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Measuring the British Thermal Unit
Lesson 3 of 4
Objective: SWBAT identify a British Thermal Unit as a measurement of energy. This lesson integrates science practices with mathematical reasoning.
Engage
As students explore energy, developing a common language is an important skill for understanding how a variety of energies are measured. As students learn about renewable and nonrenewable energies, it is important to understand how to compare the energy output of coal vs. natural gas, for example. Btus are a common standard for comparing energies.
This lesson integrates math and science as students explore how energy is measured. Students compare calories to Btus and conduct an investigation by burning cashew nuts. To integrate math we explore the formulas associated with measuring energy.
My first strategy is a Concept Map comparing Btu with calories. Student have had experience with the term calories. Using a Venn Diagram, students write Calorie on one side and British thermal unit (Btu) on the other side to compare and contrast the concepts. Student groups complete both sides and answers are shared. I use comparecontrast because it bridges one known to one unknown concept. Students are supporting in making suppositions because the two terms are linked on the Venn diagram. Typically they have never heard of a Btu.
I begin examining the calorie side because more students have background knowledge on this topic. I ask student groups to create a definition of a calorie. The whole class shares definitions and discusses the variations of definitions. I project on the SmartBoard the dictionary definition of a calorie, "The amount of heat needed to raise one gram of water 1°C." I ask the question, "How is this different than what you wrote?" Student groups discuss their definition compared to the dictionary definition.
My lesson Exploring the Law of Conservation of Energy has been taught and students review energy transfers. I explain that calories measure the amount of energy, and that calories represented on nutrition labels actually refer to kilocalories, or the calories times 1,000.
I then move to the Btu side of the Venn diagram. This side is usually less complete. Some students have exposure to Btu through family connections. Groups share their responses in the Venn diagram with the whole class and we discuss any misconceptions. Most students say it is a term a parent says but that is all they know. I give the students the dictionary definition, “One British Thermal Unit is the amount of energy required to raise the heat in one pound of water by 1°F”.
I ask students to write both the definition of a calorie and the definition of a Btu in their engineering notebooks. I explain we are going to conduct an investigation of the differences between calorie and British thermal unit with a peanut.
BTU: Strategy & Student Samples shows the introduction to the compare contrast activity. In addition students conduct the lab and samples of Venn diagrams are shown.
(Science Practice 1: Asking Questions and Defining Problems that can be investigated within the scope of the classroom with available resources and frame a hypothesis based on observations and scientific principles.)
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Explore
The purpose of the Nut Lab is to create a heat transfer investigation. Students determine the amount of energy in a nut and convert it to Btu. Investigating the energy measurement comparison between calorie and Btu will help students understand the energy used in the burning of fossil fuels in households.
The problem is, "What is the energy transferred from the nut to the water in calories and in Btu?" Students determine the procedure, variables, controls, and the data table. To help students create the data table, I show them the formula: Calorie = mcΔT. I have to explain how the lab will be conducted to help students understand formula.
My lesson Law of Conservation of Energy has been done prior to this lesson. This Btu lab investigates the relationship between the burning peanut as energy is transferred to the water, measured by temperature. Students conduct the lab. For preparation I have ring stands, beakers containing 1 pound of water, thermometers, one raw nut per group, dissecting probe pins, and a lighter. Students have timers and thermometers. They record the data.

Before 
After 
Final 
Peanut Mass




Mass of Water 








Before 
After 
Change in Temp. 
Temperature of the Water




(MSPS34. Plan an investigation to determine the relationships among the energy transferred, the type of matter, the mass, and the change in the average kinetic energy of the particles as measured by the temperature of the sample.)
(SP3 Planning and Carrying Out Investigations  Plan an investigation individually and collaboratively, and in the design: identify independent and dependent variables and controls, what tools are needed to do the gathering, how measurements will be recorded, and how many data are needed to support a claim.)(MSPS34)The amount of energy transfer needed to change the temperature of a matter sample by a given amount depends on the nature of the matter, the size of the sample, and the environment.
(MSPS33) Energy is spontaneously transferred out of hotter regions or objects and into colder ones.
Explain
With the information, student begin to calculate calories and then convert the calories to Btus. I project the formula on the SmartBoard.
Calorie = mcΔT
We discuss the formula and what the symbols mean. Calories = mass of water x heat capacity of water (1gr/C^{0}) x Change in Temperature
Students calculate the number of calories in the cashew based upon their data. I project the conversion from calorie to Btu.
1 calorie  .004 British Thermal Units.
Students record the peanut Btu conversion on their data table.
(SP5: Using Mathematics and Computational Thinking:Create algorithms (a series of ordered steps) to solve a problem.)
Evaluate
I explain that natural gas is measured in British Thermal Units and we burn the gas in our power plants, furnaces, stoves, and grills. My intention is to promote unifying ideas to make connections between calorie and Btu.
I give students an electronic copy of directions to help them work independently. They write down the last ten foods they ate. They will look up the calories and convert the calories to British Thermal Units using the formula. Students use search engines to find calories in food. My strategy is to use create a mathematical model. This will enable students to compare data with one another. They discuss the varying calories in the ten foods they last ate. Students like to see the foods their classmates wrote and there is a personal connection to a friend's data when a common food is listed.
The American Petroleum Institute has a great site called Classroom Energy. There is a handy chart in Energy, The Quick Tour. I print off this chart to highlight the difference between kilocalories and calories. My strategy is to show students how calories and Btu are related and why scientific notation is an important way to measure energy.
CalorieKilowatt Conversion Data Table
1 calorie  .004 British Thermal Units.
Food 
KiloCalorie (Calorie x 1000) 
BTUs 
Apple 
100 
400 













Using the data table, student groups compare and contrast their data. My intention is for students to double check one another and to engage in scientific discourse with one another.
In Engineering Notebook, students complete the following sentence starters and then share with their table groups. My intention is to give the students the opportunity to talk about themselves as they share their answers.
 I was surprised by…….
 The energy in a calorie is like __________________. The energy is a Btu is like _______________________.
 There are two measurements of energy because………
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Expand
At this point the students have experience relating calories to Btu. Now, I am going to Generalize Content to a different setting.The students have used Btu in relation to calories as a strategy for understanding energy measurement. My intention is to use Btu as a method for understanding how Americans use natural gas and how it compares to other energy sources.
The U.S Energy Information Agency has an Energy Calculator for kids. This handy tool is used to help compare the output of energy when measuring in kilowatt or in Btu.
My intention is to promote student understanding of the relationship between energy measurements. I project the site on the board and I walk through the page with them with three examples.
I use Btu as my common measurement. I like to use the Bunsen burner Btu as my example (1200 Btu). I place 1200 Btu in coal, electricity, natural gas and gasoline converters. I explain how energy output of the Bunsen burner is equal to a very little amount of coal, .35 kilowatts of electricity, 1.2 cubic feet of natural gas, and .001 gallons of gas.
I ask students to use their Btu data and compare it to the coal, electricity, natural gas and gasoline. The purpose is to look for patterns. Students make spreadsheets.
Btu (Nat Gas) 
Kilowatt 
Short ton (Coal) 
Calories (Food) 
Gallons (Gas) 




















I ask the question,"Which creates the most amount of energy for the least amount of resource?" Rank the order of energy units and explain why you put the numbers in the order. Check out my Btu Student Samples.
After the ranking, student table groups discuss their ideas to convince one another of their rankings. Then using a lab white board to demonstrate their work, students share their ranking with the rest of the class and defend their thinking. The purpose of the group/whole class share is to use group thinking to help students understand data analysis.
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