Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: paul.fr on 19/05/2007 09:24:52

Title: heat and temperature...whats the difference?
Post by: paul.fr on 19/05/2007 09:24:52

like the title says, what is the difference?

Title: heat and temperature...whats the difference?
Post by: lightarrow on 19/05/2007 22:38:22

Quote from: paul.fr on 19/05/2007 09:24:52

like the title says, what is the difference?

Heat is energy transferred between two bodies through a temperature difference.
 In the case of an ideal gas, there is a specific relationship between the average energy of a molecule ε and the gas temperature:
 ε = (n/2)kT
n = 3 for an atomic gas; = 5 for a biatomic gas which vibrational levels are inactive; = 7 considering vibrational levels active (higher temperatures).
k = Boltzmann constant ≈ 1.38*10^-23 J/(mol°K)

So, in that case, knowing how much energy in the form of heat you have given to the gas, you can compute its temperature increase.

Title: heat and temperature...whats the difference?
Post by: daveshorts on 19/05/2007 23:06:13

Heat is thermal energy, the amount of entirely disorganised random energy things have.

Strangely temperature is a much more subtle concept, it is really defined from its results.
If object A is at a higher temperature than object B if they are in contact heat will move from object A to object B.

This means that 2 objects of the same size can have the same amount of thermal energy but be at very different temperatures.

Title: heat and temperature...whats the difference?
Post by: lyner on 19/05/2007 23:28:25

The easiest way to think of the temperature of an object is the average energy of the particles in that object. It is independent of the mass of the object (an 'intensive' variable) whereas the heat content, of internal energy depends on its mass ( an 'extensive ' variable).

Title: heat and temperature...whats the difference?
Post by: lightarrow on 20/05/2007 11:30:27

Quote from: daveshorts on 19/05/2007 23:06:13

Heat is thermal energy, the amount of entirely disorganised random energy things have.
Strangely temperature is a much more subtle concept, it is really defined from its results.
If object A is at a higher temperature than object B if they are in contact heat will move from object A to object B.
This means that 2 objects of the same size can have the same amount of thermal energy but be at very different temperatures.

To be precise, heat is not energy things have, it's only energy transferred in a specific way. Heat is not a state function. Internal energy is what you talked about.