Ethanol Burning Lab Part 3: 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. Copy the Chemical Change Diagram below onto your whiteboard:
Chemical
Change
2. Make models of an ethanol molecule (C
2
H
5
OH) and three oxygen molecules (O
2
, with a double bond). .
3. Put these molecules on the reactant side of the Chemical Change Diagram on your whiteboard.
Report the number of high energy bonds in ethanol to Ms. Wang or Ms. Reynolds in order to receive energy twisty ties.
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. 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) Energy
Carbon Oxygen Hydrogen
Reactants
Ethanol
Oxygen
How many twisty ties? What forms of energy?
Products
Carbon
Dioxide
Water
Totals

6. Take the ethanol and the oxygen molecules apart and use the atoms from them to make carbon dioxide
(CO
2
) and water (H
2
O) molecules.
When you take apart the molecules, remove the twisty ties from the bonds to represent energy being released.
Put the newly-formed carbon dioxide and water 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 Chemical Change Diagram on your whiteboard. Carbon dioxide and water have low-energy bonds (C-O and H-O), so what forms does the chemical energy change into? Label the energy form on your whiteboard under the twisty ties.
8. Atoms last forever!! Check yourself: Did your number and type of atoms stay the same at the beginning and end of the chemical change? _____________________________
9. Energy lasts forever! Write the type of energy for reactants and products in the energy column above.
10. Write a balanced chemical equation using the molecular formulas and the yield sign (  ):
Fill out the exit ticket.