Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Big Picture MS-PS1-5. Develop and use a model to describe how the total number of atoms does not change in a chemical reaction and thus mass is conserved.

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Do now Prepare for quiz on balancing equations.

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Do now Balance the following equations. 1. Ca + N 2 → Ca 3 N 2 2. SiO 2 + C → Si + CO 3. P 4 + O 2 → P 2 O 5

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Do now Balance the following equations. 1. 3Ca + N 2 → Ca 3 N 2 2. SiO 2 + 2C → Si + 2CO 3. P 4 + 5O 2 → 2P 2 O 5

Objectives: Understand the cause and effect relationship by analyzing and interpreting data related to the balancing of chemical formulas.  Agenda  Today we will:  Complete a do now quiz.  Teacher presentation.  Group work.  Exit ticket Learning Target  Today I will: Learn how mass is conserved in a chemical reaction by balancing reactions.  So I can: Understand how mass is conserved after a reaction takes place.  I will know I got it if: I can balance a chemical equation in order to demonstrate conservation of mass. Vocabulary Chemical formula Chemical Equation Law of Conservation of mass

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Objectives Understand, create and interpret the naming of chemical formulas. Section 2 Chemical Formulas and Equations Chapter L2

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Agenda Today we will: –Complete a do now. –Learn how to balance chemical equations by teacher instruction and group work. –Exit Ticket.

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Vocabulary Ionic compound Covalent compound

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chemical Formulas A chemical formula is a combination of chemical symbols and numbers to represent a substance. A chemical formula shows how many atoms of each kind are present in a molecule. Section 2 Chemical Formulas and Equations Chapter L2

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chemical Formula Section 2 Chemical Formulas and Equations Click below to watch the Visual Concept. You may stop the video at any time by pressing the Esc key. Visual Concept Chapter L2

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chemical Formulas, continued Writing Formulas for Covalent Compounds You can use the name of a covalent compound to write its chemical formula. The names of covalent compounds use prefixes. Each prefix represents a number, as shown below. Section 2 Chemical Formulas and Equations mono-1hexa-6 di-2hepta-7 tri-3octa-8 tetra-4nona-9 penta-5deca-10 Chapter L2

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chemical Formulas, continued Writing Formulas for Ionic Compounds To write the formula for an ionic compound, make sure the compound’s charge is 0. The formula must have subscripts that cause the charges of the ions to cancel out. Section 2 Chemical Formulas and Equations Chapter L2

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 2 Chemical Formulas and Equations Chapter L2

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chemical Equations Describing Reactions by Using Equations A chemical equation uses chemical symbols and formulas as a shortcut to describe a chemical reaction. From Reactants to Products The starting materials in a reaction are reactants. The substances formed from a reaction are products. Section 2 Chemical Formulas and Equations Chapter L2

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 2 Chemical Formulas and Equations Chapter L2

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chemical Equations, continued The Importance of Accuracy The symbol or formula for each substance in a chemical equation must be written correctly or it will not correctly describe the reaction. Some formulas and symbols can be confused. Section 2 Chemical Formulas and Equations Chapter L2

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chemical Equations, continued The Reason Equations Must Be Balanced Atoms are never lost or gained in a chemical reaction, they are just rearranged. Every atom in the reactants becomes part of the products. When writing a chemical equation, make sure the number of atoms of each element in the reactants equals the number of atoms of those same elements in the products. This is called balancing the equation. Section 2 Chemical Formulas and Equations Chapter L2

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chemical Equations, continued In the 1700s, French chemist Antoine Lavoisier found that the total mass of the reactants was always the same as the total mass of the products. Lavoisier’s work led to the law of conservation of mass, which states that mass is neither created nor destroyed in ordinary chemical and physical changes. Section 2 Chemical Formulas and Equations Chapter L2

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chemical Equations, continued How to Balance an Equation To balance an equation, you must use coefficients. A coefficient is a number that is placed in front of a chemical symbol or formula. For an equation to be balanced, all atoms must be counted. So, you multiply the subscript of each element in a formula by the formula’s coefficient. The next slide shows how to use coefficients to balance an equation. Section 2 Chemical Formulas and Equations Chapter L2

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 2 Chemical Formulas and Equations Chapter L2

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu