# Kinetic energy and heat energy of molecule?

1. Jul 3, 2014

### Hardik Batra

I know that .
Average kinetic energy of a molecule is (f/2)kT (for translational motion.where f=3 )

In my textbook given that...

If the degree of freedom of the gas molecule is f then the average heat energy of each molecule of the gas is = E(avg.) = (f/2)kT

which is same as the average kinetic energy.

Are the avg. kinetic energy and heat energy both are same or there is difference between them?

2. Jul 3, 2014

### Matterwave

I think the textbook may just be using slightly sloppy language, using "heat energy" for what should be "kinetic energy". As heat is not a state function, there is no "heat energy" function that can be associated with an equation of state. Heat is energy flow into or out of a system that is not work.

3. Jul 3, 2014

### 256bits

Thermal energy might have been a better choice of words.

4. Jul 3, 2014

### Hardik Batra

thermal Energy and kinetic energy of molecule is same?

Last edited: Jul 3, 2014
5. Jul 3, 2014

### Matterwave

It depends on the definitions. I would prefer simply the phrase "total energy" of the material. For an ideal (perfect) gas the total energy is the same as the kinetic energy of the molecules, for a non-perfect gas, there can be potential energy contributions to the total energy.

Thermal energy is often just another word for "heat".