Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu A chemical reaction is the process by which one or more substances change into one or more new substances. Reactants are the original substances in a chemical reaction. Products are the substances that are created in a chemical reaction. Section 1 Describing Chemical Reactions Chapter 8 Chemical Reaction

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Visual Concepts Chemical Reaction Chapter 8

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Evidence of a Chemical Reaction Section 1 Describing Chemical Reactions Chapter 8

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Visual Concepts Click below to watch the Visual Concept. Visual Concept Signs of a Chemical Reaction Chapter 8

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Visual Concepts Click below to watch the Visual Concept. Visual Concept Precipitate Chapter 8

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Evidence of a Chemical Reaction Section 1 Describing Chemical Reactions solution color changes solution bubbles copper is used up Chapter 8

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chemical Reaction Versus Physical Change chemical change – new substance forms with properties that differ from original substance density boiling point melting point physical change - changes of state evaporation condensation melting freezing Section 1 Describing Chemical Reactions Chapter 8

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Reactions and Energy Changes Energy can be released in a chemical reaction. methane + oxygen  carbon dioxide + water + energy Energy is a product. Energy can be absorbed in a chemical reaction. dinitrogen tetroxide + energy  nitrogen dioxide Energy is a reactant. Section 1 Describing Chemical Reactions Chapter 8

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Constructing a Chemical Equation A chemical equation shows the chemical formulas and relative amounts of all reactants and products. A word equation contains the names of the reactants and products. Equations must be balanced. Section 1 Describing Chemical Reactions Chapter 8

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Writing a Word Equation or Formula Equation methane + oxygen  carbon dioxide + water ?CH 4 + ?O 2  ?CO 2 + ?H 2 O Section 1 Describing Chemical Reactions Chapter 8

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Equations and Reaction Information Physical States NaHCO 3 (s) + HC 2 H 3 O 2 (aq)  NaC 2 H 3 O 2 (aq) + CO 2 (aq) + H 2 O(l) solid liquid Section 1 Describing Chemical Reactions Chapter 8 catalyst N 2 (g) + 3H 2 (g) 2NH 3 (g) aqueous solutions Reaction Conditions 350°C, kPa

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Equations and Reaction Information Section 1 Describing Chemical Reactions Chapter 8

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Visual Concepts Click below to watch the Visual Concept. Visual Concept Chemical Equation Chapter 8

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Reactions Conserve Mass Mass cannot be created or destroyed by a chemical or physical change Equations must be balanced. ?Na + ?H 2 O  ?NaOH + ?H 2 Section 2 Balancing Chemical Equations Chapter 8

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Balancing Equations The number of atoms for each element must be the same on the reactants’ side and on the products’ side. A coefficient multiplies the number of atoms of each element in the formula that follows. H 2 O: 2 hydrogen atoms, 1 oxygen atom 2H 2 O: 4 hydrogen atoms, 2 oxygen atoms Section 2 Balancing Chemical Equations Chapter 8

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Visual Concepts Click below to watch the Visual Concept. Visual Concept Reading a Chemical Equation Chapter 8

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Visual Concepts Click below to watch the Visual Concept. Visual Concept Balancing a Chemical Equation by Inspection Chapter 8

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Balancing Equations Sample Problem A Balance the equation for the reaction of iron(III) oxide with hydrogen to form iron and water. Section 2 Balancing Chemical Equations Chapter 8

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Balancing Equations Sample Problem A Solution 1.Identify reactants and products. reactants products Section 2 Balancing Chemical Equations ReactantsProductsBalanced? Unbalanced formula equationFe 2 O 3 + H 2 Fe + H 2 O Iron atoms21no Oxygen atoms31no Hydrogen atoms22yes 332 Chapter 8 3.Insert coefficients. 2.Count atoms Fe 2 O 3 + H 2  Fe + H 2 O

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Reactions Conserve Mass Balanced equations show mass conservation ?Na + ?H 2 O  ?NaOH + ?H 2 2Na + 2H 2 O  2NaOH + H 2 Never change subscripts to balance equations Unbalanced: H 2 + O 2  H 2 O Incorrect:H 2 + O 2  H 2 O 2 H 2 O  H 2 O 2 Correct:2H 2 + O 2  2H 2 O Section 2 Balancing Chemical Equations Chapter 8

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Reactions Conserve Mass Section 2 Balancing Chemical Equations Chapter 8

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Polyatomic Ions can be balanced as a group Section 2 Balancing Chemical Equations Chapter 8

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Balancing Equations Sample Problem C Aluminum reacts with arsenic acid, HAsO 3, to form H 2 and aluminum arsenate. Write a balanced equation for this reaction. Section 2 Balancing Chemical Equations Chapter 8

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Balancing Equations Sample Problem C Solution 1. Identify reactants and products. reactants products Al + HAsO 3  H 2 + Al(AsO 3 ) 3 2. Count Atoms Section 2 Balancing Chemical Equations ReactantsProductsBalanced? Unbalanced formula equationAl + HAsO 3 H 2 + Al(AsO 3 ) 3 Iron atoms 11yes Oxygen atoms 12no Hydrogen atoms 13no 3226 Chapter 8 3. Insert coefficients

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 3 Classifying Chemical Reactions Combustion Reactions A combustion reaction is a reaction of a carbon- based compound with oxygen. Combustion of propane: C 3 H 8 + 5O 2  3CO 2 + 4H 2 O Combustion of ethanol: CH 3 CH 2 OH + 3O 2  2CO 2 + 3H 2 O Chapter 8

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Visual Concepts Click below to watch the Visual Concept. Visual Concept Chapter 8 Combustion Reaction

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 3 Classifying Chemical Reactions Synthesis Reactions In a synthesis reaction a single compound forms from two or more reactants. Two elements form a binary compound C + O 2  CO 2 2C + O 2  2CO Two compounds form a ternary compound CaO(s) + H 2 O(l)  Ca(OH) 2 (s) CO 2 (g) + H 2 O(l)  H 2 CO 3 (aq) Chapter 8

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Visual Concepts Click below to watch the Visual Concept. Visual Concept Chapter 8 Synthesis Reactions

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 3 Classifying Chemical Reactions Decomposition Reactions In a decomposition reaction a single compound breaks down, often with the input of energy, into two or more elements or simpler compounds. Decomposition of water electricity heat Chapter 8 CaCO 3 (s)CaO(s) + CO 2 (g) A metal carbonate decomposes to form a metal oxide and carbon dioxide. 2H 2 O(l)O 2 (g) + 2H 2 (g)

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Visual Concepts Click below to watch the Visual Concept. Visual Concept Chapter 8 Decomposition Reaction

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Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 3 Classifying Chemical Reactions Decomposition Reactions, continued Sample Problem D Predicting Products Predict the product(s) and write a balanced equation for the reaction of potassium with chlorine. Chapter 8

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 3 Classifying Chemical Reactions Decomposition Reactions, continued Sample Problem D Solution Reaction is most likely a synthesis reaction, so the product will be binary Potassium will lose one electron to become a 1+ ion. Chlorine will gain one electron to become a 1– ion. K + Cl 2  KCl Balance the equation. 2K + Cl 2  2KCl Chapter 8

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 3 Classifying Chemical Reactions Displacement Reactions In a displacement reaction a single element reacts with a compound and displaces another element from the compound. 2Al(s) + 3CuCl 2 (aq)  2AlCl 3 (aq) + 3Cu(s) Aluminum displaces copper. Chapter 8

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Visual Concepts Single Displacement Reaction Chapter 8

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 3 Classifying Chemical Reactions Displacement Reactions, continued The activity series ranks the reactivity of elements Chapter 8

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Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 3 Classifying Chemical Reactions Displacement Reactions, continued Sample Problem E Determining Products by Using the Activity Series Magnesium is added to a solution of lead(II) nitrate. Will a reaction happen? If so, write the equation and balance it. Chapter 8

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 3 Classifying Chemical Reactions Displacement Reactions, continued Sample Problem E Solution 1.Identify the reactants. Magnesium will attempt to displace lead from lead(II) nitrate. 2.Check the activity series. Magnesium is more active than lead and displaces it. 3.Write the balanced equation. Mg + Pb(NO 3 ) 2  Pb + Mg(NO 3 ) 2 Chapter 8

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 3 Classifying Chemical Reactions Double-Displacement Reactions In a double-displacement reaction two compounds in aqueous solution appear to exchange ions and form two new compounds. One of the products must be a solid precipitate, a gas, or a molecular compound, such as water. HCl(aq) + NaOH(aq)  HOH(l) + NaCl(aq) Chapter 8

Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Visual Concepts Chapter 8 Double-Displacement Reaction

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Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Identifying Reactions and Predicting Products Chapter 8