7 Changes in Matter Chapter 21 Introduction to Chapter 21 Types of There are many different types of reactions that occur around you all of the time. For example, when you breathe you take in oxygen, which reacts with the sugar in your cells. This produces carbon dioxide and water. It also releases energy for your Reactions cells to use or store. This type of reaction is called a combustion reaction. In this chapter you will learn how to classify reactions based on the reactants and products, and whether or not they produce or use energy. Investigations for Chapter 21 21.1 Classifying Reactions How can you predict the products in a reaction? A double-displacement reaction is a chemical reaction in which the ions from the two reactants change places. One of the new compounds formed is sometimes insoluble and forms a cloudy precipitate. In this Investigation, you will develop a set of rules for precipitate formation that will allow you to make predictions about the types of products in double-displacement reactions.
21.2 Energy in Reactions How can you classify reactions based on energy?
You will measure the energy changes in reactions and classify reactions according to how they use or produce energy.
365 Chapter 21: Types of Reactions
Learning Goals
In this chapter, you will: D Distinguish between different types of reactions. D Given the reactants, identify the type of reaction that will occur and predict the products that will be produced. D Analyze energy changes that accompany chemical reactions and classify them as exothermic or endothermic. D Observe reactions of household chemicals to develop a set of rules for precipitate formation. Use these rules to make predictions. D Demonstrate safe practices during laboratory investigations.
Vocabulary
addition reaction dissolution reaction exothermic reaction precipitate combustion reaction double-displacement reaction insoluble single-displacement reaction decomposition reaction endothermic reaction polymerization
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21.1 Classifying Reactions
Most of the products you use every day are the result of chemical reactions. How do manufacturers know which chemical reactions to use when they make their products? In this section, you will learn how to classify reactions. Being able to recognize the types of reactions will help you predict what types of substances will be produced.
Addition reactions
Compounds are In an addition reaction, two or more substances combine to form a new made in addition compound. A good example of an addition reaction is the formation of rust: reactions
A general equation for addition reactions is:
A and B are elements or compounds, and AB is a compound