Lesson 10 Types of Reactions Lesson Glossary simple composition reaction a reaction in which two or more elements combine to form a compound simple decomposition reaction a reaction in which a compound is broken down into its elements When you study for school, do you put things that are similar together? Do you look for patterns when you try solving a mathematics problem? Similarly, in chemistry, you can group chemical reactions together according to particular patterns in which the reactions occur. The most common types of reactions fall into four groups. You have already studied two of these types of reactions—combustion reactions and neutralization reactions. The other two types of reactions that most common chemical reactions fall under are simple composition reactions and simple decomposition reactions. Turn to page 44 of the textbook and read "Simple Composition Reactions." Here you will see why chemists group reactions together and what kinds of reactions belong to the group of simple composition reactions. 1. List two reasons why chemists use patterns to group reaction types. 2. a. Write the word equation for the reaction of magnesium and oxygen. b. Name the reactants and products in this reaction. c. How many elements are used as reactants? d. What happens to the reactants during this reaction? 3. Describe, in words, the general form of a simple composition reaction. 4. Write the general form of a simple composition reaction using the letters A and B. 5. Are most simple composition reactions exothermic or endothermic? 6. Why is it important to know if a reaction is exothermic or endothermic? Another type of chemical reaction is the simple decomposition reaction. In simple decomposition reactions, a compound is separated into its elements. You have seen this type of reaction in Section 2 when you looked at the electrolysis of water. This reaction requires energy to drive it. Turn to page 45 of the textbook and read "Simple Decomposition Reactions." 7. a. Write the word equation for the electrolysis of water. b. What is the reactant in this reaction? What are the products? 8. In a simple decomposition reaction, the products are always _____________. 9. Write the general form for a simple decomposition reaction using the letters C and D. 10. Most decomposition reactions are endothermic. What does this mean in terms of energy for these reactions? 11. Describe how simple composition reactions compare to simple decomposition reactions. 12. Read "Did You Know?" at the bottom of page 45 of the textbook. How do chemists today protect themselves from the hazards that past experimenters, like Sir Humphry Davy, experienced? You are most likely familiar with the next type of reaction—combustion reactions. Whenever you burn a fuel, a combustion reaction occurs. Examples of combustion reactions include a wax candle burning; a match burning; logs in a fireplace or fire pit burning; and natural gas, propane, or fuel oil burning in your furnace. Read "Combustion Reactions" on page 48 of the textbook. Study Figure 3.7 carefully. 14. a. Write the word equation for the combustion of gasoline in a car. b. What are the reactants in this equation? c. What are the products in this equation? 15. List the six materials shown in Figure 3.7 that are produced from petroleum. 16. Read "Did You Know?" on page 48 of the textbook. Which process appears to be a better use of fossil fuels—using 76 L of petroleum to move a car485 km or using 76 L of petroleum to produce all the goods listed in the reading? If you have ever taken an antacid to relieve an upset stomach, then you havefelt the effects of a neutralization reaction. In this case the antacid (a base) neutralizes the excess stomach acid (an acid) to form a salt and water. Turn to pages 48 and 49 of the textbook and read "Neutralization Reactions." 17. a. Write the word equation for a general neutralization reaction. b. What are the reactants? c. What are the products? 18. a. Write the word equation for the neutralization of stomach acid with magnesium hydroxide. b. One of the products is water. What is the general name for the other product? 19. a. Name the substance forming the white cloud in the picture on page 49 of the textbook. b. Which two substances are combining to form this compound?