Carbonated beverages are liquids infused with dissolved carbon dioxide (\(\text{CO}_2\)) gas under pressure, which provides their signature effervescence and characteristic tang. Keeping these drinks cold is a requirement for preserving quality and flavor. The physical relationship between temperature and gas solubility dictates why refrigeration is necessary for carbonated products.
Temperature’s Effect on Carbon Dioxide Solubility
The ability of a liquid to hold dissolved gas is inversely related to its temperature. When carbon dioxide is dissolved in water, the process is exothermic, meaning it releases a small amount of heat. Because of this, the \(\text{CO}_2\) molecules are more stable and remain dissolved more readily in a cooler environment. This stability is directly responsible for maintaining the beverage’s desired level of carbonation.
As the temperature of the beverage increases, the molecules within the liquid gain kinetic energy, causing them to move more rapidly. This increased thermal motion makes it easier for the dissolved \(\text{CO}_2\) molecules to overcome the forces holding them in the solution, causing the gas to escape the liquid phase. A warm carbonated drink loses its characteristic “fizz” much faster than a cold one because the elevated temperature drives the \(\text{CO}_2\) out of the solution.
The Resulting Internal Pressure
When the \(\text{CO}_2\) leaves the liquid phase due to warming, it moves into the headspace—the small volume of gas trapped between the liquid and the container’s seal. Since the container is sealed, the rapid addition of this gas increases the pressure inside the can or bottle.
If a beverage warms considerably, the increased gas volume in the headspace can raise the internal pressure beyond the container’s design limits. A warm bottle or can may hiss or spray violently upon opening, as the compressed gas rushes out. Prolonged exposure to high temperatures can cause this internal pressure to weaken the seal, leading to leaks or causing the container to rupture.
Practical Storage Considerations
Other physical factors can compromise the integrity of the beverage and its container. Placing a carbonated drink in a freezer, for example, risks causing the can or bottle to burst. This rupture occurs because water expands by approximately nine percent as it transitions into its solid, ice form. This volume increase, independent of the carbonation, exerts pressure against the rigid walls of the container.
Agitation, such as shaking or dropping the container, is another factor that causes premature \(\text{CO}_2\) release, even when the beverage remains cold. Physical movement introduces tiny air pockets and surface imperfections into the liquid. These microscopic sites act as nucleation points, where dissolved \(\text{CO}_2\) rapidly transitions into gas bubbles. This results in a sudden eruption when the seal is broken and the external pressure is released.