Namrta Bhardwaj

Background Information

Prerequisite knowledge should include nomenclature balancing chemical equations. Mole to mole and mass to mole calculation

It is important that students understand the law of conservation of mass

Students should also be skilled in using ratios and conversion factors in calculations.

Curriculum Expectations

Overall expectations:D2. Investigate quantitative relationships in

chemical reactions, and solve related problems

D3. Demonstrate an understanding of the mole concept and its significance to the quantitative analysis of chemical reactions

Specific expectationsD2.1 Use appropriate terminology related to quantities in

chemical reactions, including, but not limited to: stoichiometry, percentage yield, limiting reagent, mole, and atomic mass [C]

D2.5 Calculate the corresponding mass, or quantity in moles or molecules, for any given reactant or product in a balanced chemical equation as well as for any other reactant or product in the chemical reaction [AI]

D2.6 Solve problems related to quantities in chemical reactions by performing calculations involving percentage yield and limiting reagents [AI]

D3.4 Explain the quantitative relationships expressed in a balanced chemical equation, using appropriate units of measure (e.g., moles, grams, atoms, ions, molecules)

Place in the Curriculum

Placement Within the Unit Counting Atoms and Molecules: The Mole

The Avogadro Constant and the Mole Molar Mass

Chemical Proportions in Compounds Percentage Composition Empirical Formula of a Compound Molecular Formula of a Compound

Quantities in Chemical Reactions Stoichiometry Limiting Reactant Percentage Yield

Misconceptions / Learning Difficulties

When the mass of both reactants is given students have difficulty recognizing that one of the masses is limiting and the other mass is in excess.

randomly select one of the given masses as limiting or excess

assume that the masses are in the correct mole ratios students

assume the smaller mass is the limiting reagent.

Need to point out these are not trick questions Important to stress the common steps in converting

masses into amounts in moles in order to relate to mole ratios in balanced equations.

Demonstrate ReactionWhich reactant is limiting and which is in

excess reactant?

Use copper chloride reacting with Aluminum to illustrate a mass to mole relationship

Container Al:CuCl2 Ratio

Mass of Al Foil/g

A Control 0.00B 1:1 mass

ratio2.06

C 1:1 mole ratio

2.06

D 2:3 mass ratio

1.37

E 2:3 mole ratio

0.27

MisconceptionsIf reactants are in the same physical state the

reaction reaches completion when both reactants are totally converted

Or

If the reactants are in two different physical states (solid and liquid) the reaction reaches completion when the entire solid is consumed.

Reaction of Mg with HCl

MisconceptionsStudents have limited view of chemical

system since they have been taught to consider a reaction system as: reactants -> products

rewrite equation as: Reactants -> Products + excess reactant

Gizmo Activity

Gizmo Activity

Gizmo Activity

Supporting Diverse Student NeedsChallenge gifted students -How many grams of a

particular starting material will remain at the end of a reaction?

Encourage gifted students to develop their own methods for solving problems - do not follow given format

ELL students have difficulty understanding verbal explanations - may benefit from writing out the thought process used in solving sample problems.

Students that required more support may be given more scaffolding and support in questions.

Have students make common sense prediction when solving problems.

Lesson Sequence Teaching Strategies Learning Styles (MI) Assessment

Take up homework , Review mass to mass calculation

Use hot dogs and hot dog bun analogy to introduce concept of limiting reactants

Demo- Na – Water rxn

Have students provide alternative analogies

Copper chloride and Aluminum lab

Teacher directed – student participate

Discussion

Demo

Think-pair-share

Demo

Visual, Auditory(Logical/ Mathematical)

Auditory(Verbal/ Linguistic, Logical/ Mathematical)

Visual, Auditory (visual/ spatial)

Auditory (Verbal/ Linguistic, Intrapersonal, Interpersonal)

Visual, Auditory (visual/ spatial, Logical/ Mathematical)

For learningHomework check, assess student’s answers as homework is being taken up

Lesson Sequence Teaching Strategies Learning Styles (MI) AssessmentHave students brainstorm practical reasons for having limiting reactants

Have students conduct baking soda and vinegar lab (or Mg and HCl) lab

Discussion

Guided inquiry

Auditory(Verbal/ Linguistic)

Kinesthetic (kinesthetic, visual/spatial)

Exit pass: For the reaction of copper chloride and aluminum which of the statements is true and explain why:  Equal masses of reactants will react completely in a chemical equation. Chemicals react based on mole ratios found in a chemical equation.  Chemicals react based on mass ratios found in a chemical equation.  Equal moles of reactants will react completely in a chemical reaction.

Lesson Sequence Teaching Strategies

Learning Styles (MI) Assessment

Solve sample problems

Provide students with a flow chart to follow

Start with balanced chemical reactions that has reactants in a 1:1 mole ratio

Progress to more difficult sample problems

Direct instruction Visual, Auditory(visual/ spatial, logical/ mathematical)

For learning 3...2...13 things I know about stoichiometry.....2 things I am getting better at......1 thing I still need help with......

Lesson Sequence Teaching Strategies Learning Styles (MI) Assessment

Day 3Extra practiceHave groups display answers on white boards – gallery walk

Cooperative grouping

Visual, Auditory(visual /spatial, Logical/ Mathematical)

As learning and for learningAssess student’s cooperative skills, participation skills and answers to questions

Day 4Quiz on limiting and excess reactantsPercent Yield Calculations

Direct Instruction Visual, Auditory(Logical/ Mathematical)

Of learning – mark quiz

Day 5Conduct Limiting and excess lab with percent yield calculation

Guided inquiry Visual, Kinesthetic (visual / spatial, kinesthetic)

Of learning- collect and mark lab

Applications and Societal Implications

Careers in Chemistry – Chemical EngineerCooking recipes, industrial reactions, prescription

drug dosages, manufacturing, building (constructions)

The amount of carbon on earth is the ultimate limiting reagent for the number of people the earth can have and in the sense that carbon is our "food"... the land area of the earth is a "limiting reagent" that will limit our population before carbon does.... L. H. Holmes Jr.

Advanced PreparationDay 1Refer to Interactive Demonstrations for Mole Ratios

and Limiting Reagents (annotated reference 1) and prepare material for the lab accordingly.

Refer to How Big Is the Balloon? Stoichiometry Using Baking Soda and Vinegar (annotated reference 6) and prepare material for the lab accordingly.

Day 5Refer to pg 165 of the Nelson teacher’s resource for

percentage yield in a chemical reaction lab and prepare material for the lab accordingly.

Safety ConsiderationsRemember to always wear safety goggles. Reaction of Na with water demoNever use a piece of sodium larger than a ½ pea

r. The reaction should be carried out behind a clear

safety barrier or at a distance from the students Reaction of Copper (II) chloride with AluminumCopper(II) chloride is toxic by ingestion and

irritating to skinAluminum will also react with the solution to

produce hydrogen gas. Flames should not be used in this investigation

Reaction of baking soda with vinegarAvoid getting baking soda or vinegar in eyes

Annotated ReferencesBreyfogle, Bryan. (2006) Interactive Demonstrations for Mole Ratios and Limiting Reagents. Journal of Chemical Education,

85 (5), 741.The demonstration of the mole and mass ratios for the reaction of CuCl2 and Al were obtained from this article.  Clyde, Dillard R. (1972) Two Lecture Experiments Demonstrating Limiting Quantities. Journal of Chemical Education, 49

(12), A694.Resource used for conducting limiting reactant experiment using Mg and HCl. Gauchon, Laure, et al. (2007) Learning About Stoichiometry: From Students’ Preconceptions to the Concept of Limiting

Reactant . Chemistry Education Research and Practice, 8 (4), 362-375.Article discusses many misconceptions that student encounter with studying limiting reactants. Holmes, L. H. Jr. (1998) Limiting Reagent and Kinetics: Social Implications and Malthus' Prediction. Journal of Chemical

Education, 75 (8), 1004.Interesting article that discusses food supply and land area in terms of limiting reagents. Jenkins, Frank, et al. (2002). Chemistry 11. Toronto: Nelson. (course textbook) Journal’s Editorial Staff (1997). How Big Is the Balloon? Stoichiometry Using Baking Soda and Vinegar. Journal of Chemical

Education, 74 (2), 1328A-1328B.Article used for the Baking soda and vinegar lab. Resource used for conducting limiting reactant experiment using vinegar and baking soda.Kalanter, A.H. (1985) Limiting Reagent Problems Made Simple for Students. Journal of Chemical Education, 62 (2), 106.Article used to for the ICE method for solving limiting reactants. Mustoe, Frank, et al. (2201). Chemistry 11. Toronto: McGraw-Hill Ryerson. (course textbook)

Annotated ReferencesWebsites:http://www.chalkbored.com/lessons/chemistry-11.htmgood power point presentation on limiting/ excess

reactants, also the chart method for solving limiting reactant problems was taken from this site

 http://www.youtube.com/watch?v=xk7PSpFC7NI&feature=relateddemonstration of the flaming table and whoosh

bottle  http://www.chemprofessor.com/flow chart method was obtained from this site