# Boyle's Law

Updated on September 14, 2012

The discovery of the empirical relationships between gas laws occurred in the mid-seventeeth century. The first quantitative relationship between pressure of a gas and its volume at constant temperature was studied by Robert Boyle in 1662.

The plots of Volume vs Pressure at constant temperature are called Isotherms.

Boyles Law is stated as " At constant temperature for a given mass of a gas, the volume varies inversely as its pressure.

PV= constant or P1V1=P2V2

Boyles Law is experimentally verified as follows-

1. When 1/V vs P is plotted we get a straight line passing through the origin,

This graph demonstrates that pressure is inversely proprtional to pressure.

2. PV vs P is a straight line parallel to x-axis

3. Pressure P vs 1/V is a straight line passing through origin

4. The plot of log Pressure vs Log volume is a straight line

Applications of Boyle's Law-

1. Inside jet aeroplanes when the pressure inside the aircraft drops, the oxygen mask automatically ejects out

2. At high altitudes the gas becomes less dense as there is thinning of air.

3. When inhalation occurs, the rib cage expands and the diaphragm moves downward. This action servea to increase the volume of the lungs, thus decreasing the gas pressure inside the lungs. The atmospheric pressure then forces air into the lungs until the pressure in the lungs equals atmospheric pressure. Exhalation involves the reverse process: The rib cage contracts and the diaphragm moves up, decreasing the volume of the lungs. Air is forced out of the lungs by the increase in pressure caused by this reduction in volume.

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