To view the presentation as a slideshow, select "View" and click "Slide Show." Click the right arrow or space bar to advance slides. Click on resources or lessons in the menus to go directly to those sections. Press Esc to exit the slideshow. The presentation covers chemical reactions, including formulas, equations, and conservation of mass. Signs of reactions and energy changes are also discussed.

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2. Resources Chapter Presentation Image Bank Math Focus Bellringers Standards Assessment Visual Concepts

3. Table of Contents Section 1 Forming New Substances Section 2 Chemical Formulas and Equations Chapter 9 Chemical Reactions

4. Bellringer The formation of water from its elements may be represented as follows: 2H 2 + O 2  2H 2 O What elements are present in water? How many atoms of each element are shown in the reactants? How many atoms of each element are shown in the products? The representation 2H 2 + O 2  2H 2 O is called a chemical equation. Why do you think that the numbers of atoms do not change? Write your answers in your Science Journal. Section 1 Forming New Substances Chapter 9

5. What You Will Learn Four signs that indicate that a chemical reaction may be taking place are a change in color, the formation of a gas, the formation of a precipitate, and a change in energy. Chemical reactions produce new substances whose chemical and physical properties differ from the properties of the original substances. In a chemical reaction, chemical bonds break and atoms rearrange. Chemical reactions absorb or release energy. Chapter 9 Section 1 Forming New Substances

6. Combining Atoms Through Chemical Bonding Chemical bonding is the joining of atoms to form new substances. An interaction that holds two atoms together is called a chemical bond. When chemical bonds form when electrons are shared ( covalent and metallic bonds ), or when electrons are gained, or lost ( ionic bonds ). Section 1 Electrons and Chemical Bonding Chapter 8

7. 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 that form in a chemical reaction differ from those of the original substances. Chapter 9 Section 1 Forming New Substances

8. Chemical Reactions , continued Signs that indicate a chemical reaction may be taking place are a color change, formation of a gas or a solid, and the release or absorption of energy. A solid that is produced as a result of a chemical reaction in solution is called a precipitate. Chapter 9 Section 1 Forming New Substances

9. Precipitate Chemical Reactions Chapter 9

10. Chemical Reactions , continued Even though the signs that indicate a chemical reaction is taking place are good signals of chemical reactions, they do not always guarantee that a reaction is happening. The most important sign that a chemical reaction has taken place is the formation of new substances that have new properties. Chapter 9 Section 1 Forming New Substances

11. Bonds: Holding Molecules Together A chemical bond is a force that holds two atoms together in a molecule. For a chemical reaction to take place, the chemical bonds in the starting substances must break. The atoms then rearrange, and new bonds form to make new substances. Chapter 9 Section 1 Forming New Substances

12. Chemical Reactions Chapter 9

13. Reactions and Energy Energy is needed to break chemical bonds in the starting substances. (atoms bump into each other with enough force to break the bond). As new bonds form in the final substances, energy is released. A chemical reaction in which energy is released is called an exothermic reaction. Exothermic reactions can give off energy in several forms. Chapter 9 Section 1 Forming New Substances

14. Reactions and Energy , continued A chemical reaction in which energy is taken in is called an endothermic reaction. The energy taken in during an endothermic reaction is absorbed from the surroundings. Photosynthesis is an example of an endothermic process. Chapter 9 Section 1 Forming New Substances

15. Reactions and Energy , continued Neither mass nor energy can be created or destroyed in chemical reactions. The law of conservation of energy states that energy cannot be created or destroyed but can change from one form to another. Chapter 9 Section 1 Forming New Substances

16. Law of Conservation of Energy Chemical Reactions Chapter 9

17. Bellringer Look at the following formulas for chemical compounds, and identify the elements in each formula. NaCl KBr C 12 H 22 O 11 NH 3 SiF 4 Fe(NO 3 ) 3 H 2 O 2 MgSO 4 What is the name and symbol of each element? How many atom of each element are present in each compound? Write your answers in your Science Journal. Section 2 Chemical Formulas and Equations Chapter 9

18. What You Will Learn Chemical formulas are a simple way to describe which elements are in a chemical substance. Chemical equations are a concise way to write how atoms are rearranged in a chemical reaction. A balanced chemical equation shows the law of conservation of mass. Section 2 Chemical Formulas and Equations Chapter 9

19. 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 of element are present in a molecule . Examples: NaCl, H 2 O, NH 3 Section 2 Chemical Formulas and Equations Chapter 9

20. Chemical Formulas , continued

21. Chemical Reactions Chapter 9

22. Chemical Equations A chemical equation uses chemical formulas, chemical symbols, and coefficients to describe a reaction. Example: C + O 2  CO 2 Reactants. The starting materials in a chemical reaction Products. The substances formed from a reaction Section 2 Chemical Formulas and Equations Chapter 9

23. Chemical Equations , continued A chemical equation that has a wrong chemical symbol or formula will not describe the reaction correctly. The total number of atoms of each element in the reactants must equal the total number of atoms of that element in the products . This process is called balancing the equation. Section 2 Chemical Formulas and Equations Chapter 9

24. Chemical Equation Chemical Reactions Chapter 9

25. Chemical Equations , continued The law of conservation of mass states that mass cannot be created or destroyed in ordinary chemical and physical changes. This law means that the total mass of the reactants is the same as the total mass of the products. Section 2 Chemical Formulas and Equations Chapter 9

26. Law of Conservation of Mass Chemical Reactions Chapter 9

27. Chemical Equations , continued A coefficient is a number that is placed in front of a chemical symbol or formula. Section 2 Chemical Formulas and Equations Chapter 9

28. Chemical Equations , continued To balance an equation, change the coefficients—not the subscripts. Changing the subscripts in the formula of a compound changes the compound. Section 2 Chemical Formulas and Equations Chapter 9

29. Chemical Equations , continued

30. Balancing Chemical Equations 1. Count the atoms of each element in the reactants and in the products. If the number of atoms of each element do not match, the equation must be balanced

31. Balancing Chemical Equations

32. Balancing Chemical Equations 2. Place the needed coefficient in front of the molecule so that it gives the same amount of atoms in the reactants and products. 3. Recount the atoms to check if the equation is balanced. If it is not continue to add coefficients and keep counting until the equation is balanced.

33. Balancing Chemical Equations

34. Balancing Chemical Equations

35. Balancing Chemical Equations Try to balance the chemical equations below: Na + O 2  Na 2 O N 2 + H 2  NH 2 Mg + HCl  MgCl 2 + H 2

36. Answers: Check your answers: 4 Na + O 2  2 Na 2 O N 2 + 2 H 2  2 NH 2 Mg + 2 HCl  MgCl 2 + H 2

37. Concept Map Chapter 9 Chemical Reactions Use the terms below to complete the concept map on the next slide. products reactants chemical equations coefficients chemical reactions chemical formulas

38. Chemical Reactions Chapter 9 Concept Map

39. Chemical Reactions Chapter 9 Concept Map

40. End of Chapter 9 Show Chemical Reactions Chapter 9

41. 1. In the sentence “She wrote a chemical formula that showed the parts of the compound,” what does the word compound mean? A. a group of buildings set off and enclosed by a barrier B. a word that consists of two or more elements or parts C. a substance made up of two or more elements that are joined by chemical bonds D. a leaf whose blade is divided into at least two leaflets Chapter 9 Standards Assessment

42. 1. In the sentence “She wrote a chemical formula that showed the parts of the compound,” what does the word compound mean? A. a group of buildings set off and enclosed by a barrier B. a word that consists of two or more elements or parts C. a substance made up of two or more elements that are joined by chemical bonds D. a leaf whose blade is divided into at least two leaflets Chapter 9 Standards Assessment

43. 2. Choose the appropriate form of the word react for the following sentence: “When an atom has one electron in its outer energy level, it _____easily with other atoms.” A. reacting B. reactive C. reaction D. reacts Chapter 9 Standards Assessment

44. 2. Choose the appropriate form of the word react for the following sentence: “When an atom has one electron in its outer energy level, it _____easily with other atoms.” A. reacting B. reactive C. reaction D. reacts Chapter 9 Standards Assessment

45. 3. Which of the following phrases means “a process that changes a substance into another substance”? A. chemical reaction B. physical process C. atomic structure D. buoyant force Chapter 9 Standards Assessment

46. 3. Which of the following phrases means “a process that changes a substance into another substance”? A. chemical reaction B. physical process C. atomic structure D. buoyant force Chapter 9 Standards Assessment

47. 4. Which of the following words or phrases is the closest in meaning to the word identify ? A. observe B. pick out C. acquire D. ask Chapter 9 Standards Assessment

48. 4. Which of the following words or phrases is the closest in meaning to the word identify ? A. observe B. pick out C. acquire D. ask Chapter 9 Standards Assessment

49. Use the diagram below to answer the next question. Chapter 9 Standards Assessment

50. 5. The model above shows the reaction of hydrogen and chlorine. Which of the following best describes the result of the reaction shown in the model? A. Four new diatomic molecules form. B. Bonds are formed between two hydrogen atoms. C. The properties of the new molecules are the same as those of the original molecules. D. Two molecules of a new compound are formed. Chapter 9 Standards Assessment

51. 5. The model above shows the reaction of hydrogen and chlorine. Which of the following best describes the result of the reaction shown in the model? A. Four new diatomic molecules form. B. Bonds are formed between two hydrogen atoms. C. The properties of the new molecules are the same as those of the original molecules. D. Two molecules of a new compound are formed. Chapter 9 Standards Assessment

52. 6. Which of the following contains one oxygen atom? A. H 2 O B. CO 2 C. 2N 2 O D. Co Chapter 9 Standards Assessment

53. 6. Which of the following contains one oxygen atom? A. H 2 O B. CO 2 C. 2N 2 O D. Co Chapter 9 Standards Assessment

54. 7. Atoms are never lost or gained during a chemical reaction. They are just A. rearranged. B. changed into other atoms. C. corrected. D. converted. Chapter 9 Standards Assessment

55. 7. Atoms are never lost or gained during a chemical reaction. They are just A. rearranged. B. changed into other atoms. C. corrected. D. converted. Chapter 9 Standards Assessment

56. 8. Which chemical equation correctly shows the formation of water from hydrogen and oxygen? A. H 2 + O 2  H 2 O B. 2H 2 + O 2  2H 2 O C. H 2 + 2O  H 2 O D. H + O 2  H 2 O Chapter 9 Standards Assessment

57. 8. Which chemical equation correctly shows the formation of water from hydrogen and oxygen? A. H 2 + O 2  H 2 O B. 2H 2 + O 2  2H 2 O C. H 2 + 2O  H 2 O D. H + O 2  H 2 O Chapter 9 Standards Assessment

58. 9. According to the periodic table, what is the chemical makeup of the compound MgCl 2 ? A. the elements manganese and chromium B. the elements mendelevium and chlorine C. the elements magnesium and chlorine D. the elements molybdenum and carbon Chapter 9 Standards Assessment

59. 9. According to the periodic table, what is the chemical makeup of the compound MgCl 2 ? A. the elements manganese and chromium B. the elements mendelevium and chlorine C. the elements magnesium and chlorine D. the elements molybdenum and carbon Chapter 9 Standards Assessment

60. 10. Use the periodic table to locate the elements Na and Cl. What type of compound is created when these two elements react? A. isotopic B. covalent C. ionic D. metallic Chapter 9 Standards Assessment

61. 10. Use the periodic table to locate the elements Na and Cl. What type of compound is created when these two elements react? A. isotopic B. covalent C. ionic D. metallic Chapter 9 Standards Assessment

62. 11. Ammonium sulfate has the chemical formula (NH 4 ) 2 SO 4 . How many atoms does one unit of ammonium sulfate contain? A. 4 B. 7 C. 9 D. 15 Chapter 9 Standards Assessment

63. 11. Ammonium sulfate has the chemical formula (NH 4 ) 2 SO 4 . How many atoms does one unit of ammonium sulfate contain? A. 4 B. 7 C. 9 D. 15 Chapter 9 Standards Assessment

64. 12. Chemical reactions are endothermic or exothermic. Which of the following is an example of an endothermic reaction? A. Ice absorbs energy and melts to form liquid water. B. Wood burns and releases light and heat. C. Fireworks explode and release light. D. Water absorbs energy and decomposes to form hydrogen and oxygen. Chapter 9 Standards Assessment

65. 12. Chemical reactions are endothermic or exothermic. Which of the following is an example of an endothermic reaction? A. Ice absorbs energy and melts to form liquid water. B. Wood burns and releases light and heat. C. Fireworks explode and release light. D. Water absorbs energy and decomposes to form hydrogen and oxygen. Chapter 9 Standards Assessment

66. 13. According to the periodic table, what is the atomic number of zinc, Zn? A. 2.018 B. 30 C. 65.4 D. 19,620 Chapter 9 Standards Assessment

67. 13. According to the periodic table, what is the atomic number of zinc, Zn? A. 2.018 B. 30 C. 65.4 D. 19,620 Chapter 9 Standards Assessment

68. 14. A cake is an example of a A. solution. B. compound. C. mixture. D. nonmetal. Chapter 9 Standards Assessment

69. 14. A cake is an example of a A. solution. B. compound. C. mixture. D. nonmetal. Chapter 9 Standards Assessment

70. Use the diagram below to answer the next question. Chapter 9 Standards Assessment

71. 15. Which of the following best describes the liquids in the graduated cylinder? A. Of the six liquids, corn oil is the least dense. B. The density of the liquids increases from maple syrup to corn oil. C. The density of the top layers holds down less-dense liquids. D. Of the six liquids, maple syrup is the least dense. Chapter 9 Standards Assessment

72. 15. Which of the following best describes the liquids in the graduated cylinder? A. Of the six liquids, corn oil is the least dense. B. The density of the liquids increases from maple syrup to corn oil. C. The density of the top layers holds down less-dense liquids. D. Of the six liquids, maple syrup is the least dense. Chapter 9 Standards Assessment

73. Chapter 9