Carbonation occurs when carbon dioxide is dissolved in water or an aqueous solution.
This process yields the "fizzle" to carbonated water and sparkling mineral water, the head
to beer, and the cork pop and bubbles to champagne and sparkling wine.
<strong>Effervescence</strong>
Effervescence is the escape of gas from an aqueous solution. The term is used to describe
the foaming or fizzing that results from a release of gas. In the lab, a common example of
effervescence is the addition of hydrochloric acid to a block of limestone. If a few pieces
of marble or an antacid tablet are put in hydrochloric acid in a test tube fitted with a cork,
effervescence of carbon dioxide can be witnessed.
This process is generally represented by the following reaction, where a pressurized
dilute solution of carbonic acid in water releases gaseous carbon dioxide at
decompression:
\mbox{H}_2\mbox{CO}_3 \longrightarrow \mbox{H}_2\mbox{O} + \mbox{CO}_2
In simple terms, it is the result of the chemical reaction occurring in the liquid which
produces a gaseous product.
<strong>Fizz</strong>
"Fizzle" is a word used to describe the action or sound of gas bubbles moving through
and escaping from a liquid. Fizz also describes the formation of a foam of this gas and
liquid at the top of the liquid's container. The word itself is an example of onomatopoeia,
derived from the sound the multiple bubbles make together as they "pop" when they
escape. A carbonated beverage, such as cola or beer, will form bubbles when the
dissolved carbon dioxide is depressurized to form emulsions at the top, and it will make
"fizzing" sounds when it is opened or poured into a container. In the United Kingdom,
soft drinks are often referred to as 'fizzy drinks'. A cocktail based on carbonated water
and an acidic juice is called a Fizz, such as the Gin Fizz.
Fizz can also result from a chemical reaction, such as a solid dissolving in a liquid to
produce gas. For example, Alka-Seltzer brand tablets, used to treat stomach indigestion,
form an effervescent solution that fizzes when dropped into water. The essential chemical
reaction is:
\mbox{citric acid} + \mbox{sodium bicarbonate} \longrightarrow \mbox{water} +
\mbox{carbon dioxide} + \mbox{sodium citrate}
\mbox{C}_6\mbox{H}_8\mbox{O}_7 + \mbox{3}\mbox{Na}\mbox{HC}\mbox{O}_3
\longrightarrow \mbox{3}\mbox{H}_2\mbox{O} + \mbox{3}\mbox{CO}_2 +
\mbox{Na}_3\mbox{C}_6\mbox{H}_5\mbox{O}_7
<strong>Natural and artificial carbonation</strong>
Carbonation can occur as a result of natural processes: when yeast ferments dissolved
sugars sealed in a pressure-tolerant bottle or keg; when underground volcanic carbon
dioxide carbonates well water; or when rainwater passes through limestone into a cave
and forms a stalactite. Or it can be done artificially by dissolving carbon dioxide under
pressure into the liquid. Sometimes natural carbonation is called conditioning while the
term carbonation is reserved for the artificial process.