Summary

In this lesson students actively engage in thinking about energy issues in chemistry and the nature of energy (thermal) transfer. The idea that temperature is a measure of heat content will be challenged, and students will be given the opportunity to collect data that will allow them to clearly see that different materials transfer energy at different rates.

Grade Level

High and middle school

NGSS Standards

• MS-PS1-4: Develop a model that predicts and describes changes in particle motion, temperature, and state of a pure substance when thermal energy is added or removed.
• MS-PS3-2: Develop a model to describe that when the arrangement of objects interacting at a distance changes, different amounts of potential energy are stored in the system.
• HS-PS3-2: Develop and use models to illustrate that energy at the macroscopic scale can be accounted for as a combination of energy associated with the motions of particles (objects) and energy associated with the relative position of particles (objects).
• Science & Engineering Practices (SEP)
  • Developing and using models
  • Constructing explanations (for science) and designing solutions (for engineering)
  • Engaging in argument from evidence
• Crosscutting Concepts (CCC)
  • Cause and effect: Mechanism and explanation
  • Systems and system models
  • Energy and matter: Flows, cycles, and conservation

Objectives

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

• Construct a macroscopic model (based on temperature, density, and thermal conductivity) of how energy is transferred. (For higher level students, specific heat capacity can also be explored.)
• Explain how temperature is related to average kinetic energy if using the supplementary “What is Temperature?” demonstration.
• Explain how perception of hot or cold is related to heat and temperature.
• Use the particulate model of matter to explain how kinetic energy is demonstrated amongst the particles of a substance.

Chemistry Topics

This lesson supports students’ understanding of

• Heat
• Temperature
• Average kinetic energy
• Properties of matter
• Energy transfer
• Thermal conductivity
• Density
• Specific heat capacity

Time

Teacher Preparation: 15 minutes for Exploration #1 and 15 minutes for Exploration #2

Lesson:

• Exploration #1: 30-45 minutes
• Exploration #2: 50 minutes

Materials

• Power Point Slides
• Ice Melting Blocks (like Arbor Scientific Ice Melting Blocks) for each group
• IR Thermometers (like Thermoworks IR Pocket Thermometer) for each group
• Two Ice Cubes per group
• Paper Towels for each group
• Student Whiteboards and Markers (or chart paper and markers) for each group

Safety

• Always wear safety goggles when handling chemicals in the lab.
• Students should wash their hands thoroughly before leaving the lab.
• When students complete the lab, instruct them how to clean up their materials and dispose of any chemicals.

Teacher Notes

• Course Sequence Suggestions
  This lesson fits well when introducing ideas of energy and heat. It reveals stdents’ preconceptions about temperature and heat, and challenges the idea that temperature is the measure of how hot or cold something is.
• Additional Suggestions
  • Pre-label the tiles A and B. It is easier for the teacher if all of the polystyrene tiles have the same letter and all of the aluminum tiles have the same letter.
  • Temperature is not a measure of heat. You can define temperature as the measure of average kinetic energy of the particles during “Step 2 #9 – Share your ideas with a partner. At this stage it is essential that all students are clear that temperature is a measure of average KE, and not a measure of heat. You may want to use the “What is Temperature?” demonstration to help students understand how temperature and average kinetic energy are related.
  • After completing “Step 5: Explanation” and before starting “Analysis Questions” is a good place to introduce the concept of specific heat capacity if appropriate for your students. Please see the “Dramatic Demonstration of Thermal Conductivity” and/or the “Measuring Heat Demonstration” for ideas on how to extend.
• The activity provides several paths that can:
  • help students build an understanding that our perception of hot and cold is due to the rate of energy transfer
  • introduce or reinforce the idea that temperature is a measure of average kinetic energy
  • introduce the concept of thermal conductivity
  • guide students to understanding that heat can ONLY be measured when there is a transfer of energy from one thing to another
  • begin a discussion of heat capacity
  • facilitate modeling thermal energy transfer on a macroscopic and particulate level
  • inspire questions about entropic ideas in energy transfer and thermal equilibrium for advanced students
• A nice application lesson that can follow, is an engineering design activity called “Design a Fast Defroster for the Forgetful Chef”. In the lesson, students are asked to use their knowledge of materials to design a device that will defrost quickly.
  
• Background Information for Teachers
  Although most students have a common sense idea about what energy is, they may find it difficult to give a precise definition. Teaching students about chemical energy can be even more difficult. This may be due in part to the fact that we often postpone discussion of energy until late in the year, when we cover topics such as thermochemistry and thermodynamics; despite the fact that energy is a cross-cutting concept that accompanies every change in chemistry.
  
  As Richard Feynman said, “It is important to realize that in physics today, we have no knowledge of what energy is!” Our main experience with energy comes when we recognize energy changes. In this session we will explore changes in thermal energy, such as how we feel when we forget to put on a sweater during cold weather, or when we wear too many clothes when it’s hot outside. Students’ understanding of heat, temperature and chemical systems needs to be carefully constructed. For more background information on these topics, download the Teacher Background Information document.
  
  You might also find the opportunity to extend this activity when discussing specific heat. Many students are confused by the idea of specific heat, and think that it is how much heat something can hold. To battle that idea, one must be clear that the definition is the amount of energy needed to change the temperature of a certain amount of a substance. If we think about particles, it is the amount of energy needed to be transferred so that the particles increase their average KE. There are two supplementary demonstrations that provide observations and data for students to build a better understanding of heat capacity. See Please see the “Dramatic Demonstration of Thermal Conductivity” and/or the “Measuring Heat Demonstration”.
• Student Prerequisite Information
  • Students should have a particulate view of matter, i.e.: should know that matter consists of small particles.
  • Students should have experience with measuring temperature and with units of temperature.
  • Students should have a definition of kinetic energy being related to velocity of the particles, i.e. KE=½ mv²