Weather Unit Investigation IV: Counting Matter Lesson 1: Tower of Air Lesson 2: Lighter Than Air Lesson 3: More Than a Billion Lesson 4: Take a Breath

Weather Unit

Investigation IV: Counting MatterLesson 1: Tower of AirLesson 2: Lighter Than AirLesson 3: More Than a BillionLesson 4: Take a BreathLesson 5: Up in the CloudsLesson 6: Rain in the ForecastLesson 7: Stormy Weather

Weather Unit – Investigation IV

Lesson 1:

Tower of Air

Unit 3 • Investigation IV-X

© 2004 Key Curriculum Press.

ChemCatalyst

• What is the atmosphere? What is it made of?

• How big is the atmosphere? How do we measure it?

(cont.)



(cont.)

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air pushes down

mercury is pushed up

(cont.)



The Big Question

• How does a column of mercury measure the air pressure on the earth?



You will be able to:

Explain how a mercury barometer works



Activity

Purpose: This lesson allows you to explore why mercury is used in barometers to measure air pressure.

(cont.)



30,000 m

40,000 m

sea level

20,000 m

10,000 m

99% of the atmosphere is below ~30,000 m

90% of the atmosphere is

below 17,700 m

column of air

50% of the atmosphere is below 5,600 m

mountaintop

(cont.)

(cont.)



Substance Altitude Height of the airin m

Height of the air

in ft

Density of the air above

Air pressure

air sea level 30,000 m 99,000 m 0.00034 g/cm3 1.0 atm

air 5,600 m 24,400 m 80,500 ft 0.00022 g/cm3 0.5 atm

air 11,000 m 19,000 m 62,700 ft 0.00013 g/cm3 0.25 atm

air 17,700 m 12,300 m 40,600 ft 0.00008 g/cm3 0.1 atm

Air Pressure

(cont.)

(cont.)



Substance Height of the water in m

Height of the water in ft

Density Pressure

water 10.3 m 34.0 ft 1.0 g/cm3 1.0 atm

water 20.6 m 68.0 ft 1.0 g/cm3 2.0 atm

water 103 m 340 ft 1.0 g/cm3 10.0 atm

Water Pressure

(cont.)

(cont.)



Mercury Pressure

Substance Height of the mercury in m

Height of the mercury in ft

Density Pressure

mercury 0.76 m 2.5 ft 13.6 g/cm3 1.0 atm

(cont.)



Making Sense

• Why does the density of the air decrease as altitude increases?

• Why isn’t water used in a barometer?



• Number density means the number of particles per volume.

Notes

(cont.)



• The most important gases in the earth’s atmosphere, in terms of their effects on the health of the earth, are nitrogen, oxygen, water vapor, carbon dioxide, methane, nitrous oxide, and ozone.

• Nitrogen and oxygen make up 99% of the dry atmosphere.

• Particulate matter refers to tiny particles that are not gases, but are small enough to be airborne.

Notes (cont.)



Check-In

• Why is mercury used in a barometer and not alcohol or water or some other liquid?



Wrap-Up

• A mercury barometer is used to measure the air pressure of the atmosphere because of its high density.

• The atmosphere becomes less dense with altitude. There are less gas particles per volume as altitude increases.

• The atmosphere consists mostly of nitrogen and oxygen gases.


Lesson 2:

Lighter Than Air



ChemCatalyst

• Why do you suppose meteorologists use helium and hydrogen for weather balloons?

• Which gas would cause the weather balloon to rise faster? Explain the reasoning behind your answer.



Notes

• Equal volumes of gases at the same temperature and pressure contain equal numbers of gas particles (atoms or molecules).

• In two balloons of equal volume

# of N2 molecules = # of He atoms

Avogadro’s Hypothesis



The Big Question

• What is the relationship between the number of gas particles, the mass, and volume of different gases?




Apply Avogadro’s Hypothesis.



Activity

Purpose: The purpose of today's lesson is to explore the number of gas particles in a specified volume of gas. You will need Avogadro's Hypothesis to help you answer the questions.

(cont.)



2.0 g

321 54

22.0 g 4.0 g 28.0 g 8.0 g

He

N2

CO2

(cont.)

(cont.)



gas # of particles

mass volume pressure temperature

He 6.02 x 1023 4.0 g 22.4 L 1.0 atm 273 K

He 8.0 g 44.8 L 1.0 atm 273 K

He 11.2 L 1.0 atm 273 K

Ar 6.02 x 1023 40.0 g 22.4 L 1.0 atm 273 K

Ar 20.0 g 1.0 atm 273 K

N26.02 x 1023 28.0 g 22.4 L 1.0 atm 273 K

N23.01 x 1023 1.0 atm 273 K

N26.02 x 1023 28.0 g 11.2 L 273 K

(cont.)



Making Sense

You have:

• 5.0 L of methane (CH4) at 30°C and 1.0 atm, and

• 5.0 L of oxygen (O2) at 30°C and 1.0 atm.

(cont.)



• List at least three things that are the same.

• List at least three things that are different.

(Consider the volume, temperature, pressure, number of gas particles, identities of the gas particles, mass, and density.)

(cont.)



• If you have 22.4 L of a gas at 1 atm and 273 K, then there will be 6.02 x 1023 gas particles present, regardless of the identity of the gas.

• This number, 6.02 x 1023 is also known as Avogadro’s number.

Avogadro’s Number

Notes

(cont.)



• Standard temperature and pressure, STP, is 1 atm and 273 K.

• At STP, 6.02 x 1023 gas particles occupy 22.4 L.

• This is true for any gas.

Notes (cont.)



Check-In

One balloon has 22.4 L of Ar and another balloon has 22.4 L of Ne gas. Both balloons are at STP. • Are the balloons the same volume?• Do the balloons contain the same

number of particles? Why or why not?• Will the balloons have the same mass?

Why or why not?



Wrap-Up

• Avogadro’s hypothesis states that equal volumes of gases contain the same number of molecules if they are at the same temperature and pressure, independent of the identity of the gas.

• Standard temperature and pressure is defined as 1 atmosphere and 273 K.


Lesson 3:

More Than a Trillion



ChemCatalyst

• Why might it be useful for a chemist to know there are 6.02 X 1023 gas particles in a certain volume of gas?



The Big Question

• How is a mole used for counting particles in gases, liquids, and solids?




Use the mole as a counting unit for gases, liquids, and solids.



• There are 6.02 x 1023 particles in a mole.

• This number of particles is also called Avogadro’s number.

Notes



Activity

Purpose: In this lesson, you will explore how to count using a new unit called the mole.

(cont.)



Part I: 1 mole = 6.02 x 1023 particles

Substance # of moles # of particles total # of atoms

He (g) 1 6.02 x 1023 6.02 x 1023

He (g) 0.5 3.01 x 1023 3.01 x 1023

He (g) 2.0 1.204 x 1024

H2 (g) 1 6.02 x 1023 1.204 x 1024

H2 (g) 0.5 3.01 x 1023

H2 (g) 2.408 x 1024

Cu (s) 1

Cu (s) 0.1 6.02 x 1022

H2O (l) 1 1.806 x 1024

H2O (l) 0.5 3.01 x 1023



Part II: Counting molecules vs. atoms

Materials: (per pair of students)

24 small pieces of paper - index cards or small Post-Its® work well

(cont.)

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Formaldehyde clear liquidsmells putrid

Glucose white solidtastes sweet

C6H12O6

4 moles CH2O

24 moles

(cont.)



Making Sense

A company has a history of releasing NO2 gas into the atmosphere, which forms smog. In order to reduce their pollution, they figure out how to release N2O4 instead. For every 1.0 mole of NO2, they now release 0.75 moles of N2O4 instead.

(cont.)



• Are there fewer gas particles with the release of 0.75 moles of N2O4 instead of 1.0 moles of NO2? Explain.

• Are there fewer N atoms being released? Explain.

• If the amount of smog depends on the number of N atoms, has the company reduced the amount of smog that will be produced?

(cont.)

(cont.)



Substance Molecular formula

Formaldehyde (embalming liquid)

CH2O

Acetic acid (vinegar) C2H4O2

Glucose (one form of sugar) C6H12O6

Sucrose (table sugar) C12H22O11

A molecular formula gives the numbers of atoms that remain together as a molecule.

(cont.)

(cont.)



Here are some translations for the meaning of 1 mole of C6H12O6, glucose:

• one mole of sugar molecules

• 6.02 x 1023 molecules of C6H12O6

• 6 moles of carbon atoms

• 12 moles of hydrogen atoms

• 3.612 x 1024 oxygen atoms

• 24 moles of atoms

(cont.)



Check-In

You have 1 mole CH4 (g) and 1 mole O2 (g).

• Which has more atoms?

• Which has more molecules?

• Which has more mass?



Wrap-Up

• A mole is 6.02 x 1023 units of whatever you are counting. This number is often referred to as Avogadro’s number.


Lesson 4:

Take a Breath



ChemCatalyst

Mount Everest lies on the border between Nepal and Tibet. It is approximately 29,000 feet high. Those who climb Mount Everest usually pack along many tanks of oxygen to help them with breathing.

• Why do you think it is difficult to breathe at high altitudes?



The Big Question

• Why is it so difficult to breathe at high altitudes?




Use the ideal gas law to figure out the number of moles of gas molecules in the air.



The ideal gas law relates volume (V), temperature (T), pressure (P), and moles (n):

PV = nRT

where R = 0.082 L-atm/mole-K.

Notes



Activity

Purpose: This activity will give you practice using the ideal gas law. You will figure out the number of moles of air in an average breath.

(cont.)



Materials: (per team of four students)

2 L plastic soda bottle with capa tub or sink or other large container for water (at least 5 liters)tap water

3 feet of flexible tubing

4 straws (to fit into the tubing)

1 watercolor marker or overhead pen

1 graduated cylinder – 250 mL or 500 mL

(cont.)

(cont.)



Part I: Volume of a breath of air

The goal of this part of the activity is to determine the volume of a normal breath of air. The outline for a procedure is given below. You will need to decide how many breaths to measure and how you will figure out the air volume.

(cont.)

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(cont.)

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Part II: Moles in a breath of air

Use the volume you determined for one breath to figure out the number of moles of air in one breath at sea level and in one breath on a mountaintop.

(cont.)



Making Sense

• Use your mole calculations to explain why you breathe faster at higher altitudes.



Check-In

You fill a 1.0 L plastic bottle with 1.0 mole of air on a mountaintop where the air pressure is 0.5 atm.

• Why does the plastic bottle become crushed when you bring the bottle to sea level?

• What is the volume of the bottle at sea level?

• How many moles per liter are there at sea level?



Wrap-Up

• The ideal gas law relates volume, pressure, temperature, and the number of moles: PV = nRT, where R = 0.082 L-atm/mole-K.


Lesson 5:

Up in the Clouds



ChemCatalyst

• What is a cloud?

• How do you think clouds form?



The Big Question

• What causes clouds to form?




Explain how relative humidity and air pressure influence cloud formation.



Activity

Purpose: This activity allows you to create a tiny cloud inside a soda bottle and examine the forces that contribute to cloud formation.

(cont.)



Materials: (for groups of 2-4 students)

Two 2-liter bottles with caps. (You will need one that is dry.)

Long matches

Tap water

Hot water

(cont.)



Making Sense

• Explain how a cloud was formed in this experiment.

• What do you think pressure and temperature have to do with cloud formation?

(cont.)



• Humidity refers to the amount of water vapor in the air.

• Absolute humidity is simply the number of moles of water vapor per liter of air.

• Absolute humidity depends on how much water has evaporated.

Notes



• When air has the maximum amount of water vapor possible for a given temperature, we say that the air is saturated or that it has reached its saturation point.

Notes (cont.)

(cont.)



• Relative humidity is the amount of water vapor in the air compared to the maximum amount of water vapor possible at the current temperature.

• Relative humidity describes how close the air is to the saturation point.

• It is expressed in percent.

(cont.)



Check-In

• What information would you want to know to be able predict if clouds will form?



Wrap-Up

• Water vapor condenses and forms clouds of water droplets when the temperature drops. Temperature decreases occur in gases when there is a decrease in pressure.

• Absolute humidity is a measure of the number of moles of water vapor per liter of air.

(cont.)



• Relative humidity is a measure of the amount of water vapor in the air compared to the maximum possible for a certain temperature. It is expressed in percent.

(cont.)

(cont.)


Lesson 6:

Rain in the Forecast



ChemCatalyst

• Does it always rain when the humidity is high? Why or why not?



The Big Question

• How do you know if it will rain?




Determine the conditions for rain by considering humidity and temperature.



Activity

Purpose: This lesson allows you to explore what conditions are necessary for water vapor to condense and form rain.

Materials:

Rubbing alcohol (about 50 mL total)

Water (cont.)



Part I: Maximum absolute humidity

The line on the graph below shows the maximum absolute humidity vs. temperature. Use the graph to answer the questions below.

(cont.)

(cont.)



Absolute Humidity

0

0.001

0.002

0.003

0.004

-20 -10 0 10 20 30 40

Temperature (°C)

Absolute Humidity (moles/L)

(cont.)

(cont.)



Altitude 2000 ft 4000 ft

6000 ft 8000 ft 10000 ft

Temperature 11°C 7.2°C 3.3°C –1.1°C –5.0°C

(cont.)

(cont.)



Part II: How hot you feel

How hot you feel depends on both the humidity and the temperature. The following questions will help you understand why.

(cont.)



Making Sense

• What do you need to know to decide if it will rain?

• Under what weather conditions does sweating work well to cool you off?

(cont.)



Absolute Humidity

0

0.001

0.002

0.003

0.004

-20 -10 0 10 20 30 40

Temperature (°C)

Absolute Humidity (moles/L)

It is not possible to have values of the absolute humidity above the curve.

Rain or dew

No rain or dew

(cont.)



Check-In

• Explain how you can tell if it will rain, if you are given the absolute humidity and the temperature.



Wrap-Up

• Condensation of water (rain or dew or cloud formation) occurs when the relative humidity is 100%.

• The maximum amount of water vapor that can be in a liter of air increases as the temperature increases.

Documents

Weather Unit Investigation IV: Counting Matter Lesson 1: Tower of Air Lesson 2: Lighter Than Air Lesson 3: More Than a Billion Lesson 4: Take a Breath