Teacher Notes
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Teacher Notes![]() Balancing EquationsStudent Laboratory KitMaterials Included In Kit
Blue bingo chips, 250
Green bingo chips, 250 Magnetic wand Red bingo chips,250 Reproducible student handout Wire-rimmed counting chips, 100 Yellow bingo chips, 250 Additional Materials Required
Colored pencils (optional)*
Cup (to carry chips)* Envelope* Overhead projector† Overhead transparency sheets, 4† Scissors* *for each group †for overhead demonstration Teacher Tips
Correlation to Next Generation Science Standards (NGSS)†Science & Engineering PracticesDeveloping and using modelsUsing mathematics and computational thinking Disciplinary Core IdeasMS-PS1.A: Structure and Properties of MatterMS-PS1.B: Chemical Reactions HS-PS1.A: Structure and Properties of Matter HS-PS1.B: Chemical Reactions HS-PS2.B: Types of Interactions Crosscutting ConceptsPatternsEnergy and matter Performance ExpectationsMS-PS1-1. Develop models to describe the atomic composition of simple molecules and extended structures. Sample Data{12847_Data_Table_1_Counting atoms}
{12847_Data_Table_2_Balancing equations}
Teacher HandoutsRecommended Products
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Student Pages
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Student Pages![]() Balancing EquationsIntroductionAbstract concepts, such as conservation of matter and chemical reactions, can often be difficult to visualize. Matter is conserved during a chemical reaction; however, actually “seeing” this is not easy. In this activity, models of atoms will be used to build molecules, balance chemical equations, label reaction types and visualize how matter is conserved in a chemical reaction. Concepts
BackgroundChemical reactions are occurring all the time in the world—for example, the rusting of metal, the burning of paper, the combustion of fuel and the metabolism of food. What do all of these processes have in common? Each involves a form of chemical change in which matter combines or breaks apart to produce new kinds of matter with different properties. Evidence for a chemical change may involve the release of a gas, a color change, the formation of a precipitate, or changes in heat or light. Any chemical change involves the reorganization of the atoms in one or more substances. For example, when carbon (C) combines with oxygen gas (O2) in the air and burns, carbon dioxide gas (CO2) is formed. This process is represented by a chemical equation, a symbolic expression used in chemistry to represent a chemical reaction. The reactants (carbon and oxygen) are written on the left side of the equation and the products (carbon dioxide) are written on the right side of the equation. A plus sign is used between two substances to indicate reactants combined or products formed. An arrow represents the direction of the reaction and is read as “yields” or “produces”: {12847_Background_Equation_1}
The chemical equation for a reaction provides two important types of information: the nature of the reactants and products (indicated by the correct chemical formula) and the relative numbers of each. The equation often also gives the physical states of the reactants and the products using state symbols, the symbols in parentheses written after the chemical formulas. Solids are represented with (s), liquids with (l), gases with (g) and aqueous solutions with (aq) to indicate that the substance is dissolved in water. The basic types of chemical reactions can be broken down into five general categories: synthesis, decomposition, single replacement, double replacement and combustion. In a synthesis reaction, two or more substances react to form a single product (e.g., X + Y → Z). In a decomposition reaction, a single reactant decomposes or breaks down into two or more products (e.g., A → B + C). In a single replacement reaction, one element replaces another in a compound such that an element combines with a compound to produce an element plus a compound (e.g., X + YZ → XY + Z). In a double replacement reaction, two compounds react to produce two different compounds (e.g., AB + CD → AD + CB). Finally, in a combustion reaction, one reactant (a fuel) combines with oxygen to produce an oxide and water (e.g., Fuel + O2 → CO2 + H2O). Notice that atoms get reorganized in a chemical reaction from the reactant side to the product side. The chemical equation represents the reorganization—bonds are broken and new ones form. The Law of Conservation of Matter states that matter can neither be created nor destroyed in an ordinary chemical reaction. Thus it is important to recognize that in a chemical reaction, atoms are not created or destroyed; they are simply rearranged. All atoms present in the reactants must be accounted for among the products. In other words, there must be the same number of each type of atom on the reactant side and on the product side of the equation representing the reaction. The Law of Conservation of Matter, then, is followed when balancing a chemical equation. The relative numbers of reactants and products in a chemical reaction are indicated by the coefficients in the balanced equation. A coefficient is a small whole number that is written in front of a chemical formula in an equation. When balancing an equation, the identities of the reactants and products must not be changed; thus the formulas of the compounds must never be changed. The only way, then, to balance an equation is to add coefficients. If no coefficient is written, it is assumed to be one. The process of balancing equations involves the following steps and guidelines:
Sometimes groups of atoms act as a single unit. Such a group of atoms is called a polyatomic ion. If a polyatomic ion is used in a formula more than once, it is put in parentheses and the subscript appears outside of the parentheses. When a subscript appears outside of the parentheses, it indicates that all of the elements inside the parentheses should be multiplied by that subscript. For example, the formula for the compound Ca(NO3)2 indicates that there is one calcium atom, two nitrogen atoms and six oxygen atoms. Part I of this activity will concentrate on counting atoms in chemical formulas. Once the task of counting atoms is mastered, then the equation can be balanced. Part II of this activity consists of balancing chemical equations. To do this, colored bingo chips will be used to represent the atoms in each molecule. The “atom” chips will be counted and rearranged until all of the atoms in the equation are conserved and the equation is balanced. Materials
Bingo chips
Data tables Envelope Scissors ProcedurePart 1. Counting Atoms
Helpful Balancing Tips
Student Worksheet PDF |