Kinetic theory

• define specific heat capacity

  amount of energy needed to increase the temperature of 1kg of a substance by 1.c
• define specific latent heat

  amount of energy needed to change the state of 1kg of a substance with no change in temperature
• equation for energy required to change state

  mass × specific latent heat
• describe motion of molecules in gas

  they are in constant random motion
• what factors affect the average kinetic energy of gas molecules

  . temperature of the substance

  . higher the temperature, higher the average kinetic energy of the molecules.
• what effect does increasing temperature have on the pressure of a gas when held at constant volume

  gas pressure will increase as the temperature increases.
• why does pressure increase as temperature increases at a constant volume

  . kinetic energy of molecule increases

  . collisions between molecules becomes more frequent

  . greater rate of change of momentum

  . greater force and therefore pressure
• if gas A is at low pressure and gas B is high what can be said about rate of collisions in each gas


  . more collisions per second in gas A than B

  . the rate of collisions is higher in A
• describe force that the pressure of a gas exerts on the walls of container


  . net force acts at right angles to container's surface

  . force increases as pressure increases
• explain how increasing volume of gas results in a decrease of pressure


  .molecules become more spread out and so time between collisions increases

  . reduces rate of collisions

  . rate of change of momentum decreases, resulting in a lower pressure
• what can be said about the product of pressure and volume for a fixed mass of gas at a constant temperature

  it is constant

  p V = constant
• unit used for pressure

  pascal Pa
• what increases when you do work on a gas

  . internal energy of the gas

  . this can also lead to an increase of temperature or change in state
• why does temperature of air inside bike pump increases when pumped


  . work is done on gas when it is compressed

  . doing work on a gas increases its internal energy, so average kinetic energy of molecules increases

  . temperature increases due to the increase in average kinetic energy
• what is true when a gas is at absolute zero

  the gas molecules have no kinetic energy
• what is the kelvin scale


  temperature scale starting at absolute 0
• value of absolute 0 in degrees celsius

  -273