7.1: Whiz Bang! Chemical reactions are occurring all of the time and all around us. Some of these can be very fun to observe! 7.2: Evidence of a Chemical Reaction In a chemical change, new substances are formed. In order for this to occur, the chemical bonds of the substances break, and the atoms that compose them separate and rearrange themselves into new substances with new chemical bonds. When this process occurs, we call it a chemical reaction. We know that a chemical reaction has occurred because it is accompanied by one or more chemical changes that can be observed. 7.3: Chemical Equations A chemical reaction is the process in which one or more substances are changed into one or more new substances. Chemical reactions are represented by chemical equations. Chemical equations have reactants on the left, an arrow that is read as "yields", and the products on the right. 7.4: Balancing Chemical Equations In chemical reactions, atoms are never created or destroyed. The same atoms that were present in the reactants are present in the products - they are merely reorganized into different arrangements. This means that in a complete chemical equation, the same atoms must be present in equal amounts on the reactant and the product sides of the equation. 7.5: Classifying Chemical Reactions Chemical reactions are classified into types to help us analyze them and also to help us predict what the products of the reaction will be. The five major types of chemical reactions are synthesis, decomposition, single replacement, double replacement, and combustion. 7.6: Combustion Reactions A combustion reaction is one in which a substance reacts with oxygen gas, releasing energy in the form of heat and light. One of the most commonly used combustion reactions is the burning of hydrocarbons as fuel. 7.7: Solubility Rules for Ionic Compounds We often describe ionic compounds, or salts, as being able to dissolve in water. Under most conditions, ionic compounds will dissociate nearly completely into individual ions when dissolved, and so they are classified as strong electrolytes. However, there are some ionic compounds which are not able to be separated by water, and so they are considered insoluble and classified as weak or nonelectrolytes. Solubility rules allow us to distinguish between these two types of ionic compounds. 7.8: Precipitation Reactions A precipitation reaction is a reaction that yields an insoluble product—a precipitate—when two solutions are mixed. Thus precipitation reactions are a subclass of exchange reactions that occur between ionic compounds when one of the products is insoluble. Because both components of each compound change partners, such reactions are sometimes called double-replacement reactions. 7.9: Acid-Base and Gas Evolution Reactions Acids and bases can react with each other to form a salt and water in a double-replacement reaction known as a neutralization reaction. A gas evolution reaction is a chemical process that produces a gas, such as oxygen or carbon dioxide. 7.10: For Future Use 7.11: Exercises Template:HideTOC Thumbnail Chapter 7: Slow-motion capture of a Mylar balloon filled with hydrogen and oxygen gas exploding upon ignition during a test conducted by Anoka-Ramsey Community College chemistry faculty. This page is shared under a CK-12 license and was authored, remixed, and/or curated by Melissa Alviar-Agnew, Henry Agnew, Vicki MacMurdo (Anoka-Ramsey Community College), and Lance S. Lund (Anoka-Ramsey Community College). LICENSED UNDER