Download Measurable properties of gases: Pressure 1

Measurable properties of gases:
Pressure
1- Pressure : the force a gas exerts (per unit area) on its
surroundings. Gas pressure is caused by gas molecules colliding
with the surfaces of the surrounding substances.
Barometer : device that measures atmospheric pressure The weight of
the air pushing down on the open dish of mercury supports a column of
mercury in a closed tube
A manometer : measures the pressure of a gas trapped in a container.
Pressure is a measure of the force exerted by a gas per unit area.
Correspondingly, it has SI units of Newtons per square metre (Nm-2),
more commonly referred to as Pascals (Pa). Several other units of
pressure are in common usage, and conversions between these units and
Pascals are given below:
1 Torr = 1 mmHg = 133.3 Pa
1 bar = 1000 mBar = 100 000 Pa
Temperature :
The temperature of a gas is a measure of the amount of kinetic energy the
gas particles possess, and therefore reflects their velocity distribution. If
we followed the velocity of any single particle within a gas, we would see
it changing rapidly due to collisions with other particles and with the
walls of the container. However, since energy is conserved, these
collisions only lead to exchange of energy between the particles, and the
total number of particles with a given velocity remains constant i.e. at a
given temperature, the velocity distribution of the gas particles is
conserved.