# Internal Energy of an Ideal Gas(OCR A Level Physics)

Author

Katie M

Expertise

Physics

## Internal Energy of an Ideal Gas

• The internal energy of a gas is defined as:

The sum of the kinetic and potential energies of the particles inside the gas

• One of the assumptions of an ideal gas states:
• Electrostatic forces between particles in the gas are negligible except during collisions
• So, there is no electrostatic potential energy in an ideal gas
• All the internal energy is due to the kinetic energy of the particles

As the container is heated up, the gas molecules move faster with higher kinetic energy and therefore higher internal energy

• Change in internal energy, ΔU is equal to the total kinetic energy, EK of all the particles

• Where:
• EK = total kinetic energy (J)
• m = mass of one molecule (kg)
•  = mean square speed of a molecule (m2 s-2)
• k = Boltzmann constant
• T = temperature of the gas (K)
• N = number of molecules
• This equation shows that doubling the temperature will also double the internal energy of the particles

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