Energy Learning Community

Lesson 3 - Chemical Energy Wall

Lesson Plan

Grade Level:

High School

State Standards:

4.1 Explain how atoms combine to form compounds through both ionic and covalent bonding.
6.4 Describe the law of conservation of energy. Explain the difference between an endothermic process and an exothermic process.

Essential Question:

How is energy conserved in a chemical or a physical process?

How can you determine the amount of energy absorbed or released in a chemical or physical process?

Lesson Question:

What is the magnitude of the amount of energy consumed or released in various chemical structures and processes?

Introduction:

Remember that a chemical bond is an attraction between atoms that allows the formation of chemical substances that contain two or more atoms. Bonds can be created by either an electrostatic attraction between oppositely charged ions (ionic) or by a sharing of electrons (covalent). Chemical bonds vary in strength depending on bond type and bond order. This activity is to help you reinforce that idea, by placing different bonds on an energy wall which will allow you to have a visual representation of how bond strengths differ. In addition to looking at individual bonds we must take this idea one step further by looking at the way that bonds interact in a chemical reaction to form new substances. Recall that you can use heats of formation, Hess’s Law and bond enthalpies to determine heats of reaction.

Task:

The purpose of this activity is to link knowledge of bond properties and chemical reactions to thermochemistry concepts and to give you an appreciation for the magnitude of the amount of energy consumed or released in various chemical structures and processes.

Lesson Experiences:

1. Using the larger strip of butcher block paper, create a scale with two parallel, horizontal axes. The top axis must be in kJ and range from 150 kJ to 5000 kJ. The lower axis must be in dietary calories (Cal). Leave room to write above and below each axis. Have your instructor check your graph before moving forward.

2. Using your textbook or the CRC, look up and/or calculate the enthalpies for the following substances and processes. Write their names, formulas, equations (for reactions) and respective enthalpies on the respective color coded card. All enthalpies should be reported in kJ/mol. Remember to take direction of heat flow into account.


Bond Enthalpies – Pink Cards

Bond Type

Structure

Bond Enthalpy (kJ/mol)

I-I single bond

C-H single bond

C-C single bond

C-C double bond

C-C triple bond


Lattice Energies – Green Cards

Compound

Formula

Lattice Energy (kJ/mol)

sodium chloride

lithium chloride

magnesium chloride

calcium oxide


Reactions – Yellow Cards: Look up or utilize heats of formation, bond enthalpies or Hess’s Law to determine the enthalpy changes for the following. Clearly show calculations separately.

Process

Equation

Method

Enthalpy (kJ/mol)

vaporization of water

synthesis of ethane from carbon and hydrogen

zinc and hydrochloric acid

combustion of methane

combustion of octane

diamond from graphite

metabolism of tristearin


Food – White Cards: Find a food equivalent for at least two of the substances in each of the three categories listed above. Print out or draw an image of it, place it on a card and add it to your energy wall.



Predictions – Orange Cards: *Do not complete this portion of the activity until after the class discussion.* Pick a substance or a chemical process not yet discussed and guesstimate where that card will fall on your energy wall. Place the card on the wall and then look up the true value. What about your reasoning was correct or incorrect?

Conclusion:

Take a few minutes to analyze your wall. See if you notice any patterns or correlations to previously discussed chemical phenomena. Make a list of these items and, as a group, decide on one of these discoveries to focus on. State your claim and defend it with the Claim, Evidence and Reasoning model. (See rubric below). You will present findings.

Assessments:

This activity will be assessed in two ways. First, the students will be expected to analyze their energy walls and come up with a pattern or an interesting observation about what they see occurring. They must then present this finding to the class using the Claim, Evidence, Reasoning (CER) model in the form of a prezi or glogster. These presentations will lead to a class-wide discussion of enthalpy, bonding and chemical reactions. The second mode of assessment is for the student to, individually, write a one or two paragraph statement that summarizes what was done in the activity, what was learned and how the activity connects to another part of the curriculum and will then post on their edmodo page.

Assessment Rubric

Resources:

Claim Evidence Reasoning rubric
http://www.nsta.org/elementaryschool/connections/201104ClaimsEvidenceRubric.pdf
Ionic Bond animation

Tra at the English language Wikipedia [GFDL (http://www.gnu.org/copyleft/fdl.html) or CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0/)], from Wikimedia Commons

http://commons.wikimedia.org/wiki/File%3AIonic_bonding_animation.gif

Carbon Covalent Bond animation

By Edguy99 (Own work) [Public domain], via Wikimedia Commons

http://commons.wikimedia.org/wiki/File%3ACarbonCarbon2Point.gif

Diamond Lattice Animation

By original uploader: Brian0918 [CC0], via Wikimedia Commons

http://commons.wikimedia.org/wiki/File%3ADiamond_Cubic-F_lattice_animation.gif

Gingerbread lattice

By Dean Michaud, 2008, via Wikimedia Commons

http://commons.wikimedia.org/wiki/File:Gingerbread_house_lattice_wall.jpg

Thermally_Agitated_Molecule

By en:User:Greg L [GFDL (www.gnu.org/copyleft/fdl.html) or CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0/)], via Wikimedia Commons

http://commons.wikimedia.org/wiki/File%3AThermally_Agitated_Molecule.gif

Methane Combustion

David Gaya, Created with KPovModeler, via Wikimedia Commons

http://commons.wikimedia.org/wiki/File:Methane_combustion.jpg