Contributed by:

The highlights are:

1. States of matter

2. Characteristics of gases

3. Kinetic theory of gases

4. Real gases

5. Pressure

6. Boyle law

7. Charles law

8. Gay-Lussac's law

9. Combined gas law

1. States of matter

2. Characteristics of gases

3. Kinetic theory of gases

4. Real gases

5. Pressure

6. Boyle law

7. Charles law

8. Gay-Lussac's law

9. Combined gas law

1.
Introduction to

Gases

EQ:

How do we use the

Kinetic Molecular

Theory to explain the

behavior of gases?

Gases

EQ:

How do we use the

Kinetic Molecular

Theory to explain the

behavior of 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

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.

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

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

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)

‘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???

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

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

force

pressure

area

Which shoes create the most pressure?

force

pressure

area

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?

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

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) N

760 torr kPa 2

m

14.7 psi (pounds per square inch)

At Standard Atmospheric Pressure (SAP)

101.325 kPa (kilopascal)

1 atm (atmosphere)

760 mm Hg

(millimeter Hg) N

760 torr kPa 2

m

14.7 psi (pounds per square inch)

13.
Standard Temperature &

STP

Standard Temperature & Pressure

0°C 273 K

-OR-

1 atm 101.325 kPa

STP

Standard Temperature & Pressure

0°C 273 K

-OR-

1 atm 101.325 kPa

14.
Temperature: The Kelvin

Always use absolute temperature

(Kelvin) when working with gases.

-273 0 100

K

0 273 373

C K 273 K = ºC + 273

Always use absolute temperature

(Kelvin) when working with gases.

-273 0 100

K

0 273 373

C K 273 K = ºC + 273

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:

Comparing the Celsius and Kelvin Scale:

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:

Comparing the Celsius and Kelvin Scale:

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 -5 oC we can’t use

2x(-5oC) because we would get -10oC!)

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 -5 oC we can’t use

2x(-5oC) because we would get -10oC!)

17.
Kelvin Scale vs Celsius Scale

18.
Converting between Kelvin and

Celsius

C K 273 K = ºC + 273

a) 0oC =_____K

b) 100oC= _____K

c) 25oC =______K

d) -12oC = ______K

e) -273K = ______oC

f) 23.5K = ______oC

g) 373.2K= ______oC

Celsius

C K 273 K = ºC + 273

a) 0oC =_____K

b) 100oC= _____K

c) 25oC =______K

d) -12oC = ______K

e) -273K = ______oC

f) 23.5K = ______oC

g) 373.2K= ______oC

19.
How 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

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

20.
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

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

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?

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

V

The pressure and volume of a gas are

inversely proportional (as one increases,

the other decreases, and vice versa

• at constant mass & temp

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

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.

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?

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?

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.
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

T

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

T

30.
2. Charles’ Law

31.
2. Charles’ Law

Charles’ Law leads to the mathematical

expression:

*Assuming pressure remains constant

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?

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?

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

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?

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.
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

T

The pressure and absolute temperature

(K) of a gas are directly proportional (as

temperature rises, so does pressure)

• at constant mass & volume

T

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:

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:

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.

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?

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

By combining Boyle’s, Charles’ and Gay

Lussac’s Laws, the following equation is

P1V1 P2V2

=

T1 T2

By combining Boyle’s, Charles’ and Gay

Lussac’s Laws, the following equation is

P1V1 P2V2

=

T1 T2

40.
Example Problem:

A gas occupies 7.84 cm3 at 71.8 kPa & 25°C. Find

its volume at STP.

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

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.
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

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