Properties of Gases and Ideal Gas Law

Introduction

• Inflated objects feel different in summer vs. winter due to gas behavior.
• Changes in gas behavior are related to temperature, volume, and pressure.

Ideal Gases

• Ideal Gas Definition:
  • Consist of moving particles with negligible volume.
  • No intermolecular forces during collisions.
• Characteristics:
  • Gases are smaller than their containers, allowing volume neglect.
  • Particles are far apart and move at high speeds.
  • Collisions are elastic (no kinetic energy loss).
• Real Gases Deviations:
  • Deviate under low temperatures (intermolecular forces increase).
  • Deviate at high pressures (particle volume significant).

Ideal Gas Equation

• PV = nRT
  • P: Pressure (Pascals)
  • V: Volume (m³)
  • n: Moles (Gas particles count)
  • T: Temperature (Kelvin)
  • R: Universal gas constant (8.314 J/mol·K)
• Temperature Conversion:
  • Kelvin = Celsius + 273.15
• Molar Volume at STP:
  • Standard Temperature and Pressure (STP): 273.15K and 100KPa.
  • 1 mole of gas = 22.7 dm³ at STP.

Calculations and Gas Laws

• Boyle's Law (P1 * V1 = P2 * V2):
  • Pressure inversely proportional to volume.
  • As volume decreases, pressure increases.
• Gay-Lussac's Law (P1 / T1 = P2 / T2):
  • Pressure directly proportional to temperature.
  • As temperature increases, pressure increases.
• Charles's Law (V1 / T1 = V2 / T2):
  • Volume directly proportional to temperature.
  • As temperature increases, volume increases.
• Combined Gas Law (P1V1/T1 = P2V2/T2):
  • Combines Boyle's, Gay-Lussac's, and Charles's Laws.
  • Useful for prediction with changing conditions.

Example Problem

• Given:
  • P1 = 101 kPa, V1 = 10 m³, T1 = 300K
  • V2 = 5 m³, T2 = 200K
• Find new pressure (P2):
  • Use combined gas law.
  • Result: P2 = 135,000 Pa

Summary

• Key assertions and limitations of the ideal gas model.
• Real gas deviations under certain conditions.
• Understanding these concepts aids in understanding gas behavior in daily life.