Jacques Charles: 1746-1823 Balloonist, noticed relation between temperature and volume At constant P: V=kT or V/T=k More commonly V 1 /T 1 =V 2 /T 2
Charles noticed that no matter what the starting volume was, if P is constant and he increased T, the V also increased
Graphing the relationship between V and T produces a straight line This is a direct proportion Note that if you extend the lines, you can reach a temperature at which volume is ZERO!
1824-1907 Extended work of Joule, Charles and others to use gas as thermometer Gas volume changes 1/273 for every degree change Kelvin scale: based on T at which volume of gas is zero
To use temperature in gas law equations, you MUST convert the temperature to Kelvins Otherwise, you may end up calculating a negative volume! 0 K = -273.15 o C To go from o C to K, add 273.15 To go from K to o C, subtract 273.15
A 2.0 L sample of air is collected at 298 K then cooled to 278 K. The pressure is held constant at 1.0 atmo. What is the new volume of the air? A sample of gas at 15 o C has a volume of 2.58 L. The temperature is then raised to 38 o C. What is the new volume? A child blows a soap bubble at 28 o C with a volume of 1.0 L. As the bubble rises, it encounters a pocket of cold (18 o C air). What is the new volume of the bubble?
Gas volume has been used as a way to measure temperature (gas thermometer). If a gas has a volume of 0.675 L at 35 o C and 1 atmo P, what is the temperature of a room if the gas has a volume of 0.535 L in the room (at 1 atmo P)?