Leaving a can of pop or soda in the freezer for too long often results in a ruptured container. This phenomenon involves two distinct scientific processes: a lowered freezing point and the unique expansion of ice. The combination creates internal pressure that the container cannot withstand. Understanding the temperature range and the physics involved can help prevent this issue.
Freezing Point Depression in Carbonated Beverages
Carbonated beverages do not freeze at the same temperature as pure water, \(0^{\circ}C\) (\(32^{\circ}F\)). This difference is due to dissolved solutes, primarily sugars or artificial sweeteners, which interfere with the formation of a stable ice crystal structure. This chemical effect is known as freezing point depression.
The freezing point for regular, sugar-sweetened soda typically falls between \(-1^{\circ}C\) and \(-4^{\circ}C\) (\(30^{\circ}F\) and \(25^{\circ}F\)). This range is significantly lower than pure water because the high concentration of sugar molecules disrupts the ice lattice structure.
Diet sodas generally freeze at a slightly higher temperature than their sugary counterparts. Since artificial sweeteners are potent, diet soda contains a lower overall concentration of dissolved particles. This results in less freezing point depression, meaning diet drinks begin to freeze faster and at a higher temperature than sugar-filled beverages.
The Mechanics of Container Rupture
The rupture is caused by the physical consequences of the liquid changing state inside a sealed container. Water expands by approximately nine percent when it transitions from liquid to solid ice. Since the container is rigid and sealed, the formation of ice crystals immediately puts immense strain on the packaging.
This initial volume increase is the primary force stressing the container walls, but carbonation plays a significant secondary role. Carbon dioxide gas is dissolved under pressure in the liquid to create the fizz. As the water begins to freeze, it forces the dissolved \(\text{CO}_2\) out of solution, as ice cannot hold the gas.
The released carbon dioxide collects in gas pockets, dramatically increasing the internal pressure. This combination of physical expansion from the ice and chemical pressure quickly exceeds the packaging’s structural integrity. Aluminum cans often rupture along weak seams. Plastic bottles may bulge or split vertically.
Prevention and Safe Handling
The simplest way to avoid rupture is to prevent the beverage from reaching its freezing point. Avoid leaving carbonated drinks in cold environments, such as a car trunk during winter or near a refrigerator’s cooling element.
If quick chilling is necessary, wrap the can or bottle in a wet paper towel before placing it in the freezer for a few minutes. The moisture conducts the cold quickly, and the short timeframe prevents deep freezing.
Handling Frozen Containers
If a container is accidentally frozen but has not ruptured, it is important to handle it with caution. The container is under extreme pressure from the ice expansion and concentrated carbon dioxide.
Never attempt to thaw a frozen beverage using a microwave or direct heat, as this rapid temperature change can cause the container to fail instantly. The safest thawing method is to place the frozen item in a sealed plastic bag or a deep bowl in the refrigerator.
This allows the ice to melt slowly, giving the pressurized carbon dioxide time to safely re-dissolve into the water. Once the ice has completely melted, the internal pressure normalizes, and the beverage can be safely handled.