Introduction to NetLogo: Rusting & Rates of Reaction

TimeThis lesson will take 2-3 periods (42 minutes each). Students will need one period to explore the NetLogo program and rusting reaction. The second period will be used to complete their discoveries and insights from their designed

experiment. Part of the second period will be needed to summarize the results. Students can complete the homework section after the second day.

If students present their experiment, you will use a 3rd period.

LevelHigh School level Chemistry (regular and honors)

PurposeThe purpose of this lesson is to investigate the factors that influence the rate at which iron rusts- surface area, concentration, temperature, orientation of reactants, intensity of light, and catalysts. The basic principle of this rusting model is that oxygen gas particles are assumed to have three elementary actions: 1) they move, 2) they collide, - either with other gas particles or with any other objects such as non-reacting solid surfaces (walls), 3) and they can react with iron particles. By exploring this model, students learn how iron rusts by oxidation. The

chemical reaction in the model requires three oxygen molecules and four iron atoms as reactants to create two rust molecules. The rusting model can be used to study the behavior of gas particles, oxidation reactions, reaction types, spontaneity of reactions, or reaction rates.

OverviewStudents will use the rusting model to investigate the factors that affect the rate of rust formation. Each group selects a variable to investigate, analyze their results, make a conclusion, and present their findings to the class with evidence from their model.

Student OutcomesLearner Objectives

I can explain the factors that affect the rate of chemical reactionsNext Generation Science Standards

PS1.B Chemical ReactionsComputational Thinking (CT) STEM taxonomy chart:

1e. Analyzing Data. See appendix C1f Visualizing Data: See appendix D3a Using Computational Modeling to Understand a Concept: See Appendix E3c Assessing Computational Models: See Appendix F

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PrerequisitesStudents should know the parts of a chemical reaction and levels of emergent properties (submicroscopic, symbolic, and macroscopic).

Teaching NotesThe gas particles are modeled as hard balls with no internal energy except that which is due to their motion. Solid particles are modeled as hard balls with internal energy represented as rotational energy. Collisions between particles are elastic.

The basic principle of all gas behavior in the Connected Chemistry models, including this one, is the following algorithm:

1. A particle moves in a straight line without changing its speed, unless it collides with another particle or bounces off the wall.

2. Two particles "collide" if they find themselves on the same patch.3. A random axis is chosen, as if they are two balls that hit each other and this axis is the line

connecting their centers.4. They exchange momentum and energy along that axis, according to the conservation of

momentum and energy. This calculation is done in the center of mass system.5. Each particle is assigned its new velocity, energy, and heading.6. If a particle finds itself on or very close to a wall of the container, it "bounces" -- that is,

reflects its direction and keeps its same speed.7. If a particle ever penetrates into the solid iron/rust matrix, it has moved too far forward in

the last simulation time step, and is bounced back out to the closest open spot (patch).

Presentation: There are 7 factors that affect rust formation that this Netlogo model allows students to investigate:

air temperature amount of oxygen in the air shape of the iron object size of the iron object presence of water iron exposure to ultraviolet light removing rust that is formed on an object.

In order for all students to learn about each factor affecting rust formation, we recommend having the students work in groups to investigate one of the 7 factors, and then present their results to the class. Have students work in groups of four for the presentation, but gather data in groups of two. Have each group select one of the 7 factors (on a first-come, first-served basis, so all 7 factors are covered). A presentation rubric and summary chart (for all students to complete during the presentations) are included in the handouts.

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Instruction on how to use the rusting model:Initial settings:

1. INITIAL-GAS-TEMPERATURE: Sets the initial kinetic energy of each of the gas particles2. INITIAL-OXYGEN-MOLECULES: Sets the number of initial oxygen gas particles3. ACTIVATION-ENERGY: Sets the energy threshold required for a reaction to occur

between the products. The sum of the energies of the reactants must exceed this level for a reaction to occur.

4. IRON-BLOCK-GEOMETRY: Sets possible size and location of the iron block.5. RUST-FORMS-AT: Determines whether rust molecules form within the metal block or on

the surface of it or both.6. MOUSE-INTERACTION: Gives the user options to "add water", "remove water", "remove

rust", and "shine a UV beam on the iron".7. The SETUP button will set the initial conditions.8. The GO/STOP button will run the simulation.

In this model, iron atoms next to a patch with water and the necessary oxygen molecule reactants in it are pulled away from the iron metal block when rust forms. This leads to the deposition of rust above the surface of the iron as well as pitting of the iron block. This pitting effect occurs in reality. As you drag away rust (using the mouse cursor), you expose more iron to the air, speeding up the rusting process. The model demonstrates other emergent phenomena of when oxygen and iron react to form rust. Some of these phenomena include how surface area affects the rate of the reaction, how temperature of the reactants affects the rate of the reaction, and how a catalyst (such as water) can speed up the rate of a reaction. Other phenomena, such as atomic conservation in chemical reactions and limiting agents in chemical reactions are also visible in the model.

Pre-class PreparationTeacher should make sure NetLogo is working on student computers. Decide if you will assign a variable to each group before students begin. The students will learn more if each group has a different variable to test.

Materials and Tools1. NetLogo: http://ccl.northwestern.edu/netlogo/models/ConnectedChemistryRustingReaction2. Student worksheet – one packet per pair of students.3. Optional: rusted nails or other rusted objects.

AssessmentFormative and Summative assessments can be used to measure student understanding. The student worksheet may be collected for completion, and/or each group can write a formal lab report. The students will design an experiment to test which factor will affect the rate of rusting. Each individual can write a final conclusion after each group presents their results.

Additional InformationLab experiments and activities would extend the unit further.

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a. Chemical Kinetics Reaction Order and Rate Laws Labb. Factors affecting solution formation: http://chemhnhs.com/ChemHNHS%20Website/PC

%20Chap16/Pearson_Resources16/CHEM12_C1600_LABT.pdfc. Factors Affecting the rate of a reaction:

http://www.chm.uri.edu/gdombi/chm105/10_rates_fall_2010.pdf

AcknowledgementsWilensky, U., Levy, S. T., & Novak, M. (2004). Connected Chemistry curriculum. http://ccl.northwestern.edu/curriculum/chemistry. Center for Connected Learning and Computer-Based Modeling, Northwestern Institute on Complex Systems, Northwestern University, Evanston, IL.

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