fire unit investigation ii: conditions for change lesson 1: no smoking zone lesson 2: you’re...
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Fire Unit
Investigation II: Conditions for ChangeLesson 1: No Smoking ZoneLesson 2: You’re Fired!Lesson 3: All-A-GlowLesson 4: Fuelish ChoicesLesson 5: SparklersLesson 6: Kablooie!
Fire Unit – Investigation II
Lesson 1:
No Smoking Zone
Unit V • Investigation II
© 2004 Key Curriculum Press.
ChemCatalyst
• What conditions are necessary for a fire to take place? Describe at least two situations that result in fire.
Unit V • Investigation II
© 2004 Key Curriculum Press.
The Big Question
• What are the necessary questions for fire to exist?
Unit V • Investigation II
© 2004 Key Curriculum Press.
You will be able to:
• Describe the conditions necessary to support a fire.
Unit V • Investigation II
© 2004 Key Curriculum Press.
Activity
Purpose: By observing a series of demonstrations you will explore the conditions that lead to fire.
(cont.)
Unit V • Investigation II
© 2004 Key Curriculum Press.
Demonstration Prediction
What will you observe
when lit?
Observation
Smoking machine
Paper
Wet paper (paper + water)
Drunk paper(paper + isopropanol)
Dollar bill(dollar+water+isopropanol)
Carbon dioxide balloon
(cont.)
Unit V • Investigation II
© 2004 Key Curriculum Press.
Making Sense
Pick three things from the list below to build a fire. Explain your choices.
• water
• aluminum
• helium
• sugar
• oxygen
• wax
• match
• coal
Unit V • Investigation II
© 2004 Key Curriculum Press.
Notes
(cont.)
Unit V • Investigation II
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• Combustion reaction: The reaction of a fuel with oxygen, resulting in the production of heat and light.
(cont.)
Unit V • Investigation II
© 2004 Key Curriculum Press.
Check-In
• There is a small fire in the trashcan in your classroom. Name three things your teacher can do to put out the fire. Explain how each method works.
Unit V • Investigation II
© 2004 Key Curriculum Press.
Wrap-Up
• Combustion is defined as a reaction of a fuel with oxygen, which releases heat and light.
• Dry fuel, a spark of some sort, and oxygen are the three items necessary for combustion.
• Limiting the supply of oxygen, or adding water, extinguishes fires.
(cont.)
Unit V • Investigation II
© 2004 Key Curriculum Press.
• Cigarette smoking is a form of combustion that has many by-products, several of them harmful to your health.
(cont.)
Fire Unit – Investigation II
Lesson 2:
You’re Fired!
Unit V • Investigation II
© 2004 Key Curriculum Press.
ChemCatalyst
• Name three substances that will combust or burn.
• Name three substances that do not combust.
Unit V • Investigation II
© 2004 Key Curriculum Press.
The Big Question
• How can we predict whether or not a substance is combustible?
Unit V • Investigation II
© 2004 Key Curriculum Press.
You will be able to:
• Identify several properties that help us determine whether a substance will be combustible or not.
Unit V • Investigation II
© 2004 Key Curriculum Press.
Activity
Purpose: The goal of this lesson is to allow you to make generalizations about substances that combust and substances that do not combust.
(cont.)
Unit V • Investigation II
© 2004 Key Curriculum Press.
Substance Chemical Formula Type of Bond Combust?
Water H2O molecular covalent no
Wood chains of C6H12O6 units extended covalent yes
Baking soda NaHCO3ionic no
Ethanol CH3CH2OH yes
Zinc oxide ZnO no
Copper Cu metal yes
Hexane CH3CH2CH2CH2CH2CH3yes
Magnesium Mg yes
Carbon dioxide
CO2no
Hydrogen H2yes
Helium He no
Unit V • Investigation II
© 2004 Key Curriculum Press.
Substance Chemical Formula Combust?
(prediction)
Combust?
(outcome)
Oil C21H39O6 (one example)
Sodium chloride NaCl
Calcium carbonate
CaCO3
Iron Fe
(cont.)
Unit V • Investigation II
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Making Sense
• Based on your data, what generalizations can you make about substances that combust?
• What generalizations can you make about substances that do not combust?
Unit V • Investigation II
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Combust Do Not Combust
CH3CH2CH2OH
C6H12O6 units (wood)
CH3CH2OH
CH3CH2CH2CH2CH2 CH3
C21H39O6 (one example)
H2
Cu
Fe
Mg
H2O
CO2
ZnO
NaHCO3
NaCl
CaCO3
Notes
(cont.)
Unit V • Investigation II
© 2004 Key Curriculum Press.
• Most ionic compounds are not combustible.
• Most molecular covalent compounds are combustible (especially those that contain carbon and hydrogen). These compounds make good fuels.
• Most metallic compounds are combustible.
(cont.)
(cont.)
Unit V • Investigation II
© 2004 Key Curriculum Press.
• Substances that contain a high percentage of oxygen atoms may not be combustible because they may not be able to react with any more oxygen.
• Water and carbon dioxide do not combust.
(cont.)
Unit V • Investigation II
© 2004 Key Curriculum Press.
Check-In
Which of the following substances are likely to combust? What is your reasoning?
• CH4, methane
• CaBr2, calcium bromide
• Na, sodium
Unit V • Investigation II
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Wrap-Up• Most ionic salts do not combust.
• Most molecular covalent compounds do combust.
• Most metals combust. Most metals do not produce a flame when they combust. Most metals combust very slowly.
• Substances that already contain a high percentage of oxygen atoms are less apt to be combustible.
• Carbon dioxide and water do not combust. They are the products of combustion.
Fire Unit – Investigation II
Lesson 3:
All-A-Glow
Unit V • Investigation II
© 2004 Key Curriculum Press.
ChemCatalyst
The following table shows the balanced chemical equations for four combustion reactions.
• List three patterns you notice.
Substance Combustion reaction
methane CH4 + 2 O2 CO2 + 2 H2O
ethanol C2H6O + 3 O2 2 CO2 + 3 H2O
glucose C6H12O6 + 6 O2 6 CO2 + 6 H2O
magnesium 2 Mg + O2 2 MgO
Unit V • Investigation II
© 2004 Key Curriculum Press.
The Big Question
• How do we write a chemical equation for a combustion reaction?
Unit V • Investigation II
© 2004 Key Curriculum Press.
You will be able to:
• Write the balanced equations for various kinds of combustion reactions.
Unit V • Investigation II
© 2004 Key Curriculum Press.
C2H6 + O2 CO2 + H2O
Notes
Unit V • Investigation II
© 2004 Key Curriculum Press.
Activity
Purpose: The goal of this lesson is to allow you to examine chemical equations that describe combustion reactions.
(cont.)
Unit V • Investigation II
© 2004 Key Curriculum Press.
Combustion Reactions of Alkanes
methane CH4 + 2 O2 CO2 + 2 H2O
ethane C2H6 + 3.5 O2 2 CO2 + 3 H2O
propane C3H8 + O2 CO2 + H2O
butane C4H10 + O2 CO2 + H2O
pentane C5H12 + O2 CO2 + H2O
hexane C6H14 + 9.5 O2 6 CO2 + 7 H2O
(cont.)
(cont.)
Unit V • Investigation II
© 2004 Key Curriculum Press.
Combustion Reactions of Carbon and Carbon-Containing Molecules
methane CH4 + 2 O2 CO2 + 2H2O
methanol CH4O + O2 CO2 + H2O
carbon C + 1 O2 CO2
carbon monoxide CO + 0.5O2 CO2
carbon dioxide CO2 + 0 O2 no reaction
(cont.)
(cont.)
Unit V • Investigation II
© 2004 Key Curriculum Press.
Combustion Reactions with Metals
magnesium Mg + 0.5 O2 MgO
magnesium oxide MgO + 0 O2 no reaction
magnesium chloride MgCl2 + 0 O2 no reaction
titanium Ti + 1 O2 TiO2
titanium oxide TiO2 + 0 O2 no reaction
titanium fluoride TiF4 + 0 O2 no reaction
(cont.)
Unit V • Investigation II
© 2004 Key Curriculum Press.
Making Sense
• What are the products of the combustion of carbon-containing molecules?
• What are the products of the combustion of metals?
• What are the products of the combustion of salts?
Unit V • Investigation II
© 2004 Key Curriculum Press.
Check-In
Pick a substance that combusts from the list below and write the balanced chemical reaction.
• Ar
• Al
• C
• CH4O
Unit V • Investigation II
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Wrap-Up
• The products of the combustion of carbon-containing molecules are carbon dioxide and water.
• Flames are gases emitting light. Flames are the result of gases that are produced during a combustion reaction.
(cont.)
Unit V • Investigation II
© 2004 Key Curriculum Press.
• In a combustion reaction, the longer the carbon chain in the fuel, the more oxygen it reacts with.
• The products of the combustion of metals are solid metal oxides. These reactions usually do not produce enough gases to support a flame.
(cont.)
Fire Unit – Investigation II
Lesson 4:
Fuelish Choices
Unit V • Investigation II
© 2004 Key Curriculum Press.
ChemCatalyst
Standard automobiles use a mix of carbon-based compounds (high in octane) as fuel. The cars that race in the Indianapolis 500 use methanol as fuel. And top dragsters use nitromethane as fuel.
• Balance the equations for the combustion of these fuels.
• Why do you think they use different fuels for different types of driving?
Unit V • Investigation II
© 2004 Key Curriculum Press.
(Below are the balanced chemical equations for these combustion reactions):
(octane)
C8H18 + O2 CO2 + H2O
(methanol)
CH4O + O2 CO2 + H2O
(nitromethane)
CH3NO2 + O2 CO2 + H2O + NO2
Notes
Unit V • Investigation II
© 2004 Key Curriculum Press.
The Big Question
• What properties of a substance can be used to predict its usefulness as a fuel for combustion?
Unit V • Investigation II
© 2004 Key Curriculum Press.
You will be able to:
• Identify the properties of substances that would make them good fuels for combustion.
Unit V • Investigation II
© 2004 Key Curriculum Press.
Activity
Purpose: In this activity, you will compare fuels to one another by examining their combustion reactions and calorie output.
(cont.)
Unit V • Investigation II
© 2004 Key Curriculum Press.
Combustion Reactions
Substance Chemical Formula
Energy (cal/mole)
Chemical Reaction
Octane C8H18 (l)1,300,000 2 C8H18 + 25 O2 16 CO2 + 18 H2O
Hexane C6H14 (l)995,000 2 C6H14 + 19 O2 12 CO2 + 14 H2O
Hexanol C6H14O (l)951,000 2 C6H14O + 18O2 12 CO2 + 14 H2O
Butane C4H10 (l)687,000 2 C4H10 + 13 O2 8 CO2 + 10 H2O
Butanol C4H10O (l)638,000 C4H10O + 6 O2 4 CO2 + 5 H2O
Ethane C2H6 (g)373,000 2 C2H6 + 7 O2 4 CO2 + 6 H2O
Ethanol C2H6O (l)327,000 C2H6O + 3 O2 2 CO2 + 3 H2O
Methane CH4 (g)213,000 CH4 + 2 O2 CO2 + 2 H2O
Methanol CH4O (l)174,000 2 CH4O + 3 O2 2 CO2 + 4 H2O
Nitromethane
CH3NO2 (l)175,000 4 CH3NO2 + 7 O2 4 CO2 + 6 H2O + 4
NO2
Hydrogen H2 (g)58,000 2 H2 + O2 2 H2O
Unit V • Investigation II
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Substance Chemical Formula
Energy kcal/mol
Mol. Wt.
g/mol
Energy kcal/gram
Octane C8H18 1,300 114 11.4
Hexane C6H14 995 86 11.5
Hexanol C6H14O
Butane C4H10 58
Butanol C4H10O 638 74
Ethane C2H6 373
Ethanol C2H6O 46
Methane CH4 213
Methanol CH4O 32 5.4
Hydrogen H2 58
Nitromethane CH3NO2 61
Unit V • Investigation II
© 2004 Key Curriculum Press.
Making Sense
• Do you think the best fuel is the one that has the greatest energy output in calories per mole? Explain your reasoning.
Unit V • Investigation II
© 2004 Key Curriculum Press.
• kilocalories or kcal: 1 kcal is equal to 1000 calories. It is also equal to 1 food Calorie
• kiloJoule or kJ: 1 kJ is equal to 4.184 kcal. Joules are the metric units in common use by scientists.
Notes
Unit V • Investigation II
© 2004 Key Curriculum Press.
Check-In
Which molecule of the three listed below would you expect to release the most energy per mole of fuel combusted? What is your reasoning?
• propane, C3H8
• propanol, C3H8O
• pentane, C5H12
Unit V • Investigation II
© 2004 Key Curriculum Press.
Wrap-Up
• Substances consisting mostly of carbon and hydrogen atoms are good fuels.
• Trends show that the larger the carbon compound, the more energy is released per mole of fuel when that compound combusts.
• Molecules without oxygen atoms tend to release more energy than comparable molecules that contain oxygen (e.g., CH4 > CH3OH).
(cont.)
Unit V • Investigation II
© 2004 Key Curriculum Press.
• The number of calories released during combustion is dependent on the size of the molecule.
• Chemists use kJoules as a unit of energy. One kcal = 4.184 kJoules.
Fire Unit – Investigation II
Lesson 5:
Sparklers
Unit V • Investigation II
© 2004 Key Curriculum Press.
ChemCatalyst
• I have several matches, a large tree trunk from a fallen tree, and plenty of oxygen in the atmosphere. Nevertheless, I cannot get the tree trunk to burn using just a lit match. If I have all three legs of the fire triangle, why is it difficult to make a fire?
Unit V • Investigation II
© 2004 Key Curriculum Press.
The Big Question
• Once a combustion reaction has been started, what is it that keeps it going?
Unit V • Investigation II
© 2004 Key Curriculum Press.
You will be able to:
• Explain why a combustion reaction keeps on going even after the source of ignition has been removed.
Unit V • Investigation II
© 2004 Key Curriculum Press.
Activity
Purpose: In this lesson you will create sparklers using several metals and several ionic compounds.
SAFETY NOTE: Remember to wear goggles during today's lab.
(cont.)
Unit V • Investigation II
© 2004 Key Curriculum Press.
Substance Mass of watch glass + powder
(minus) Mass of
watch glass
(equals) Mass of powder needed
Starch 2.0 g
Iron powder (Fe) 3.3 g
Copper powder (Cu) 0.4 g
Magnesium powder (Mg) 0.2 g
Aluminum powder (Al) 0.7 g
Potassium chlorate (KClO3)
2.0 g
Barium nitrate (Ba(NO3)2) 8.3 g
(cont.)
Unit V • Investigation II
© 2004 Key Curriculum Press.
Making Sense
• Why does a sparkler keep going after you light it? Why doesn't it go out?
Unit V • Investigation II
© 2004 Key Curriculum Press.
Check-In
• No Check-In.
Unit V • Investigation II
© 2004 Key Curriculum Press.
Wrap-Up
• The combustion of various metals can be used to create a colorful sparkler.
• There appears to be another condition necessary for fire, beyond the three legs of the fire triangle.
Fire Unit – Investigation II
Lesson 6:
Kablooie!
Unit V • Investigation II
© 2004 Key Curriculum Press.
ChemCatalyst
• What is an explosion?
• What causes explosions?
• Have you ever seen or experienced an explosion? Explain.
Unit V • Investigation II
© 2004 Key Curriculum Press.
The Big Question
• What are the conditions that affect the rate of a combustion reaction?
Unit V • Investigation II
© 2004 Key Curriculum Press.
You will be able to:
• Explain how the rate of a combustion reaction is affected by the conditions in which it is occurring.
Unit V • Investigation II
© 2004 Key Curriculum Press.
Activity
Purpose: In this lesson you will be allowed to test your sparkler. Then you will observe a series of demonstrations related to explosions. Finally, you will be introduced to the Fire Tetrahedron.
(cont.)
Unit V • Investigation II
© 2004 Key Curriculum Press.
(cont.)
(cont.)
Unit V • Investigation II
© 2004 Key Curriculum Press.
(cont.)
Unit V • Investigation II
© 2004 Key Curriculum Press.
Making Sense
• What conditions appear to be necessary for an explosion to take place?
Unit V • Investigation II
© 2004 Key Curriculum Press.
• An explosion is defined as the effect that occurs when there is a violent expansion of gases.
(cont.)
Notes
Unit V • Investigation II
© 2004 Key Curriculum Press.
(cont.)
Unit V • Investigation II
© 2004 Key Curriculum Press.
Check-In
• Explain what is meant by the statement, “Fuels with small molecular masses (such as CH3OH, methanol) burn better than fuels with large molecular masses (such as C8H14, octane).” Why do you think this is true?
Unit V • Investigation II
© 2004 Key Curriculum Press.
Wrap-Up
• An explosion is a rapid expansion of gases.• Not all fires involve explosions.• Some explosions do not involve fire at all.• The surface area of a fuel, and the
availability of oxygen to the fuel, are factors that affect the rate of combustion.
• There are four conditions necessary for fire. These four conditions are represented in the fire tetrahedron: oxygen, fuel, heat (or spark), and chemical chain reaction.