Overview
This lecture covers the fundamental laws describing gas behavior, the derivation and meaning of the Ideal Gas Law, and key gas-related terms.
Behavior of Gases
- Gases are all around us and interact with their environment by molecules moving and colliding.
- Theoretical, experimental, and mathematical descriptions of gases are simple when gases behave ideally.
Boyle’s Law and Its History
- Boyle’s Law: In a closed system at constant temperature, pressure times volume equals a constant (P × V = constant).
- The law was originally discovered by Henry Power and Richard Towneley but is commonly attributed to Robert Boyle.
- Boyle emphasized publishing experimentally-backed scientific work rather than relying on intuition.
Other Gas Laws
- Charles’s Law: At constant pressure, the volume of a gas divided by its temperature equals a constant (V/T = constant).
- Avogadro’s Law: At constant pressure and temperature, the volume divided by the number of moles is constant (V/n = constant).
The Ideal Gas Law
- The Ideal Gas Law combines all earlier gas laws: P × V = n × R × T.
- P: pressure (measured in pascals or atmospheres), V: volume, n: moles of gas, R: universal gas constant, T: temperature (in kelvins).
- The law applies to ideal gases, but real gases deviate at high pressure or low temperature.
- Knowing any three variables allows calculation of the fourth.
- Example: Cooling and reducing the amount of gas in a can causes a pressure drop, letting outside pressure crush the can.
Important Terms and Conditions
- Standard Temperature and Pressure (STP): 0°C and 100 kilopascals (100,000 pascals).
- At STP, one mole of an ideal gas occupies 22.4 liters.
- Absolute zero: The theoretical temperature at which all particle motion stops (0 K or -273.15°C).
Key Terms & Definitions
- Pressure (P) — Force per unit area exerted by gas particles (measured in pascals or atmospheres).
- Volume (V) — Space that gas particles occupy.
- Mole (n) — Amount of substance; represents a specific number of molecules.
- Gas constant (R) — Universal constant; value is 8.3145 L·kPa/(K·mol).
- Temperature (T) — Measure of average kinetic energy of particles, in kelvins.
- Ideal Gas Law — Mathematical relation: P × V = n × R × T.
- Standard Temperature and Pressure (STP) — 0°C and 100 kPa.
- Absolute zero — The lowest possible temperature, 0 K.
Action Items / Next Steps
- Review the Ideal Gas Law and practice solving for different variables.
- Memorize the definitions of key terms and constants, especially STP and R.