Behaviour Of Gases - Chemistry

Behaviour Of Gases:

    The assumptions of kinetic theory account for most of the properties associated with gases and we can obtain better understanding of gas behaviour. 

Diffusibility:

    The distribution or spreading of gas molecules through out the vessel is  known as the diffusion. Unlike liquids or solids, the gases diffuse very rapidly. A drop of perfume for instance, slowly evaporates out the fragrant gas announces the presence of wearer. It is due to the diffusion of perfume through the air.

    In terms of kinetic theory, diffusion is explained as follows. The molecules of a gas are widely separated and there are large empty spaces due to which they are free to move. Due to this free movement the molecules of gases intermingle and spread out easily throughout the vessel. The opposite of diffusion is effusion in which a gas passes through the pores or tiny holes in the vessel, the air effuses from the tire as a result of which the tire loses pressure gradually.

Compressibility: 

    In contract to liquids or solids, all the gases are easily compressed or squeezed. In terms of "Kinetic theory" gases are easily compressed due to large empty spaces. By applying pressure, the molecule come closer. Air, for instance is squeezed into automobile tires. When the tire is punctured, the air rushes out. It is the reverse of compressibility - the expansibility, thus volumes of gases are highly affected by the changes in pressure.  Volume is measured in cubic decimetres, dm3 or cubic centimetres, cm3 (1 dm3 =1000 cm3).

Pressure: 

    All the gases exert pressure. It may appear surprising but it is a fact that we are being pressed upon by an enormously heavy blanked of atmosphere. The mass of atmosphere on our body at steal level and at 0 c is 14.7 psi (Pounds per square inch) or there is about 20 tons total pressure on our bodies.  

    When a gas is confined in a closed container, it exerts pressure on the walls of the container which is due to the collisions of gas molecules with the walls. The tires of automobiles are filled with air until the gauge shows the pressure of about 28 psi. This means that the pressure inside the tire is 28 psi greater than the outside pressure since the external atmospheric pressure is 14.7 psi, hence the total pressure inside the tire is 28 + 14.7 = 42.7 psi.

     Since pressure is defined as a force pushing on a unit of area, therefore pressure may be measured in psi, kilo grams per square meter (kg / m2). The unit is however newtons per square meter (N / m2 or pascals, Pa). Since units of a newton of force are kg. m/s , the S.I units of pressure are :

Pressure= Force/Area = newton/m2 = Kg m s2/ m2 = kg/ ms2

Normal atmospheric pressure at sea level at 273 K is expressed in several ways.