The Fizzy Science Behind Soda!

Who does not appreciate a cold fizzy drink on a warm day to cool themselves, or after a hearty meal to wash those calories down? Soda has that fizzy, slightly acidic taste which is beloved by most, and is one of the most consumed beverages around the world. So, how exactly does soda get that fizzy tingling sensation that everyone loves? We’ll break it down for you!

Introduction:

A soda, also known as soft drinks, is usually a water based drink, with added sweeteners and in most cases with carbonation. The flavors of sodas range from being natural to being artificial, and it may also contain ingredients such as caffeine, preservatives and food grade colorings. The sweeteners used may include sugar, high fructose corn syrup, fruit juice and also a sugar substitute (in case of diet soda).

Note, they are called soft drinks because even if there is some alcohol present, the alcohol concentration must be under 0.5% of the total volume of the drink. Otherwise, the beverage can’t be classified as non-alcoholic.

Why Does Soda Fizz?

To put it simply, soda fizzes because it has been carbonated, which means the bubbles or the fizz we see is made of Carbon Dioxide (CO2) gas. Carbonated drinks are infused with this colorless, odorless gas at high pressures during production until the liquid becomes supersaturated with the gas. When we pop open a soda, we’re releasing carbon dioxide (CO₂) gas, which is dissolved under pressure inside the can. While the can is sealed, the high pressure keeps the CO₂ mixed with the liquid, forming a weak carbonic acid (H₂CO₃). This carbonic acid adds a slight tang to your drink, but it doesn’t stay around for long. As soon as you open the can, the pressure drops and the CO₂ can no longer stay dissolved in the liquid, so it escapes as bubbles!

And if we go deeper, we can see after soda is infused with carbon dioxide, the gas effervescently escapes due to a principle in physical chemistry known as Henry's law, proposed by British chemist William Henry in 1803. Henry's law states that the amount of a gas dissolved in a liquid is proportional to the pressure of that same gas in the liquid's surroundings.

When soda is canned or bottled, the space above the drink is usually filled with carbon dioxide at a pressure slightly above that of standard atmospheric pressure (about 14.7 pounds per square inch, or about 101.325 kilopascals).  Because of Henry's law — and the pressure of the gas trapped at the top of the sealed container — the carbon dioxide that's dissolved in the beverage stays within the fluid.

However, when a soda container is opened, the pressurized carbon releases into the air. This venting gas produces the signature hiss one expects to hear from a newly opened soda bottle or can. IT has been suggested that since the atmospheric concentration of CO2 gas is around 0.04%, the gas in the bottle naturally tries to reach that concentration when it is exposed to air.

What happens when we shake a bottle before opening?

 If a can or bottle has been shaken or otherwise disturbed before it is opened, gas trapped within the liquid can escape to join the gas above the beverage, increasing the pressure in the gas above the fluid and resulting in the soda bursting out when the container is opened.

Why Soda Fizzes More When It Is Being Poured?

Soda fizzes even more when it is poured into a glass because the act of pouring greatly increases the surface area of the liquid and helps the bubbles escape. This is similar to that of beer, as you will notice a giant head of foam forming whenever beer is poured.

Here’s a tip, if you wish to decrease the fizzing when pouring so that it will remain carbonated for longer, pour on the side of the glass! This decreases surface area drastically, so less fizzing!

How Does Soda Eventually Go Flat?

We already know the bubbles of carbon dioxide escape when a soda is opened, and they naturally try to reach the atmospheric concentration.

As such, when a can or bottle of soda has sat around open a long time, the carbon dioxide dissolved inside it eventually bubbles out — it will want to come into equilibrium with the carbon dioxide in the outside air. When the soda is less fizzy, we call it flat.

Shaking a soda can or bottle will make the soda go flat more quickly by helping the carbon dioxide within it escape. Shaking mixes air in the empty space of the bottle or can with the rest of the liquid, resulting in bubbles. These bubbles can then serve as sites of nucleation, or spots where atoms and molecules can cluster together, a bit like how dust in the air can help snowflakes form.

The nucleation sites lead tiny bubbles of carbon dioxide in the soda to join together. The resulting larger bubbles can more easily escape the liquid's surface tension, which is the energy needed for liquid molecules to separate from each other.

How does temperature affect the fizz?

Want more fizz? Temperature matters! When your soda is warm, CO₂ escapes faster because gases are less soluble in warm liquids. That’s why warm soda fizzes a lot more when you open it than cold soda!

As temperatures soar, the gases inside the beverage container expand, creating higher pressure. This heightened pressure can push the carbon dioxide out of the liquid, further accelerating the loss of carbonation. It's like a tiny, invisible force working against the fizziness we know and love.

Which means warm soda will fizz much more when we open it, but it will also lose its carbonation faster.

 Conclusion

And that is it of us exploring the why, what and how of sodas! We hope this article has provided you an insight into the fizzy sensational world of this carbonated beverage. The next time you pop open a soda, think about the chemistry that occurs, as the fizz tingles your taste-buds!

• References:

• Wikipedia (n.d) “Soft Drinks”

• Live Science (2022) “Why Does Soda Fizz”

• Live Science (2022) “Why Soda Goes Flat”