Difference between heat and temperature

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Discussion Overview

The discussion centers on the distinction between heat and temperature, exploring their definitions, properties, and implications in thermodynamics. Participants engage in clarifying concepts and sharing insights related to both theoretical and practical aspects of these terms.

Discussion Character

  • Conceptual clarification
  • Debate/contested
  • Technical explanation

Main Points Raised

  • Some participants assert that temperature is a quantitative measure of a material's thermal energy, while heat is described as the transfer of thermal energy between materials.
  • One participant introduces a heuristic model involving entropy, suggesting that "heat" can refer to the entropy of a system or the energy carried by a flow of entropy, with temperature acting as a pressure on this entropy.
  • Another participant notes the practical difference in thermal effects, stating that one can place a hand in a 400-degree oven without harm, unlike in boiling water, which raises questions about the efficiency of heat transfer between air and water.
  • A participant highlights that temperature is an intensive property while heat is extensive, indicating that doubling the amount of material at the same temperature results in double the heat content.
  • Discussion includes the idea that temperature can be related to the energy states of gas molecules, with different types of gases holding varying amounts of heat energy at the same temperature.

Areas of Agreement / Disagreement

Participants express varying interpretations of the concepts of heat and temperature, with no consensus reached on a singular definition or understanding. Multiple competing views remain, particularly regarding the relationship between heat, temperature, and entropy.

Contextual Notes

Some claims rely on specific definitions of terms like heat and temperature, which may vary across different contexts or educational resources. The discussion also touches on the practical implications of these concepts in real-world scenarios, which may not align with theoretical definitions.

prane
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I know there is a difference between heat and temperature as once I was told what it is. I remember it being very subtle and that's probably why I cannot remember the details anymore. Would anybody be so kind as to refresh my memory?
 
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Yes. Temperature is a quantitative measure of a material's thermal energy. Heat is the transfer of thermal (internal) energy between materials.
 
prane said:
I know there is a difference between heat and temperature as once I was told what it is. I remember it being very subtle and that's probably why I cannot remember the details anymore. Would anybody be so kind as to refresh my memory?

There is a good PF Library entry about Heat by user Hootenanny:

https://www.physicsforums.com/library.php?do=view_item&itemid=121

.
 
cheers
 
prane said:
I know there is a difference between heat and temperature as once I was told what it is. I remember it being very subtle and that's probably why I cannot remember the details anymore. Would anybody be so kind as to refresh my memory?
This isn't the way heat is described in introductory textbooks on physics. However, the following picture has helped me do thermodynamics problems with mathematics. If you are entering an advanced class in physics, maybe telling you this heuristic model will help more than refreshing your memory.
There is a fluid like quantity called entropy. It isn't a "real" fluid. On a microscopic scale, entropy is the same as disorder. However, entropy behaves like a indestructible fluid on a macroscopic scale. The unit of entropy is an energy unit divided by a time unit.
With the fluid properties of entropy in mind:
The word "heat" often refers to the entropy of a system.
Sometimes, the word "heat" refers to the energy carried by a flow of entropy rather than the entropy itself. In this case, the heat is measured in units of energy.
"Temperature" is the pressure that the entropy is under. Like a fluid spontaneously flows from high pressure to low pressure, entropy spontaneously flows from high temperature to low temperature. "Temperature" is in units of degrees, but really refers to a type of entropy pressure.
If it confuses you, ignore it.
 
You can stick your hand in a 400 degree oven with no ill effects. That's not true if you stick it in a pot of boiling water. The water has more heat, although the air in the oven has a higher temperature.
 
Vanadium 50 said:
You can stick your hand in a 400 degree oven with no ill effects. That's not true if you stick it in a pot of boiling water.

Yes agreed

The water has more heat, although the air in the oven has a higher temperature.

is that just a case of the water being more efficient at conducting the heat to the hand
than the air is ?

After all they say air is a poor conductor of heat

Just wondering :)

Dave
 
prane said:
I know there is a difference between heat and temperature as once I was told what it is.
The most obvious difference is that temperature is an intensive property and heat is an extensive one. That is, if you have twice as much material at the same temperature it holds twice the heat.
You could get past that by changing your question to be the difference between temperature and heat per unit of substance (mass, volume, whatever...). In fact, temperature is a measure of heat energy per something, but the something is a little unusual - it's state. In an ideal gas, for example, there can be several states per molecule. For a monatomic gas, there are three energy states - velocities in the 3 dimensions. A diatomic gas also has spin about two axes, making 5 states. For statistical reasons, each state tends to have the same average energy, so a diatomic gas holds more heat energy than the same number of molecules of a monatomic gas at the same temperature.
 

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