Conditions Under Which Real Gases Behave Like Ideal Gases

Gases are often modeled using the ideal gas law, which greatly simplifies the study and application of gas behavior under various conditions. However, in reality, real gases do not always adhere strictly to this law. Under certain conditions, though, real gases can behave very much like ideal gases. This article explores these conditions, the criteria, and why these conditions exist.

The Criteria for a Perfect Gas

The perfect gas, or ideal gas, is a theoretical model that assumes perfect conditions to describe the behavior of gases. The behavior of a gas closely follows the ideal gas law (PVnRT) under specific conditions, which include: The size of particles is negligible, behaving like point particles. There is no attraction or repulsion between particles. Particles move randomly with elastic collisions, meaning no energy is lost.

Real Gases and Ideal Gases

For real gases to behave like ideal gases, the conditions must align with those required for the ideal gas law to hold. This typically requires a low-pressure environment where the volume taken up by the gas is minimal. In such conditions, the molecules are far apart from each other, resulting in minimal intermolecular forces. Therefore, a gas close to being an ideal gas is helium, which has a single atom and no dipole moment, making it less affected by intermolecular forces.

The Role of Pressure and Temperature

Low Pressure and High Temperature At low pressures and high temperatures, the particles in real gases are well separated, making the behavior resemble that of ideal gases. In the van der Waals equation, corrections are made to account for the intermolecular forces. When the intermolecular forces are neglected, the behavior more closely resembles the ideal gas law.

Near Absolute Zero

At extremely low temperatures near absolute zero, the molecules of gas stop vibrating as they no longer possess kinetic energy. At this point, the behavior might approach that of an ideal gas, but it is not possible for an ideal gas to be achieved because no gas can perfectly adhere to the ideal gas equation under all conditions.

High Pressure and Low Temperature

When the pressure is high and the temperature is low, the contrary is true: the intermolecular forces play a significant role. At these conditions, the behavior of real gases deviates significantly from that of an ideal gas.

Summary of Conditions

Low Density and High Kinetic Energy Low density can be achieved by low pressure, which means the molecules are far apart. High kinetic energy is achieved by high temperature, which keeps the molecules spread out and moving fast.

In conclusion, real gases can behave like ideal gases under specific conditions. These conditions include high temperature and low pressure, where the intermolecular forces become negligible. Understanding these conditions is crucial for predicting and modeling real gas behavior accurately in various industrial and scientific applications.