#### Materials

- • Ice Melting Blocks Pre-label the tiles A and B . It is easier for the teacher if all of the • Ice Melting Blocks Pre-label the tiles A and B . It is easier for the teacher if all of the polystyrene tiles have the sameletter and all of the aluminum tiles have the same letter.
- • Ice Cubes per Group • Ice Cubes per Group
- • Towels • Towels
- • IR thermometer • IR thermometer

#### Safety

- • wear safety goggles when handling chemicals in the lab. • wear safety goggles when handling chemicals in the lab.
- • should wash their hands thoroughly before leaving the lab. • should wash their hands thoroughly before leaving the lab.
- • the teacher's instructions for cleanup and disposal of materials. • the teacher's instructions for cleanup and disposal of materials.

#### Teacher Notes

- • Sequence Suggestions: This lesson was originally designed to follow a lesson • Sequence Suggestions: This lesson was originally designed to follow a lesson on particulate energy transfer. Click here to view the previous lesson.
- • matter on the particle level: Use Modeling Energy Transfer as well as • matter on the particle level: Use Modeling Energy Transfer as well as this lesson to establish particle-level conceptions of energy immediately after establishing particle-level conceptions of matter. Modeling matter provides a natural transition to modeling energy. Students may ask (or you may prompt) questions like 'What is the difference between hot and cold water at the particle level?' Establishing particle-level energy conceptions early allows for those conceptions (and energy in general) to be woven into the classroom more often and more effectively. You may wish to skip the bar graph modeling initially and revisit the phenomenon later in the year, possibly when the study of energy becomes more quantitative. This not only limits the time required, but allows for the iterative nature of modeling to take place.
- • in phase changes: This lesson may be used within a more traditional energy • in phase changes: This lesson may be used within a more traditional energy unit, such as in exploring energy associated with phase changes (ex. Heat of fusion) or establishing conservation of energy. This lesson will help develop a particle-level conception as well as begin a more quantitative discussion of energy. During the energy bar graph portion of the activity students may ask (or you may prompt) questions like 'How could we more exactly quantify how much kinetic energy an object possesses?' or later on 'Imagine you have two samples of a substance. They're both at the same temperature, but one is twice the mass of the other. How does the kinetic energy of the two objects compare?' These conversations lead to a need for quantitative ideas like specific heat and heats of fusion/vaporization. While developing a quantitative understanding of these ideas, you may wish to revisit the energy bar graphs. Have students draw approximate energy bar graphs for a scenario (Ex. Liquid water at 20 C o being cooled to -5 C) and then build quantitative versions with correct scales and values o o o for the same scenario (Ex. 10g of water cooling from 20 C to -5 C) using their specific heat and heat of fusion tools.
- • and solids: Why is an investment of energy required for a substance to • and solids: Why is an investment of energy required for a substance to transition from solid to liquid? Do all substances require the same investment of energy to transition from solid to liquid? Why does this transition occur at different temperatures for different substances? Use this lesson as a starting point for using energy data to explore interparticle attractions and how they may vary between substances.

American Association of Chemistry Teachers |1-291