Glossary
Average kinetic energy
The mean kinetic energy of all the particles within a gas sample, which is directly proportional to the gas's absolute temperature.
Example:
At the same temperature, a sample of oxygen gas and a sample of nitrogen gas will have the same average kinetic energy, even though their individual molecules have different masses and average speeds.
Elastic collisions
Collisions between gas particles where the total kinetic energy of the system is conserved, meaning no net energy is lost or gained during the impact.
Example:
According to KMT, gas particles undergo elastic collisions, similar to billiard balls bouncing off each other without losing energy to friction or deformation.
Gay-Lussac's law
A gas law stating that for a fixed amount of gas at constant volume, the pressure is directly proportional to its absolute temperature (P₁/T₁ = P₂/T₂).
Example:
If you heat a sealed aerosol can, the pressure inside increases significantly, which can be predicted using Gay-Lussac's law.
Ideal gases
Hypothetical gases that perfectly obey the ideal gas law and the assumptions of the Kinetic Molecular Theory, characterized by negligible particle volume and no intermolecular forces.
Example:
While no real gas is perfectly ideal, hydrogen (H₂) and helium (He) are often treated as ideal gases in calculations due to their small size and weak intermolecular attractions.
Kinetic Energy (KE)
The energy possessed by an object due to its motion, calculated as KE = 1/2mv², where 'm' is mass and 'v' is velocity.
Example:
As a gas molecule speeds up, its kinetic energy increases, leading to more energetic collisions with other particles and container walls.
Kinetic Molecular Theory (KMT)
A theoretical model that describes the behavior of ideal gases based on the motion of their particles and a set of five core assumptions.
Example:
The Kinetic Molecular Theory explains why increasing the temperature of a gas in a balloon causes the balloon to expand, as the gas particles move faster and collide more frequently and forcefully with the balloon's inner surface.
Maxwell-Boltzmann Distributions
Graphical representations that show the distribution of molecular speeds (and thus kinetic energies) for a gas sample at a given temperature.
Example:
A Maxwell-Boltzmann distribution for a gas at a higher temperature will appear broader and flatter, with its peak shifted towards higher speeds, indicating a wider range of velocities among the molecules.
PLIGHT (Ideal Gas Conditions)
An acronym (Pressure Low, Ideal gas behavior, High Temperature) used to remember the conditions under which real gases most closely approximate ideal gas behavior.
Example:
To minimize deviations from ideal behavior in an experiment, chemists often work under PLIGHT conditions, such as using a vacuum pump to achieve low pressure.
Rigid container
A container whose volume remains constant and does not change in response to variations in temperature or pressure of the gas it holds.
Example:
When a gas is heated in a rigid container, like a steel tank, its volume cannot expand, leading to a direct increase in pressure.