# Absolute zero

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Thread starter 4 months ago
#1
So I'm revising physics and I don't quite get this. Absolute zero is where a substance has 0J internal energy which I get. But internal energy=kinetic energy + potential energy. And when a substance is in a solid state it has a very negative potential energy. So surely a substance can have negative energy if it is a solid with none of the particles moving. How is it that at absolute zero there is no energy?
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4 months ago
#2
(Original post by Sannah21)
So I'm revising physics and I don't quite get this. Absolute zero is where a substance has 0J internal energy which I get. But internal energy=kinetic energy + potential energy. And when a substance is in a solid state it has a very negative potential energy. So surely a substance can have negative energy if it is a solid with none of the particles moving. How is it that at absolute zero there is no energy?
Absolute zero is interpreted as the temperature at which all the particles are in the lowest energy state available.
Generally these states do not have zero energy. So there is still molecular energy (zero-point energy) at absolute zero.
For an ideal gas, the kinetic energies of all particles would be zero at zero kelvin. An ideal gas can have no potential energy.
Last edited by Stonebridge; 4 months ago
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Thread starter 4 months ago
#3
(Original post by Stonebridge)
Absolute zero is interpreted as the temperature at which all the particles are in the lowest energy state available.
Generally these states do not have zero energy. So there is still molecular energy (zero-point energy) at absolute zero.
For an ideal gas, the kinetic energies of all particles would be zero at zero kelvin. An ideal gas can have no potential energy.
Thank you so much. That explains it. its because in the textbook it talks about internal energy=ke+ep and then absolute zero without making the distinction. Much appreciated
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