weather unit investigation iv: counting matter lesson 1: tower of air lesson 2: lighter than air...
TRANSCRIPT
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.)
Unit 3 • Investigation IV-X
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(cont.)
(cont.)
Unit 3 • Investigation IV-X
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air pushes down
mercury is pushed up
(cont.)
Unit 3 • Investigation IV-X
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The Big Question
• How does a column of mercury measure the air pressure on the earth?
Unit 3 • Investigation IV-X
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You will be able to:
Explain how a mercury barometer works
Unit 3 • Investigation IV-X
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Activity
Purpose: This lesson allows you to explore why mercury is used in barometers to measure air pressure.
(cont.)
Unit 3 • Investigation IV-X
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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.)
Unit 3 • Investigation IV-X
© 2004 Key Curriculum Press.
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.)
Unit 3 • Investigation IV-X
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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.)
Unit 3 • Investigation IV-X
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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.)
Unit 3 • Investigation IV-X
© 2004 Key Curriculum Press.
Making Sense
• Why does the density of the air decrease as altitude increases?
• Why isn’t water used in a barometer?
Unit 3 • Investigation IV-X
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• Number density means the number of particles per volume.
Notes
(cont.)
Unit 3 • Investigation IV-X
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• 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.)
Unit 3 • Investigation IV-X
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Check-In
• Why is mercury used in a barometer and not alcohol or water or some other liquid?
Unit 3 • Investigation IV-X
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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.
Weather Unit – Investigation IV
Lesson 2:
Lighter Than Air
Unit 3 • Investigation IV-X
© 2004 Key Curriculum Press.
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.
Unit 3 • Investigation IV-X
© 2004 Key Curriculum Press.
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
Unit 3 • Investigation IV-X
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The Big Question
• What is the relationship between the number of gas particles, the mass, and volume of different gases?
Unit 3 • Investigation IV-X
© 2004 Key Curriculum Press.
You will be able to:
Apply Avogadro’s Hypothesis.
Unit 3 • Investigation IV-X
© 2004 Key Curriculum Press.
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.)
Unit 3 • Investigation IV-X
© 2004 Key Curriculum Press.
2.0 g
321 54
22.0 g 4.0 g 28.0 g 8.0 g
He
N2
CO2
(cont.)
(cont.)
Unit 3 • Investigation IV-X
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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.)
Unit 3 • Investigation IV-X
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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.)
Unit 3 • Investigation IV-X
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• 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.)
Unit 3 • Investigation IV-X
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• 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.)
Unit 3 • Investigation IV-X
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• 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.)
Unit 3 • Investigation IV-X
© 2004 Key Curriculum Press.
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?
Unit 3 • Investigation IV-X
© 2004 Key Curriculum Press.
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.
Weather Unit – Investigation IV
Lesson 3:
More Than a Trillion
Unit 3 • Investigation IV-X
© 2004 Key Curriculum Press.
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?
Unit 3 • Investigation IV-X
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The Big Question
• How is a mole used for counting particles in gases, liquids, and solids?
Unit 3 • Investigation IV-X
© 2004 Key Curriculum Press.
You will be able to:
Use the mole as a counting unit for gases, liquids, and solids.
Unit 3 • Investigation IV-X
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• There are 6.02 x 1023 particles in a mole.
• This number of particles is also called Avogadro’s number.
Notes
Unit 3 • Investigation IV-X
© 2004 Key Curriculum Press.
Activity
Purpose: In this lesson, you will explore how to count using a new unit called the mole.
(cont.)
Unit 3 • Investigation IV-X
© 2004 Key Curriculum Press.
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
Unit 3 • Investigation IV-X
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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.)
(cont.)
Unit 3 • Investigation IV-X
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Formaldehyde clear liquidsmells putrid
Glucose white solidtastes sweet
C6H12O6
4 moles CH2O
24 moles
(cont.)
Unit 3 • Investigation IV-X
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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.)
Unit 3 • Investigation IV-X
© 2004 Key Curriculum Press.
• 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.)
Unit 3 • Investigation IV-X
© 2004 Key Curriculum Press.
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.)
Unit 3 • Investigation IV-X
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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.)
Unit 3 • Investigation IV-X
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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?
Unit 3 • Investigation IV-X
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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.
Weather Unit – Investigation IV
Lesson 4:
Take a Breath
Unit 3 • Investigation IV-X
© 2004 Key Curriculum Press.
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?
Unit 3 • Investigation IV-X
© 2004 Key Curriculum Press.
The Big Question
• Why is it so difficult to breathe at high altitudes?
Unit 3 • Investigation IV-X
© 2004 Key Curriculum Press.
You will be able to:
Use the ideal gas law to figure out the number of moles of gas molecules in the air.
Unit 3 • Investigation IV-X
© 2004 Key Curriculum Press.
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
Unit 3 • Investigation IV-X
© 2004 Key Curriculum Press.
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.)
Unit 3 • Investigation IV-X
© 2004 Key Curriculum Press.
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.)
Unit 3 • Investigation IV-X
© 2004 Key Curriculum Press.
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.)
(cont.)
Unit 3 • Investigation IV-X
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(cont.)
(cont.)
Unit 3 • Investigation IV-X
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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.)
Unit 3 • Investigation IV-X
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Making Sense
• Use your mole calculations to explain why you breathe faster at higher altitudes.
Unit 3 • Investigation IV-X
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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?
Unit 3 • Investigation IV-X
© 2004 Key Curriculum Press.
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.
Weather Unit – Investigation IV
Lesson 5:
Up in the Clouds
Unit 3 • Investigation IV-X
© 2004 Key Curriculum Press.
ChemCatalyst
• What is a cloud?
• How do you think clouds form?
Unit 3 • Investigation IV-X
© 2004 Key Curriculum Press.
The Big Question
• What causes clouds to form?
Unit 3 • Investigation IV-X
© 2004 Key Curriculum Press.
You will be able to:
Explain how relative humidity and air pressure influence cloud formation.
Unit 3 • Investigation IV-X
© 2004 Key Curriculum Press.
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.)
Unit 3 • Investigation IV-X
© 2004 Key Curriculum Press.
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.)
Unit 3 • Investigation IV-X
© 2004 Key Curriculum Press.
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.)
Unit 3 • Investigation IV-X
© 2004 Key Curriculum Press.
• 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
Unit 3 • Investigation IV-X
© 2004 Key Curriculum Press.
• 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.)
Unit 3 • Investigation IV-X
© 2004 Key Curriculum Press.
• 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.)
Unit 3 • Investigation IV-X
© 2004 Key Curriculum Press.
Check-In
• What information would you want to know to be able predict if clouds will form?
Unit 3 • Investigation IV-X
© 2004 Key Curriculum Press.
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.)
Unit 3 • Investigation IV-X
© 2004 Key Curriculum Press.
• 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.)
Weather Unit – Investigation IV
Lesson 6:
Rain in the Forecast
Unit 3 • Investigation IV-X
© 2004 Key Curriculum Press.
ChemCatalyst
• Does it always rain when the humidity is high? Why or why not?
Unit 3 • Investigation IV-X
© 2004 Key Curriculum Press.
The Big Question
• How do you know if it will rain?
Unit 3 • Investigation IV-X
© 2004 Key Curriculum Press.
You will be able to:
Determine the conditions for rain by considering humidity and temperature.
Unit 3 • Investigation IV-X
© 2004 Key Curriculum Press.
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.)
Unit 3 • Investigation IV-X
© 2004 Key Curriculum Press.
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.)
Unit 3 • Investigation IV-X
© 2004 Key Curriculum Press.
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.)
Unit 3 • Investigation IV-X
© 2004 Key Curriculum Press.
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.)
Unit 3 • Investigation IV-X
© 2004 Key Curriculum Press.
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.)
Unit 3 • Investigation IV-X
© 2004 Key Curriculum Press.
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.)
Unit 3 • Investigation IV-X
© 2004 Key Curriculum Press.
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.)
Unit 3 • Investigation IV-X
© 2004 Key Curriculum Press.
Check-In
• Explain how you can tell if it will rain, if you are given the absolute humidity and the temperature.
Unit 3 • Investigation IV-X
© 2004 Key Curriculum Press.
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.