Soda cans exploding in a refrigerator can be a messy experience. This phenomenon is not random; it results from specific scientific principles related to the beverage’s composition and temperature changes. Understanding these mechanisms explains why such incidents occur.
The Science Behind the Fizz
The characteristic fizz in soda comes from carbonation, a process where carbon dioxide (CO2) gas is dissolved into a liquid under pressure. Manufacturers chill the liquid and introduce CO2 gas under high pressure, forcing the gas molecules to dissolve into the water. This process creates carbonic acid, which contributes to the beverage’s tangy taste. Even at room temperature, a sealed soda can contains internal pressure due to this dissolved CO2.
The amount of pressure inside a can varies depending on the type of soda and its temperature. For instance, a 12-ounce soda can stored at 20°C might have an internal pressure of around 250 kPa (approximately 36 psi). This inherent pressure is why soda fizzes when opened, as the release of external pressure allows the dissolved CO2 to escape as bubbles.
Temperature’s Explosive Impact
Temperature plays a significant role in causing soda can explosions, primarily through two mechanisms. The most common cause of an actual explosion is the expansion of water when it freezes. Unlike most liquids, water expands by about 9% in volume when it transforms into ice due to the formation of a hexagonal crystalline structure. If a soda can reaches freezing temperatures, which can occur in the coldest sections of a refrigerator or near freezer vents, the water content within the soda begins to freeze.
As the water freezes, this volumetric expansion exerts immense pressure on the rigid confines of the can. The can is not designed to accommodate such a substantial increase in internal volume, leading to its structural failure and rupture. While the sugar in regular sodas can lower their freezing point slightly, diet sodas, lacking this sugar, may freeze more readily and explode faster.
Beyond freezing, temperature also affects the solubility of carbon dioxide in the liquid. Gases are generally less soluble in warmer liquids and more soluble in colder liquids. If a can that has been chilled is then rapidly warmed, or if the liquid begins to freeze, the CO2 is forced out of solution, contributing to an increase in internal pressure. This additional gas pressure, combined with the expansion of freezing water, intensifies the stress on the can’s structure.
Beyond Temperature: Can Integrity and Other Stressors
While temperature is a primary factor, other elements can also contribute to a soda can’s failure. Physical damage, such as dents or creases, can compromise the structural integrity of the can. A compromised can might rupture at pressures it would normally tolerate, leading to an unexpected explosion.
Rarely, manufacturing defects can also play a part. Issues like inconsistent wall thickness or flaws in the can’s seams can create inherent weaknesses. These uncommon defects mean a can might not meet expected pressure tolerance, making it more susceptible to rupture.
Agitation, such as vigorous shaking, can also impact a soda can, although it does not directly increase the static pressure in a sealed can at equilibrium. Shaking introduces numerous tiny bubbles, known as nucleation sites, into the liquid. When the can is opened, these sites allow the dissolved CO2 to rapidly come out of solution, leading to a sudden and forceful release of gas and liquid. While shaking alone might not cause an explosion in a sealed can at equilibrium, it can accelerate the pressure release upon opening, which could be problematic if the can is already compromised.
Preventing and Managing Can Explosions
Preventing soda can explosions primarily involves careful management of temperature and physical handling. To avoid freezing, store soda cans in parts of the refrigerator that are not excessively cold. This means keeping them away from the back wall or freezer vents, which can be significantly colder than the rest of the compartment. Ensure that cans are not placed in a freezer unless rapid chilling is necessary, and if so, monitor them closely to prevent them from freezing solid.
Handling cans gently helps maintain their structural integrity. Avoid dropping or mishandling cans, as dents can weaken the aluminum and make them more prone to bursting under pressure. Storing cans in organized racks or dispensers can also reduce the likelihood of accidental damage from falling or shifting. Refrain from shaking cans, as this can lead to an explosive release of contents upon opening.
If an explosion does occur, safety and cleanup are important. Allow any remaining frozen contents to thaw or settle before attempting to clean. Wearing protective gloves and eyewear is advisable to prevent contact with sticky residues or any sharp can fragments. Dispose of the ruptured can and its contents properly, and clean the affected area thoroughly with warm, soapy water to remove all sugary residue.