1. The Gas Laws

2. Unit 6 groups! :0) 1: Sydney, Garrett, Christina
2. Makayla, Madison, Heiu, Bryan
3:Chandler, Kaitlyn, Tristan, Mia
4: Leo, Shyann, Kennedi, Corey
5: Cole, Gavin, Firas, Madlen
6: Kalheil, Emma Green, Dominic, Brennin
7: Dennis, Zach, Tyrianna, Emma Dunn

3. Scuba Diving
Scuba divers must be aware of some basic gas laws in order to dive safely
The air we breathe contains 78% Nitrogen and 21% Oxygen. A scuba divers tank might need to be adjusted from these percentages depending on how deep they are diving so that they do not develop nitrogen narcosis.
What important variable changes as a diver descends into water?

4. What do you already know?
Groups 1 and 4: What is a gas?
Groups 2 and 5: If you were to draw the arrangement and motion of gas molecules inside a container, what would it look like?
Groups 3,6,7: What are properties of gases (shape, movement of molecules, density)?

5. Characteristics of Gases
highly compressible.
occupy the full volume of their containers.
exert a uniform pressure on all inner surfaces of a container
diffuse (mix) easily and quickly
have very low densities.

6. Kinetic Molecular Theory
Gases consist of a large number of molecules in constant random motion.
Volume of individual molecules negligible compared to volume of container.
Intermolecular forces (forces between gas molecules) negligible.
Collision of gas particles are elastic so no kinetic energy is lost
As temperature increases the gas particles move faster, hence increased kinetic energy.
Gases only occupy about 0.1 % of the volume of their containers.

7. Four Physical Quantities for Gases
Phys. Qty.
Symbol
SI unit
Other common units
pressure P
Pascal (Pa)
atm, mm Hg, torr, psi
volume V m3
dm3, L, mL, cm3
temp. T K
°C, °F
moles n
mol

8. Temperature
Always use absolute temperature (Kelvin) when working with gases. ºF ºC K
-459 32
212
-273
100
273
373
K = ºC + 273

9. Kelvin Practice
What is the approximate temperature for absolute zero in degrees Celsius and kelvin?
Calculate the missing temperatures
0C = _______ K 100C = _______ K
100 K = _______ C – 30C = _______ K
300 K = _______ C 403 K = _______ C
25C = _______ K 0 K = _______ C
Absolute zero is – 273C or 0 K
273
373
– 173
243 27
130
298
– 273

10. Pressure Which shoes create the most pressure?
Pressure (P ) is defined as the force exerted per unit area. The atmospheric pressure is measured using a barometer.
Which shoes create the most pressure?

11. What causes pressure?

12. Pressure KEY UNITS AT SEA LEVEL 101.325 kPa (kilopascal) 1 atm
760 mm Hg
760 torr
1 atm = 760 mmHg = 760 torr = kPa.

13. How can you convert between pressure units?
Example: convert 2.3atm to mmHg
Set up proportion, cross multiply, solve for x

14. Pressure
Barometer
measures atmospheric pressure

15. Standard Temperature & Pressure
STP
STP
Standard Temperature & Pressure
273 K
kPa or 1 atm

16. -BOYLES -CHARLE -GAY-LUSSAC
The Gas Laws P V T
-BOYLES -CHARLE -GAY-LUSSAC

17. Tentative schedule Wednesday (today): gas laws notes
Thursday: Gas laws practice problems
Friday: Gas laws post lab
Monday: Quiz- multiple choice portion and group short answer portion
Tuesday and Wednesday-review
Thursday – exam for 1st period
Friday – exam for 3rd period

18. Goals for this unit
MATH: Using the 5 gas law equations, solve for an unknown variable (picking apart a word problem and plugging into an equation)
CRITICAL THINKING: Given a real life scenario, predict outcomes or explain the given outcomes using your knowledge of the gas laws and how the variables of temperature, pressure, volume, and amount relate to each other (example: scuba diving: as a diver comes up from deep waters why could it be fatal for them to hold their breath?)

19. Boyle’s Law
The pressure and volume of a gas are inversely related at temperature P V

20. A. Boyle’s Law

21. Practice
A sample of chlorine gas occupies a volume of 946 mL at a pressure of 726 mmHg. What is the pressure of the gas (in mmHg) if the volume is reduced at constant temperature to 154 mL?

22. P1 x V1 = P2 x V2 P1 = 726 mmHg P2 = ? V1 = 946 mL V2 = 154 mL P1 x V1
A sample of chlorine gas occupies a volume of 946 mL at a pressure of 726 mmHg. What is the pressure of the gas (in mmHg) if the volume is reduced at constant temperature to 154 mL?
P1 x V1 = P2 x V2
P1 = 726 mmHg
P2 = ?
V1 = 946 mL
V2 = 154 mL
P1 x V1 V2
726 mmHg x 946 mL
154 mL =
P2 =
= 4460 mmHg

23. Charles’ Law
The volume and absolute temperature (K) of a gas are directly related at constant mass & pressure V T

24. Charles’ Law

25. Practice
A sample of gas occupies 3.5 L at 300 K. What volume will it occupy at 200 K?
If a 1 L balloon is heated from 22°C to 100°C, what will its new volume be?

26. For more lessons, visit www.chalkbored.com
A sample of gas occupies 3.5 L at 300 K. What volume will it occupy at 200 K?
V1 = 3.5 L, T1 = 300K, V2 = ?, T2 = 200K
3.5 L / 300 K = V2 / 200 K
V2 = (3.5 L/300 K) x (200 K) = 2.3 L
If a 1 L balloon is heated from 22°C to 100°C, what will its new volume be?
V1 = 1 L, T1 = 22°C = 295 K
V2 = ?, T2 = 100 °C = 373 K
V1/T1 = V2/T2, 1 L / 295 K = V2 / 373 K
V2 = (1 L/295 K) x (373 K) = 1.26 L
For more lessons, visit

27. V1/T1 = V2/T2 V1 = 3.20 L V2 = 1.54 L T1 = 398.15 K T2 = ? V2 x T1 V1
A sample of carbon monoxide gas occupies 3.20 L at 125 0C. At what temperature will the gas occupy a volume of 1.54 L if the pressure remains constant?
V1/T1 = V2/T2
V1 = 3.20 L
V2 = 1.54 L
T1 = K
T2 = ?
V2 x T1 V1
1.54 L x K
3.20 L =
T2 =
= 192 K

28. Gay-Lussac’s Law
The pressure and absolute temperature (K) of a gas are directly related at constant mass & volume P T

29. Gay-Lussac’s Law

30. Combined Gas Law
P1V1 T1 =
P2V2 T2
P1V1T2 = P2V2T1

31. A gas occupies 473 cm3 at 36°C. Find its volume at 94°C.

32. E. Gas Law Problems
A gas occupies 473 cm3 at 36°C. Find its volume at 94°C.
CHARLES’ LAW
GIVEN:
V1 = 473 cm3
T1 = 36°C = 309K
V2 = ?
T2 = 94°C = 367K T V
WORK:
P1V1T2 = P2V2T1
(473 cm3)(367 K)=V2(309 K)
V2 = 562 cm3

33. A gas occupies 100. mL at 150. kPa. Find its volume at 200. kPa.

34. E. Gas Law Problems
A gas occupies 100. mL at kPa. Find its volume at 200. kPa.
BOYLE’S LAW
GIVEN:
V1 = 100. mL
P1 = 150. kPa
V2 = ?
P2 = 200. kPa P V
WORK:
P1V1T2 = P2V2T1
(150.kPa)(100.mL)=(200.kPa)V2
V2 = 75.0 mL

35. Practice
A gas occupies 7.84 cm3 at 71.8 kPa & 25°C. Find its volume at STP.

36. E. Gas Law Problems COMBINED GAS LAW P T V V1 = 7.84 cm3
A gas occupies 7.84 cm3 at 71.8 kPa & 25°C. Find its volume at STP.
COMBINED GAS LAW
GIVEN:
V1 = 7.84 cm3
P1 = 71.8 kPa
T1 = 25°C = 298 K
V2 = ?
P2 = kPa
T2 = 273 K
P T V
WORK:
P1V1T2 = P2V2T1
(71.8 kPa)(7.84 cm3)(273 K)
=( kPa) V2 (298 K)
V2 = 5.09 cm3

37. A gas’ pressure is 765 torr at 23°C
A gas’ pressure is 765 torr at 23°C. At what temperature will the pressure be 560. torr?

38. E. Gas Law Problems
A gas’ pressure is 765 torr at 23°C. At what temperature will the pressure be 560. torr?
GAY-LUSSAC’S LAW
GIVEN:
P1 = 765 torr
T1 = 23°C = 296K
P2 = 560. torr
T2 = ? P T
WORK:
P1/T1= P2/T2
765/296= 560/x
T2 = K

39. Avogadro’s Principle
Equal volumes of all gases contain equal numbers of moles at constant temp & pressure. V n

40. Ideal Gas Law: relates volume, temperature, pressure, and amount
Basically sums up all of the gas laws into one equation

41. UNIVERSAL GAS CONSTANT
B. Ideal Gas Law
PV=nRT
UNIVERSAL GAS CONSTANT
R= Latm/molK

42. What is R??
It is a constant of proportionality that relates the energy scale in physics to the temperature scale.
Since this is not a physics course all you need to know is the number and where to use it (ideal gas law)

43. Gay Lussac’s Law of combined volumes of gas
At constant temperature and pressure, volumes of gases can be expressed as small whole number ratios
2H2 + O2  2H2O
2 L hydrogen gas react with 1 liter of oxygen gas to make 2 liters of water vapor

44. R = 0. 0821 liter·atm/mol·K R = 8. 3145 J/mol·K R = 8
R = liter·atm/mol·K R = J/mol·K R = m3·atm/mol·K R = L·Torr/mol·K or L·mmHg/mol·K

45. Calculate the pressure in atmospheres of 0
Calculate the pressure in atmospheres of mol of He at 16°C & occupying 3.25 L.

46. B. Ideal Gas Law IDEAL GAS LAW P = ? atm n = 0.412 mol
Calculate the pressure in atmospheres of mol of He at 16°C & occupying 3.25 L.
IDEAL GAS LAW
GIVEN:
P = ? atm
n = mol
T = 16°C = 289 K
V = 3.25 L
R = Latm/molK
WORK:
PV = nRT
P(3.25)=(0.412)(0.0821)(289)
L mol Latm/molK K
P = 3.01 atm

47. Solve the following problem:
Find the volume of 85 g of O2 at 25°C and kPa.