Aerated drinks are beverages in which carbon dioxide (CO₂) gas is dissolved under high pressure, giving them their characteristic fizz. When the container is opened, the pressure decreases and CO₂ escapes as bubbles, producing the fizzing sensation. The dissolved CO₂ reacts with water to form carbonic acid (H₂CO₃), which gives aerated drinks their slightly acidic taste.
CO₂ is dissolved in aerated drinks under pressures of 3–6 atmospheres.
Henry's Law governs CO₂ solubility: higher pressure = more gas dissolved.
CO₂ + H₂O ⇌ H₂CO₃ (carbonic acid) — makes drinks mildly acidic.
pH of aerated drinks ranges from 2.5 (cola) to 4.5 (sparkling water).
Cold temperatures increase CO₂ solubility, keeping drinks fizzier.
Opening a bottle releases pressure, reducing CO₂ solubility and causing fizz.
Carbonic acid can erode tooth enamel with prolonged exposure.
Champagne is naturally carbonated via fermentation (CO₂ produced by yeast).
Carbon dioxide is forced into the liquid under pressures typically ranging from 3 to 6 atmospheres (atm). According to Henry's Law, the solubility of a gas in a liquid is directly proportional to the partial pressure of the gas above the liquid. At high pressure, more CO₂ dissolves into the drink. When the bottle or can is sealed, this high-pressure environment is maintained. Opening the container releases the pressure, reducing the solubility of CO₂ and causing it to escape rapidly as bubbles.
When CO₂ dissolves in water, it partially reacts to form carbonic acid:
CO₂ + H₂O ⇌ H₂CO₃
Carbonic acid is a weak diprotic acid that partially dissociates: H₂CO₃ ⇌ H⁺ + HCO₃⁻ (bicarbonate ion) HCO₃⁻ ⇌ H⁺ + CO₃²⁻ (carbonate ion)
This makes aerated drinks mildly acidic with a pH typically between 2.5 and 4.5, depending on other ingredients like phosphoric acid in cola drinks.
Henry's Law states: C = kH × P, where C is the concentration of dissolved gas, kH is Henry's constant for the gas at a given temperature, and P is the partial pressure of the gas. For CO₂ in water at 25°C, kH ≈ 3.4 × 10⁻² mol/(L·atm). Carbonation is done at low temperatures as CO₂ is more soluble in cold water, which is why chilled aerated drinks retain their fizz better than warm ones.
Common aerated beverages include:
The carbonation level is measured in volumes of CO₂ per volume of liquid. Soft drinks typically contain 3–4 volumes of CO₂.
The carbonic acid in aerated drinks can erode tooth enamel over time. The low pH of many sodas (especially colas at pH ~2.5–3) contributes to dental erosion. Regular consumption is also associated with increased caloric intake (if sugar-sweetened) or potential effects on bone density. Sugar-free aerated drinks still carry the acid-related concerns. Carbonated water (sparkling water) without added sugars or acids has a much milder effect on teeth.
Carbon dioxide (CO₂) is the gas dissolved in aerated drinks under high pressure, responsible for the fizz and bubbles.
CO₂ + H₂O ⇌ H₂CO₃. Carbon dioxide reacts with water to form carbonic acid (H₂CO₃), a weak diprotic acid that gives aerated drinks their acidic taste.
Henry's Law explains this: the solubility of a gas in a liquid is directly proportional to the partial pressure of the gas above the liquid. High pressure during bottling forces more CO₂ to dissolve.
When you open an aerated drink, the pressure inside the container drops suddenly. According to Henry's Law, lower pressure reduces CO₂ solubility, so the dissolved CO₂ rapidly escapes from the liquid as bubbles, causing fizzing.
Aerated drinks are acidic. The dissolved CO₂ forms carbonic acid (H₂CO₃) and many sodas also contain phosphoric or citric acid. The pH ranges from about 2.5 (cola) to 4.5 (sparkling water).
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