# Pure heat (joules) what is it

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I have not thought about heat and its definition in quite a while.

does heat exist independantly of matter and radiation or are these "mediums" required to transport " joules" as we know them.

The reason im asking , is that i cannot think of any instance where heat is not measured by transporting photons or particles from one physical state to another.

IS THIS CORRECT?

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Heat is the flow of energy from one system to another and can't happen without some sort of carrier. Not to be confused with temperature, which describes the average motion energies of single particles within a system (but it also is a property of matter and thus can't exist independently).

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Heat is the flow of energy from one system to another and can't happen without some sort of carrier.

By that definition, wouldn't heat be "everything"?

• a knock on the door
• a voice in the wind
• cold air blown from an AC unit and hitting one's skin

Those all seem like a flow of energy from one system to another. Or would it be a constant flow of energy?

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so as i understand , measuring temprature is proportional to measuring motion in molexules in a closed system

pv = nrt

but heat " transfer of energy"

can pure energy exist in any other form other than photons or inside " nuclei " of atoms or rather molecules i.e nuclei and electrons

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so as i understand , measuring temprature is proportional to measuring motion in molexules in a closed system

pv = nrt

but heat " transfer of energy"

can pure energy exist in any other form other than photons or inside " nuclei " of atoms or rather molecules i.e nuclei and electrons

Is there any other kind of existence?

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Is there any other kind of existence?

Don't subatomic things pop into existence out in space, in pairs then annihilating each other? They would probably fit under "energy".

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Don't subatomic things pop into existence out in space, in pairs then annihilating each other? They would probably fit under "energy".

Isn't that still photons or matter?

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Isn't that still photons or matter?

Wouldn't know.

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A somewhat simplistic view of heat is that heat is the transfer of energy between an object and its surroundings due to temperature differences. To understand heat you first need to understand the concept of temperature. The zeroth law of thermodynamics says that two objects in thermal equilibrium with each other have the same temperature. Objects that aren't at the same temperature will come into thermal equilibrium by transfer of heat.

One way to look at temperature is as a part of the total internal energy of an object. A lot of failed explanations of heat didn't work out because while objects can indeed have a temperature, objects do not have "heat".

What does work out is describing heat as a energy transfer process between a system and its surroundings. Suppose some system does some work on its surroundings, absorbs heat from its surroundings, and changes its internal energy as a result. The change in the system's internal energy ($\Delta U$) is related to the heat transferred into the system ($\Delta Q$) and the work done by the system ($\Delta W$) via

$\Delta U = \Delta Q - \Delta W$

This is the first law of thermodynamics. The $\Delta Q$ is heat transfer. It is a process variable. Temperature and mass are state variables. You can take some object's temperature with a thermometer and measure its mass with a scale.

A state variable depends only on an object's current state (hence the name). Suppose you have a pile of rocks with a mass of 10 kilograms. If you add 5 kilograms and then 10 kilograms of rocks to the pile the pile will now have a mass of 25 kilograms. The same mass results if you had reversed the order, or added 5 kilograms to the pile three separate times, or plopped all 15 kilograms at once. The order (process) in which you added by which you added mass doesn't matter; all that matters is the total mass added.

The same does not apply to the first law of thermodynamics. The heat transfered into or out of a system depends on the path taken between states. That is why I said earlier that heat is a process variable. Your air conditioner and car engine use that different paths between states result in different heat transfers to their advantage.

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Heat is the flow of energy from one system to another

...due solely to a difference in temperature of the systems.

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