Thermal physics

• Why does increasing the temperature of an ideal gas increase pressure

  Particles have greater kinetic energy so there is a greater rate of collisions and greater change in momentum per collision. This increases the force on the walls of the container and pressure = F/A so the pressure increases
• What is 3/2NkT equal to

  Total internal energy of an ideal gas
• Whys is there no potential energy in an ideal gas

  Because there are no forces between particles (expect during collisions)
• Assumptions of the kinetic theory of gases

  RAVED

  R - Rapid, random motion of a large number of particles

  A - Attraction - none between particles

  V - Volume - molecules have negligible volume compared to the gas

  E - Elastic collisions - kinetic energy is conserved

  D - Duration of collisions is very short compared to the time between collisions
• Why does increasing the volume of an ideal gas decrease the pressure

  Force exerted decreases as the rate of collisions with the container decreases and the surface area increases. As p=F/A as force decreases and are increases pressure decreases
• What are the two sources of error in thermal experiments? What precautions should you take?

  1. Energy losses to the surroundings, ensure the experiment is insulated
  2. Thermal lag between the thermometer and the substance the thermometer is measuring. Ensure the temperature changes slowly to reduce thermal lag and keep the thermometer very close to the sample substance
• What is an ideal gas

  A gas where all collisions between atoms or molecules are perfectly elastic and there are no intermolecular attractive forces. If an ideal gas is heated all the energy goes to increasing the kinetic energy of its molecules so its temperature increases
• Why is there no temperature change if you heat a substance so it melts or vapourises

  Because all the energy is going into increasing the potential energy of its molecules rather than increasing the kinetic energy of its molecules