Classroom Resource

Balancing Chemical Equations

Subject Area

Science

Grade(s)

9, 10, 11, 12

Overview

In this PhET activity, students will be able to visualize chemical reactions by viewing 3D representations of atoms and molecules. Students will balance chemical equations by adding or taking away certain numbers of molecules to demonstrate that atoms, and therefore mass, are conserved during a chemical reaction. This activity can be used to introduce the law of conservation of mass or to reinforce the skill of balancing equations.

Science (2015) Grade(s): 09-12 - Physical Science

SC15.PS.5

Use mathematical representations to support and verify the claim that atoms, and therefore mass, are conserved during a simple chemical reaction.

Unpacked Content

UP:SC15.PS.5

Vocabulary

  • Atoms
  • Conservation
  • Chemical reaction
  • Mass
  • Balanced chemical equation
  • Reactants
  • Products
  • Molar mass
  • Avogadro's number
  • Stoichiometry
  • Ion
  • Molecule
  • Law of conservation of mass
  • Polyatomic ion

Knowledge

Students know:
  • Matter can be understood in terms of the types of atoms present and the interactions both between and within them.
  • Chemical reactions, which underlie so many observed phenomena in living and nonliving systems alike, conserve the number of atoms of each type but change their arrangement into molecules.

Skills

Students are able to:
  • Students use the mole to convert between the atomic and macroscopic scale in the analysis.
  • Given a chemical reaction, students use the mathematical representations to predict the relative number of atoms in the reactants versus the products at the atomic molecular scale.
  • Given a chemical reaction, students use the mathematical representations to calculate the mass of any component of a reaction, given any other component.

Understanding

Students understand that:
  • When substances react chemically with other substances to form new substances with different proporties, the atoms are combined and rearranged to form new substances, but the total number of each atom is conserved and the mass does not change.
  • The property of conservation can be used to help describe and predict the outcomes of reactions.

Scientific and Engineering Practices

Using Mathematics and Computational Thinking

Crosscutting Concepts

Energy and Matter
Science (2015) Grade(s): 09-12 - Chemistry

SC15.CHM.5

Plan and conduct investigations to demonstrate different types of simple chemical reactions based on valence electron arrangements of the reactants and determine the quantity of products and reactants.

Unpacked Content

UP:SC15.CHM.5

Vocabulary

  • Chemical reactions
  • Valence electrons
  • Reactants
  • Products
  • Macroscopic level
  • Atomic/ molecular/ particulate level
  • Ionic bonds
  • Covalent/ molecular bonds
  • Types of reactions:
    • synthesis
    • decomposition
    • single replacement/ displacement
    • double replacement/ displacement
    • combustion
  • Chemical reactions
  • Reactants
  • Products
  • Chemical equations
  • Coefficients
  • Subscripts
  • Mass
  • Moles
  • Mole ratio
  • Ratio
  • Atoms
  • Conservation of matter
  • Quantitative
  • Qualitative
  • Stoichiometry

Knowledge

Students know:
  • The total number of atoms of each element in the reactants and in the products is the same.
  • The number and types of bonds that each atom forms is determined by their valence electron arrangement.
  • The valence electron state of the atoms that make up the reactants and the products is based on their location on the periodic table.
  • Patterns of attraction allow the prediction of the type of reaction that occurs.
  • Chemical equations are a mathematical representation of chemical reactions.
  • Coefficients of a balanced chemical equation indicate the ratio in which substances react or are produced.
  • Substances in a chemical reaction react proportionally.
  • The mole is used to convert between the atomic/ molecular/ particulate and macroscopic levels.
  • Mathematical representations may include calculations, graphs or other pictorial depictions.
  • Matter cannot be created or destroyed but is conserved during a chemical change.
  • Substances in a chemical reaction react proportionally.
  • Conversion between the atomic/ molecular/ particulate and macroscopic levels requires the use of moles and Avogadro's number.
  • Mathematical representations may include calculations, graphs or other pictorial depictions of quantitative information.

Skills

Students are able to:
  • Plan an investigation that outlines the experimental procedure, including safety considerations, how data will be collected, number of trials, experimental setup, and equipment required.
  • Conduct an investigation to collect and record data that can be used to classify reactions and determine the quantity of reactants and products.
  • Write correct chemical formulas of products and reactants using valence electron arrangement.
  • Demonstrate that the numbers and types of atoms are the same both before and after the reaction.
  • Identify the numbers and types of bonds in both the reactants and products.
  • Describe how the patterns of reactivity at the macroscopic level are determined using the periodic table.
  • Identify reactants and products in a chemical reaction using a chemical equation.
  • Balance chemical equations.
  • Determine the number of atoms/ molecules and number of moles of each component in a chemical reaction using a balanced chemical equation.
  • Determine the molar mass of all components of a chemical reaction.
  • Calculate the mass number of atoms, molar mass and number of moles of substances in a chemical reaction.
  • Calculate the mass of a component in a chemical reaction given the mass or number of moles of any other component using proportional relationships.
  • Predict the number of atoms in the reactant and product at the atomic or molecular scale.
  • Use mathematical representations to support the claim that atoms and therefore mass are conserved during a chemical reaction.

Understanding

Students understand that:
  • Theories and laws that describe the natural world operate today as they did in the past and will continue to do so in the future.
  • Scientists plan and conduct investigations individually and collaboratively to produce data to serve as the basis for evidence.
  • The periodic table orders elements horizontally by the number of protons and places those with similar properties into columns, which reflect patterns of valence electrons.
  • The fact that atoms are conserved, together with knowledge of chemical properties of the elements involved, can be used to describe and predict chemical reactions.
  • Different patterns may be observed at each level (macroscopic, atomic/ molecular, etc.) and can provide evidence to explain phenomena.
  • Mathematical representations of phenomena are used to support claims and may include calculations, graphs or other pictorial depictions of quantitative information.
  • The total amount of energy and matter in closed systems is conserved.
  • Science assumes the universe is a vast single system in which basic laws are consistent.
  • Mathematical representations of phenomena are used to support claims and may include calculations, graphs or other pictorial depictions of quantitative information.
  • The fact that atoms are conserved, together with the knowledge of the chemical properties of the substances involved, can be used to describe and predict chemical reactions.
  • The total amount of energy and matter in closed systems is conserved.
  • Science assumes the universe is a vast single system in which basic laws are consistent.

Scientific and Engineering Practices

Planning and Carrying out Investigations; Using Mathematics and Computational Thinking

Crosscutting Concepts

Patterns; Scale, Proportion, and Quantity; Energy and Matter
Science (2015) Grade(s): 09-12 - Chemistry

SC15.CHM.5b

Use mathematics and computational thinking to support the claim that atoms, and therefore mass, are conserved during a chemical reaction.
Link to Resource
Balancing Chemical Equations

CR Resource Type

Interactive/Game

Resource Provider

PhET
Accessibility
License

License Type

Attribution

Comments or Notes

Founded in 2002 by Nobel Laureate Carl Wieman, the PhET Interactive Simulations project at the University of Colorado Boulder creates free interactive math and science simulations. PhET sims are based on extensive education research and engage students through an intuitive, game-like environment where students learn through exploration and discovery.

If the teacher does not have a PhET account, he/she can create a FREE account. (More information on how PhET works can be found at Getting Started.)

This work is attributed to:

PhET Interactive Simulations

University of Colorado

https://phet.colorado.edu.

Approved Date

Georgeann Hester
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