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. A synthesis reaction 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 (cont.) 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. Section 9-2

Decomposition Reactions A decomposition reaction 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. Section 9-2

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 Section 9-2

Replacement Reactions (cont.) 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. Section 9-2

Replacement Reactions (cont.) Halogens frequently replace other halogens in replacement reactions. Halogens also have different reactivities and do not always replace each other. Section 9-2

Replacement Reactions (cont.) Double replacement reactions occur when ions exchange between two compounds. This figure shows a generic double replacement equation. Section 9-2

Replacement Reactions (cont.) 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. Section 9-2

Replacement Reactions (cont.) This table shows the steps to write double replacement reactions. Section 9-2

Replacement Reactions (cont.) This table summarizes different ways to predict the products of a chemical reaction. 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