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ACTIVITY in Balancing Equations, Combustion, Stoichiometry, Unlocked Resources. Last updated October 13, 2021.

Summary

In this activity, students apply their knowledge of writing and balancing chemical equations and stoichiometry calculations to estimate their carbon footprint. Students are also asked to reflect on their carbon footprint and what it means.

Grade Level

High School

NGSS Alignment

This activity will help prepare your students to meet the performance expectations in the following standards:

  • HS-ETS1-3: Evaluate a solution to a complex real-world problem based on prioritized criteria and trade-offs that account for a range of constraints, including cost, safety, reliability, and aesthetics as well as possible social, cultural, and environmental impacts.
  • Scientific and Engineering Practices:
    • Using Mathematics and Computational Thinking
    • Analyzing and Interpreting Data

Objectives

By the end of this activity, students should be able to

  • Describe the top 3 ways that humans are producing carbon dioxide from fossil fuels.
  • Write and balance combustion reactions for commonly used fossil fuels.
  • Use stoichiometry to calculate an estimate of how much CO2 is produced each year per person (carbon footprint).

Chemistry Topics

This activity supports students’ understanding of

  • Chemical Reactions
  • Writing chemical equations
  • Balancing chemical equations
  • Combustion reactions
  • Stoichiometry
  • Gases
  • Relationship between human activity (burning fossil fuels) and increasing CO2 levels in Earth’s atmosphere

Time

Teacher Preparation: 1 hour (first time using this lesson), 10 minutes (after first time)

Lesson: 60 minutes

Materials

  • Student handouts

Safety

  • There are no safety considerations for this lesson.

Teacher Notes

  • The topic of climate change is one that I consider to be of utmost importance, in that it is both broadly applicable to all of the science disciplines and many of the basic principles are not well understood by the public. As such, it is something that I try to integrate into as many chemistry concepts as possible to develop a better understanding of the basic tenets of what is causing the earth to warm and climate to change.
  • This particular lesson is not the first time discussing climate change with students in my chemistry class. As such, they have some understanding of global warming and greenhouse gases. Even if students have not studied those topics before, the background provided should be a sufficient introduction to the context of estimating a carbon footprint and considering how daily human activities contribute to rising CO2 levels in the atmosphere.
  • If you wish to refresh your knowledge of the evidence for anthropogenic climate change, the American Chemical Society has an excellent overview of the core science. The narratives and presentations section may also prove useful for researching ideas to engage in climate topics with students and find answers to questions students have.
  • Other helpful resources and ideas for teaching can be found at the Climate Literacy and Energy Awareness Network (CLEAN), which provides lessons, guidelines, and suggestions for teaching about climate and energy topics.
  • The activity as it is currently written is also specific to the location of the author, who lives and teaches in Minnesota. I highly recommend adapting the data for your local area, as this will provide another layer of engagement for students to know what is happening in their state. The graph in part 2 and basic fuel consumption data were obtained from the US Energy Information Administration, and each individual state has data that can be used. It did involve some basic calculations to get a usable amount of each fuel consumed per person per year, and details of these calculations can be requested from the author (olsonj[at]district279.org).
  • To find out more about teaching the topic of Climate Change in Chemistry, read the associated article in the May 2017 issue of Chemistry Solutions.

For the Student

Background

Fossil fuels are naturally occurring deposits of organic matter that have formed over millions of years from decomposing plants and animals. Some have been used by humans for thousands of years; others have only been used for the past century. What is common in fossil fuels is that they are all used to produce some form of energy through combustion, and that their use has increased dramatically over the last 150 years.

Some concerns about the use of fossil fuels has to do with one of the main products of combustion: carbon dioxide (CO2). Carbon dioxide is a greenhouse gas, which means that it absorbs radiant heat from the earth’s surface and prevents it from escaping into space. While some amount of greenhouse gases are needed to prevent the earth from getting too cold, too much can result in an increase in global temperatures. The International Panel on Climate Change (IPCC) has identified human use of fossil fuels as the main driving cause of global warming and climate change.

We might not realize it, but many of our everyday activities directly or indirectly use fossil fuels and consequently produce CO2. In this activity, you will use your knowledge of chemical reactions and stoichiometry to calculate an estimate of the amount of CO2 you produce each year; a quantity known as your “carbon footprint”.

Introductory Questions

  1. What is a footprint? Why do we need to think about the “footprints” we leave behind?
  2. What is a fossil fuel?
  3. What are the reactants and products in a combustion reaction?

Problem
How much CO2 do you produce every year from normal, everyday activities?

Part 1: Main sources of greenhouse gases in the U.S.
Go to the EPA’s site about greenhouse gas emissions (https://www.epa.gov/ghgemissions/sources-greenhouse-gas-emissions). Use the information to answer the following questions:

  1. Who or what is responsible for the increase in greenhouse gases in the atmosphere over the last 150 years?
  2. What are the top 3 sources of greenhouse gases in the U.S.?

Part 2: Fossil fuel use in Minnesota
Use the graph below to answer the following questions:

  1. What are the top 3 fuels that are consumed (burned) in MN? List them below:
  2. What are these fuels used for? Do an internet search if you are not sure.

Part 3: Estimates of fossil fuel use

  1. Coal is mostly carbon (C). When it is burned, it reacts with oxygen in the air in a combustion reaction.
    1. Write and balance the equation for the combustion of coal:
    2. In MN, 43% of the electricity generated in MN uses coal. On average, each person in MN uses 2680 kg of coal per year to generate electricity that they use.
  2. Natural gas is mostly methane (CH4). When it is burned, it reacts with oxygen in the air in a combustion reaction.
    1. Write and balance the equation for the combustion of natural gas:
    2. In MN, natural gas is used for generating electricity, heating homes, and cooking. 10% of electricity generated in MN uses natural gas. It is also the main fuel used for heat and cooking. On average, each person in MN uses 1974 kg of natural gas per year for heat, cooking, and electricity.
  3. Gasoline is mostly octane (C8H18). When it is burned, it reacts with oxygen in the air in a combustion reaction.
    1. Write and balance the equation for the combustion of gasoline.
    2. In MN, gasoline is the main fuel used for motor vehicles. The amount of gasoline someone uses per year can vary greatly from person to person.
  4. Estimate the number of miles driven per year using the questions below: (It still counts even if you are not the one driving!)
    1. How far do you live away from school in miles? (Google if needed)
    2. We have approximately 180 days of school per year, how many miles of riding/driving would that be for a whole year? (0 miles if you walk to school, but not if you ride the bus!)
      Total miles to and from school: ______
    3. If you have a job, how far do you ride/drive to get there? ______
    4. How many days a week do you work? Use this to figure out how many trips you make (days working per week x 52 weeks per year; adjust if you work more in the summer)
      Total miles to and from work: ______
    5. Do you make any other regular trips by car (visiting friends, family, vacation, etc.)? Estimate how many miles as best you can.
      Extra miles for regular trips: ______
    6. Add up the total miles you ride/drive per year: ______
    7. The average vehicle in the U.S. gets around 21.6 miles per gallon of gasoline. Calculate how many gallons of gas you based on your yearly mileage (if you know the exact mpg of your vehicle you can use that, if not use the average above):
      Gallons of gasoline used per year: ______
    8. 1 gallon is equal to 3.785 L. Calculate how many liters of gasoline were used.
      Liters of gasoline used per year: ______
    9. The density of gasoline is 0.7 kg/L. Calculate how many kilograms of gasoline were used.
      Kilograms of gasoline used per year      : ______

Part 4: Calculations

Using the data and balanced equations in Part 3, complete stoichiometric calculations for Coal, Natural Gas and Octane in the table below:

Stoichiometry Calculations
Use data and equations from part 3

Grams CO2

Pounds CO2
(1 lb = 454 g)

Coal:





Natural Gas:





Octane:





Total pounds CO2:


Analysis

  1. What is your carbon footprint (in pounds of CO2)?
  2. How does your carbon footprint compare to the US average of 45,000 lbs CO2 per year?
  3. How does your carbon footprint compare to the world average of 8,800 lbs CO2 per year?
  4. Do your answers above surprise you? Why or why not?
  5. How could you reduce your carbon footprint? List at least 3 ways.
    1. Are you willing to make these changes? Why or why not?
  6. In this activity, we focused on the top 3 human activities that produce CO2. What other activities might directly or indirectly contribute to your carbon footprint that we didn’t include? Describe them below.