Final answer:
In a carbon dioxide extinguisher, compressed gas helps expel the CO2, which can exist as a liquid below its critical temperature of 31 °C. On a hot day, exceeding the critical temperature, CO2 cannot liquefy regardless of pressure, remaining purely gaseous.
Step-by-step explanation:
In a carbon dioxide extinguisher, compressed air or inert gas within the container forces the agent out of the extinguisher nozzle when the operator presses the handle. Upon shaking a CO2 fire extinguisher on a cool day with temperatures below 31 °C (the critical temperature of CO2), liquid carbon dioxide can be heard inside the cylinder due to the temperature being low enough to keep the CO2 in a liquid state even under high pressure. Conversely, on a hot day where temperatures exceed 31 °C, the internal pressure and temperature of the fire extinguisher rise, and the carbon dioxide is above its critical temperature, existing only in gaseous form and not as a liquid.
The sloshing sound of liquid CO2 inside a fire extinguisher on a cool day indicates that the temperature is below CO2's critical temperature, allowing it to remain in liquid form due to high pressure. On a hot day, temperatures above the critical temperature prevent the CO2 from liquefying, thus no liquid is present inside the extinguisher. This relationship between temperature, pressure, and the physical state of carbon dioxide is critical to understand for the proper functioning of a CO2 fire extinguisher.
Observations Regarding Temperature and State of CO2
- On a cool day (below 31 °C), liquid CO2 can exist within a CO2 fire extinguisher due to being under high pressure yet below the critical temperature.
- On a hot day (above 31 °C), no liquid CO2 can form inside the extinguisher as the temperature exceeds the critical temperature of carbon dioxide, resulting in a fully gaseous state regardless of the pressure.