Balancing Chemical Equations

Learning Resource Type

Learning Activity

Subject Area

Science

Grade(s)

9, 10, 11, 12

Overview

This activity introduces balancing chemical equations through a YouTube video, and then students will model balancing chemical equations.  

This activity is a result of the ALEX Resource Development Summit.

Phase

Before/Engage
During/Explore/Explain
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.

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

Learning Objectives

The students will count the number of atoms in each compound in the chemical equation and then balance chemical equations.

Activity Details

The students will watch the YouTube video to introduce the concept of balancing chemical equations. After watching the video, the students will be given an activity sheet with unbalanced chemical equations (Balancing Chemical Equations Activity Sheet). The students will use neon Expo markers to model the molecules in the chemical equation. They will work together in pairs and will have at least four different colors of Expo markers. For each equation, the students will assign the atoms or polyatomic ions a color and draw a circle for each atom. They will then draw circles to balance the chemical equation.

Assessment Strategies

The teacher will walk around the room to ask the students questions and then will be able to assess the students formatively or summatively after the students complete the sheet of equations.

Variation Tips

If neon Expo markers are not available or they will not work on the desk or table tops, the teacher can use regular markers and butcher paper. Chalk markers also work well with the desk and table tops. If the teacher would like, bingo chips, pop beads or any other items that the teacher may have in at least four different colors may be used for this activity. The teacher can use this method of balancing chemical equations with any sheet of reactions.

Background / Preparation

The teacher will need to make copies of the sheet of equations and obtain four different colored neon Expo markers for each student pair.   

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