why we keep fixed mass in case of gas laws
Answers
It states that under a constant temperature when the pressure on a gas increases its volume decreases. In other words according to Boyle's law volume is inversely proportional to pressure when the temperature and the number of molecules are constant.
The Gas Laws
All gases generally show similar behaviour when the conditions are normal. But with a slight change in physical conditions like pressure, temperature or volume these show a deviation. Gas laws are an analysis of this behaviour of gases. The variables of state like the Pressure, Volume and Temperature of a gas depict its true nature. hence gas laws are relations between these variables. Let us study more about the important gas laws!
Boyle’s Law
Boyle’s law states the relation between volume and pressure at constant temperature and mass. Robert Boyle conducted an experiment on gases to study the deviation of its behaviour in changed physical conditions.
It states that under a constant temperature when the pressure on a gas increases its volume decreases. In other words according to Boyle’s law volume is inversely proportional to pressure when the temperature and the number of molecules are constant.
p ∝ 1/V
p = k1 1/V
k1 here is a proportionality constant, V is the Volume and p is the pressure. On rearranging, we get: k1= pV. Now, if a fixed mass of gas undergoes an expansion at constant temperature then the final volume and pressure shall be p2 and V2. The initial volume and initial pressure here is p1 and V1 then according to Boyle’s law: p1×V1 = p2×V2 = constant (k1)
p1/p2 = V2/V1
So according to Boyle’s law, if the pressure is doubled then at constant temperature the volume of that gas is reduced to half. The reason being the intermolecular force between the molecules of the gaseous substance. In a free state, a gaseous substance occupies a larger volume of the container due to the scattered molecules.
When a pressure is applied to the gaseous substance, these molecules come closer and occupy a lesser volume. In other words, the pressure applied is directly proportional to the density of the gas. Boyle’s law can be graphically represented as follows:
