Recreational Vehicle (RV) Technician Practice Test

What factor does the pressure inside a propane container vary with?

1. Humidity

2. Temperature

3. Volume of gas

4. Age of the cylinder

The correct answer is: Temperature

The pressure inside a propane container is primarily influenced by temperature due to the principles outlined in the gas laws, particularly Gay-Lussac's law. This law states that the pressure of a given mass of gas is directly proportional to its absolute temperature when the volume is held constant. As the temperature increases, the kinetic energy of the gas molecules rises, causing them to collide with the walls of the container more forcefully and frequently, which results in higher pressure. Conversely, as the temperature decreases, the pressure inside the container also decreases because the molecules move less vigorously. Other factors like humidity, volume of gas, and the age of the cylinder do not have a direct impact on pressure in the same way temperature does. Humidity mainly pertains to water vapor and does not significantly affect the pressure of propane. The volume of gas remains constant in a closed container unless gas is added or vented, which means any change in pressure due to volume is not a primary consideration in this context. The age of the cylinder is more about the integrity and safety of the container rather than affecting the internal pressure directly.