Lecture Notes: Kinetic Molecular Theory and Ideal Gas Behavior

Introduction

Kinetic Molecular Theory (KMT): Describes behavior of gases under changing conditions.
Purpose: Understand macroscopic behavior based on molecular motion.

Constant Random Motion:
- Gas molecules are always moving quickly.
- Motion is random and continuous; they never stop moving (e.g., air remains a gas).
Negligible Molecular Volume:
- Actual volume occupied by molecules is negligible compared to the space they occupy.
- Example: Molecules in a room take up minimal space relative to the room's volume.
Non-Interacting Molecules (Ideal Gas Behavior):
- Molecules collide and bounce off without interactions.
- Ideal gas conditions prevent interactions despite proximity (e.g., polar molecules like water).
Constant Average Kinetic Energy:
- Average kinetic energy is constant over time.
- Upon collision, energy is transferred rather than lost, maintaining constant kinetic energy.
Kinetic Energy and Temperature:
- Average kinetic energy is proportional to absolute temperature (measured in Kelvin).
- Temperature defines average kinetic energy; must use Kelvin to avoid meaningless values (e.g., negative temperature).

Large Volume:
- Greater space reduces interaction likelihood, leading to more ideal behavior.
Low Pressure:
- Larger volume correlates with lower pressure, promoting ideal behavior.
High Temperature:
- Higher temperature increases kinetic energy, reducing interaction chances.
- Faster moving molecules are less likely to interact (elastic collisions).

Conditions Affect Behavior:
- Same gas can behave ideally or non-ideally based on conditions (temperature, volume, pressure).
Real Gas:
- Behaves less ideally as conditions (temperature decrease, volume compression) deviate.
- Real gas equations exist but focus here is on ideal gases.

Understanding KMT helps in identifying ideal gas behaviors.
Ideal behavior is condition-dependent, and real gases deviate based on those conditions.