Question

(a) Explain why carbonated beverages must be stored in sealed containers. (b) Once the beverage has been opened, why does it maintain more carbonation when refrigerated than at room temperature?

Short answer

(a) Carbonated beverages must be stored in sealed containers to maintain a high pressure inside the container, which keeps the carbon dioxide (CO2) gas dissolved in the liquid, preserving fizziness. If stored in an unsealed container, the CO2 would escape, resulting in a flat beverage. (b) An opened carbonated beverage maintains more carbonation when refrigerated because the lower temperature decreases the pressure of the CO2 gas, according to the combined gas law (P1/T1 = P'1/T'1), allowing the CO2 to stay dissolved in the liquid longer. At room temperature, the higher pressure of CO2 causes it to escape more quickly, leading to a faster loss of carbonation.

Step-by-step solution

(a) Importance of Sealed Containers for Carbonated Beverages)

Carbonated beverages contain dissolved carbon dioxide (CO2) gas. The CO2 gas is what gives the beverages their characteristic fizziness. In order to retain the fizziness in the beverage, it is crucial to prevent the CO2 gas from escaping. When a container is sealed, it maintains a higher pressure inside it than the surrounding atmospheric pressure. This increased pressure helps to keep the CO2 gas dissolved in the liquid. If a carbonated beverage is stored in an unsealed container, the CO2 gas will escape, leading to a decrease in carbonation and a flat beverage.

(b) Maintaining Carbonation When Refrigerated versus Room Temperature)

Once a carbonated beverage has been opened, the CO2 gas starts to escape due to the pressure difference between the inside of the container and the surrounding atmosphere. To maintain the carbonation levels in the beverage, it is recommended to store the opened beverage in the refrigerator. The reason behind this recommendation is the relationship between temperature and pressure. According to the Gas Laws, specifically the combined gas law, the pressure of a gas is inversely proportional to its temperature (P1/T1 = P'1/T'1), provided the volume is constant. This means that as the temperature decreases, the pressure of the gas also decreases, as long as the volume remains constant. When the beverage is refrigerated, the temperature of the CO2 gas decreases, causing a decrease in pressure. Consequently, the dissolved CO2 gas stays in the liquid for a longer time, preserving the carbonation. In contrast, at room temperature, the CO2 gas has a higher pressure, which leads to its faster escape from the liquid, resulting in a quicker loss of carbonation.