Thermal Physics: Water vs. Wood at 50°C

[Peter G.]

Hi,

I am learning about thermal physics and I have a doubt:

Say that water and a box of wood, both with the same mass, are at 50 degrees Celsius.

This does not mean that they have the same amount of energy (internal energy in this case?) right?

That is because in water for example, the molecules are further spaced away, meaning their molecules have more potential energy?

Thanks,
Peter G.

 

[Andrew Mason]

Hi,

I am learning about thermal physics and I have a doubt:

Say that water and a box of wood, both with the same mass, are at 50 degrees Celsius.

This does not mean that they have the same amount of energy (internal energy in this case?) right?

That is because in water for example, the molecules are further spaced away, meaning their molecules have more potential energy?

Temperature of matter is a measure of the average kinetic energy of the centres of mass of the molecules that make up that matter.

The translational kinetic energies of the molecules are not all the same. They follow a distribution that is characteristic of particles in thermal equilibrium. If you were to plot the distribution of those energies (translational kinetic energy vs. number of molecules with that TKE) they would form a particular kind of curve called a http://en.wikipedia.org/wiki/Maxwell%E2%80%93Boltzmann_distribution" .

So when two objects are in thermal equilibrium with each other, this simply means that the distributions of kinetic energies of the molecules in both objects are the same - ie. the average kinetic energies of the centres of mass of the molecules in both objects are the same.

AM