Chapter 9 Chemical Reactions
National Standards for Chapter 9 • UCP.3 – Change, constancy, and measurement • UCP.5 – Form and function • A.1 –Abilities necessary to do scientific inquiry • A.2 – Understandings about scientific inquiry • B-2 – Structure and properties of matter • B-3 – Chemical reactions • B-6 – Interactions of energy and matter
Vocabulary/Study Guide • Define each term using the Glossary • Either write on the handout, or use your own paper • This is due on Test Day (tentatively, Thursday, March 6)
Section 1: Reactions and Equations • National Standards: • UCP.3 – Change, constancy, and measurement • UCP.5 – Form and function • A.1 –Abilities necessary to do scientific inquiry • B-2 – Structure and properties of matter • B-3 – Chemical reactions • B-6 – Interactions of energy and matter
Objectives – Section 1 • Recognize evidence of chemical change. • Represent chemical reactions with equations. • Balance chemical equations. REVIEW VOCABULARY: chemical change:a process involving one or more substances changing into a new substance
New Vocabulary chemical reaction reactant product chemical equation coefficient Chemical reactions are represented by balanced chemical equations.
Launch Lab Title: How do you know when a chemical change has occurred? (page 280)
Chemical Reactions • The process by which one or more substances are rearranged to form different substances is called a chemical reaction.
Chemical Reactions • Evidence that a chemical reaction may have occurred: • Change in temperature • Change in color • Odor • Gas bubbles • Appearance of a solid (precipitate)
Representing Chemical Reactions • Chemists use statements called equations to represent chemical reactions. • Reactantsare the starting substances. • Productsare the substances formed in the reaction. • This table summarizes the symbols used in chemical equations.
Representing Chemical Reactions • In word equations, aluminum(s) + bromine(l) → aluminum bromide(s) reads as “aluminum and bromine react to produce aluminum bromide”. • Skeleton equations use symbols and formulas to represent the reactants and products. Al(s) + Br(l) → AlBr3(s) • Both word and skeleton equations lack information about how many atoms are involved in the reaction.
Representing Chemical Reactions • A chemical equationis a statement that uses chemical formulas to show the identities and relative amounts of the substances involved in a chemical reaction.
Representing Chemical Reactions • Practice Problems #1-3, page 284
Balancing Chemical Equations • This figure shows the balanced equation for the reaction between aluminum and bromine.
Balancing Chemical Equations • A coefficientin a chemical equation is the number written in front of a reactant or product, describing the lowest whole-number ratio of the amounts of all the reactants and products.
Representing Chemical Reactions • Practice Problems #4-6, page 287
Balancing Chemical Equations • The most fundamental law in chemistry is the law of conservation of mass. • Balanced equations show this law.
Homework, Section 1 • SECTION 1 REVIEW, Page 288 • Questions #7-13 • Answer with complete sentences • Due tomorrow
Section 2: Classifying Chemical Reactions • National Standards: • UCP.3 – Change, constancy, and measurement • UCP.5 – Form and function • A.1 –Abilities necessary to do scientific inquiry • B-2 – Structure and properties of matter • B-3 – Chemical reactions
Objectives – Section 2 • Classify chemical reactions. • Identify the characteristics of different classes of chemical reactions. Review Vocabulary: metal: an element that is a solid at room temperature, a good conductor of heat and electricity, and is generally shiny
New Vocabulary synthesis reaction combustion reaction decomposition reaction single-replacement reaction double-replacement reaction precipitate There are four types of chemical reactions: synthesis, combustion, decomposition, and replacement reactions.
Types of Chemical Reactions • Chemists classify reactions in order to organize the many types.
Synthesis Reactions • A synthesis reaction is a reaction in which two or more substances react to produce a single product. • When two elements react, the reaction is always a synthesis reaction.
Combustion Reactions • In a combustion reaction, oxygen combines with a substance and releases energy in the form of heat and light. • Heated hydrogen reacts with oxygen to produce heat and water in a combustion reaction. This is also a synthesis reaction.
Combustion Reactions • Practice Problems #14-17, page 291
Decomposition Reactions • A decomposition reactionis one in which a single compound breaks down into two or more elements or new compounds. • Decomposition reactions often require an energy source, such as heat, light, or electricity, to occur.
Decomposition Reactions • Practice Problems #18-20, page 292
Replacement Reactions • A reaction in which the atoms of one element replace the atoms of another element in a compound is called a single replacement reaction. A + BX → AX + B
Replacement Reactions • A metal will not always replace a metal in a compound dissolved in water because of differing reactivities. • An activity series can be used to predict if reactions will occur.
Replacement Reactions • Halogens frequently replace other halogens in replacement reactions. • Halogens also have different reactivities and do not always replace each other.
Replacement Reactions Title: Analyze Trends, page 294
Replacement Reactions • Practice Problems #21-24, page 295
Replacement Reactions • Double replacement reactionsoccur when ions exchange between two compounds. • This figure shows a generic double replacement equation.
Replacement Reactions • The solid product produced during a chemical reaction in a solution is called a precipitate. • All double replacement reactions produce either water, a precipitate, or a gas.
Replacement Reactions • This table shows the steps to write double replacement reactions.
Replacement Reactions • Practice Problems #25-28, page 297
Replacement Reactions • This table summarizes different ways to predict the products of a chemical reaction.
Homework, Section 2 • SECTION 2 REVIEW, Page 298 • Questions #29-34 • Answer with complete sentences • Due tomorrow