Name: ______________________________________________ Per. _________
Date Due: _______________________
The Energy
Question
The Carbon Question
The Movement
Question
Ethanol Burning Lab Part 1: What do you predict you will observe when ethanol burns?
Macroscopic scale: Make predictions about
what you will observe.
Atomic-molecular scale: Explain your predictions using the Three Questions.
Predictions about mass
What do you think will gain mass?
Draw labeled arrows to show how atoms or molecules might be moving into and out of
the flame.
Where do you think matter is moving
Where do you think matter is going?
from?
Reactants
Products
What do you think will lose mass?
Predictions about changes in BTB
Do you think that BTB will change color
if it’s in a closed container with the
flame? If YES, what color change do
you predict?
What molecules do you think carbon
atoms are a part of before the ethanol
burns?
What molecules do you think carbon
atoms are a part of after the ethanol
burns?
Chemical
Change
What other reactants do you think are
needed in order for ethanol to burn?
Predictions about energy
What forms of energy do you think you
will observe?
What forms of energy do you think are
in the reactants?
Energy
Transformation
Stamp for Part 1:
What forms of energy do you think are
in the products?
Ethanol Burning Lab Part 2: Lab Procedure
Use this worksheet to complete the ethanol burning investigation and to record your
observations, measurements, and class results.
Steps in the investigation: Check the box as you complete each step.
1. ☐ Add 1 dropper-full of ethanol to a watch glass or glass Petri dish.
2. ☐ Turn on a digital scale so that it reads “0.00” g. Place the dish with ethanol on the scale.
Record the mass of the ethanol and dish in the data table.
3. □ Place a piece of Cobalt Blue Paper next to the dish and record the initial color.
4. ☐ Place 5 drops of BTB on another watch glass. Record the time and color of the BTB the
data table.
5. ☐ Place the dish with BTB next to the dish with ethanol so that the large plastic container
lined with aluminum will be able to fit on top of the two dishes.
6. ☐ Light the ethanol with the lighter. Then, immediately put the large container on top of both
the dish with burning ethanol and the dish of BTB. Observe: the flame will go out quickly
inside the container
7. ☐ Wait 5 minutes before taking the lid off the container. Observe the color of the BTB.
Record this in your data table.
8. ☐ Place the dish with ethanol on the digital scale and record the mass.
9. □ Record the color of the BTB and Cobalt Blue Paper after the experiment.
10. □ Calculate the change in mass for ethanol and record on the data table.
11. □ Record your results on the class data table.
Observations during the investigation: Record your macroscopic-scale observations below.
Use drawings and/or words.
Measurements Before Burning
Mass of Watch glass with ethanol
Measurements After Burning
Mass of Watch glass with ethanol
Mass: _______________ grams
Mass: _______________ grams
Color of BTB
Change in mass: ____________ grams
Changes in color of BTB
Color of BTB:
________________________
Color: _______________________
Change in color? Yes / No
Color of Cobalt Chloride Paper
Changes in color of Cobalt Chloride Paper
Color of paper:
________________________
Color: _______________________
Change in color? Yes / No
Results for the whole class: Make notes about how the observations and measurements of
other groups compared to yours. Describe patterns in your class data.
1. Changes in mass of the Petri dish with ethanol:
2. Changes in color of BTB:
Summary
of Class
Data
Change in
Mass (g)
Final Color
BTB
Final Cobalt
Chloride
Control
(no
burning)
Class
Data
Average
Ethanol Burning Lab Part 3: Constructing an Evidence-based Conclusion
Constructing Your Conclusion: For each of the Three Questions, consider the evidence you have from your class investigation, the conclusion(s) you can draw
based on your evidence, and what questions you are still unable to answer. Check Yourself: Be sure that you follow the rules of matter and energy conservation.



Evidence: What patterns in your observations or measurements help you answer the Three Questions?
Conclusion: Based on your evidence, what can you conclude about the answers to the Three Questions?
Unanswered Questions: What questions can you NOT answer without more evidence?
The Movement Question: Where are atoms moving?
Evidence
Conclusion
Unanswered Questions
Check Yourself
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?
Evidence
Conclusion
Unanswered Questions
Check Yourself
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: food, fuels, living and dead
plants and animals.
The Energy Question: What is happening to chemical energy?
Evidence
Conclusion
Unanswered Questions
Check Yourself
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, and motion.
Burning Ethanol Lab Part 4: Molecular Models
You will use models to learn about ethanol burning at the atomic-molecular scale, as you
continue to look for answers to “unanswered questions” from your investigation.
Introduction
There are many different kinds of alcohol. The most common is ethanol, which is the kind of
alcohol in alcoholic drinks and in biofuels. (The next time you get gasoline, check the pump to
see if it says “10% ethanol.”) Ethanol is a good fuel because it has chemical energy stored in
its high-energy bonds: C-C and C-H bonds. When ethanol burns, it reacts with oxygen (O2) in
the air to produce carbon dioxide (CO2) and water (H2O). When high energy bonds are broken
and low energy bonds (C-O and O-H) are formed, chemical energy is transformed into heat and
light energy. Use the molecular models to show how this happens.
Using molecular models to show the chemical change
1. Work with your partner to make models of the reactant molecules: ethanol and oxygen.
Using the models, show how chemical energy is stored in the high-energy bonds of ethanol.
a. ☐ Make models of an ethanol molecule (C2H5OH) and oxygen molecules (O2, with a
double bond). The air has lots of oxygen; make three O2 molecules. Put these
molecules on the reactant side of the Molecular Models Placemat.
b. ☐ When you are finished creating the reactant molecules (O2 and ethanol), put away
all extra pieces that you didn’t use from the molecule kit. This is an important step!
c. ☐ Use twist ties to represent chemical energy. Put a twist tie around each highenergy bond (C-C and C-H bonds) in the ethanol molecule.
d. ☐ Complete the reactants section of the table (on the back of this paper) to keep
track of atoms and energy.
STOP. Get a teacher or another group that has already completed this step to check your
set-up. Make sure you and your partner understand what is represented at this point.
If you are not sure, ask for help.
2. 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.
a. ☐ Take the ethanol and oxygen molecules apart and recombine them into carbon
dioxide (CO2) and water (H2O) molecules. Put these molecules on the product side
of the Molecular Models Placemat. Answer these questions:
i. How many oxygen molecules reacted with 1 ethanol molecule? ____
ii. How many carbon dioxide molecules were produced? _____
iii. How many water molecules were produced? _____
b. ☐ Energy lasts forever, so move the twist ties to the product side of the Molecular
Models Placemat. Carbon dioxide and water have only low-energy bonds (C-O and
H-O), so what forms does the chemical energy change into? (Re-read the
introduction if you aren’t sure.)
c. ☐ Complete the products section of the table (on the back of this paper) to keep
track of atoms and energy.
STOP. With your partner, practice explaining out loud what happens at the atomicmolecular scale when ethanol burns. Get a teacher or another group that has already
completed this step to check your explanation. If you are not sure, ask for help.
Atoms last forever! Energy lasts forever!
Review the table below to account for all the atoms and types of energy in your models. Then
answer the “Check Yourself” questions below the table.
MATTER
ENERGY
How many How many
How many
How many twist
What forms of
ties?
energy?
carbon
oxygen
hydrogen
atoms?
atoms?
atoms?
Reactants
Ethanol
Oxygen
REACTANTS
TOTALS
Products
Carbon
Dioxide
Water
PRODUCTS
TOTALS
Check Yourself!
1. Did the number and type of atoms stay the same at the beginning and end of the
chemical change? ____
2. Did the number of twist ties (representing energy) stay the same at the beginning and
end of the chemical change? ____
3. Why do the numbers of atoms and twist ties have to stay the same?
Write a balanced chemical equation using the molecular formulas and the yield sign ():