Internal Energy

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  • Internal energy
    • Internal energy and absolute zero
      • Internal energy is the sum of the randomly distributed kinetic and potential energies of atoms or molecules within a substance
      • Absolute zero is the lowest temperature possible
      • The kinetic energy of molecules or atoms is zero i.e. they have stopped moving
      • However, internal energy isn't zero, because there is still electrostatic potential energy stored between the particles
    • Increasing internal energy of a body
      • Increasing the temperature of a body increases its internal energy
      • As temperature increases, average kinetic energy in the body also increases
      • When a substance changes phase, temperature and kinetic energy remain constant, but electrostatic potential energy increases significantly
      • Electrostatic potential energy increases as electrical forces between atoms or molecules change
      • Once a phase change is complete, the kinetic energy of atoms and molecules increases and the temperature increases again
      • Different phases have differing electrostatic potential energies
        • Gases have zero electrostatic potential energy because there are negligible electrical forces between molecules
        • In liquids, electrostatic forces give the electrostatic potential energy a negative value, because energy has to be supplied to break the atomic or molecular bonds
        • In solids, electrostatic forces are very large, so the electrostatic potential energy has a large negative value

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