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Learn about chemical reactions and how to represent them with equations. Understand the evidence of chemical change and how to balance chemical equations. (223 characters)
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Chemical Reactions Section 9.1Reactions and Equations Section 9.2Classifying Chemical Reactions Section 9.3Reactions in Aqueous Solutions Click a hyperlink or folder tab to view the corresponding slides. Exit Chapter Menu
Section 9.1 Reactions and Equations • Recognizeevidence of chemical change. chemical change:a process involving one or more substances changing into a new substance • Representchemical reactions with equations. • Balancechemical equations. chemical reaction reactant product chemical equation coefficient Chemical reactions are represented by balanced chemical equations. Section 9-1
Chemical Reactions • The process by which one or more substances are rearranged to form different substances is called a chemical reaction. Section 9-1
Chemical Reactions (cont.) • Evidence of a chemical reaction • Change in temperature • Change in color • Odor, gas, or bubbles may form. Section 9-1
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. Section 9-1
Representing Chemical Reactions (cont.) • In word equations, aluminum(s) + bromine(l) → aluminum bromide(s) reads as “aluminum and bromine react to produce aluminum bromide”. Section 9-1
Representing Chemical Reactions (cont.) • Skeleton equations use symbols and formulas to represent the reactants and products. Al(s) + Br(l) → AlBr3(s) • Skeleton equations lack information about how many atoms are involved in the reaction. Section 9-1
Representing Chemical Reactions (cont.) • A chemical equationis a statement that uses chemical formulas to show the identities and relative amounts of the substances involved in a chemical reaction. Section 9-1
Balancing Chemical Equations • This figure shows the balanced equation for the reaction between aluminum and bromine. Section 9-1
Balancing Chemical Equations (cont.) • 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. Section 9-1
Balancing Chemical Equations (cont.) Section 9-1
Balancing Chemical Equations (cont.) Section 9-1
Balancing Chemical Equations (cont.) Section 9-1
Balancing Chemical Equations (cont.) • The most fundamental law in chemistry is the law of conservation of mass. • Balanced equations show this law. Section 9-1
Balancing Chemical Equations (cont.) Section 9-1
A B C D Section 9.1 Assessment Which of the following is NOT a chemical reaction? A.a piece of wood burning B.a car rusting C.an ice cube melting into water D.red litmus paper turning blue Section 9-1
A B C D Section 9.1 Assessment What is the coefficient of bromine in the equation 2Al(s) + 3Br2(l) → 2AlBr3(s)? A.1 B.2 C.3 D.6 Section 9-1