Difference between heat, thermal energy, and temperature

[Snazzy]

This isn't really a homework question per se. I'm studying for my MCAT and I'm having trouble trying to firmly get down some of the concepts in thermodynamics.

As far as I know, heat is the means of energy transfer that isn't work from one substance to another due to a difference in temperature between the two substances.

Thermal energy is the total amount of kinetic and potential energy in a substance.

Temperature is the average (per particle) amount of kinetic and potential energy in a substance.

So something that has a lower temperature, like a big chunk of ice, may have more thermal energy than something like a small heated nail.

Am I on the right track? I'm not too sure whether temperature/thermal energy is a measure of potential energy and kinetic energy, or just one or the other.

Thanks for your help.

 

[Ygggdrasil]

Thermal energy and temperature refer to kinetic energy, and not potential energy. For example, it when you add heat to ice at 0^oC, the heat does not change the thermal energy or temperature of the ice. Instead the heat changes the ice into water, increasing the potential energy of the water molecules.

 

[Snazzy]

Is not thermal energy also related to the potential energy of the molecules?

 

[Ygggdrasil]

It depends what you mean by thermal energy (I'm not so sure this is a well defined term). Certainly the internal energy and enthalpy of molecules are dependent on both the kinetic and potential energy of the molecules.

 

[DeeNos]

You are on the right track! Heat, thermal energy, and temperature are all related to each other, but they are not the same thing.

Heat is a form of energy that is transferred between two substances due to a difference in temperature. It is a measure of the total amount of energy that is being transferred, rather than the amount of energy in a single substance.

Thermal energy, on the other hand, is the total amount of kinetic and potential energy in a substance. This includes the energy of all the particles in the substance, whether they are moving (kinetic energy) or held in bonds (potential energy). So, a larger object may have more thermal energy than a smaller object, even if they are at the same temperature.

Temperature, as you mentioned, is the average amount of kinetic and potential energy per particle in a substance. It is a measure of the average speed at which the particles are moving and the strength of the bonds between them. This means that temperature is directly related to the thermal energy of a substance, but it is not the same thing.

In the example you provided, the ice may have a lower temperature than the heated nail, but it has more thermal energy because it has a larger mass. This means that even though the individual particles in the ice may have less kinetic energy than the particles in the nail, there are more particles overall, resulting in a higher thermal energy.

I hope this helps clarify the differences between heat, thermal energy, and temperature. Remember that they are all related, but they are not the same thing. Best of luck with your studies for the MCAT!