Lecture Notes: Kinetic Molecular Theory of Gases

Introduction to Kinetic Molecular Theory (KMT)

• Focuses on gases and their properties.
• Aims to explain gas pressure and factors affecting it.
• Kinetic Energy: Energy of motion; particles of matter are in constant motion.

Basic Principles of Kinetic Theory of Gases

• Gas Particles:

  • Made up of tiny particles with negligible volume.
  • Far apart with no significant attraction or repulsion.
  • Move independently, allowing gases to expand to fill containers.

• Particle Motion:

  • Described as diffusion: particles move out and have no definite volume.
  • Move rapidly (thousands of km/h).
  • Random walk motion: move in straight lines until collision.

• Collisions:

  • Elastic in nature; kinetic energy transferred but not lost.

Gas Pressure

• Caused by collisions of gas particles with container walls.

• Factors Affecting Pressure:

  • More collisions increase pressure.
  • Increase in temperature leads to increased pressure due to higher kinetic energy.

• Demonstrations:

  • Popcorn kernel example: Water vaporization causes popping.
  • Marshmallow in vacuum example: Removing air pressure shows expansion due to lack of collisions.

Atmospheric and Standard Pressure

• Atmospheric Pressure:

  • Caused by air in the atmosphere.
  • Varies with weather and altitude (higher altitude = lower pressure).

• Standard Pressure:

  • Defined at sea level.
  • Three units:
    • 1 atmosphere (atm)
    • 760 mm of mercury (Hg)
    • 101.3 kPa (kilopascals)

• Barometer:

  • Device to measure atmospheric pressure using mercury column height.

Conclusion

• Understanding of kinetic molecular theory provides insights into gas behavior and pressure.
• Encouragement to ask questions for further understanding.

Note: This guide is intended to help understand the kinetic molecular theory and its implications on gas behavior and pressure.