1. Gases

2. Pressure Pressure = force/area Atmospheric pressure
Because air molecules collide with objects
More collisions  greater pressure

5. Pressure is a measure of the number of collisions between atoms or molecules with the walls of the container

6. Pressure Units Atmosphere If Atm =1 Pounds per square inch (psi)=14.7
mm Hg =760
Torr = 760
Pascal (Pa) or kilopascal (kPa)=101.3

7. Temperature Temperature is a measure of average kinetic energy.
Temperature measures how quickly the particles are moving. (Heat IS NOT the same as temperature!)
If temperature increases, kinetic energy increases.

8. Kelvin-Celsius Conversions
K = oC
oC = K –
Mass to Moles is Hard to Find

9. Kelvin-Celsius Conversions
K = oC
oC = K –
Try to divide all the time

10. Kelvin-Celsius Conversions
K = oC
oC = K –
Mass to Moles is Hard to Find

11. Physical Characteristics of Gases Physical Characteristics
Typical Units
Volume, V
liters (L)
Pressure, P
atmosphere
(1 atm = 1.015x105 N/m2)
Temperature, T
Kelvin (K)
Number of atoms or molecules, n
mole (1 mol = 6.022x1023 atoms or molecules)
Before the IA we had been looking at gases Here is a refresher of the units that we must use.
To make the ideal gas equation work we must use volume in L Pressure in Atms Temp in K

12. “Father of Modern Chemistry” Chemist & Natural Philosopher
Boyle’s Law
Pressure and volume are inversely related at constant temperature.
PV = K
As one goes up, the other goes down.
P1V1 = P2V2
“Father of Modern Chemistry”
Robert Boyle
Chemist & Natural Philosopher
Listmore, Ireland
January 25, 1627 – December 30, 1690

13. Boyle’s Law: P1V1 = P2V2

14. Boyle’s Law: P1V1 = P2V2
An inverse proportion graph is always an exponential decay curve. Notice as volume doubles pressure is halved
Teacher will highlight this on the graph

15. Jacques-Alexandre Charles Mathematician, Physicist, Inventor
Charles’ Law
Volume of a gas varies directly with the absolute temperature at constant pressure.
V = KT
V1 / T1 = V2 / T2
PPP per Prince Charles keeps PPP Pressure constant. So he varied volume and temperature
Jacques-Alexandre Charles
Mathematician, Physicist, Inventor
Beaugency, France
November 12, 1746 – April 7, 1823

16. Charles’ Law: V1/T1 = V2/T2
This is a direct proportionality double the temp in K and the volume would double

17. Charles’ Law: V1/T1 = V2/T2
This give a straight line graph

18. Gay-Lussac Law
At constant volume, pressure and absolute temperature are directly related.
P = k T
P1 / T1 = P2 / T2
Gay-Lussac kept volume constant and so varied pressure and temp this is another direct correlation
Experimentalist
Limoges, France
December 6, 1778 – May 9, 1850

19. Avogadro’s Law
At constant temperature and pressure, the volume of a gas is directly related to the number of moles.
V = K n
V1 / n1 = V2 / n2
Amedeo Avogadro
Physicist
Turin, Italy
August 9, 1776 – July 9, 1856

20. Avogadro’s Law: V1/n1=V2/n2

21. KMT outline Particles in an ideal gas… have no volume.
have elastic collisions.
are in constant, random, straight-line motion.
don’t attract or repel each other.
have an avg. KE directly related to Kelvin temperature.

22. Only at very low P and high T
Differences Between Ideal and Real Gases
Ideal Gas
Real Gas
Obey PV=nRT
Always
Only at very low P and high T
Molecular volume
Zero
Small but nonzero
Molecular attractions
Small
Molecular repulsions

23. Real Gases
Real molecules do take up space and do interact with each other (especially polar molecules).
Need to add correction factors to the ideal gas law to account for these.

24. Ideally, the VOLUME of the molecules was neglected:
at 1 Atmosphere Pressure
at 10 Atmospheres Pressure
at 30 Atmospheres Pressure
Ar gas, ~to scale, in a box 3nm x 3nm x3nm

25. In other words the measured volume will always be slightly higher than expected but there is always a molecular volume which needs to be accounted for so the measured volume is higher than the theoretical