention in 1886. H2O is again added, creating the finished uncarbonated beverage. Adding CO2 gas is the final touch that carbonates the beverage, and gives it the magical zest.

A third year specialist in Integrative Biology at the University of Toronto at Scarborough, loves the experience of a can of Coke. “It gives me a sudden burst of energy,” she explains with enthusiasm. “No other drink has ever made me feel so good.”

You can make your very own virtual Coca-Cola with the click of a mouse. To do so visit: www.vpt.coca-cola.com/vpt_index.html

Patrick Clarke is a first year student of the University of Toronto at Scarborough. He is doing a specialist in Journalism and a major in English. Patrick wishes to pursue a career in Broadcast Journalism. His brother, who is two years his senior, also attends UTSC, and because they look so much alike, Patrick's friends often mistake him for his brother, and vice versa. 


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