1. < BackNext >PreviewMain Chemical Reactions Preview Section 1 Forming New SubstancesForming New Substances Section 2 Chemical Formulas and EquationsChemical Formulas and Equations Section 3 Types of Chemical ReactionsTypes of Chemical Reactions Section 4 Energy and Rates of Chemical ReactionsEnergy and Rates of Chemical Reactions Chapter 14 Concept Mapping

2. < BackNext >PreviewMain Bellringer What do baking bread, launching the space shuttle, and digesting food have in common? Write your answer in your science journal. Chapter 14 Section 1 Forming New Substances

3. < BackNext >PreviewMain Objectives Describe how chemical reactions produce new substances that have different chemical and physical properties. Identify four signs that indicate that a chemical reaction might be taking place. Explain what happens to chemical bonds during a chemical reaction. Chapter 14 Section 1 Forming New Substances

4. < BackNext >PreviewMain Chemical Reactions A chemical reaction is a process in which one or more substances change to make one or more new substances. The chemical and physical properties of the new substances differ from those of the original substances. Chapter 14 Section 1 Forming New Substances

5. < BackNext >PreviewMain Chemical Reactions, continued Signs of Chemical Reactions include color changes, gas formation, the formation of a precipitate (a solid substance formed in a solution), and energy given off as light, thermal energy, or electrical energy. A Change of Properties The most important sign of a chemical reaction is the formation of new substances that have different properties. Chapter 14 Section 1 Forming New Substances

6. < BackNext >PreviewMain Bonds: Holding Molecules Together A chemical bond is an attraction that holds atoms together in a molecule. Breaking and Making Bonds If molecules bump into each other with enough energy, the chemical bonds in the molecules break. The atoms then rearrange, and new bonds form to make new substances. Chapter 14 Section 1 Forming New Substances

7. < BackNext >PreviewMain Chapter 14 Section 1 Forming New Substances

8. < BackNext >PreviewMain Bonds: Holding Molecules Together, continued New Bonds, New Substances Whenever new substances form, their properties differ from the properties of the starting substances. For example, sodium is a violently reactive metal and chlorine is a greenish poisonous gas. The two elements combine to form a white solid called sodium chloride, or table salt. Chapter 14 Section 1 Forming New Substances

9. < BackNext >PreviewMain Bellringer Write the following chemical symbols in your science journal. Then, try to write the names of the elements matching the symbols. HOCNaNClK MgCaAlAuFCuFe Chapter 14 Section 2 Chemical Formulas and Equations

10. < BackNext >PreviewMain Objectives Interpret and write simple chemical formulas. Write and balance simple chemical equations. Explain how a balanced equation shows the law of conservation of mass. Chapter 14 Section 2 Chemical Formulas and Equations

11. < BackNext >PreviewMain Chemical Formulas A chemical formula is a combination of chemical symbols and numbers to represent a substance. A chemical formula shows how many atoms of each kind are present in a molecule. Chapter 14 Section 2 Chemical Formulas and Equations

12. < BackNext >PreviewMain Chemical Formula Chapter 14 Section 2 Chemical Formulas and Equations Click below to watch the Visual Concept. Visual Concept

13. < BackNext >PreviewMain Chemical Formulas, continued Writing Formulas for Covalent Compounds You can use the name of a covalent compound to write its chemical formula. The names of covalent compounds use prefixes. Each prefix represents a number, as shown below. Chapter 14 Section 2 Chemical Formulas and Equations mono-1hexa-6 di-2hepta-7 tri-3octa-8 tetra-4nona-9 penta-5deca-10

14. < BackNext >PreviewMain Chemical Formulas, continued Writing Formulas for Ionic Compounds To write the formula for an ionic compound, make sure the compound’s charge is 0. The formula must have subscripts that cause the charges of the ions to cancel out. Chapter 14 Section 2 Chemical Formulas and Equations

15. < BackNext >PreviewMain Chapter 14 Section 2 Chemical Formulas and Equations

16. < BackNext >PreviewMain Chemical Equations Describing Reactions by Using Equations A chemical equation uses chemical symbols and formulas as a shortcut to describe a chemical reaction. From Reactants to Products The starting materials in a reaction are reactants. The substances formed from a reaction are products. Chapter 14 Section 2 Chemical Formulas and Equations

17. < BackNext >PreviewMain Chapter 14 Section 2 Chemical Formulas and Equations

18. < BackNext >PreviewMain Chemical Equations, continued The Importance of Accuracy The symbol or formula for each substance in a chemical equation must be written correctly or it will not correctly describe the reaction. Some formulas and symbols can be confused. Chapter 14 Section 2 Chemical Formulas and Equations

19. < BackNext >PreviewMain Chemical Equations, continued The Reason Equations Must Be Balanced Atoms are never lost or gained in a chemical reaction, they are just rearranged. Every atom in the reactants becomes part of the products. When writing a chemical equation, make sure the number of atoms of each element in the reactants equals the number of atoms of those same elements in the products. This is called balancing the equation. Chapter 14 Section 2 Chemical Formulas and Equations

20. < BackNext >PreviewMain Chemical Equations, continued In the 1700s, French chemist Antoine Lavoisier found that the total mass of the reactants was always the same as the total mass of the products. Lavoisier’s work led to the law of conservation of mass, which states that mass is neither created nor destroyed in ordinary chemical and physical changes. Chapter 14 Section 2 Chemical Formulas and Equations

21. < BackNext >PreviewMain Chemical Equations, continued How to Balance an Equation To balance an equation, you must use coefficients. A coefficient is a number that is placed in front of a chemical symbol or formula. For an equation to be balanced, all atoms must be counted. So, you multiply the subscript of each element in a formula by the formula’s coefficient. The next slide shows how to use coefficients to balance an equation. Chapter 14 Section 2 Chemical Formulas and Equations

22. < BackNext >PreviewMain Chapter 14 Section 2 Chemical Formulas and Equations

23. < BackNext >PreviewMain Bellringer Are the products of a reaction always more complex than the reactants? Could products be simpler than the reactants? Explain your answers. Write your responses in your science journal. Chapter 14 Section 3 Types of Chemical Reactions

24. < BackNext >PreviewMain Objectives Describe four types of chemical reactions. Classify a chemical equation as one of four types of chemical reactions. Chapter 14 Section 3 Types of Chemical Reactions

25. < BackNext >PreviewMain Synthesis Reactions A synthesis reaction is a reaction in which two or more substances combine to form one new compound. For example, a synthesis reaction takes place when sodium reacts with chlorine to produce sodium chloride, which you know as table salt. Chapter 14 Section 3 Types of Chemical Reactions

26. < BackNext >PreviewMain Decomposition Reactions A decomposition reaction is a reaction in which a single compound breaks down to form two or more simpler substances. Decomposition is the reverse of synthesis. Chapter 14 Section 3 Types of Chemical Reactions

27. < BackNext >PreviewMain Single-Displacement Reactions A single-displacement reaction is a reaction in which an element replaces another element that is part of a compound. The products of single-displacement reactions are a new compound and a different element. Reactivity of Elements In a single-displacement reaction, a more reactive element can displace a less reactive element in a compound. Chapter 14 Section 3 Types of Chemical Reactions

28. < BackNext >PreviewMain Double-Displacement Reactions A double-displacement reaction is a reaction in which ions from two compounds exchange places. One of the products of this type of reaction is often a gas or a precipitate. The next slide shows models of each of the four types of chemical reactions. Chapter 14 Section 3 Types of Chemical Reactions

29. < BackNext >PreviewMain Chapter 14 Section 3 Types of Chemical Reactions

30. < BackNext >PreviewMain Bellringer Now that you know a little about chemical reactions, think about the many chemical reactions that take place around you every day. Describe your favorite chemical reaction. How do you think energy is involved in the reaction? Write your answer in your science journal. Chapter 14 Section 4 Energy and Rates of Chemical Reactions

31. < BackNext >PreviewMain Objectives Compare exothermic and endothermic reactions. Explain activation energy. Interpret an energy diagram. Describe five factors that affect the rate of a reaction. Chapter 14 Section 4 Energy and Rates of Chemical Reactions

32. < BackNext >PreviewMain Reactions and Energy By comparing the chemical energy of the reactants with the chemical energy of the products, you can decide if energy is released or absorbed in the reaction. Exothermic Reactions are reactions in which energy is released. Energy can be released as light, electrical energy, or thermal energy. Chapter 14 Section 4 Energy and Rates of Chemical Reactions

33. < BackNext >PreviewMain Reactions and Energy, continued Endothermic Reactions are reactions in which energy is taken in. The Law of Conservation of Energy states that energy cannot be created or destroyed. The energy released in exothermic reactions was first stored in the chemical bonds of the reactants. And the energy taken in during endothermic reactions is stored in the products. Chapter 14 Section 4 Energy and Rates of Chemical Reactions

34. < BackNext >PreviewMain Rates of Reactions The speed at which new particles form is called the rate of a reaction. Activation Energy is the smallest amount of energy that molecules need to react. A chemical reaction needs a boost of energy greater than or equal to the activation energy before the reaction can start. Chapter 14 Section 4 Energy and Rates of Chemical Reactions

35. < BackNext >PreviewMain Rates of Reactions, continued Sources of Activation Energy Friction is one source of activation energy. In a match, friction provides the energy needed to break the bonds in the reactants and allow new bonds to form. An electric spark in a car’s engine is another source of activation energy. This spark begins the burning of gasoline. Light can also be a source of activation energy for a reaction. Chapter 14 Section 4 Energy and Rates of Chemical Reactions

36. < BackNext >PreviewMain Activation Energy and Chemical Reactions Chapter 14 Section 4 Energy and Rates of Chemical Reactions Click below to watch the Visual Concept. Visual Concept

37. < BackNext >PreviewMain Factors Affecting Rates of Reactions Temperature A higher temperature causes a faster rate of reaction. At high temperatures, particles of reactants move quickly and collide hard and often. At low temperatures, particles move slowly and collide less often. Chapter 14 Section 4 Energy and Rates of Chemical Reactions

38. < BackNext >PreviewMain Factors Affecting Rates of Reactions, continued Concentration In general, a high concentration of reactants causes a fast rate of reaction. Concentration is a measure of the amount of one substance when it is dissolved in another substance. When concentration is high, there are many reactant particles in a given volume. So, there is little distance between particles and the particles collide more often and react faster. Chapter 14 Section 4 Energy and Rates of Chemical Reactions

39. < BackNext >PreviewMain Factors Affecting Rates of Reactions, continued Surface Area is the amount of exposed surface of a substance. Increasing the surface area of solid reactants increases the rate of a reaction. Inhibitors are substances that slow down or stop a chemical reaction. The rate of a reaction decreases in the presence of an inhibitor. Chapter 14 Section 4 Energy and Rates of Chemical Reactions

40. < BackNext >PreviewMain Factors Affecting Rates of Reactions, continued Catalysts are substances that speed up a reaction without being permanently changed. Because it is not changed, a catalyst is not a reactant. A catalyst lowers the activation energy of a reaction, which allows the reaction to happen more quickly. Catalysts called enzymes speed up most reactions in your body. Chapter 14 Section 4 Energy and Rates of Chemical Reactions

41. < BackNext >PreviewMain Concept Mapping Chapter 14 Chemical Reactions Use the terms below to complete the Concept Mapping on the next slide. products reactants chemical equations coefficients chemical reactions chemical formulas

42. < BackNext >PreviewMain Chapter 14 Chemical Reactions

43. < BackNext >PreviewMain Chapter 14 Chemical Reactions