# Lesson:Counting Calories

### Quick Look

Time Required: 3 hours

(can be split into three 60-minute sessions)

Lesson Dependency: None

Subject Areas: Chemistry, Physics

### Summary

The students discover the basics of heat transfer in this activity by constructing a constant pressure calorimeter to determine the heat of solution of potassium chloride in water. They first predict the amount of heat consumed by the reaction using analytical techniques. Then they calculate the specific heat of water using tabulated data, and use this information to predict the temperature change. Next, the students will design and build a calorimeter and then determine its specific heat. After determining the predicted heat lost to the device, students will test the heat of solution. The heat given off by the reaction can be calculated from the change in temperature of the water using an equation of heat transfer. They will compare this with the value they predicted with their calculations, and then finish by discussing the error and its sources, and identifying how to improve their design to minimize these errors.
This engineering curriculum aligns to Next Generation Science Standards (NGSS).

### Engineering Connection

Chemical engineers design and operate among other things large plants and processes that make usable products from chemicals, ranging from electrical power, food products, medicines, materials, fuels and refined chemicals. In order to safely and efficiently apply and control these processes, an engineer must know how much heat will be generated in a given reaction. If too much heat is generated, proteins denature, products burn or decompose, or a reactor might violently explode. If too little heat is generated, chemicals do not react, not enough energy is generated, or the wrong products are favored. Additionally, an engineer has to be aware of how the process equipment itself will affect the chemical process. By being able to predict how much heat will be produced in a reaction (as well as pressure), systems can be designed with specific tolerances in mind and reaction conditions maximized.

### Learning Objectives

After this activity, students should be able to:

• Describe several basic principles of thermodynamics and heat transfer in action.
• Compare and contrast the differences between real-world application and on-paper analysis.

### Educational Standards Each TeachEngineering lesson or activity is correlated to one or more K-12 science, technology, engineering or math (STEM) educational standards. All 100,000+ K-12 STEM standards covered in TeachEngineering are collected, maintained and packaged by the Achievement Standards Network (ASN), a project of D2L (www.achievementstandards.org). In the ASN, standards are hierarchically structured: first by source; e.g., by state; within source by type; e.g., science or mathematics; within type by subtype, then by grade, etc.

###### NGSS: Next Generation Science Standards - Science
NGSS Performance Expectation

HS-PS3-1. Create a computational model to calculate the change in the energy of one component in a system when the change in energy of the other component(s) and energy flows in and out of the system are known. (Grades 9 - 12)

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This lesson focuses on the following Three Dimensional Learning aspects of NGSS:
Science & Engineering Practices Disciplinary Core Ideas Crosscutting Concepts
Create a computational model or simulation of a phenomenon, designed device, process, or system.

Alignment agreement:

Energy is a quantitative property of a system that depends on the motion and interactions of matter and radiation within that system. That there is a single quantity called energy is due to the fact that a system's total energy is conserved, even as, within the system, energy is continually transferred from one object to another and between its various possible forms.

Alignment agreement:

Conservation of energy means that the total change of energy in any system is always equal to the total energy transferred into or out of the system.

Alignment agreement:

Energy cannot be created or destroyed, but it can be transported from one place to another and transferred between systems.

Alignment agreement:

Mathematical expressions, which quantify how the stored energy in a system depends on its configuration (e.g. relative positions of charged particles, compression of a spring) and how kinetic energy depends on mass and speed, allow the concept of conservation of energy to be used to predict and describe system behavior.

Alignment agreement:

The availability of energy limits what can occur in any system.

Alignment agreement:

Models can be used to predict the behavior of a system, but these predictions have limited precision and reliability due to the assumptions and approximations inherent in models.

Alignment agreement:

Science assumes the universe is a vast single system in which basic laws are consistent.

Alignment agreement:

###### Common Core State Standards - Math
• Solve linear equations and inequalities in one variable, including equations with coefficients represented by letters. (Grades 9 - 12) More Details

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• Solve simple rational and radical equations in one variable, and give examples showing how extraneous solutions may arise. (Grades 9 - 12) More Details

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###### International Technology and Engineering Educators Association - Technology
• Energy cannot be created nor destroyed; however, it can be converted from one form to another. (Grades 9 - 12) More Details

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• Energy can be grouped into major forms: thermal, radiant, electrical, mechanical, chemical, nuclear, and others. (Grades 9 - 12) More Details

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###### State Standards
• Solve linear equations and inequalities in one variable, including equations with coefficients represented by letters. (Grades 9 - 12) More Details

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• Use appropriate measurements, equations and graphs to gather, analyze, and interpret data on the quantity of energy in a system or an object (Grades 9 - 12) More Details

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• Use direct and indirect evidence to develop predictions of the types of energy associated with objects (Grades 9 - 12) More Details

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• Identify different energy forms, and calculate their amounts by measuring their defining characteristics (Grades 9 - 12) More Details

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### More Curriculum Like This

Heat Transfer: From Hot to Not

Students learn the fundamental concepts of heat transfer and heat of reaction. This includes concepts such as physical chemistry, an equation for heat transfer, and a basic understanding of energy and heat transfer.

High School Lesson
Hot Potato, Cool Foil

Students explore material properties by applying some basic principles of heat transfer. They use calorimeters to determine the specific heat of three substances: aluminum, copper and another of their choice.

High School Activity

### Pre-Req Knowledge

Algebra: Students need to know how to perform basic algebraic manipulation of equations and substitution techniques.

Chemistry: Students should be aware that chemicals interact in reactions that change the chemical and/or physical properties of a system. Also, students should have some experience with mole balances or stoichiometry (the math behind chemistry).

Physical Science: Students should be familiar with concept of energy, that it can be exchanged, and that it comes in different forms.

### Introduction/Motivation

Do you ever wonder exactly how it is known how many calories are in a delicious bag of chips? Or how much energy is in a refreshing can of pop? What about chemical reactions like hydrogen and oxygen? It reacts so quickly, how can a scientist or engineer even begin to measure the energy released? How can we scale reactions for different sizes and amounts of the reactants? Many of you might be thinking "Well, they look it up of course!" Ultimately, the data had to come from somewhere. The answer to all these questions is calorimetry. If we react our item of interest in the presence of a substance with a known heat capacity, we can measure the temperature change of the known substance using a calorimeter. Oftentimes, this substance is water. We can then relate the temperature change to the amount of heat transferred using certain equations of heat transfer.

This activity demonstrates not only the heats of solution, but how we measure these values and certain problems we encounter in trying to do this accurately and inexpensively in real-world situations.

### Vocabulary/Definitions

adiabatic: Does not conduct heat, Q=0. Impermeable to heat

calorimeter: A device designed to measure transferred energy, or heat.

calorimetry: The applied use of a calorimeter.

constant pressure heat capacity : (Cp) The amount of energy required to raise or lower a given amount of a substance by one unit temperature at a constant pressure.

enthalpy: A special value used in engineering to describe the amount of energy in a system including pressure and volume, relative to a reference state.

equilibrate: To go to equilibrium; to come to a balanced, stable state.

heat: Energy transferred between two systems as a result of a temperature difference.

heat of solution: The energy generated or consumed when dissolving one substance in another.

### Assessment

Pre-Activity Assessment

Brainstorming: In small groups, have the students engage in open discussion. Remind students that no idea or suggestion is "silly." All ideas should be respectfully heard. Encourage wild ideas and discourage criticism of ideas. Before showing students the available supplies, have students begin to think about how to make a calorimeter the most effectively. Should they use a glass jar vs. a plastic container vs. a paper or foam cup. Give them time to come up with wild ideas as well as feasible ideas so that they begin to think like engineers.

Worksheet: Instruct the students to complete the Wait, What Just What Happened? Worksheet. Review their answers to gauge their mastery of the subject.

Activity Embedded Assessment

Your Calorimeter and You Worksheet: Have the students complete the Your Calorimeter and Your Lab Worksheet. Review their answers to gauge their mastery of the subject.

Post-Activity Assessment

Worksheet: Have the students complete the Evaluation and Improvement Worksheet. Review their answers to gauge their mastery of the subject.

### Lesson Extension Activities

To add another real-world dimension to the activity, give each group a starting amount of fake money (for example, Thermodollars) and require them to "buy" each item. This puts some constraints on their designs, such as only being able to afford two cups and one piece of foil instead of three cups and unlimited foil.

### References

U.S. Department of Energy, Office of Science, Fermi National Accelerator Laboratory, January 29, 2004, accessed November15, 2009. http://www.fnal.gov/pub/today/archive_2004/today04-01-29.html

### Contributors

James Prager; Megan Schroeder; Malinda Zarske; Janet Yowell

### Supporting Program

Integrated Teaching and Learning Program, College of Engineering, University of Colorado Boulder

### Acknowledgements

The contents of this digital library curriculum were developed under a grant from the Fund for the Improvement of Postsecondary Education (FIPSE), U.S. Department of Education and National Science Foundation GK-12 grant no. 0338326. However, these contents do not necessarily represent the policies of the Department of Education or National Science Foundation, and you should not assume endorsement by the federal government.