If pressure in one room is higher than pressure in the room next to it, what does it mean? more molecules?

Question

Does higher pressure mean more oxygen and nitrogen moleculesin the air? More particles in the air?

Answer 1

At the most fundamental level it means that a detector on the floor of one of the room would experience a greater force in the room with more pressure- the force is simply the number of molecules hitting the detector every second times the average momentum (in the direction perpendicular to the detector) of the molecues.

So in an ideal gas the pressure depends on the temperature of the particles and their number density.

Answer 2

It depends on the volume of the rooms (and also the temperature).

The rooms of course do need to be air tight if they are next to eachother.

If the 2 rooms are the same volume then a higher pressure in one would mean more air molecules in that room.

Another example is having the exact same amount of air molecules in both rooms, but one room is smaller. The gas in the smaller room would therefore be exerting a higher pressure than the gas in the larger room.

A higher temperature gives a higher pressure (because the molecules have more kinetic energy so exert a greater force on the walls) without changing the volume or the number of molecules.

This can all be related by the equation:

pV = nRT

p is the pressure

V is the volume

n is the number of moles

R is the gas constant (8.314 J K^-1  mol^-1)

T is the temperature

I won't bore you with the units (if I havn't bored you already!)

If you rearrange the ideal gas equation to make pressure the subject...

p = (nRT) / V

You can see that large values for number of moles and the temperature give a high pressure. And a small volume will give you a low pressure.

Answer 3

The room could be smaller, hotter or yes, just contain more gas

They'd both have to be isolated from each other though, and that's never the case in a house, the pressure throughout a house is pretty equalized.  Not quite though, you may notice that if you ever open the windows in a house, doors slam much easier, because the pressures in different areas are equalized now(they're both at the exterior pressure)