Grade 9 Module 11 Lesson 1 Gases

Draw

Quick Sketch:

Draw your favorite holiday memory and share it.

Poll

If you could teleport to a dream vacation spot, where would it be?

• A cozy mountain cabin, as in saint Tropez 🏔️

• A sunny beach, like malideves 🌴

• A bustling city, like NYC 🌆

• Somewhere magical like Hogwarts ✨

Two Truths and a Lie

Poll

How would you describe your vacation in one word?

• fun

• busy

• boring

• short

States of Matter

Module 11

Module Introduction

Module Introduction
Lesson 1: Gases
Lesson 2: Forces of Attraction
Lesson 3: Liquids and Solids
Lesson 4: Phase Changes
Module Wrap-Up

Why does water naturally exist as a solid, liquid, and gas on Earth?

ENCOUNTER THE PHENOMENON

Open Ended

Why does water naturally exist as a solid, liquid, and gas on Earth?

Gases

Lesson 1

Focus Question

Do all gases behave the same way?

New Vocabulary

kinetic-molecular theory

elastic collision

barometer

temperature

pressure

pascal

diffusion

atmosphere

Graham’s law of effusion

Dalton’s law of partial pressures

Poll

Do all gases behave the same way?

• yes

• no

Recap Prior Knowledge

Multiple Select

physical properties

• color

• texture

• mass

• reactivity

Multiple Select

Chemical properties

• length

• flammability

• acidity

• melting point

Differentiate between chemical and physical properties of matter

The composition (the types of atoms present) and

structure (their arrangement) determine the

chemical properties of matter and also affect the

physical properties of matter.

What determines these properties?

Gold

Mercury

Can you distinguish some materials by looking at them?

Graphite

Based solely on physical appearance, you can distinguish between the
solids and liquids,

substances that are
gases at room
temperature usually
display similar
physical properties
despite their different
compositions.

Why is there so little variation in behavior among gases?

Why are the physical properties of gases different from those of liquids
and solids?

but this is not true for many gases.

About 1860, chemists Ludwig Boltzmann and James Maxwell,
each proposed a model to explain the properties of gases.

That model is the kinetic -molecular theory.

Open Ended

Think pair share

In 3 sentences at least, share what you understood from the video

The kinetic-molecular theory

describes the behavior of matter in terms of

particles in motion.

The model makes several assumptions about

the size

motion

energy of particles.

• Gases consist of small

particles that are
separated from one
another by empty
space.

• Because gas particles

are far apart, they
experience no
significant attractive
or repulsive forces.

Particle size

• kinetic energy: energy due to motion.
• The kinetic energy of a particle depends on mass & velocity.

Temperature

is a measure of the average kinetic energy of the particles in a sample of matter.

In a sample of a single gas, all particles have

the same mass,

but all particles do not have the same velocity.

Therefore, all particles do not have the same

kinetic energy.

Particle Energy

• Gas particles are in constant, random motion.
• Particles move in a straight line until they collide with other

particles or with the walls of their container.

Particle motion

Collisions between gas particles are elastic

An elastic collision is
one in which no kinetic

energy is lost.

Kinetic energy can be
transferred between

colliding particles, but the
total kinetic energy of the

two particles does not

change.

Multiple Choice

Collision in which no kinetic energy is lost; kinetic energy can be transferred between the colliding particles, but the total kinetic energy of the two particles remains the same.

• Inelastic collision
• Elastic collision
• Perfectly inelastic collision
• Superelastic collision

Multiple Choice

In a sample of single gas, all particles have the same mass and velocity

• True

• False

Kinetic Molecular Theory:

This theory assumes that gas molecules are in constant, random motion and that they collide elastically (without energy loss). These assumptions hold for most gases under normal conditions, leading to similar behavior regardless of the type of gas.

Multiple Choice

A measure of the average kinetic energy of the particles in a sample of matter.

• heat

• energy

• temperature

• enthalpy

Multiple Select

Gas particles move in,

• fixed positions
• random directions
• circular paths
• straight lines

The kinetic-molecular theory helps explain the behavior of gases.

Explaining the Behavior of Gases

•Low density
•Compression and expansion
•Diffusion and effusion
•Gas Pressure

Low Density

Low density

Density is mass per unit volume

Gold is more than 6700 times as dense as chlorine. WHY?

The density of
chlorine gas is

0.002898

g/mL at 20°C

the density of
solid gold is
19.3 g/mL .

Open Ended

Gold is more than 6700 times as dense as chlorine, why?

This large difference cannot be due only to the difference in mass between
gold atoms and chlorine molecules (about 3:1).

As the kinetic molecular theory states, a great deal of space exists between gas particles.

Thus, there are fewer chlorine molecules than gold atoms in the same volume.

Low density

Density is mass per

unit volume

Gold is more than 6700 times as dense as chlorine. WHY?

The density of
chlorine gas is

0.002898

g/mL at 20°C

the density of
solid gold is
19.3 g/mL .

Compression & Expansion

In a closed container,
compression and expansion change the volume occupied
by a constant mass of particles.

Compression and Expansion

reduce its volume.

The large amount of empty space

between the particles in the air allows air

to be squeezed into a smaller volume.

When the volume of a container is made larger, the constant random motion of the gas particles allows a gas to expand until it fills the available space.

Compression and Expansion

Open Ended

Think Pair Share

Why does gase fill their container?

Why gas fills a container?

The constant motion of gas particles allows a gas to expand until it fills its container.

Diffusion & Effusion

Diffusion is the term used to describe the movement of one material through another.

Diffusion

According to the kinetic-molecular theory, there are no significant forces of attraction between gas particles.
Thus, gas particles can flow easily past each other. Often, the space into which a gas flows is already occupied by another gas.
The random motion of the gas particles causes the gases to mix until they are evenly distributed

What happens when you

puncture a container,
such as a balloon or a

tire?

Effusion

Effusion is a process related to diffusion.
During effusion, a gas escapes through a tiny opening.

Graham’s law of effusion states that the rate of effusion for a gas is inversely proportional to the square root of its molar mass.

In 1846, Thomas Graham conducted
experiments to measure the rates of

effusion for different gases at the same

temperature.

Graham’s law also applies to diffusion.

The rate of diffusion depends mainly on the mass of the particles involved
Lighter particles diffuse more rapidly than heavier particles.

Using Graham’s law,
you can set up
a proportion to
compare the
diffusion rates
for two gases.

Diffusion and Effusion

For two gases A and B,

Multiple Choice

Graham’s law of effusion states that, .........

• The rate of effusion of a gas is directly proportional to its molar mass.
• The rate of effusion of a gas is independent of its molar mass.
• The rate of effusion of a gas is proportional to the square of its molar mass.
• The rate of effusion of a gas is inversely proportional to the square root of its molar mass.

Multiple Choice

Lighter particles diffuse more rapidly than heavier particles.

• true

• false

GRAHAM’S LAW

Ammonia has a molar mass of 17.0 g/mol; hydrogen chloride has a molar mass of 36.5 g/mol. What is the ratio of their diffusion rates?

KNOWN

UNKNOWN

molar massHCl = 36.5 g/mol

ratio of diffusion rates = ?

molar massNH3 = 17.0 g/mol

Multiple Choice

Ammonia has a molar mass of 17.0 g/mol; hydrogen chloride has a molar mass of 36.5 g/mol. What is the ratio of their diffusion rates?

• 2.10
• 1.47

• 1.00
• 0.75

Extra Exercises

1. Methane (CH4) effuses at a rate of 2.45 mol/s. What will be the effusion rate of argon (Ar) under the same conditions?

Multiple Choice

Methane (CH4) effuses at a rate of 2.45 mol/s.

What will be the effusion rate of argon (Ar) under the same conditions?

• 1.94 mol/s
• 3.00 mol/s
• 2.00 mol/s
• 1.55 mol/s

Extra Exercises

1. Methane (CH4) effuses at a rate of 2.45 mol/s. What will be the effusion rate of argon (Ar) under the same conditions?

Extra Exercises

2. The effusion rate of hydrogen sulfide (H2S) is 1.50 mol/s. Another gas under similar conditions effuses at a rate of 1.25 mol/s.
What is the molar mass of the second gas?

Multiple Choice

The effusion rate of hydrogen sulfide (H2S) is 1.50 mol/s. Another gas under
similar conditions effuses at a rate of 1.25 mol/s.
What is the molar mass of the second gas?

• 32.07 g/mol
• 18.02 g/mol
• 48.96 g/mol

• 44.01 g/mol

Extra Exercises

2. The effusion rate of hydrogen sulfide (H2S) is 1.50 mol/s. Another gas under similar conditions effuses at a rate of 1.25 mol/s.
What is the molar mass of the second gas?

Open Ended

Think Pair Share

Compare between diffusion and effusion, give example for each.

Gas Pressure

Pressure
Force per unit area.

Gas Pressure

Gas particles exert pressure when they
collide with the walls of their container.

Multiple Choice

Gas pressure is due to, ......

• the weight of the gas in the container

• the temperature of the gas
• the volume of the gas in the container

• gas particles colliding with walls of conttainer

• Earth is surrounded by an atmosphere that extends into
space for hundreds of kilometers.

• Because the particles in air move in every direction, they exert pressure in all directions. This pressure is called atmospheric pressure, or air pressure.

• Air pressure varies at different points on Earth.

Air Pressure

Fewer particles at higher
elevations exert less force
than the greater
concentration of particles
at lower altitudes.

Therefore, air
pressure is less at
higher altitudes than
it is at sea level.

Multiple Choice

Compare the air pressure on top of mountain and inside a cave.

• Air pressure inside a cave is higher than at the top of a mountain.
• Air pressure is the same at the top of a mountain and inside a cave.
• Air pressure inside a cave is lower than at the top of a mountain.
• Air pressure at the top of a mountain is higher than inside a cave.

Measuring air pressure

Torricelli was the first to design equipment to show that the atmosphere
exerted pressure.
The device that Torricelli invented is called a Barometer.
A barometer is an instrument used to measure atmospheric pressure.

At sea level, the

height of the
mercury in a

barometer is usually

about 760 mm

A manometer is an instrument used to measure gas pressure in a closed container. 

In a manometer, a flask is connected to a U-tube that contains mercury.

When the valve is opened, gas particles diffuse into the
U-tube. The gas particles push down on the mercury in
the heights in the two arms are no longer equal.

Measuring GAS pressure

Before gas is released into the U-tube, the
mercury is at the same height in each arm.

The difference in the

height of the mercury in
the two arms is used to
calculate the pressure of

the gas in the flask.

Multiple Choice

The instrument that is used to measure gas pressure in a closed container:

• Manometer
• Voltmeter

• Thermometer
• Barometer

Open Ended

The device used to measure Air Pressure, ......

Units of Pressure

• The SI unit of pressure is the pascal (Pa) .
• It is named for Blaise Pascal (1623–1662),

a French mathematician and philosopher.

• Many fields of science still use more

traditional units of pressure.

1 atm = 1 bar =760 mmHg = 760 torr = 101.3 kPa = 14.7 psi

engineers often report
pressure as pounds per

square inch (psi)

There is also a unit called
the torr and another unit

called a bar.

Pressure can be expressed in terms of mmHg, Atm, Pa, Torr, psi, and bar. Do the following conversions

1 atm = 1 bar= 760 mmHg = 760 torr = 101.3 kPa = 14.7 psi

a. 60 mmHg to bar b. 0.45 atm to psi








c. 57 mm Hg to Kpa d. 346 Kpa to atm

Multiple Choice

Convert; 60 mmHg to bar

• 0.05 bar
• 0.1 bar
• 0.08 bar
• 0.06 bar

Multiple Choice

Convert; 0.45 atm to psi

• 6.62 psi

• 8.00 psi
• 7.25 psi
• 5.12 psi

Multiple Choice

Convert; 57 mmHg to Kpa

• 10.2 kPa
• 7.596 kPa
• 3.8 kPa
• 5.5 kPa

Multiple Choice

Convert; 346 Kpa to atm

• 3.42 atm
• 3.00 atm
• 4.10 atm
• 2.98 atm

Pressure can be expressed in terms of mmHg, Atm, Pa, Torr, psi, and bar. Do the following conversions

1 atm = 1 bar= 760 mmHg = 760 torr = 101.3 kPa = 14.7 psi

a. 60 mmHg to bar 0.08 bar b. 0.45 atm to psi 6.62 psi







c. 57 mm Hg to Kpa 7.596 kPa d. 346 Kpa to atm 3.42 atm

Units of Pressure

• The SI unit of pressure is the pascal (Pa) .
• It is named for Blaise Pascal (1623–1662),

a French mathematician and philosopher.

• Many fields of science still use more

traditional units of pressure.

1 atm = 1 bar =760 mmHg = 760 torr = 101.3 kPa = 14.7 psi

engineers often report
pressure as pounds per

square inch (psi)

There is also a unit called
the torr and another unit

called a bar.

Multiple Choice

Convert; 200 Kpa to bar

1 atm = 1 bar= 760 mmHg = 760 torr = 101.3 kPa = 14.7 psi

• 1.5 bar
• 0.5 bar
• 3 bar
• 2 bar

•When Dalton studied the properties of gases, he found that each gas in a mixture exerts pressure independently of the other gases present.
•The portion of the total pressure contributed by a single gas is called its partial pressure.
•The total pressure of the mixture is equal to the sum of the partial pressures of the individual gases.
T

What happens to the pressure
when gases are mixed together?

The partial pressure of a gas depends on the number of moles of gas, the size of the container, and the temperature of the mixture.
It does not depend on the identity of the gas.
At a given temperature and pressure, the partial pressure of 1 mol of any gas is the same.

the total pressure of a mixture of gases is equal to the sum of the pressures of all the gases in the mixture.

Dalton’s law of partial
pressures states that

Multiple Select

The partial gas pressure depends on:

• identity of the gas

• moles of the gas

• temperature

• size of container

Multiple Choice

At a given temperature and pressure, the partial pressure of 1 mol of any gas is the same. 

• true

• false

THE PARTIAL PRESSURE OF A GAS

A mixture of oxygen (O₂), carbon dioxide (CO₂), and nitrogen (N₂) has a total pressure of 0.97 atm.
What is the partial pressure of O₂ if the partial pressure of CO₂ is 0.70 atm and the partial pressure of N₂ is 0.12 atm?

KNOWN

UNKNOWN

PN2 = 0.12 atm

PO2 = ? atm

PCO2 = 0.70 atm

Ptotal = 0.97 atm

Multiple Choice

A mixture of oxygen (O₂), carbon dioxide (CO₂), and nitrogen (N₂) has a total pressure of 0.97 atm.
What is the partial pressure of O₂ if the partial pressure of CO₂ is 0.70 atm and the partial pressure of N₂ is 0.12 atm?

• 0.50 atm
• 0.15 atm
• 0.25 atm
• 0.10 atm

Multiple Choice

What is the formula to calculate the partial pressure of a gas in a mixture?

• Total pressure + partial pressure of other gases

• Total pressure - partial pressures of other gases

• Total pressure × partial pressures of other gases

• Total pressure ÷ partial pressures of other gases

THE PARTIAL PRESSURE OF A GAS

A mixture of oxygen (O₂), carbon dioxide (CO₂), and nitrogen (N₂) has a total pressure of 0.97 atm.
What is the partial pressure of O₂ if the partial pressure of CO₂ is 0.70 atm and the partial pressure of N₂ is 0.12 atm?

KNOWN

UNKNOWN

PN2 = 0.12 atm

PO2 = ? atm

PCO2 = 0.70 atm

Ptotal = 0.97 atm

Solve Practice Problems B.P.

Solve CHECK YOUR PROGRESS B.P.

EXIT_TICKETS_GASES

Open Ended

In pairs, solve the following questions

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