# Interpreting Kinetic Temperature for Solids / Liquids

• Alexander83
In summary, the conversation discusses the interpretation of temperature as derived from kinetic theory and how it relates to more complicated systems with additional degrees of freedom. The speaker questions whether it is still reasonable to think of temperature as a measure of the average translational kinetic energy in solids and liquids, and whether differences in this energy ultimately drive heat flow. The suggestion is made to consider the contributions of rotations, internal rotations, vibrations, and electronic states to the heat capacities of molecules.
Alexander83
Hi all,
I'm brushing up on some thermodynamics, and having been reading up on the interpretation of temperature as derived from kinetic theory. I can follow the derivation for an ideal, monatomic gas which relates temperature to the average, translational kinetic energy of the molecules. Most textbooks I've been perusing seem to stop there and don't bother extending this to more complicated systems.

I understand that more complicated arrangements of atoms have additional degrees of freedom and that the internal energy of such systems increases beyond just the translational kinetic energy as a result of these additional degrees of freedom.

I'll be perfectly honest and say that the kinetic interpretation of temperature has always made the most intuitive sense to me. I'm curious about how well this can be extended to say an everyday solid or liquid (not some exotic condensate or something).

My question is: as an operational definition, is it still reasonable to think of temperature as a measure of the average translational kinetic energy of molecules in solids and liquids?

As a follow-up question, I recall reading somewhere that, while solids and liquids have portions of their internal energy associated with rotational and vibrational motion, it is ultimately differences in the average translational kinetic energy between substances that drives heat flow (since this is what would lead to collisions between substances) - is this correct?

Thanks!

Alexander.

You might want to try thinking in terms of contributions of the rotations, internal rotations, vibrations, and electronic states to the heat capacities of molecules.

## 1. What is kinetic temperature?

Kinetic temperature is a measure of the average kinetic energy of the particles in a substance. It is a type of temperature scale that is based on the motion of particles rather than the traditional concept of heat.

## 2. How is kinetic temperature different from traditional temperature?

Kinetic temperature takes into account the movement of particles in a substance, while traditional temperature is based on the amount of heat energy present in a substance. This means that kinetic temperature can be different from traditional temperature, especially in situations where there is a significant difference in the amount of heat energy between substances.

## 3. How is kinetic temperature measured for solids and liquids?

Kinetic temperature for solids and liquids is typically measured using a thermometer. However, the thermometer must be in contact with the substance in order to accurately measure the kinetic temperature. This is because the thermometer measures the rate at which particles in the substance are moving, which is affected by the temperature of the substance.

## 4. What factors can affect kinetic temperature for solids and liquids?

The kinetic temperature of solids and liquids can be affected by factors such as pressure, volume, and the type of particles present in the substance. For example, increasing the pressure on a substance can cause the particles to move faster, resulting in a higher kinetic temperature.

## 5. How is kinetic temperature used in scientific research?

Kinetic temperature is an important concept in many areas of scientific research, particularly in the fields of chemistry and physics. It allows scientists to understand and predict the behavior of particles in a substance, which is crucial for many experiments and studies.

• Thermodynamics
Replies
32
Views
2K
• Atomic and Condensed Matter
Replies
83
Views
5K
• Thermodynamics
Replies
16
Views
1K
• Thermodynamics
Replies
10
Views
1K
• Thermodynamics
Replies
6
Views
1K
• Thermodynamics
Replies
3
Views
1K
• Thermodynamics
Replies
2
Views
1K
• Thermodynamics
Replies
17
Views
2K
• Thermodynamics
Replies
4
Views
2K
• Thermodynamics
Replies
4
Views
3K