1. Postulates of Kinetic Molecular Theory (describes gas behaviors)
1. Gas particles move randomly in all directions at various speeds. 2. Particles which make up a gas each have a mass. 3. Distances separating particles are relatively large. 4. IMF – intermolecular forces (attractive/repulsive) are nearly zero*. 5. Collisions between particles are perfectly elastic. 6. The average kinetic energy of a gas is proportional to its temperature.

2. Gases Science never sucks it only pushes or pulls
4 main properties of gases
(we will study relationships between them)
1. Pressure
2. Volume
3. Temperature
4. Moles

3. Pressure
1.Pressure=(P) gases exert pressure on their surroundings ( P= force /area )
force= mass x acceleration
Pressure is related to the frequency of collisions between particles and the walls of their container.
Units used for pressure : equivalencies for conversions
101,300 Pa = kPa = 1 atm = 760 mmHg= 760 torr
(Pascal) (kilopascal) (atomospheres) ( mmof Mercury) (Torricellis)
mmHg and torr –
at sea level the height of a Hg barometer averages 760 mm, the Hg barometer was invented by Italian scientist Evangelista Torricelli
Chemistry mostly uses the atm

4. Volume
2. Volume -is related to the amount of space something occupies.
1 dm3=1L=1000mL=1000cm3
1cm3=1mL

6. Temperature
3.Temperature - is related to the average kinetic energy of a substance.
SI Units: Kelvins = oC + 273
In order to solve gas problems, you must always use Kelvin temperatures.
Convert the following:
308
-61

7. Moles
4. Moles -are related to the molar mass of a substance

8. Standard Temp and Pressure
Standard temperature and pressure (STP) - is a designation scientists use to correlate results that they discover anywhere in the world.
Based off readings at sea level
For STP
Temperature: 273 K or 0oC
Pressure: 1 atm or 760 mmHg or kPa

9. Boyle’s Law (P & V)
Relates the pressure and volume of a gas
temperature and moles (amount) must remain constant
P1V1 = P2V2
Pressure is inversely related to volume
Increased volume = decreased pressure
“If you increase the volume you decrease the pressure and visa versa if you decrease the volume you increase the pressure”

10. Charles’ Law (V & T)
Relates the volume and temperature of a gas at two conditions.
* Temp must be in Kelvins
Which gas variables are constant?
What type of relationship?

11. Gay-Lussac’s Law (P & T)
Relates the pressure and temperature of a gas at two conditions.
* Temp must be in Kelvins
Which gas variables are constant?
What type of relationship?

12. Combined Gas Law (P, V & T)
Relates the pressure, volume and temperature of a gas
* Temp must be in Kelvins
Which gas variable is constant?

14. This idea lead to the idea of ideal gases
This idea lead to the idea of ideal gases. Because gases move so quickly and don’t interact unless they collide they act without intermolecular forces. This is called an ideal gas. If you have an IDEAL GASES you can use the combined gas law along with Avogadro to calculate information.
In addition, at what scientists have labeled STANDARD TEMPERATURE AND PRESSURE, the volume of one mole of gas will be 22.4L.
What is STANDARD TEMPERATURE AND PRESSURE?
Standard Temperature=0C. Aka 273K (no negative numbers)
Standard Pressure = 1 atm= kPa *(SI unit) =760 mmHg

15. Throwing in moles: Molar Volume at STP
STP = Temp 273 K Pressure 1 atm
Standard Molar Volume (V): the volume of mole of any gas at STP = 22.4 L
Avogadro’s Principle: so if any two gases have the same T, P and V they also have the same number of molecules/moles (this would be an ideal gas)
Using this information if you have any 3 of the 4 variables you can determine the remaining variable
With this information the ideal gas constant and the ideal gas law was formulated

16. Summing it up
Ideal gas conditions
1 atm
273 K
1 mole (n)
22.4 L

17. Ideal Gas Law 4th variable included P1 V1 = P2 V2 n1 T1 n2 T2
To make this easier we can compare any gas to STP. At STP
P=1 atm
V=22.4 L/mol
n=1 mol
T=273K

18. Ideal Gas Law - General equation is PV = nRT P = pressure V = volume
n = moles
T = temperature
R = ideal gas constant = (L*atm)/(mol*K)