Introduction to Modeling and Chemical Reactions Physical Science Module 4: Lesson 1-5 Introduction to Modeling and Chemical Reactions

Is solubility in water a physical or chemical property? Chemistry Concepts Physical Properties of matter Color, melting point, boiling point, density, … Can you think of other physical Properties? Chemical Properties of matter Why is Gold and diamond expensive? Why is Hydrogen gas so dangerous? Why does Peroxide bubble when poured on an wound? Is solubility in water a physical or chemical property? Electrical conductivity, thermal conductivity are physical properties of matter Gold and Diamond do not react with much other matter, making it precious as it is meant to last forever. Additional discussion question: When you eat food and it is digested by enzymes, can we get that food back? Solubility in water is a physical property. Water can be evaporated and we get back our compound.

Atoms and Periodic Table Elements are arranged in the Periodic Table according to their atomic number, which determines their chemical properties and chemical reactivity.

Chemical Symbols & Ions Some elements react to give away electrons and some elements react to gain electrons. Examples: Sodium: Na likes to lose an electron to become Na+ Silver: Ag loses an electron  Ag+ Chlorine: Cl gains an electron  Cl- Oxygen: O likes to gain two electrons  O-2 Copper: Cu can lose 1 or 2 electrons  Cu+1 or Cu+2 Aluminum: Al loses 3 electrons to become Al+3 Definition of ion: an atom or molecule with a net electric charge due to the loss or gain of one or more electrons.

Ionic Compounds Ionic Compounds are made of positive ions (cations) and negative ions (anions) held tightly together. When (inorganic) ionic compounds dissolve in water, they separate into their positive and negative ions. States of matter: solid, liquid, gas. Matter that dissolves in water has Aqueous state, and we have a solution. You can discuss how ionic compounds are like magnets. Only water is strong enough to separate the positive ions from the negative ions, allowing those ions to react with other ions in solution. Discuss the reason for the “subscripts” in the ionic compound formula. No need to explain inorganic versus organic compounds.

Examples of Ionic Compounds NaCl (Table Salt) in water: Saline solution AgCl: silver nitrate CuCl2: Copper Chloride Al2O3: aluminum Oxide AgCl (s) in water  AgCl (aq)  Ag+1 (aq) + Cl- (aq)

Video or Live Demonstration Aqueous Silver Nitrate and solid Copper reaction Signs of a chemical reaction: Color change  Formation of gas: bubbles or funny odor Formation of precipitate  Change of temperature  After the video or live demonstration, ask the students which signs of a chemical reaction do they observe: Color change of solution and of the copper rod, but really it is color change in solution and silver precipitate forming on the copper.

StarLogo Nova Base Model Water Molecules setup Silver Nitrate setup Copper rod Setup 150 steps would be enough. With agents created right in the center of Spaceland, the agents can move 50 steps in any 90 degrees direction. But to count agents in the corners of Spaceland, with Pythagoras theorem, the diagonal would be equal to square root of (50)2 + (50)2 about 71 steps from center, there fore about 142 steps between an agent on one corner with another diagonally across at the other corner. Why 200 steps? Would 150 steps be enough?

Running the Model: Simulation What signs of a chemical reaction do you see in this simulation? Assumptions (Abstractions) in this model? Assumptions: Each atom of silver or copper is represented by one computer modelling agent. Each compound of silver nitrate is represented by one computer modelling agent. Each water agent in model corresponds to water molecule (H2O) Copper atoms are stationary and present in a single location. Fluid motion is represented the “Wiggle Walk” for each agent – see silver nitrate tab in workspace.

Lesson 2: Modeling Chemical Reactions Physical Science Lesson 2: Modeling Chemical Reactions

Student Activity #1 Analyzing the Model Use Model Observation Form Download the StarLogo Nova Base model: “silver nitrate and copper reaction” Remix and rename Run the model and have fun analyzing

Student Activity #2 Use the Student Activity Sheet Challenge 1: Modify the model to add or remove some or all of the water molecules in the model. Challenge 2: Modify the code to move the copper rod somewhere else in the solution keeping the number of agents of copper the same.

Lesson 3: Products of Chemical Reactions Physical Science Lesson 3: Products of Chemical Reactions

2 AgNO3 (aq) + Cu (s)  Cu(NO3)2 (aq) + 2 Ag (s) Chemistry Concepts Observed behavior Aqueous silver nitrate added to solid copper will react to form aqueous copper nitrate and solid silver. Chemical Reaction 2 AgNO3 (aq) + Cu (s)  Cu(NO3)2 (aq) + 2 Ag (s) Reactants  Products Balancing chemical equations Limiting reactant and reactant in excess Limiting Reactant - The reactant in a chemical reaction that limits the amount of product that can be formed.  The reaction will stop when all of the limiting reactant is consumed. Excess Reactant - The reactant in a chemical reaction that remains when a reaction stops when the limiting reactant is completely consumed.  The excess reactant remains because there is nothing with which it can react. (http://www.chem.tamu.edu/class/majors/tutorialnotefiles/limiting.htm)

Computer Science Concepts Agents represented by breeds. Default breed in StarLogo Nova is “Turtle”. Breeds can be added and can be renamed. What is missing from the model? What is missing from the model that is in the chemical reaction? One of the products is missing to make this chemical reaction complete.

Computer Science Concepts What is missing from the model? 2 AgNO3 (aq) + Cu (s)  Cu(NO3)2 (aq) + 2 Ag (s) Reactants  Products Did we capture all of the reactants and products in our model? Does our model accurately represent the conservation of mass? What is missing from the model that is in the chemical reaction? One of the products is missing to make this chemical reaction complete.

“silver nitrate and copper reaction” Student Activity #1 Remix and Rename the StarLogo Nova base model: “silver nitrate and copper reaction” Use Student Activity Sheet for guidelines. Challenge: Change the code to add copper nitrate agents to represent the missing chemical product from the model.

Student Activity #2: Experiment Start with the your modified model. Use Experimental Design Form. Challenge: Run experiment at different initial quantities of copper or silver nitrate and get the amount of silver produced. How much silver is produced in each case? Which is the limiting reactant and reactant in excess in each case?

Lesson 4: Complex Ions in Solution Physical Science Lesson 4: Complex Ions in Solution

Ions in water Silver nitrate, Ag(NO3) in water dissociates to one ion of Ag+ and one ion of (NO3)- . Ag(NO3) (s) in water  Ag+ (aq) + NO3- (aq) Copper nitrate, Cu(NO3)2, is an ionic compound that is soluble in water. In water, it dissociates to Cu+2 [or Cu(II)] and two (NO3)- ions. Cu(NO3)2 (aq)  Cu+2 (aq) + 2 (NO3)- (aq)

Copper Nitrate.3H2O or Cu(II).3H2O Complex Ions Copper ions [Cu+2 [or Cu(II)] in water form a complex ion with 3 water molecule which produces the blue hue in the solution. This complex can be referred to as Copper Nitrate.3H2O or Cu(II).3H2O Note: NO3- is a complex negative ion but it a spectator ion in this reaction Ionic Reaction: 2 Ag+ (aq) + 2 NO3- (aq) + Cu (s) ---> Cu2+ (aq) + 2 NO3- (aq) + 2 Ag (s)

Student Activity #1 Copper nitrate in water forms a complex with 3 water molecules, turning solution blue. Challenge: Change the code to create additional breeds Cu(II).H2O Cu(II).2H2O Cu(II).3H2O Start with StarLogo Nova modified model from Lesson 3. Remix and Rename. Use Student Activity Sheet for guidance. Execute your model every time you add a piece of code. Debug if needed. Save often.

Rate of a Reaction Increasing the temperature increases the rate of the reaction because the kinetic energy of the reactants increases. Rate of reaction is determined by how fast the reactants are used up or products formed over time.

Lesson 5: Impacts on rate of reaction Physical Science Lesson 5: Impacts on rate of reaction

Model Abstraction: Mixing In the model, we can change the mixing of ions in solution by altering the Wiggle Walk. Change the maximum number of degrees turned in the left and right turn commands. See the impact of changing how agents move.

Model Abstraction: Kinetic Energy In the model, we can change the number of forward steps from 1 to 2 to 3, to mimic the kinetic energy of ions and molecules.

Student Activity #2: Experiment Challenge: Run experiment at different kinetic energy levels OR different mixing and measure time when half of the copper is used up. Make sure the initial amount of copper and silver nitrate is the same throughout the experiment. Change the number of forward steps from 1 to 2 to 3 for each experiment OR change the maximum turn radius. Measure Time when half the reaction occurred. Multiple trials are needed at every different setting of initial amounts used, at each experiment.

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