Leaving a carbonated beverage inside a car on a hot day sets the stage for a physical reaction. The interior of a parked vehicle can become an oven, with temperatures quickly climbing far past the ambient air temperature. This intense heat directly impacts the stability of the liquid and the gas sealed within the container. The answer to whether a soda can explode is yes; the extreme pressure created inside the sealed container can easily cause a rupture.
The Physics Behind Pressure Build-Up
The increase in internal pressure stems from two distinct physical phenomena driven by rising temperatures. Carbonated drinks contain dissolved carbon dioxide (\(\text{CO}_2\)), held in solution under pressure during manufacturing. As the liquid heats up, the solubility of \(\text{CO}_2\) decreases, forcing the gas out of the liquid and into the small air pocket, or headspace, at the top of the container.
Gas Expansion
According to the gas laws, as the temperature of a gas increases, the kinetic energy of its molecules also rises. These faster-moving \(\text{CO}_2\) molecules strike the container walls with greater frequency and force.
The combination of the liquid expelling dissolved \(\text{CO}_2\) and the thermal expansion of that gas exponentially increases the pressure inside the can or bottle. On a hot day, the interior of a car can quickly reach temperatures exceeding 140 degrees Fahrenheit. Internal pressure can rise to five or six times the normal atmospheric pressure, pushing the container to its failure point.
Container Materials and Rupture Risk
The type of container material plays a role in determining the point and manner of failure. Standard aluminum cans are strong and engineered to withstand internal pressures up to approximately six atmospheres. When they fail, failure is often sudden, involving the can peeling open at a seam or the top section giving way entirely.
Aluminum Cans
Manufacturers design the tops of aluminum cans with a slight accordion-like structure to act as a pressure relief zone. This feature allows the metal to deform and bulge outward slightly to absorb some pressure before a rupture occurs. If the pressure is too extreme, the can will burst at its weakest point, which can create dangerous, sharp aluminum edges.
Plastic Bottles
Plastic bottles, typically made from PET (polyethylene terephthalate), are less rigid than aluminum and more permeable to \(\text{CO}_2\). Over long periods, carbonation can slowly escape through the plastic walls, making the soda go flat. When subjected to high heat, a plastic bottle may visibly swell and stretch before a failure occurs.
Practical Steps for Safe Storage
To prevent a beverage from rupturing, the most effective strategy is to manage temperature exposure. Never leave carbonated drinks in direct sunlight on the dashboard or seats, as this accelerates the heating process. Placing them in the trunk or under a seat will minimize their exposure to intense heat.
Insulated Storage
Using insulated storage, such as a cooler bag or an ice chest, is the surest way to keep the internal temperature stable. Even without ice, the thermal barrier provided by a quality cooler will drastically slow the rate at which the beverages heat up. If you must leave a drink in a hot car, open the windows slightly to allow some heat to escape and reduce the greenhouse effect.
Handling Swollen Containers
If you return to your car and find a can or bottle that is visibly swollen or hot to the touch, do not shake or immediately open it. Sudden agitation can trigger the rapid release of \(\text{CO}_2\) and cause a messy spray or rupture. Let the can cool down, perhaps by running the car’s air conditioning, before attempting to handle or open it.