Intro-to-Gases-and-Gas-Laws-2(1).ppt_20231206_071411_0000.pdf

Kinetic Molecular Theory of ‘Ideal’
Gases
Particles in an ideal gas…
have no volume.
have elastic collisions (ie. billiard ball
particles exchange energy with eachother,
but total KE is conserved
are in constant, random, straight-line
motion.
don’t attract or repel each other.
have an avg. KE directly related to
temperature ( temp= motion= KE)Characteristics of Gases
Gases can be compressed.
no volume = lots of empty space
Gases undergo diffusion & effusion (across a barrier with small holes).
Characteristics of Gases
Gases expand to fill any container.
random motion, no attraction
Gases are fluids (like liquids).
no attraction
Gases have very low densities.
no volume = lots of empty spaceKinetic Energy , States of Matter & Temperature
Gases have a higher kinetic energy because their particles move a lot more than
in a solid or a liquid
As the temperature increases, there gas particles move faster, and thus kinetic
energy increases.States of Matter
2 main factors determine state:
The forces (inter/intramolecular) holding particles together
The kinetic energy present (the energy an object possesses due to its motion of the particles) Real Gases
At STP, molecules of gas are moving fast and are very
far apart, making their intermolecular forces and
volumes insignificant, so assumptions of an ideal gas
are valid under normal temp/pressure conditions.
BUT…
at high pressures: gas molecules are pushed closer
together, and their interactions with each other
become more significant due to volume
at low temperatures: gas molecules move slower
due to KE and intermolecular forces are no
Real Gases
Particles in a REAL gas…
have their own volume
attract each other (intermolecular
forces)
Gas behavior is most ideal…
at low pressures
at high temperatures
Why???Atmospheric Pressure
The gas molecules in the atmosphere are pulled
toward Earth due to gravity, exerting pressure
Units of Pressure
At Standard Atmospheric Pressure (SAP)
101.325 kPa (kilopascal)
1 atm (atmosphere)
760 mm Hg
(millimeter Hg)
760 torr
14.7 psi (pounds per square inch)Standard Temperature & Pressure
Standard Temperature & Pressure
0°C
273 K
1 atm
101.325 kPa
Temperature: The Kelvin Scale
ºC
K
-273
0
100
0
273
373
K = ºC + 27Kelvin and Absolute Zero
Scottish physicist Lord Kelvin suggested that -273ᵒC (0K) was the temperature at which the motion particles
within a gas approaches zero.. And thus, so does volume)
Absolute Zero:
http://www.youtube.com/watch?v=JHXxPnmyDbk
Comparing the Celsius and Kelvin Scale:
http://www.youtube.com/watch?vHow Did We Do So Far?
Learning Goal:
I will be able to understand
what kinetic energy is and
how it relates to gases and
temperature, describe the
properties of a real and ideal
gas and understand what
Absolute Zero is and how to
convert between the Kelvin
and Celsius temperature
scales.T
Part B: The Gas Laws
Part B:
Learning Goals
I will be able to describe
Boyle’s, ChaKelvin and Absolute Zero
Scottish physicist Lord Kelvin suggested that -273ᵒC (0K) was thT

1. EQ:
How do we use the Kinetic
Molecular Theory to explain
the behavior of gases?
Topic #32: Introduction to
Gases

2. States of Matter
2 main factors determine state:
The forces (inter/intramolecular) holding particles together
The kinetic energy present (the energy an object possesses due to its motion of the particles)
KE tends to ‘pull’ particles apart

3. Kinetic Energy , States of Matter & Temperature
Gases have a higher kinetic energy because their particles move a lot more than
in a solid or a liquid
As the temperature increases, there gas particles move faster, and thus kinetic
energy increases.

4. Characteristics of Gases
Gases expand to fill any container.
random motion, no attraction
Gases are fluids (like liquids).
no attraction
Gases have very low densities.
no volume = lots of empty space

5. Characteristics of Gases
Gases can be compressed.
no volume = lots of empty space
Gases undergo diffusion & effusion (across a barrier with small holes).
random motion

6. Kinetic Molecular Theory of ‘Ideal’
Gases
Particles in an ideal gas…
have no volume.
have elastic collisions (ie. billiard ball
particles exchange energy with eachother,
but total KE is conserved
are in constant, random, straight-line
motion.
don’t attract or repel each other.
have an avg. KE directly related to
temperature ( temp= motion= KE)

7. Real Gases
Particles in a REAL gas…
have their own volume
attract each other (intermolecular
forces)
Gas behavior is most ideal…
at low pressures
at high temperatures
Why???

8. Real Gases
At STP, molecules of gas are moving fast and are very
far apart, making their intermolecular forces and
volumes insignificant, so assumptions of an ideal gas
are valid under normal temp/pressure conditions.
BUT…
at high pressures: gas molecules are pushed closer
together, and their interactions with each other
become more significant due to volume
at low temperatures: gas molecules move slower
due to KE and intermolecular forces are no
longer negligible

9. Pressure
Which shoes create the most pressure?

10. Atmospheric Pressure
The gas molecules in the atmosphere are pulled
toward Earth due to gravity, exerting pressure
Why do your ears ‘pop’ in an airplane?

11. Pressure
Barometer
measures atmospheric pressure
Mercury Barometer

12. Units of Pressure
At Standard Atmospheric Pressure (SAP)
101.325 kPa (kilopascal)
1 atm (atmosphere)
760 mm Hg
(millimeter Hg)
760 torr
14.7 psi (pounds per square inch)

13. Standard Temperature & Pressure
Standard Temperature & Pressure
0°C 273 K
1 atm 101.325 kPa
-OR-
STP

14. Temperature: The Kelvin Scale
ºC
K
-273 0 100
0 273 373
K = ºC + 273
Always use absolute temperature
(Kelvin) when working with gases.

15. Kelvin and Absolute Zero
Scottish physicist Lord Kelvin suggested that -273ᵒC (0K) was the temperature at which the motion particles
within a gas approaches zero.. And thus, so does volume)
Absolute Zero:
http://www.youtube.com/watch?v=JHXxPnmyDbk
Comparing the Celsius and Kelvin Scale:
http://www.youtube.com/watch?v=-G9FdNqUVBQ

16. Why Use the Kelvin Scale?
Not everything freezes at 0ᵒC, but for ALL substances, motion stops at 0K.
It eliminates the use of negative values for temperature! Makes mathematic
calculations possible (to calculate the temp. twice warmer than -5ᵒC we can’t use
2x(-5ᵒC) because we would get -10ᵒC!)

17. Kelvin Scale vs Celsius Scale

18. Converting between Kelvin and Celsius
0ᵒC =_____Ka.
100ᵒC= _____Kb.
25ᵒC =______Kc.
-12ᵒC = ______Kd.
-273K = ______ᵒCe.
23.5K = ______ᵒCf.
373.2K= ______ᵒCg.
K = ºC + 273

19. Learning Goal:
I will be able to understand
what kinetic energy is and
how it relates to gases and
temperature, describe the
properties of a real and ideal
gas and understand what
Absolute Zero is and how to
convert between the Kelvin
and Celsius temperature
scales.
How Did We Do So Far?

20. P
V
T
Part B: The Gas Laws
Part B:
Learning Goals
I will be able to describe
Boyle’s, Charles’ and
Gay-Lussac’s Laws
relating T, P and/or V
and be able to calculate
unknown values using
the equations derived
from these laws, as well
as the combined gas
law.

21. 1. Intro to Boyle’s Law
Imagine that you hold the tip of a syringe on the tip of your finger
so no gas can escape. Now push down on the plunger of the
syringe.
What happens to the volume in the syringe?
What happens to the pressure the gas is exerting in the
syringe?

22. 1. Boyle’s Law

23. 1. Boyle’s Law
The pressure and volume of a gas are
inversely proportional (as one increases,
the other decreases, and vice versa
at constant mass & temp
P
V

24. 1. Boyle’s Law
Boyle’s Law leads to the mathematical
expression: *Assuming temp is constant
P₁V₁=P₂V₂
Where P₁ represents the initial pressure
V₁ represents the initial volume,
And P₂ represents the final pressure
V₂ represents the final volume

25. Example Problem:
A weather balloon with a volume of 2000L at a pressure of 96.3 kPa
rises to an altitude of 1000m, where the atmospheric pressure is
measured to be 60.8kPa. Assuming there is no change in the
temperature or the amount of gas, calculate the weather balloon’s
final volume.

26. You Try:
Atmospheric pressure on the peak of Kilimanjaro can be as low as
0.20 atm. If the volume of an oxygen tank is 10.0L, at what pressure
must the tank be filled so the gas inside would occupy a volume of 1.2
x 10³L at this pressure?

27. 2. Intro to Charles’ Law
Imagine that you put a balloon filled with gas in liquid
nitrogen
What is happening to the temperature of the gas in the
balloon?
What will happen to the volume of the balloon?

28. 2. Charles’ Law

29. V
T
2. Charles’ Law
The volume and absolute temperature (K) of
a gas are directly proportional (an increase
in temp leads to an increase in volume)
at constant mass & pressure

30. 2. Charles’ Law

31. 2. Charles’ Law
Charles’ Law leads to the mathematical
expression:
*Assuming pressure remains constant

32. Example Problem:
A birthday balloon is filled to a volume of 1.5L of helium gas in an
air-conditioned room at 293K. The balloon is taken outdoors on a
warm day where the volume expands to 1.55L. Assuming the
pressure and the amount of gas remain constant, what is the air
temperature outside in Celsius?

33. You Try:
A beach ball is inflated to a volume of 25L of air at 15ᵒC. During
the afternoon, the volume increases by 1L. What is the new
temperature outside?

34. 3. Intro to Gay-Lussac’s Law
Imagine you have a balloon inside a container that ensures it has a
fixed volume. You heat the balloon.
What is happening to the temp of the gas inside the balloon?
What will happen to the pressure the gas is exerting on the balloon?

35. P
T
3. Gay-Lussac’s Law
The pressure and absolute temperature (K)
of a gas are directly proportional (as
temperature rises, so does pressure)
at constant mass & volume

36. 2. Gay-Lussac’s Law
Gay-Lussac’s Law leads to the
mathematical expression:
*Assuming volume remains constant
Egg in a bottle to show Gay-Lussac's Law:
T & P relationship:
http://www.youtube.com/watch?v=r_JnUBk1JPQ

37. Example Problem:
The pressure of the oxygen gas inside a canister with a fixed
volume is 5.0atm at 15ᵒC. What is the pressure of the oxygen gas
inside the canister if the temperature changes to 263K? Assume the
amount of gas remains constant.

38. You Try:
The pressure of a gas in a sealed canister is 350.0kPa at a room
temperature of 15ᵒC. The canister is placed in a refrigerator that
drops the temperature of the gas by 20K. What is the new pressure in
the canister?

39. 4. Combined Gas Law
P₁V₁
T₁
=
P₂V₂
T₂
By combining Boyle’s, Charles’ and Gay
Lussac’s Laws, the following equation is
derived:

40. Example Problem:
A gas occupies 7.84 cm³ at 71.8 kPa & 25°C.
Find its volume at STP.

41. Any Combination Questions 
a) A gas occupies 473 cm³ at 36°C. Find its volume at 94°C
b) A gas’ pressure is 765 torr at 23°C. At what temperature will the
pressure be 560. torr

42. P
V
T
How Did You Do?
Part B:
Learning Goals
I will be able to describe
Boyle’s, Charles’ and
Gay-Lussac’s Laws
relating T, P and/or V
and be able to calculate
unknown values using
the equations derived
from these laws, as well
as the combined gas
law.