Whats the difference between thermal and kinetic energy?

#1
Thermal energy is like the average of all the kinetic molecules in a body. Thermal energy comes from the kinetic energy of the molecules. As the kinetic energy of the molecules increase, they will become 'hotter' and the molecule will have more thermal energy and vice versa.

So now I am confused, whats the difference between thermal and kinetic energy? People say kinetic energy is the energy due to movement, but the energy due to movement is the same as thermal energy?

Thanks
0
10 years ago
#2
Microscopically there is no difference. Thermal energy is the result of the motion of the molecules, and measured by their mean kinetic energy. The important factor here is that thermal kinetic energy is random. That is, it is a bulk property of a large number of molecules all moving randomly. The sort of kinetic energy you normally deal with is for just a single particle with a well defined velocity in a specific direction, not millions of molecules all moving with different velocities in different directions.
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#3
(Original post by Stonebridge)
Microscopically there is no difference. Thermal energy is the result of the motion of the molecules, and measured by their mean kinetic energy. The important factor here is that thermal kinetic energy is random. That is, it is a bulk property of a large number of molecules all moving randomly. The sort of kinetic energy you normally deal with is for just a single particle with a well defined velocity in a specific direction, not millions of molecules all moving with different velocities in different directions.
I see, so it really is only difference in size of the object. For example, if a football is moving, on a macroscopic level, you will say the ball has kinetic energy. But if you look at all the individual molecules in the ball, the thermal energy is the mean kinetic energy of all the molecules only, and not just the kinetic energy of one molecule.
0
10 years ago
#4
Yes. Thermal energy is a bit meaningless if you only have one molecule. The whole point is that it is a statistical effect of a large number of particles.
0
6 years ago
#5
Hello!

Actually temperature is the measure of average kinetic energy in a body. Thermal energy is the total quantity of kinetic and potential energy. This means that you cannot actually calculate the total amount of thermal energy in an objet b/c you would have to determine the thermal energy of each and every particle. So, we use temperature which is the average kinetic/thermal energy in a body. What this means is that the majority of particles in a warmer substance has more thermal energy than the majority of particles in a colder substance. (Not ALL the particles in a warmer substance always has more thermal energy than the particles of a colder substance.)

Thermal energy = kinetic + potential energy

- Potential energy: energy possessed by an object due to its position in its environment

ex. If you lift a pencil 1 m from the ground, and keep it there, the pencil is not moving, so it does not have kinetic energy. But it has potential energy because it has the ability to gain kinetic energy if it is dropped.

To sum it up: Potential energy is gained as the pencil is lifted up. The pencil has no kinetic energy when it is at rest above ground. Pencil gains kinetic energy when dropped (b/c it is moving). (To clarify, when pencil is dropped it loses potential energy b/c it comes closer to the ground.)

So when you refer to thermal energy, it refers to total quantity of potential and kinetic energy, whereas kinetic energy is only the energy possessed by moving particles. Potential energy is actually associated with the attraction between the particles, whereas kinetic is associated with the movement.

Also, when thermal energy is transformed into kinetic and potential energy, the potential energy does not cause the temperature to increase, until it becomes kinetic energy.
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