The time it takes for a carbonated beverage, or “pop,” to freeze is highly variable. Unlike plain water, which reliably freezes at \(32^\circ\text{F}\) (\(0^\circ\text{C}\)), pop can take anywhere from 30 minutes to over four hours to solidify. This wide range depends on the beverage’s unique chemical composition and the physical conditions of the environment. Understanding the science of the liquid and the physics of heat transfer is necessary to predict the time accurately.
The Science Behind Delayed Freezing
The primary reason pop takes longer to freeze than water is freezing point depression. This occurs because solutes dissolved in the water interfere with the formation of the rigid ice crystal lattice. Sugar, typically sucrose or high-fructose corn syrup, is the most abundant solute, and its molecules physically block water molecules from aligning and solidifying.
A standard can of pop contains a high concentration of sugar, which lowers the freezing point by several degrees, often resulting in a freezing temperature closer to \(28^\circ\text{F}\) (around \(-2^\circ\text{C}\)) or lower. Diet sodas experience less freezing point depression than regular sodas because artificial sweeteners have a lesser overall effect. The dissolved carbon dioxide (\(\text{CO}_2\)) also contributes to this effect as another solute.
The carbonation itself plays a complex role in delaying ice crystal formation. The \(\text{CO}_2\) gas is dissolved under pressure, which temporarily inhibits water molecules from expanding and forming ice. When the liquid is cooled below its depressed freezing point, it can remain in a supercooled liquid state while sealed. Ice crystals rapidly nucleate and solidify only when the temperature drops substantially lower or when the seal is broken and the pressure is released.
Practical Factors That Influence Freezing Time
The external conditions of the freezer and the container’s physical characteristics greatly affect the cooling rate. The freezer’s temperature setting is the single most dominant factor determining the overall freezing time. A commercial freezer set to \(-10^\circ\text{F}\) will freeze a beverage much faster than a standard home freezer set closer to \(0^\circ\text{F}\).
The container’s material dictates how quickly heat transfers away from the liquid. Aluminum cans are the most efficient heat conductors, allowing the pop to cool and freeze the quickest. Plastic bottles are notably slower because plastic is a poor thermal conductor, insulating the liquid and slowing the heat exchange process.
The total volume and the container’s shape also influence the freezing rate. A smaller volume always freezes faster than a larger volume; for example, a 12-ounce can freezes quicker than a 2-liter bottle. Furthermore, a container with a high surface area-to-volume ratio, such as a wide, shallow container, allows heat to escape more efficiently than a tall, narrow one.
The starting temperature of the beverage contributes significantly to the total time required. A can of pop starting at room temperature, around \(70^\circ\text{F}\), requires a greater reduction in thermal energy than one pre-chilled to \(40^\circ\text{F}\). Pre-refrigerating the beverage can cut the total freezer time needed by a substantial margin.
The Risk of Rupture: Why Pop Containers Explode
The main danger of freezing pop in its original container is the risk of rupture, often called an explosion. This occurs because water expands when it transitions from a liquid to a solid state, increasing its volume by approximately 9% when it freezes into ice.
When this expansion occurs inside a rigid, sealed container like an aluminum can or glass bottle, the ice creates immense internal pressure. The container is not designed to withstand this force, and the pressure quickly exceeds the structural integrity of the can or bottle. This results in the container rupturing and dispersing the contents.
To avoid this hazardous outcome, it is not recommended to fully freeze a sealed carbonated beverage. If the goal is to create a slushie, the process must be carefully monitored, and the container removed before it becomes fully solid. Using a plastic bottle with some empty headspace provides a small buffer for initial expansion, though constant monitoring is still necessary.