By Blake Flournoy | Updated Aug 30, 2022
When the water inside a soda turns to ice in a freezer, it expands, forcing the dissolved carbon dioxide to escape. The sudden pressure build‑up can cause the can or bottle to rupture, leaving a mess behind. Every household has a story of a frozen soda that exploded.
Soda explodes when frozen because water expands as ice, pushing CO₂ out. The pressurized gas and expanding ice exceed the container’s limits, causing a burst.
Soda is ~95‑99 % water, sweet syrup, and high‑pressure CO₂ that gives it its fizz. During bottling, the headspace is filled with CO₂ to keep the liquid from flattening. When the temperature drops, CO₂ molecules slow and the pressure inside the sealed container changes.
Temperature governs molecular motion. Cooling generally contracts most liquids, but water is the notable exception. CO₂ molecules occupy less space as they slow down, but water molecules rearrange into a rigid lattice when freezing, increasing the volume.
Water’s crystalline structure takes up ~9 % more space than liquid water. In a sealed can, that expansion forces CO₂ out of solution and raises internal pressure. When the pressure exceeds the can’s tensile strength, the container ruptures.
Once the can or bottle bursts, the remaining liquid often contains a thin layer of ice crystals that melt into a slushy consistency. The shape of the container may also become distorted, and the carbonation level drops dramatically.
Understanding the science helps you avoid the mess: keep beverages at or above 0 °C, or use a dedicated freezer‑safe container.
