Gas laws , Boyle's law and properties of gaseous materials

From Online Sciences - November 10, 2017

Particles of any material are moving in a continuous random motion , this type of motion differs according to the state of matter , So , we find that Solid molecules move in vibrational motion only , Liquid molecules move in translational and vibrational motion and Gas molecules move in random translational motion .

Properties of gaseous materials

Brown motion is a group of random motion of fluid particles ( liquid or gas ) in all directions for short distances , Brown ( Scottish scientist ) discovered in 1827 that tiny pollen grains suspended in water move in a random motion .

Air ( gas ) molecules move in haphazard ( random ) motion in all directions with different velocities , During their motion they collide with each other and collide with the walls of the box , The reason for this is that the gas molecules are in a free motion and in continuous collision , so , they change their direction randomly .

Gas molecules move in random motion , During this motion , they collide with each other and collide with the walls of the container which contain them .

The compressibility of gases

If the gas is compressible , The large intermolecular spaces between molecules decreases , thus the volume occupied by the gas decreases , The volume of a gas is affected by changes in pressure as well as in temperature or both while in case of solids or liquids , Volume changes as the temperature changes but not the pressure as they are incompressible , thus :

The experiments performed to evaluate the thermal expansion of a gas are complicated , In order to make a full study of the behavior of a gas , The relations between three variables which are the volume , pressure and temperature , which are known as ( Gases laws ) .

Gas laws

Boyles law

The relation between the volume and the pressure of a gas at constant temperature ( Boyles law ) .

Apparatus structure : It consists of a burette ( A ) connected by a rubber tube to a glass reservoir ( B ) containing a suitable amount of mercury ( A ) and ( B ) are mounted side by side onto a vertical stand with a ruler attached to a base where the stand is adjusted vertically .

The reservoir ( B ) is movable along the stand either upwards or downwards and can be fixed at any desired position , The two tubes contain a suitable amount of mercury .

The following factors should be constant to verify Boyles law : temperature , mass of the gas and atmospheric pressure , The burette ( A ) should be of uniform cross-sectional area so that the length of a trapped air column be a measure of a gas volume .

As the pressure of gas increases , the volume of the gas decreases and vice versa , So , the relation between the volume and the pressure of gas is an inverse proportionality relation .

Vol1 / P

At constant temperature , the product of( Vol ) and ( P ) of any given mass of gas is constant .

P Vol = Constant

Boyles law statement

The volume of a fixed mass of a gas is inversely proportional to the pressure , at constant temperature .

Or at constant temperature , the product of a certain volume of any given mass of a gas and its pressure is constant .

PV = Constant = P1 V1 = P2 V2 = P3 V3

P Vol ( mix. ) = P1 ( Vol )1 + P2 ( Vol )2
( Pa +gh ) ( Vol )1 = Pa ( Vol )2
Pa l1 = ( Pah ) l2
Pa l1 = ( Pa + h ) l2


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