Section 9.1 Reactions and Equations Recognize evidence of chemical change. chemical change: a process involving one or more substances changing into a new substance Represent chemical reactions with equations. Balance chemical 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 ___________________________ This involves a chemical change – where you change the identity of the substance. Section 9-1

Chemical Reactions (cont.) Evidence of a chemical reaction Change in temperature Exothermic (higher T) vs Endothermic (lower T) Change in color Odor, gas, or bubbles may form. Form a precipitant (????) Emission of Light Section 9-1

______________are the starting substances. Chemists use statements called equations to represent chemical reactions. ______________are the starting substances. ______________are the substances formed in the reaction. 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”. 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 _____________________is 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 ______________________in 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. So what are the coefficients on the previous reaction? *Table 9.2 in book shows steps for balancing equations Section 9-1

Balanced equations show this law. Why balance equations? One of the most fundamental laws in chemistry is the law of conservation of mass. Balanced equations show this law. A balanced equation is also like a recipe. 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 A B C D 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 A B C D Section 9-1

Section 9.2 Classifying Chemical Reactions Classify chemical reactions. metal: an element that is a solid at room temperature, a good conductor of heat and electricity, and is generally shiny Identify the characteristics of different classes of chemical reactions. Section 9-2

Section 9.2 Classifying Chemical Reactions (cont.) 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. Section 9-2

Types of Chemical Reactions Chemists classify reactions in order to organize the many types. Why do this? Help predict products before a reaction happens. (Table 9.4 in book) A ________________or_________________ is a reaction in which two or more substances react to produce a single product. Section 9-2

Types of Chemical Reactions (cont.) When two elements react, the reaction is always a synthesis reaction. Section 9-2

Types of Chemical Reactions A __________________________is 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. H2O → H2 + O2 Section 9-2

Types of Chemical Reactions (cont.) In a ______________________oxygen combines with a hydrocarbon (made mostly of C and H) and releases carbon dioxide, water, heat, and light. CH4 + O2 → CO2 + H2O Section 9-2

Types of Chemical Reactions A reaction in which the atoms of one element replace the atoms of another element in a compound is called a _____________________________ A + BX → AX + B “The Player at the Prom” Section 9-2

Replacement Reactions (cont.) _______________________occur when ions exchange between two compounds. “The Perfect Prom” Section 9-2

Replacement Reactions (cont.) The solid product produced during a chemical reaction in a solution is called a ______________________. All double replacement reactions produce either water, a precipitate, or a gas. Section 9-2

A B C D Section 9.2 Assessment Which of the following is NOT one of the four types of reactions? A. deconstructive B. synthesis C. single replacement D. double replacement A B C D Section 9-2

A B C D Section 9.2 Assessment The following equation is what type of reaction? KCN(aq) + HBr(aq) → KBr(aq) + HCN(g) A. deconstructive B. synthesis C. single replacement D. double replacement A B C D Section 9-2

Section 9.3 Reactions in Aqueous Solutions Describe aqueous solutions. Write complete ionic and net ionic equations for chemical reactions in aqueous solutions. Predict whether reactions in aqueous solutions will produce a precipitate, water, or a gas. solution: a uniform mixture that might contain solids, liquids, or gases Section 9-3

Section 9.3 Reactions in Aqueous Solutions (cont.) solute solvent complete ionic equation spectator ion net ionic equation Double-replacement reactions occur between substances in aqueous solutions and produce precipitates, water, or gases. Section 9-3

The solvent is the most plentiful substance in a solution. Aqueous Solutions An ________________________contains one or more dissolved substances (called solutes) in water. The solvent is the most plentiful substance in a solution. Section 9-3

Aqueous Solutions (cont.) Water is always the solvent in aqueous solutions. There are many possible solutes: ie: sugar, alcohol Compounds that produce hydrogen ions in aqueous solutions are acids. Ionic compounds can also be solutes in aqueous solutions. When ionic compounds dissolve in water, their ions separate in a process called dissociation. Gatorade and electrolytes !!! Section 9-3

Types of Reactions in Aqueous Solutions When two solutions that contain ions as solutes are combined, the ions might react. If they react, it is always a ____________________________ reaction. Three products can form: precipitates, water, or gases. Section 9-3