A level Thermal Physics Edexcel

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  • Thermal Physics
    • Heat and Temperature
      • Temperature
        • Heating an object causes its temperature to rise
        • If  the average  Kinetic energy of the molecules of a substance increases, then it has a higher temperature
        • It is the internal energy that determines the temperature
      • Heat transfer
        • Heating will becomes distributed  throughout a substance, with the heat being passed from hotter areas to colder ones.
      • Absolute zero is the point when the molecules will no longer be moving at all.  (-273 C)
    • Specific heat capacity
      • Depends on three things
        • 1. The amount of heat energy transferred
        • 2. The mass of the object
        • 3. The Specific heat capacity of the material from which the object is made.
      • A material has a given property known as its Specific Heat Capacity, C.
        • This is the energy needed to raise the temperature of 1kg of a particular substance by 1K
      • }E= mc}temp
        • Jkg-1 K-1
    • Iternal energy
      • If we sum the kinetic and the potential energies of a substance, we have measured its internal energy.
      • The internal energy is randomly distributed across all the molecules according to the      Maxwell-Boltzmann Distribution.
    • The Maxwell-Boltzmann distribution
      • If we plot the kinetic energy against the number of molecules that have that energy, we get a curved graph called the Maxwell-Boltzmann distribution
      • The characteristic shape of the graph shows that:
        • There are no molecules with zero energy.
        • Only a few molecules have high energies.
        • There is no maximum value for the energy a molecule can have.
      • The graph is for one specific temperature. As the temp changes so the graph changes.
      • Molecular kinetic energy
        • 1/2m<c2>=3/2kT
          • Were k is the Boltzmann constant, 1.38x10-23 JK-1
          • T is temp and it must be in kelvin
    • Root-Mean-Square Speed
      • This has the symbol ?<c2>
      • This is the speed associated with the average kinetic energy,  1/2m<c2>
      • To find the R.M.S
        • First, find the Square of each value
        • Then the average of the square values is.
        • Finally, take the square root to get the R.M.S speed.
    • Boyle's law
      • A law stating that the pressure of a given mass of an ideal gas is inversely proportional to its volume at a constant temperature.
        • P  & 1/v
    • Charles's law
      • The density of an ideal gas at constant pressure varies inversely with the temperature.
        • V & T
    • The Pressure law
      • For a constant mass of gas at a constant volume, the pressure exerted by the gas is proportion to its absolute temp
        • P & T
    • Ideal gases
      • 1. the molecules have zero size.
      • 2.  The molecules are identical.
      • 3. The molecules collide with each other and the wall of there container without any loss of energy, in collisions which take zero time.
      • 4. The molecules exert no forces on each other, except during collisions.
      • 5. There are enough molecules so that statistic can be applied.
      • pV=NkT
        • pV=nRT
          • n is the number of moles of the gas; R is the Universal gas constant,     R= 8.31 Jkg-1 mol-1
            • pV=NkT
              • pV=nRT
                • n is the number of moles of the gas; R is the Universal gas constant,     R= 8.31 Jkg-1 mol-1


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