# Kinetic theory of gas

1. Aug 11, 2006

### gandharva_23

Can we explain the rising of smoke on the basis of kinetic theory of gas ?

2. Aug 11, 2006

### gandharva_23

If it were possible for a gas in a container to reach the temperature of 0 K , its pressure will be zero . would the molecules not collide with the wall ? would they not transfer any momentum to the walls .

3. Aug 11, 2006

### gandharva_23

It is said that the assumptions of kinetic theory are good for gases having low density . Suppose a container is so evacuated that only one molecule of gas is left in it . Will all the assumptions of kinetic theory still be valid ? Can we assign a temperature to this gas ?

4. Aug 11, 2006

### alfredbester

If a gas could reach absolute zero then it would have no volume, velocity or anything so nol.
The third law of thermodynamics states the entropy of a pure substance at absolute zero temperature is zero. The ideal gas equations imply that as S=0, before T=0K but the approximation still holds for high values of V/N.

Try looking at thermodynamic books, particulary the ideal gas laws.

Last edited: Aug 11, 2006
5. Aug 11, 2006

### alfredbester

Look up the definition of a gas, the single molecule will behave like a molecule not a gas :).

6. Aug 11, 2006

### tarbag

Not at all.
A gas, before reaching the absolute temperature zero, changes state, and it becomes a solid at the end.
Its volume changes but is not null. There will be no shocks between the atoms, not of movement, They are frozen.

7. Aug 11, 2006

### alfredbester

I was assuming he was talking about an ideal gas, by the level of his other questions.

8. Aug 12, 2006

### Staff: Mentor

One molcule of gas is have a particular speed, and that will only be affected by collision with the atoms of its container.

How is thermal statistics related to the kinetic theory of a gas?

9. Aug 12, 2006

### Staff: Mentor

He does not solidify at 0K, and in fact, it really cannot get to 0 K (at least for 1 atm (0.101325 MPa), although http://en.wikipedia.org/wiki/Noble_gases#Physical_Properties shows that the melting point of He is ~1 K (-272 °C), but
In a vacuum, He at or near 0 K is a liquid.

At 0 K, if the gas molcules would not stick to the wall, which they should since 0 K implies no speed, then they would fall downward (under influence of gravity) and contact the base or floor of whatever vessel in which the gas was occupying. The volume of the gas would be the volume of the atoms or molecules, and the pressure would be zero, since the atoms or molecules would have no momentum, if they are 'frozen' in place.