Is heat extensive or intensive property?

I surfed the Internet for the same and found quite different answers. Like, heat is not a property, so it is neither. One said that since heat depends on the amount of substance, it is extensive. I thought about the latter one as well.

So, my question could be primarily divided into:

1. Is heat a property of matter?

2.1. If yes, is it extensive or intensive? Why?

2.2. If no, why?


In thermodynamics, heat is not a function of state but a process function. So for the question

Is heat a property of matter?

the answer is no.

... is it extensive or intensive?

Since the concept of intensive and extensive properties only applies to physical properties that are a function of state, heat is neither intensive nor extensive.

As Chester said in the comments, it is worth noting that heat (as well as work) applied to a system can cause changes in the thermodynamic equilibrium state of the system.

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  • $\begingroup$ Am I right if I say that heat is transfer of thermal energy? $\endgroup$ – PolarBear Apr 7 '18 at 18:12
  • $\begingroup$ Yes, you can say so. $\endgroup$ – aventurin Apr 7 '18 at 18:47
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    $\begingroup$ This was a wonderful concise answer. I would add that heat and work cause a change in the thermodynamic equilibrium state of a material. $\endgroup$ – Chet Miller Apr 7 '18 at 19:15

You seem to be confused between internal energy and heat.

An object does not "possess" heat. The correct term to describe the energy possessed by it due to molecular motions and other microscopic properties is internal energy.

Heat is the energy that flows due to temperature difference between two points.

Thus, at any point of time, you can state that a body "has" internal energy but you cannot declare that it "has" heat rather, the latter is flowing through the body.

This article might be helpful.

Conclusion: Since heat is a path function, it is not a "property of matter" and hence cannot be described by "intensive" or "extensive".

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Heat means different things at different times, and to different people.

1) If some particular matter has been injected with an amount of heat when referred to that same matter at some other temperature, it has a quantity of heat energy with units of calories or joules. This quantity of heat will be dependent on the size of the system; therefore, the heat (energy content) is called an extensive property of the system.

2) The particular matter has a temperature and can be subdivided into smaller pieces. They will all have the same temperature. This property of the system is independent of the size of the pieces, so temperature is called an intensive property.

So, heat content (amount) is extensive, but heat level (i.e., temperature) is intensive.

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