Carbon TIME
Modeling & Explaining Ethanol Burning
Entry Task:
Which atoms form HIGH Energy Bonds?
Which atoms form LOW Energy Bonds?
What happens when…
An atom leaves a high energy bond and forms a low energy
bond?
C – C  C -- O
Evidence Based Argument Tool
Share with a neighbor,
compare the evidence you selected to help you
answer each question.
How are your ideas alike?
How are your ideas different?
Compare your claims
How are they alike and different?
About Evidence
Mass provides good evidence to answer the Movement
question
BTB evidence provides only a partial answer to the Carbon
question.
• We know Carbon ends up in CO2 detected by the BTB
• We DON’T know where the carbon came from in the ethanol
The observation of heat and light in the flame also provide only
a partial answer to the Energy question
• We know that energy is released
• We DON’T know where the energy came from
Making the Reactant Molecules:
Ethanol and Oxygen
The flame of burning ethanol comes when ethanol (C2H5OH)
reacts with oxygen (O2).
1. Make a molecules of ethanol and oxygen on the reactant
side of your Molecular Models Placemat.
2. Use twist ties to represent energy.
3. Use the Forms of Energy cards to show which form of
energy the twist ties represent.
Follow along with your worksheet…
• Read Part A
• Complete steps B.1a-d
6
What’s the hidden
chemical change
when ethanol burns?
?
Oxygen
Carbon Dioxide
Water
Ethanol
7
How Atoms Bond Together in
Molecules
• Atoms in stable molecules always have a certain number of
bonds to other atoms:
• Carbon –
• Oxygen –
• Hydrogen –
• Oxygen atoms do NOT bond to other oxygen atoms if they can
bond to carbon or hydrogen instead.
• Chemical energy is stored in bonds between atoms
8
Photo of reactant molecules: C2H5OH (ethanol) and O2 (oxygen)
Start by making the molecules and energy units of the reactants and putting them on
the reactants side, then rearrange the atoms and energy units to show the products.
Chemical
change
Ethanol
Oxygen
Reactants
Products
Remember: Atoms last forever (so you can rearrange atoms into new molecules, but can’t add or 9
subtract atoms). Energy lasts forever (so you can change forms of energy, but energy units can’t
appear or go away)
Important:
When you are
finished constructing
the reactants, put all
extra pieces away.
10
Rearranging the Atoms to Make Product
Molecules: Carbon Dioxide and Water
The flame of burning ethanol comes when ethanol
(C2H5OH) reacts with oxygen (O2) to produce carbon
dioxide (CO2) and water (H2O). Show how this can
happen:
Follow along on your worksheet…
Complete steps B.2.a-c
11
Photo of product molecules: CO2 (carbon dioxide) and H2O (water)
Start by making the molecules and energy units of the reactants and putting them on
the reactants side, then rearrange the atoms and energy units to show the products.
Water
Chemical
change
Reactants
Carbon
dioxide
Products
Remember: Atoms last forever (so you can rearrange atoms into new molecules, but can’t add or 12
subtract atoms). Energy lasts forever (so you can change forms of energy, but energy units can’t
appear or go away)
Comparing photos of reactant and product molecules
Start by making the molecules and energy units of the reactants and putting them on
the reactants side, then rearrange the atoms and energy units to show the products.
Water
Chemical
change
Ethanol
Carbon
dioxide
Oxygen
Reactants
Products
Remember: Atoms last forever (so you can rearrange atoms into new molecules, but can’t add or 13
subtract atoms). Energy lasts forever (so you can change forms of energy, but energy units can’t
appear or go away)
What happens
to atoms and energy
when ethanol burns?
Carbon Dioxide
Ethanol
Reactants
Chemical change
Water
Products
Oxygen
Heat and light energy
What happens
to carbon atoms
when ethanol burns?
Carbon Dioxide
Ethanol
Reactants
Chemical change
Water
Products
Oxygen
Carbon atoms in
ethanol become
part of carbon
dioxide molecules.
Heat and light energy
What happens
to oxygen atoms
when ethanol burns?
Carbon Dioxide
Ethanol
Reactants
Chemical change
Water
Products
Oxygen
Oxygen atoms
become part of
carbon dioxide and
water molecules.
Heat and light energy
What happens
to hydrogen atoms
when ethanol burns?
Carbon Dioxide
Ethanol
Reactants
Chemical change
Water
Products
Oxygen
Hydrogen atoms
become part of
water molecules.
Heat and light energy
What happens
to chemical energy
when ethanol burns?
Carbon Dioxide
Ethanol
Reactants
Chemical change
Water
Products
Oxygen
Chemical energy is
transformed into heat
and light energy.
Heat and light energy
What happens
to atoms and energy
when ethanol burns?
Carbon Dioxide
Ethanol
Reactants
Chemical change
Water
Products
Oxygen
Atoms last forever!
Energy lasts
forever!
Heat and light energy
Writing a Chemical Equation
• Chemists use chemical equations to show how atoms of
reactant molecules are rearranged to make product
molecules.
• Writing the equation in symbols. Chemists use an arrow to
show how reactants change into products.
• Equations must be balanced. Remember: Atoms last
forever.
• Try it: Can you write a balanced chemical equation to show
the chemical change when ethanol burns?
20
Chemical equation for ethanol
burning
C2H5OH + 3O2  2 CO2 + 3 H2O
(in words: ethanol reacts with oxygen to yield carbon
dioxide and water)
21
Finish What Happens when
Ethanol Burns:
Complete “Molecular Models for Ethanol Burning Worksheet
Part C & D
Complete “Explanation Tool: What happens when ethanol
burns?”
• Combine everything you learned about what happens when
ethanol burns into one explanation
• Consider evidence from the investigation and observations
from the modeling activity
(15 Minutes)
Molecular Modeling:
Methane Burning
You can use what you
know about Ethanol
burning to explain
many other molecules
burning too!
Same Rules for Atoms
and Energy Apply
The bottom of flame at atomic-molecular scale
Oxygen
Nitrogen
Carbon Dioxide
Water
Methane
24
The top of flame at atomic-molecular scale
Oxygen
Nitrogen
Carbon Dioxide
Water
Methane
25
What happened between the bottom and the top of the flame?
Top of the flame
Oxygen
Nitrogen
Carbon Dioxide
Water
Methane
Bottom of the
flame
26
What’s the hidden
chemical change
when methane burns?
?
Oxygen
Carbon Dioxide
Water
Methane
27
Always answer the 3 Qs
Whenever you explain a chemical change
(reaction)
Use the next slide to help you practice answering
the 3 Qs for Methane Burning
Three Questions Poster
Question
Rules to Follow
Connecting Atoms to Evidence
The Movement Question: Where
are atoms moving?
Where are atoms moving from?
Where are atoms going to?
Atoms last forever in combustion
and living systems.
All materials (solids, liquids, and
gases) are made of atoms.
When materials change mass,
atoms are moving.
When materials move, atoms are
moving.
The Carbon Question: What is
happening to carbon atoms?
What molecules are carbon atoms
in before the process?
How are the atoms rearranged into
new molecules?
Carbon atoms are bound to other
atoms in molecules.
Atoms can be rearranged to make
new molecules.
The air has carbon atoms in CO2.
Organic materials are made of
molecules with carbon atoms:
•
foods
•
fuels
•
living and dead plants and
animals.
The Energy Question: What is
happening to chemical energy?
What forms of energy are involved?
How is energy changing from one
form to another?
Energy lasts forever in combustion
and living systems.
C-C and C-H bonds have more
stored chemical energy than C-O
and H-O bonds.
We can observe indicators of
different forms of energy:
•
organic materials with chemical
energy
•
light
•
heat energy
•
motion.
29
Making the Reactant Molecules:
Methane and Oxygen
Read Part A
Complete Part B.1a-c
Put ALL extra pieces away!!!
Then check your work with Ms KL before continuing
30
Photo of reactant molecules: CH4 (methane) and O2 (oxygen)
Start by making the molecules and energy units of the reactants and putting them on
the reactants side, then rearrange the atoms and energy units to show the products.
Chemical
change
Methane
Oxygen
Reactants
Products
Remember: Atoms last forever (so you can rearrange atoms into new molecules, but can’t add or 31
subtract atoms). Energy lasts forever (so you can change forms of energy, but energy units can’t
appear or go away)
Important:
When you are
finished constructing
the reactants, put all
extra pieces away.
32
Rearranging the Atoms to Make Product
Molecules: Carbon Dioxide and Water
Complete Steps B.2.a-c
Check with Ms KL before continuing
Complete Steps C & D
33
Photo of product molecules: H2O (water) and CO2 (carbon dioxide)
Start by making the molecules and energy units of the reactants and putting them on
the reactants side, then rearrange the atoms and energy units to show the products.
Water
Chemical
change
Reactants
Carbon
dioxide
Products
Remember: Atoms last forever (so you can rearrange atoms into new molecules, but can’t add or 34
subtract atoms). Energy lasts forever (so you can change forms of energy, but energy units can’t
appear or go away)
Comparing photos of reactant and product molecules
Start by making the molecules and energy units of the reactants and putting them on
the reactants side, then rearrange the atoms and energy units to show the products.
Water
Chemical
change
Methane
Carbon
dioxide
Oxygen
Reactants
Products
Remember: Atoms last forever (so you can rearrange atoms into new molecules, but can’t add or 35
subtract atoms). Energy lasts forever (so you can change forms of energy, but energy units can’t
appear or go away)
What happens
to atoms and energy
when methane burns?
Carbon Dioxide
Methane
Reactants
Chemical change
Water
Products
Oxygen
Heat and light energy
36
What happens
to carbon atoms
when methane burns?
Carbon Dioxide
Methane
Reactants
Chemical change
Water
Products
Oxygen
Carbon atoms in
methane become
part of carbon
dioxide molecules.
Heat and light energy
37
What happens
to oxygen atoms
when methane burns?
Carbon Dioxide
Methane
Reactants
Chemical change
Water
Products
Oxygen
Oxygen atoms
become part of
carbon dioxide and
water molecules.
Heat and light energy
38
What happens
to hydrogen atoms
when methane burns?
Carbon Dioxide
Methane
Reactants
Chemical change
Water
Products
Oxygen
Hydrogen atoms
become part of
water molecules.
Heat and light energy
39
What happens
to chemical energy
when methane burns?
Carbon Dioxide
Methane
Reactants
Chemical change
Water
Products
Oxygen
Chemical energy is
transformed into heat
and light energy.
Heat and light energy
40
What happens
to atoms and energy
when ethanol burns?
Carbon Dioxide
Ethanol
Reactants
Chemical change
Water
Products
Oxygen
Atoms last forever!
Energy lasts
forever!
Heat and light energy
41
Writing a Chemical Equation
• Chemists use chemical equations to show how atoms of reactant
molecules are rearranged to make product molecules
• Writing the equation in symbols: Chemists use an arrow to show
how reactants change into products:
[reactant molecule formulas] [product molecule formulas]
• Saying it in words: Chemists read the arrow as “yield” or “yields:”
[reactant molecule names] yield [product molecule names]
• Equations must be balanced: Atoms last forever, so reactant and
product molecules must have the same number of each kind of
atom
• Try it: can you write a balanced chemical equation to show the
chemical change when methane burns?
42
Chemical equation for methane
burning
CH4 + 2O2  CO2 + 2 H2O
(in words: methane reacts with oxygen to yield carbon
dioxide and water)
43
Homework:
Complete “Molecular Models for Methanol Burning Worksheet
Part C & D”
Complete “Explanation Tool: What happens when Methanol
burns?”
• Combine everything you learned about what happens when
methanol burns into one explanation
• Consider evidence from the investigation about ethanol and
observations from the methanol modeling activity