Carbonated Drinks: What Are You Really Drinking When You Drink Those Fizzy Sodas?

To many people they like the refreshing fizz of a soda , champagne, beer or sparkling water. When you take a sip, the gas bubbles in the drink burst and the released gas it tickles his nose. But, Have you ever wondered how carbonation really works?

I am a professor who teaches chemistry and fermentation and I’m a soft drink enthusiast and home brewer. Although the basic carbonation process is relatively simple, Various factors, from temperature to surface tension, can affect the taste and quality of beverages.

The carbonation consists of dissolving colorless and odorless carbon dioxide (CO₂) in a liquid. When carbon dioxide is added to a sealed bottle or can containing water, the pressure in the bottle or can increases and the carbon dioxide dissolves in the liquid.

The CO₂ above the liquid and the CO₂ dissolved in the liquid achieve chemical equilibrium . Chemical equilibrium basically means that the rate at which CO₂ is dissolved in the liquid is equal to the rate at which CO₂ is released from the liquid. It is based on the amounts of CO₂ both in the air and in the liquid.

Some dissolved CO₂ reacts with water to form carbonic acid, which has the chemical formula H₂CO₃. So once some of the dissolved CO₂ is converted to H₂CO₃, more CO₂ from the air above can dissolve into the liquid and restore chemical equilibrium.

When you open a bottle or a can, the pressure on the carbonated liquid drops to equal the pressure outside the bottle or can. The release of pressure results in a hissing sound and you will see bubbles rising in the liquid as the H₂CO₃ converts back to CO₂ and this gas escapes to the surface . The carbonic acid in the drink is what gives it a slightly bitter taste .

Another important factor influencing carbonation is temperature . Most gases, including carbon dioxide, do not dissolve well in liquids because they increases the temperature of the liquid . That’s why soft drinks go flat if you leave them at room temperature.

Conversely, if you put your favorite carbonated drink in the fridge and let it cool, more dissolved carbon dioxide will remain in the drink while it’s still sealed. When you open the cold bottle or can, the liquid bubbles more because there was more dissolved carbon dioxide in the cold drink.

A final important factor for carbonation is the surface tension of the liquid. The surface tension of a liquid is determined by the force with which the the molecules of the liquid interact with each other . For most beverages, these molecules are water molecules, but diet sodas contain dissolved artificial sweeteners. These sweeteners can weaken the interactions between water molecules, creating a lower surface tension. A lower surface tension means that carbon dioxide bubbles forms faster and lasts longer .

This is the reason why it takes a little longer to serve Diet Coke on the rocks, a problem you might notice on an airplane. The artificial sweetener’s lower surface tension means there’s more fizz and it lasts longer, compared to other soft drinks. Next, flight attendants must wait for the bubbles in the cup to break before you can fill the cup with more Diet Coke.

Surface tension is also the reason Diet Coke works so well on the famous Mentos experience during which Mentos candies are placed in 2 liter Diet Coke bottles. Caramel helps weaken the interactions between water molecules and CO₂ molecules, which reduces surface tension and allows easier release of CO₂ molecules. A bubbling ‘geyser’ of Diet Coke quickly rises above the 2 liter bottle as CO₂ molecules rapidly form on the surfaces of the candies and force the Diet Coke out of the bottle.

In an effort to make the water similar to that of mineral springs, the carbonation process was invented by Joseph Priestley in England in the 1760s and commercialized by Jacob Schweppe. Do you recognize the name? – in Switzerland in the 1780s . Priestley reacted chalk with sulfuric acid, producing CO₂, and hung a container filled with water above the reaction to infuse water with CO₂ .

Today, most commercial beers, sodas, sodas, and sparkling waters are created by “forced” carbonation. This is when manufacturers inject carbon dioxide directly into the drink under high carbon dioxide pressure .

A second common way to introduce carbon dioxide into a liquid is to fermentation . Champagne makers and some home brewers Toddlers follow this method by sealing a source of sugar and live yeast into their bottles. Yeast produces alcohol and carbon dioxide, and this carbon dioxide increases the pressure in the bottle, resulting in carbonated champagne and beer . But this process is not as controlled and can lead to exploding bottles .

Large brewers often capture CO₂ produced during a fermentation process and they pump this gas into the tanks that hold beer to carbonate the beer. This is normally a controlled process that allows the introduction of known amounts of carbon dioxide in beverages to achieve exceptional consistency.

Carbonation is a marriage between physics and chemistry, that turns ordinary liquids into fizzy treats . The next time you drink a soft drink, take a moment to appreciate the science behind these dancing bubbles.

* Michael W. Crowder Professor of Chemistry and Biochemistry, University of Miami