Lesson 2: Balancing Chemical Equations and Conservation of Mass

Why is it important to balance chemical equations?

How does the law of conservation of mass apply to chemical reactions?

How can we use balanced equations to make quantitative predictions about chemical reactions?

Chemical equation

Reactants

Products

Coefficient

Subscript

Law of conservation of mass

Balanced equation

NGSS HS-PS1-7: Use mathematical representations to support the claim that atoms, and therefore mass, are conserved during a chemical reaction.

Practice interpreting and analyzing chemical equations.

Develop skills in quantitative reasoning and problem-solving.

Reinforce understanding of proportional relationships.

Students will learn to write and balance chemical equations, understand the law of conservation of mass, and apply these concepts to predict the outcomes of chemical reactions.

To develop students' ability to represent chemical reactions mathematically and understand the fundamental principle of mass conservation in chemical processes.

DOK 1: Recall and reproduce (e.g., identify parts of a chemical equation)

DOK 2: Skills and concepts (e.g., balance simple chemical equations)

DOK 3: Strategic thinking (e.g., predict products and balance more complex equations)

Discuss how balancing equations is used in industrial chemical processes, such as the production of fertilizers or pharmaceuticals.

Explore how different cultures have historically used chemical reactions in cooking, metallurgy, or traditional medicine, emphasizing the universal nature of chemical principles.

Students may think that changing subscripts is an acceptable way to balance equations.

Students might believe that mass is lost or gained during chemical reactions.

Confusion between coefficients and subscripts in chemical formulas.

For struggling learners: Provide step-by-step guides and visual aids for balancing equations.

For advanced learners: Introduce more complex equations or extend to limiting reagent problems.

Use manipulatives or digital simulations to represent atoms and molecules in reactions.

Daily exit tickets with simple balancing problems.

Lab report on a simple reaction demonstrating conservation of mass.

Quiz on balancing equations and applying the law of conservation of mass.

Textbook: Chemistry

Molecular model kits

Digital balance for lab activity (PhET: Balancing Chemical Equation: https://phet.colorado.edu/en/simulations/balancing-chemical-equations)

Equation Writing and Predicting Products https://docs.google.com/document/d/1u-ihlfH8yb7FPbzlWionWYxMow4LBRmn1iuR7BXrjZU/edit?usp=sharing

Worksheets on balancing equations

PhET simulation: "Balancing Chemical Equations"

Video: "Conservation of Mass in Chemical Reactions" (e.g., from Khan Academy)