1. The Gas Laws

2. What is a gas?
As a substance changes from solid to liquid to gas, it has more entropy (randomness). It will also have more kinetic energy.
Can you think of an exception? (hint: water)

3. Kinetic Theory of Gases
The kinetic theory of gases says that moving gas molecules collide with the container they are in. These collisions cause gas pressure.
What would cause more collisions?

4. Kinetic Theory of Gases
Basis: all matter is composed of tiny particles called molecules that are in constant motion.
Gas molecules:
are small compared with the average distances between them
collide without loss of kinetic energy
exert almost no forces on one another outside of collisions
Thus, a gas is mostly an empty space
The absolute temperature of a gas is proportional to the average kinetic energy of its molecules . Explain.

5. Boyle’s Law
Boyle’s law relates gaseous volume and pressure under constant temperature P1 V2 --- = ---- P2 V1 OR P1V1=P2V2

6. Boyle’s Law

7. Examples of Boyle’s Law

8. Charles Law Charles Law relates V (volume) and T (temp).
As temperature increases, volume _____?
Both Charles and Boyles Laws assume something is constant. What is it?

9. Charles Law Each of these balloons is at a different temperature.
Find the one placed in the freezer, the one outdoors in the sun and the one in the classroom.

10. Examples of Charles’ Law
V1 = V2
T1 T2

11. Combined Gas Law
Combined Boyle’s and Charles’ laws give the ideal gas law
p1 V p2 V2 =
T T2
At constant T (T1 = T2) we have Boyle’s law
At constant p (p1 = p2) we have Charles’ law
p V
----- = const T

12. Explain This!
Watch it!

13. What about this?
Watch it!

14. Can you explain this? (take a deep breath first)
Watch it!

15. Finally, try this one
Watch it!

16. Ideal Gas Law
An ideal gas has particles that do not have any mass or size. The collisions of particles with one another are elastic (no energy is lost)
Real gases are not ideal, but ideal gas laws do approximate true conditions except at very high pressure and temperature.

17. Ideal Gas Law PV = nRT P= pressure V= volume n-= number of moles
R= gas constant
Either 8.31 L Kpa K-1mol-1 or
X 10-2 L atm K-1mol-1--
T= temperature in Kelvin (why Kelvin??)
(Kelvin = Celsius

18. What is the volume of 1 mole of gas?
Volume is related between all gases by Avogadro's hypothesis, which states: Equal volumes of gases at the same temperature and pressure contain equal numbers of molecules
Sing along with Michael Offutt!

19. So, a mole of gas has a volume of 22. 4 L
So, a mole of gas has a volume of 22.4 L. Any gas will do—as long at it is at STP

20. What is STP? Standard Temperature and Pressure IUPAC :
temperature of  K (0 °C)
absolute pressure of 1 atm,
An unofficial, but commonly used standard (SA(ambient)TP)
temperature of  K (25 °C, 77 °F)
absolute pressure 1 atm).