The bubbles in lemonade have tickled taste buds for centuries. However, all good things fizzle out, and eventually the fizz of soda fades away. But why?
It turns out that gas in the drinks pushes the bubbles out.
Carbonated drinks fizz because of bubbles carbon Carbon dioxide are infused into the liquid during production. “It dissolves in the same way that sugar and salt can dissolve in water,” Mark Jones, a chemistry consultant and member of the American Chemical Society, told Live Science.
Carbon dioxide or CO2 is about 1.5 times heavier than air, according to the Columbia Climate School (opens in new tab) at Columbia University in New York City. Based on that fact alone, you might not expect CO2 to rise into the air.
Related: Why does eating pineapple tingle in the mouth?
However, soda starts to become supersaturated with carbon dioxide. As a result due to a physical principle Chemistry known as Henry’s Law, the gas experiences a pressure that causes it to escape the soda. British chemist William Henry proposed Henry’s Law in 1803, to Britannica (opens in new tab). Henry’s law states that the amount of a gas dissolved in a liquid is proportional to the pressure of the same gas in the liquid’s environment. This law affects whether a gas enters or exits a liquid.
When soda is bottled or canned, the space above the beverage is typically filled with carbon dioxide at a pressure slightly above standard atmospheric pressure (about 14.7 pounds per square inch, or 101.325 kilopascals), said Joe Glajch, an analytical chemist and Chemical Consultant 40 years of experience in the chemical and pharmaceutical industries, said Live Science. As such, due to Henry’s Law, the carbon dioxide in the beverage remains in the liquid.
When a soda is first opened, this pressurized carbon dioxide is released into the air. “This escaping gas results in the fizz that you’d expect from a new lemonade,” Glajch said.
Carbon dioxide makes up about 0.04% of the earth’s atmosphere, according to the Columbia University Climate School (opens in new tab). If soda is left exposed to air, Henry’s law suggests that the carbon dioxide in the soft drink naturally wants to reach the same concentration in the liquid as in the air.
“If a can or bottle of soda has been sitting around open for a long time, the carbon dioxide that’s dissolved in it eventually bubbles out — it’s going to want to equilibrate with the carbon dioxide in the outside air,” Jones said. “If the soda is less fizzy, we call it flat.”
Shaking a soda can or bottle empties the soda faster by releasing the carbon dioxide it contains. Shaking causes air in the empty space of the bottle or can to mix with the rest of the liquid, creating bubbles. These bubbles can then serve as sites for nucleation, or places for atoms and molecules to clump together — a bit like dust in the air can help snowflakes form.
The nucleation sites cause tiny bubbles of carbon dioxide in the soda to coalesce. The resulting larger bubbles can more easily escape the liquid’s surface tension, which is the energy it takes for liquid molecules to separate from one another, Jones said.
“The same thing happens if you throw in a teaspoon of salt or sugar,” Glacjh said. “The solid grains of powder act as nucleation sites and make the soda fizz” as the carbon dioxide escapes.
Originally published on Live Science on February 4, 2013 and updated on June 8, 2022.
https://www.livescience.com/32461-why-do-soft-drinks-go-flat.html Why do soft drinks go flat?