# Homework Help: Question about gas and volume

1. Jan 1, 2009

### f24u7

Hi, I have a few question about gas and its volume

1. How to define the volume of gas (is it the sum of the volume of each atom)?

2. If ideal gas does not consider atom to occupy space, then how does it accounts for
the basic definition of temperature (the collision of atoms)

3. What is the deviations between ideal gas and real gas ( I really don't get this even
though I read the text book several times, I will assume that the attraction between
atoms must play a big role in the deviations for I don't see the relations between the
deviations and finite volume)

2. Jan 2, 2009

### Staff: Mentor

Voulme of atoms is constant, so this sum will be constant as well. Obviously it is not, so this definition sounds incorrect.

I am not sure if I follow - temperature is not directly related to collisions. It is related to average energy of the gas atoms (molecules). Could be you have no idea to collide two atoms that don't have a size - you may try to imagine they interact like identical charges, repelling itself.

If atoms (molecules) don't have intrinsic volume, gas can be compressed into as small volume as you wish, you just have to use pressure high enough. However, if they have some intrinsic volume, at some point increasing the pressure will not change volume of the substance, its compressibility will abruptly change from close to 1 to much closer to zero. That's the end of ideality.

3. Jan 3, 2009

### f24u7

if my assumption for number 1 is incorrect then how do we define the volume of gas ( the space in which the gas is allow to move? then wouldn't it be infinity ?)

4. Jan 3, 2009

### Mapes

Yes; at equilibrium a gas fills its available volume.