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San Jose CA. 95113
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Consuming Coal
Post-Lab Activity: Green by Design
This activity is meant to extend your students’ knowledge of the topics covered in our Green by Design lab. Through
this activity, students will find out just how much coal it takes to power the classroom and create a plan to reduce
the amount of energy used in the classroom.
Grade Level: 4-8
Estimated Time: 30-45 minutes
This is primarily a math activity, so no materials are required other than paper and pencil
Student Outcomes:
1. Students will be able to calculate the amount of electricity used by classroom lights and use that information to
calculate how much coal it takes to power the classroom lights.
Next Generation Science Standards
Earth Science Grade 4: 4-ESS3-1
Disciplinary Core Idea ESS3.A Natural Resources, ESS3.C
Human Impacts on Earth Systems
Common Core Math Standards
Grade 4: OA.2; Grade 5: NBT.7; Grade 6: RP.3b;
Grade 7: EE.3
Common Core ELA Standards
Grades 4-5: Writing W.7; W.8
Grade 4: Speaking and Listening 4.SL.1b-d
Grade 5: Speaking and Listening 5.SL.1b-d
Grades 6-8: Writing W.7; Speaking and
Listening SL.1b-e
Vocabulary
Familiarity with these terms and concepts will enhance students’ experience in the activity
• Coal: a sedimentary type of rock with a high amount of carbon. Coal is highly combustible and is classified as a
non-renewable energy source. It is burned to generate electricity in our homes.
• Electricity: The flow of charged particles from one source to another
• Kilowatt hour (kWh): the unit of measurable electric power; 1 kWh is equivalent to 1 kW of power expended for
one hour.
• Fluorescent light bulb: a non-energy efficient type of light bulb-requires more kilowatts to run per hour than an
energy efficient bulb.
• LED (Light Emitting Diode): an energy efficient type of light bulb-requires fewer kilowatts to run per hour than a
fluorescent bulb.
Background Information
• How coal is made:
o Coal takes millions of years to form making it a non-renewable resource.
o Coal is formed by plants that have been covered by layers of dirt and rocks for millions of years. Over time,
more and more layers of dirt and rocks were formed over the dead plants, putting a lot of pressure and
heat on the plants. Under the pressure and heat, the plants decayed and formed coal.
• How coal is removed from the Earth:
o Coal is mined, or dug up, from the Earth.
o Shallow coal deposits can be mined using large machines to dig through the surface.
o Deeper coal deposits have to be mined through underground mining, which is very dangerous. Miners go
down deep holes in the Earth using machines to dig very deep to reach coal.
• How is coal used?
o 93% of the coal consumed in the US is for electricity
o The following video provides an excellent explanation for how coal is burned to produce electricity.
https://www.youtube.com/watch?v=SeXG8K5_UvU
• How does coal affect the environment?
Consuming Coal
Post-Lab Activity: Green by Design
201 S. Market St.
San Jose CA. 95113
1-408-294-8324
thetech.org
o Surface mining is very damaging to the mountains where coal is mined. Contaminated water can also be a
problem in areas where coal mining takes place.
o Burning coal produces 77% of carbon dioxide emissions from electricity production in the US. Carbon
dioxide emissions are what lead to the Green House Effect.
• For more in depth information on coal as an energy source, please check out the following sites:
http://www.eia.gov/kids/energy.cfm?page=coal_home-basics
http://teachcoal.org/converting-coal-into-electricity
Procedure:
1. Discussion
a. Most schools still use fluorescent light bulbs in their classrooms because they are inexpensive to buy. But
fluorescent bulbs are not very energy efficient. Fluorescent bulbs use an average of .018 kilowatts of
electricity per hour. An LED bulb only uses about .008 kilowatts of electricity per hour.
b. How much coal do you think needs to be burned to produce 1 kilowatt hour of electricity?
• It takes 1 pound of coal to generate 1.25 kilowatt hours of electricity
c. How many kilowatt hours do you think your classroom uses per day? How about the school? How much
coal do you think that would take?
2. For older students, you can use the word problem on the next page and have them solve independently or as a
group.
3. For younger students, please see the attached worksheet. The following are step by step directions:
4. Students will first calculate how many kilowatt hours of electricity it takes to power the lights in the classroom
and how much it costs.
a. Begin by having students count the number of fluorescent tubes in the light fixtures (each fixture
generally contains 2-4 tubes).
b. It costs approximately three tenths of a cent ($0.003) to run one fluorescent tube for one hour.
c. Multiply the number of fluorescent tubes by $0.003 to get the cost of running all of the fluorescent tubes
for one hour.
• If your classroom has 32 tubes:
32 tubes x $0.003 = $0.096 per hour (round up to $0.10)
d. The lights are generally on in the classroom for 8-10 hours. Calculate how much it costs to run the tubes
for 10 hours.
• If your lights are running for 10 hours:
$0.10 x 10 hours = $1.00 per 10 hour day
e. This doesn’t seem like a lot but how much would it cost if every classroom in the school had their lights on
for 10 hours? What about the cafeteria, library, and other rooms? Does your classroom use electricity for
other items besides lights? How much electricity do you think those items use?
f. This is only the monetary cost; what about the amount of coal that would need to be burned to power the
classroom lights?
5. Students will now calculate how much coal it will take to generate the amount of electricity needed to power the
lights.
a. Each fluorescent tube uses 0.018 kilowatts per hour. Calculate how many kilowatt hours the tubes in the
classroom use in one hour.
32 tubes x 0.018 kWh = .576 kWh
b. Now calculate how many kWh are used in a 10 hour day
.576 kWh x 10 hours = 5.760 kWh
c. It takes one pound of coal to generate 1.25 kWh. How many pounds of coal will it take to generate the
electricity needed to run the lights for a 10 hour day?
1 pound coal x 5.760 kWh = 4.6 pounds coal per day!
Consuming Coal
Post-Lab Activity: Green by Design
201 S. Market St.
San Jose CA. 95113
1-408-294-8324
thetech.org
1.25 kWh
d. How much coal would it take to power the lights for the whole school year (assuming a 180 day year)?
What about for all of the classrooms?
4.6 pounds coal x 180 days = 828 pounds per classroom!!!
6. Is using this much coal good for the environment? What are some alternatives or energy saving techniques that
can be implemented?
For students in grades 6-8:
Your principal wants to make the classrooms more “green” and is debating on switching the fluorescent
lights in the classrooms to LED’s. You have been asked by your principal to prepare a presentation about the
cost (monetary and environmental) of running fluorescent light bulbs in the classrooms. The specs on the
current fluorescent lights show that each light tube uses 0.018 kW per hour and the LED’s she is considering
use 0.008 kW per hour. The current rate on electricity from PG&E is $0.12 per kWh. How much will it cost to
run each of the light types for the full 180 day school year assuming the lights are on for 10 hours per day?
Remember, there is more than one fluorescent tube or LED used in each light fixture. The principal wants
to know the cost for your whole classroom…not just one fluorescent tube or LED.
The principal would also like to know how the school’s electricity usage is affecting the environment. Given
that it takes one pound of coal burned to generate 1.25 kWh, how many pounds of coal is the school (all
classrooms) currently using and how much would the school use if they switch to LED’s?
201 S. Market St.
San Jose CA. 95113
1-408-294-8324
thetech.org
Consuming Coal
Post-Lab Activity: Green by Design
Worksheet for students in grades 4-5
1. How many fluorescent tubes are in your classroom? ______
2. It costs $0.003 to power each tube per hour. How much does it cost to run all of the tubes for 1 hour?
_________ x $0.003 = $_____________
Number of tubes
3. How much will it cost to run all the tubes for 10 hours?
_________ x 10 hours = $_____________
Answer from #2
4. Each tube uses 0.018 kW of electricity per hour. How much energy are all of the tubes using per
hour?
_________ x 0.018 kW = __________kW
Number of tubes
5. How much energy are all of the tubes using in 10 hours?
_________ x 10 hours = __________kW
Answer from #4
6. When one pound of coal is burned, it produces 1.25 kWh of electricity. How many pounds of coal
need to be burned to generate the electricity needed to run all of the lights for a whole day?
1 pound
1.25 kWh
X ________kWh
= _________ pounds of coal
Answer from #5
7. How many pounds of coal would be needed to run the classroom for a whole school year?
___________ x 180 days = _____________ pounds
Answer from # 6