Send me an email and I will send you the Powerpoint of this.Basic Gas Laws
M. Edmondson
Chemistry
1999
Boyle’s Law
Deals with the relationship between the pressure on a gas and the volume it occupies as long as the temperature is constant
Characteristics of Gases
Expansion
Expansion.
A gas will expand to fill its container.
Diffusion
Diffusion.
A gas will move spontaneously (without help) from an area of high concentration to an area of lower concentration.
Low density
Low density.
Gases possess low levels of matter per unit volume.
Pressure
Pressure.
Pressure is a consequence of the moving gas molecules striking the sides of the container.
As the collisions increase, the pressure rises (unless the volume is allowed to increase to accommodate the increasing pressure.)
Pressure results from the collision of particles with the sides of a container.
As the volume of a confined gas decreases, the pressure of the gas increases.
As the volume of a confined gas increases the pressure decreases.
The relationship between pressure and volume is referred to as an inverse relationship.
An inverse relationship means that as one variable increases (or decreases) the other variable decreases (or increases)
If you begin with some pressure, it will have some volume. When you change the pressure you then change the volume the gas occupies.
P1 V2
___ = ___
P2 V1
Remember that the pressure and volume are inversely related. Thus, the arrangement you see above
P1
This is the original pressure.
P2
This is the new pressure.
V1
This is the original volume.
V2
This is the new volume.
The units of pressure are in atmospheres, abbreviated atm, in mm Hg (millimeters mercury,) or in kPa.
An atmosphere is the pressure exerted by the atmosphere of earth at sea level and 0 degrees Celsius.
One atmosphere
(1 atm) equals 760 mm Hg.
This is the pressure required to support a 1 cm diameter column of mercury 760 mm tall.
1 atm = 101.325 kPa
Charles’ Law
Deals with the relationship between the temperature on a gas and the volume it occupies as long as the pressure is constant
Temperature is the measurement of the heat content of the particles that compose a substance.
As heat rises the motion of the particles in the substance rise.
This motion is caused by the presence of kinetic energy (energy of motion.)
As the kinetic energy rises, the heat content is also rising. This generates an increase in the temperature.
The temperature is measured in Kelvin, which is found by adding 273.15 to the Celsius temperature.
C +273.15 = K
As Kelvin temperature rises, the volume rises. As the Kelvin temperature falls the volume decreases.
The relationship between temperature and volume is a direct relationship.
This is also called a linear relationship.
As Kelvin temperature rises (or falls) the volume increases (or decreases) proportionally, so long as the pressure is held constant.
T1 V1
___ = ___
T2 V2
This shows that the relationship between temperature and volume is a direct one.
T1
This is the original temperature.
V1
This is the original volume.
T2
This is the new temperature.
V2
This is the new volume.
Combined Boyle’s and Charles’ Law
Sometimes (in fact most times) temperature and pressure both change at the same time.
When this happens the volume changes.
There is an equation which allow you to change both temperature and pressure at the same time using the same variables you have been shown already.
The Combined Gas Law merges temperature, pressure, and volume.
P1V1 P2V2
--------- = ----------
T1 T2
The variables and units are the same as previously stated.
