Which pressures and temperatures are used when applying gas laws?

When applying gas laws, it is essential to use absolute pressures and temperatures. Absolute pressure is measured from absolute zero pressure (theoretical vacuum) rather than from atmospheric pressure, which is crucial for accurate calculations in gas law applications. Absolute temperature, measured in Kelvin, is vital because gas laws, such as the Ideal Gas Law, rely on direct proportional relationships between temperature, volume, and pressure.

By using absolute values, it ensures that calculations reflect the true behavior of gases under various conditions, avoiding errors that could arise from using gauge pressures or temperatures measured in other scales. For instance, gauge pressure does not take into account atmospheric pressure, which can lead to incorrect calculations when determining the behavior of gases in a closed system.

In practical terms, when dealing with real-world HVAC and refrigeration applications, using absolute measurements helps technicians reliably predict how gases will respond to changes in temperature and pressure, which is critical for system design and troubleshooting.