The Math: Charles's Law

General Chemistry Index

Where are we going with this? Getting to the current models of atomic theory didn't happen over night. This page will support the ability to use the kinetic molecular theory with the combined and ideal gas laws to explain changes in volume, pressure, moles and temperature of a gas and apply the ideal gas equation (PV = nRT) to calculate the change in one variable when another variable is changed and the others are held constant.

The Math: Charles's Law
I told you there'd be mat! 

Charles's Law

The volume of a gas is directly proportional to its temperature in kelvins if the pressure and number of molecules are constant.

V1T1=V2T2 

Again, the subscripts. The subscripts indicate different observations of the gas, with the 1 usually being the first observation and the 2 the second.

This formula means that, dividing V by T always results in the same number. As one goes up, then, the other has to go up:

4           8               16

--    =    --       =      --

2           4                8

That means that changing either T1 of V1 requires the other to change, too. Hence:

• increasing the temperature increases the volume
• decreasing the temperature decreases the volume
• increasing the volume increases the temperature
• decreasing the volume decreases the temperature

In all cases above, the pressure and number of molecules stays the same.