Final answer:
The presence of liquid CO₂ inside a fire extinguisher depends on the temperature relative to the critical temperature of CO₂. Above this temperature, CO₂ cannot liquefy irrespective of pressure. Containers with gases have safety warnings due to the risk of increased pressure and explosion when heated.
Step-by-step explanation:
The question relates to the behavior of CO₂ (carbon dioxide) in a fire extinguisher under different temperature conditions and how it relates to the critical temperature of CO₂. On a cool day at 18 °C, CO₂ exists as a liquid inside the extinguisher because the temperature is well below CO₂'s critical temperature of 31.1 °C (87.98 °F). At this temperature, given sufficient pressure, the gas can liquefy. However, on a hot day at 35 °C, which is above the critical temperature, the CO₂ cannot become liquid regardless of pressure and thus we will not hear liquid sloshing.
When discussing the internal pressure of a CO₂ fire extinguisher left in a car at a high temperature, we can refer to the increase in pressure following the ideal gas law, where PV=nRT. If a fire extinguisher filled at a certain pressure and temperature is subjected to higher temperatures, the pressure inside increases as long as the volume of the cylinder and the amount of gas remains constant.
Similarly, for safety reasons, containers of gases like the ones in spray cans are labeled with warnings against exposing to high temperatures or incineration because the pressure can increase significantly, posing an explosion risk. The final pressure in a heated can be calculated using the ideal gas law, taking into account the initial pressure, the initial temperature, and the final temperature.
Different formulations like the fluorinated solution in fire extinguishers help in effectively extinguishing fires by spreading over burning surfaces.