Thermal physics 2

• Ideal Gas Equation


  Experimental relationships between p, V, T and mass of gas
• Gas Laws


  Experimental relationships between p, V, T and mass of gas
• Molecular Kinetic Theory


  Model to explain gaseous behaviour
• Ideal Gas Equation


  1. Rearrange into the form pV/T = nR

  2. Use the equation p1V1/T1 = p2V2/T2 in calculations
• Kinetic Theory Model of Gases


  • Originally conceived to explain gaseous behaviour
  • Based on assumptions, from which mathematical deductions are made
  • Only applies to ideal gases
• Assumptions of Kinetic Theory


  • Total volume is a negligible fraction of the total space occupied by a gas
  • All collisions are perfectly elastic
  • Particles are so far apart that they exert no forces on each other
  • Particles are in constant random, rapid and chaotic motion
• Ideal Gas


  Theoretical model of a gas, simplified to make it easier to calculate their behaviour based on Newton's Laws of Motion
• Real Gas


  Gases that exist in the world around us, where atoms (or molecules) deviate from the assumptions of the ideal gas model
• Real gases


  Follow ideal gas behaviour at relatively low pressures and large volumes
• Average Molecular Kinetic Energy


  Related to the temperature of the gas, given by ½kT where k is the Boltzmann Constant
• Gas Laws


  • Pressure Law - pressure vs temperature
  • Charles' Law - volume vs temperature
  • Boyle's Law - pressure vs volume
• Pressure Law


  Pressure is directly proportional to the temperature of an ideal gas if the temperature is measured in kelvins (K) and the volume is kept constant
• At the point where the pressure reaches 0, the temperature is -273°C, known as absolute zero
• Absolute Zero


  The coldest temperature that can be reached, where all particles in a solid won't vibrate at all
• Charles' Law


  Volume is directly proportional to the temperature of an ideal gas if the temperature is measured in kelvins (K) and the pressure is kept constant
• At the point where the volume reaches 0, the temperature is -273°C, known as absolute zero
• Boyle's Law


  Pressure is directly proportional to 1/volume of an ideal gas if the temperature is constant
• Equation of State


  Connects the measurable quantities that define the physical state of a system, giving the combined gas equation: pV = constant, p = constant/T
• Doing work on a gas increases its internal energy, which can increase its temperature
• You can do work on a gas mechanically (e.g. bicycle pump)