Leaving a beverage in a vehicle during winter can quickly turn a simple can of soda into a messy science experiment. When temperatures drop below freezing, the liquid inside a sealed container begins a physical transformation that can rupture the packaging. Understanding the temperature at which this process begins and the physics behind it is the best way to prevent a sticky situation in your car.
The Freezing Point Threshold
A can of regular, high-sugar soda will not freeze at the same temperature as pure water. While water freezes at 32°F (0°C), a typical carbonated soft drink usually begins to solidify in the approximate range of 28°F to 30°F (-1°C to -2°C). This slight depression is directly related to the ingredients dissolved within the water content of the beverage.
Diet sodas, which contain artificial sweeteners instead of large amounts of sugar, will freeze closer to the 32°F mark. These beverages lack the high concentration of dissolved solids that significantly lowers the freezing point. Therefore, a diet soda is more likely to freeze and cause container damage at temperatures only slightly below the freezing point of water.
Factors Lowering the Freezing Temperature
The reason soda freezes at a lower temperature than water is due to freezing point depression, which is a colligative property. Colligative properties depend only on the number of dissolved particles, or solutes, in a solvent. In soda, the two main solutes are sugar and carbon dioxide.
The most significant factor is the high concentration of dissolved sugars, typically high-fructose corn syrup, which interferes with the formation of the ordered crystalline structure of ice. For water molecules to solidify into ice, they must align themselves into a hexagonal lattice. The presence of numerous sugar molecules physically disrupts this alignment, requiring the temperature to drop further to allow ice crystals to nucleate and grow.
Dissolved carbon dioxide gas also contributes to the lowering of the freezing point, though to a lesser extent than the sugar. The carbon dioxide molecules, dissolved under pressure, act as additional solutes that disrupt the water molecules’ ability to bond and form ice. This combined effect means that a sugary, carbonated drink must be exposed to an air temperature several degrees below the standard freezing point before it begins to solidify.
The Physical Mechanism of Container Failure
The primary reason a frozen soda container fails is the unique molecular structure of water in its solid state. When water converts from a liquid to a solid form, its volume increases by approximately nine percent. This is because the water molecules arrange themselves into a less dense, open hexagonal lattice structure, forcing them farther apart than they were in the liquid state.
In a sealed container, this expansion has nowhere to go, generating immense internal pressure. This pressure can rapidly exceed the structural integrity of the container. The force exerted by the expanding ice can reach up to 25,000 pounds per square inch, easily capable of causing a rupture.
Aluminum cans are particularly susceptible to failure, often rupturing at the weakest points, such as the seams along the sides or the top and bottom seals. Plastic bottles are generally more flexible and may bulge significantly, but they can still burst violently. Glass bottles offer no flexibility and typically crack or shatter as the ice expands within the rigid material.