Explaining what happens when ethanol burns
A. Answering the movement question Use PowerPoint “Zooming into a Flame” to answer the questions:
Drawing motions of atoms: Draw arrows to show how atoms move into, through, and out of the flame.
Bottom of the flame: What kinds of
molecules do you see in the bottom of the
flame?
Top of the flame: What kinds of molecules do you see at the
top of the flame?
Where did those molecules come from?
Which molecules are different from those at the bottom of the
flame?
What atoms are those molecules made of?
Are the atoms at the top of the flame different from the atoms
at the bottom of the flame?
B. Using molecular models to show the chemical change.
Ethanol is a good fuel because it has a lot of __________________ stored in its bonds. Energy is stored in its
high-energy ___________: C-C and C-H bonds. When ethanol burns, it reacts with ____________ in the air
to produce ______________________ and ________________________________. Since carbon dioxide and
water have only low-energy ___________(C-O and H-O), the chemical energy is released as _____________
and ______________.
1. Make models of an ethanol molecule (C2H5OH) and three oxygen molecules (O2, with a double bond). .
2. Copy the Process Tool for Molecular Models onto your whiteboard:
Reactants
Chemical
Change
Products
3. Put these molecules on the reactant side of the Process Tool for Molecular Models on your whiteboard.
4. Use twisty ties to represent chemical energy. Put a twisty tie around each high-energy bond (C-C and C-H
bonds) in the ethanol molecule. Put the “Chemical Energy” card under the ethanol molecule to label the
energy in the C-C and C-H bonds. Note how many energy units (twisty ties) there are in the ethanol.
5. Use the table below to record information about the atoms and energy for the reactant side of the equation:
Matter (list number of atoms)
Carbon
Oxygen
Hydrogen
Energy
How many twisty ties?
What forms of energy?
Reactants
Ethanol
Oxygen
Totals
Oxygen
Products
Carbon
Dioxide
Water
Totals
6. Show how the atoms of the reactant molecules can recombine into product molecules—carbon dioxide and
water—and show how chemical energy is released when this happens. Take the ethanol and some of the
oxygen molecules apart and recombine them into carbon dioxide (CO2) and water (H2O) molecules. Put
these molecules on the product side of the whiteboard.
a)
How many oxygen molecules reacted with one ethanol molecule? _____
b)
How many carbon dioxide molecules were produced? _____
c)
How many water molecules were produced? _____
7.
Energy lasts forever, so move the twisty ties to the product side of the Process Tool for Molecular Models
whiteboard. Carbon dioxide and water have low-energy bonds (C-O and H-O), so what forms does the
chemical energy change into? Put the correct energy cards under the twisty ties.
8. Take the ethanol and the oxygen molecules apart and recombine them into carbon dioxide (CO2) and water
(H2O) molecules.
C. Atoms last forever!! Check yourself: Did your number and type of atoms stay the same at the beginning
and end of the chemical change? _____________________________
What principle in science explains that atoms last forever? ________________
D. Energy lasts forever! Write the type of energy for reactants and products in the energy column above.
What principle in science explains that energy lasts forever? _______________________________
E. Write a balanced chemical equation using the molecular formulas and the yield sign ():
E. Revise your answers to the Process Tool with Three Questions from ws 4-1 with a different color.