Final answer:
The presence or absence of liquid CO2 in a fire extinguisher on different days is due to the critical temperature of carbon dioxide, with liquid CO2 being present below 31 °C and absent above this temperature.
Step-by-step explanation:
The observations made when shaking a carbon dioxide fire extinguisher on different temperature days can be explained by understanding the critical temperature of carbon dioxide (CO2). On a cool day with temperatures below 31 ℃ (304 K), the internal temperature of the extinguisher is also below the critical temperature of CO2, allowing liquid CO2 to exist. This is why we hear liquid sloshing around inside the cylinder. On a hot day, when the temperature is above 31 ℃, the temperature inside the extinguisher exceeds the critical temperature of CO2. Above the critical temperature, CO2 cannot be liquified regardless of the pressure, and as a result, no liquid CO2 is present in the extinguisher, which is why it doesn't slosh when shaken.