Why Does Soft Drink Expand in the Freezer and What Happens When You Open It?

Have you ever placed a soft drink in the freezer overnight, only to discover it has expanded or even exploded when you open it? Let's explore the science behind this common phenomenon and what happens to the contents of the can when it's opened.

The Science Behind Freezing Expansion

When a beverage is placed in a freezer, part of the liquid freezes first, forming pure ice crystals. As these ice crystals form, they leave behind a concentrated solution of dissolved solids, such as sugars, preservatives, and other components. This concentrated liquid has a lower freezing point, allowing the remaining liquid to freeze at a higher temperature.

Partial Freezing and Concentration of Solute

If the freezer temperature is around -10°C, not all of the liquid may freeze, and the drink may expand slightly due to the formation of ice crystals. However, if the freezer is more efficient and the temperature drops to -18°C, all of the liquid should freeze. At this lower temperature, there is a significant increase in the volume of the ice crystals, as water expands by approximately 10% when it turns into ice.

Concentration of Dissolved Gases

When the pure ice thaws, it releases the dissolved gases, which include carbon dioxide. This gas is initially concentrated in the remaining liquid and also in the headspace of the container. As the temperature rises, the pressure inside the container increases significantly. Depending on the volume of the container and the amount of dissolved gas, this pressure can reach dangerous levels, such as 150 psi.

What Happens When You Open the Can?

The sudden release of pressure when the can is opened can cause the dissolved carbon dioxide to come out of solution rapidly. This rapid release of carbon dioxide can lead to several outcomes, including:

Drinking directly from the can may result in the drink fizzing over, leading to a mess. In extreme cases, the pressure can be so high that the can may explode, which is fortunate in your case that it didn't blow up in the freezer. Opening the can slowly can help release the pressure in a controlled manner, reducing the risk of a messy situation.

Preventing the Mess

To minimize the risk of a mess when opening a frozen soft drink, consider the following steps:

Let the can warm up slightly before opening it. This allows for a gradual release of the pressure inside the container. Open the can slowly to release the pressure gradually, reducing the risk of a sudden pressure release and the associated mess. If the drink is completely frozen, allow it to thaw in the refrigerator before opening it.

Conclusion

Freezing beverages can cause them to expand due to the formation of ice crystals and the concentration of dissolved gases. When you open the beverage, the rapid release of these gases can lead to a messy situation, but by taking some precautions, you can minimize the risk of spills and accidents.