At what temperature is propane considered to be in a liquid state?

Propane is a hydrocarbon that exists in both gaseous and liquid states depending on temperature and pressure conditions. At atmospheric pressure, propane vaporizes at a temperature of -42°F. As such, when the temperature falls below -42°F, propane condenses into a liquid. This characteristic is critical for the safe handling and storage of propane, as it allows the fuel to be transported and stored in a more compact liquid form.

The other choices outline temperatures that are not suitable for propane to be in a liquid state at standard atmospheric pressure. For instance, temperatures above -42°F allow propane to exist primarily as a gas, while the range mentioned in other options (such as 32°F) does not apply to propane since it is only liquid below its boiling point of -42°F. Therefore, below -42°F is the definitive threshold for propane to transition into a liquid state under normal conditions.