2. Unit 8- Chemical Reactions

3. Mass and Change Lab Goal- What happens to the mass of an object when they are changed? Part 1:Change the shape of steel wool Part 2: Melting ice Part 3: Burning steel wool Part 4: Dissolved sugar in water Part 5:Dissolved Alka-Seltzer

4. Data The lab groups should report their results on the board so that the entire class data can be recorded. Change should be recorded as + (for a gain) or – (for a loss). Change the shape of steel wool Prediction- Mass Before Mass After Change GroupChange in mass (g)

5. Law of Conservation of Mass This law was developed by a French chemist named Antoine Lavoisier. Lavoisier carefully measured the mass of the reactants and products when carrying out chemistry experiments. He noticed that in every case, the mass of the reactants was ALWAYS equal to the mass of the products.

6. Historical Context- Year was 1776. – He was the first scientist to recognize and name the elements hydrogen and oxygen. – In 1789, he wrote the first chemistry textbook. Oxygen, nitrogen, hydrogen, phosphorus, mercury, zinc and sulphur (list also included 'light' and 'caloric‘). – He was executed, along with hundreds of other nobles, during the French Revolution. Law of Conservation of Mass

7. Key Concept 1: The law of conservation of mass states that mass is neither created nor destroyed in a chemical reaction, it is conserved.law of conservation of mass The mass of the reactants equals the mass of the products. mass reactants = mass products Law of Conservation of Mass

8. Plan of Attack 1.Take pre-assessment on back. 2.Follow the directions step by step. - app i-nigma to read the qr-code 3.I will be walking around to verbally asses understanding and stamping. 4.If you get done and I have not stamped you, please raise your hand and quietly wait.

9. N 2 (g) + H 2 (g) -------> NH 3 (g)

10. End of Day

11. Chemical Reactions Key Concept 2: The process by which one or more substances are rearranged to form different substances is called a chemical reaction.chemical reaction What are some examples of evidence of a chemical reaction?

12. Representing Chemical Reactions Chemists use statements called equations to represent chemical reactions. Reactants are the starting substances.Reactants Products are the substances formed in the reaction.Products This table summarizes the symbols used in chemical equations.

13. Representing Chemical Reactions (cont.) In word equations, aluminum(s) + bromine(l) → aluminum bromide(s) reads as “aluminum and bromine react to produce aluminum bromide”. Key Concept 3: Skeleton equations use symbols and formulas to represent the reactants and products. Al(s) + Br(l) → AlBr 3 (s) Skeleton equations lack information about how many atoms are involved in the reaction.

14. Representing Chemical Reactions (cont.) Key Concept 4: A chemical equation is a statement that uses chemical formulas to show the identities and relative amounts of the substances involved in a chemical reaction.chemical equation

15. Balancing Chemical Equations This figure shows the balanced equation for the reaction between aluminum and bromine.

16. Balancing Chemical Equations (cont.) Subscripts describe the number of atoms present in one molecule (if it is a molecular compound) or in one formula unit (if it is an ionic compound). N 2 (g) + H 2 (g) -------> NH 3 (g) Coefficients are generally used for balancing the chemical equations in accordance with the law of conservation of mass. N 2 (g) + 3 H 2 (g) -------> 2 NH 3 (g)

17. Balancing Chemical Equations (cont.)

20. Key Concept 5: The most fundamental law in chemistry is the law of conservation of mass. Balanced equations show this law.

21. Balancing Chemical Equations (cont.) Key Concept 6: Steps

22. Balancing Chemical Equations (cont.) Two helpful hints 1)Never start with balancing oxygen; you can get into a crazy never ending loop. (But, if oxygen is odd, try to make them not odd at the start). 2)If a polyatomic ion exists on both sides of the equation you can keep it together if balancing is giving you trouble.

23. Balancing Chemical Equations (cont.) Key Concept 7: H 2 + O 2 → H 2 O C 2 H 2 + O 2 → H 2 O + CO 2

24. Balancing Chemical Equations (cont.) Key Concept 8: Dinitrogen pentoxide gas in the presence of a platinum catalyst and high enough temperature forms nitrogen gas and oxygen gas.

25. Balancing Chemical Equations (cont.) Voltage is applied to two electrodes in a solution of iron (III) chloride and a yellow-green gas bubbles form on one electrode and metallic deposits form on the other electrode.

26. A.A B.B C.C D.D Assessment What is the coefficient of bromine in the equation 2Al(s) + 3Br 2 (l) → 2AlBr 3 (s)? A.1 B.2 C.3 D.6

27. Jeopardy Closure 1.Answer: These are added to chemical reactions to not break the Law of Conservation of Matter 2.Answer: When balancing a chemical reaction these cannot be changed 3.Answer: These are changed into a new substances after a reaction.

28. End of Day

29. Types of Chemical Reactions synthesis reaction combustion reaction decomposition reaction single-replacement reaction double-replacement reaction precipitate

30. Classifying Chemical Reactions Key Concept 9: There are four types of chemical reactions: synthesis, combustion, decomposition, and replacement reactions.

31. Types of Chemical Reactions

32. Type of Reaction: Key Concept 10: Synthesis reaction Explanation: Reaction in which two or more simpler substances (elements) react to produce a single product (compound).

33. Types of Chemical Reactions (cont.) Other: When two elements react, the reaction is always a synthesis reaction. General Equation: A+BAB

34. Types of Chemical Reactions Type of Reaction: Key Concept 11: Decomposition Reaction Explanation: Reaction in which a single compound breaks down into two or more elements or new compounds.

35. Decomposition Reactions Other: Decomposition reactions often require an energy source, such as heat, light, or electricity, to occur. General Equation: ABA+B

36. Types of Chemical Reactions Type of Reaction: Key Concept 12: Combustion Reaction Explanation: Reaction where oxygen combines with a substance (normally contains carbon) and releases energy in the form of heat and light.

37. Types of Chemical Reactions (cont.) General Equation: ___+O 2 H 2 O + CO 2 Hunting the ElementsHunting the Elements (Start at 9:40 to 20:12) CH 4 (g) + O 2 (g)  CO 2 (g) + H 2 O (g)

38. Types of Chemical Reactions Correctly Identify the type of reaction: S = synthesisD = decompositionC = combustion 1.NH 3 + H 2 SO 4  (NH 4 ) 2 SO 4 2.C 5 H 9 O + O 2  CO 2 + H 2 O 3.H 2 + O 2  H 2 O 4.NH 4 OH  NH 3 + H 2 O 5.KClO 3 (s)  KCl (s) + O 2 (g) 6.Al (s) + S (s)  Al 2 S 3 (s) 7.NaNO 3 (s)  NaNO 2 (s) + O 2 (g) 8.CO (g) + O 2 (g)  CO 2 (g) 9.CH 4 (g) + O 2 (g)  CO 2 (g) + H 2 O (g) 10.Mg + N 2  Mg 3 N 2

40. Types of Chemical Reactions Type of Reaction: Key Concept 13: Single Replacement Explanation: Reaction in which the atoms of one element replace the atoms of another element in a compound.

41. Replacement Reactions General Equation: MetalsA + BX AX + B HalogenY 2 + BXBY + X 2 Other Info: A metal will not always replace a metal in a compound dissolved in water because of differing reactivates. An activity series can be used to predict if reactions will occur. Hydrogen gas goes here

42. Types of Chemical Reactions Write a balanced chemical equation for each single-replacement reactions involving metals. Zn (s) + AgNO 3 (aq) Zn(s) + H 2 SO 4 (aq) Na(s) + H 2 O(l)

43. Types of Chemical Reactions Write a balanced chemical equation for each single-replacement reactions involving halogens Cl 2 (g) + HBr(aq) I 2 + HCl 2 (aq) Simulations

44. Types of Chemical Reactions Type of Reaction: Key Concept 14: Double Replacement Explanation: Reaction in which the ions exchange between two compounds.

45. Replacement Reactions (cont.) General Equation:

46. Replacement Reactions (cont.) Other: All double replacement reactions produce either water, a precipitate, or a gas. The solid product produced during a chemical reaction in a solution is called a precipitate. precipitate

47. Replacement Reactions (cont.)

48. Types of Chemical Reactions Write a balanced chemical equation for each double-replacement reactions BaCl 2 (aq) + K 2 CO 3 (aq) (a precipitate of barium carbonate is formed) FeS (s) + HCl (aq)(Hydrogen sulfide gas is formed) Get out your practice problems.

49. A.A B.B C.C D.D Exit Pass The following equation is what type of reaction? 1. KCN(aq) + HBr(aq) → KBr(aq) + HCN(g) A.decomposition B.synthesis C.combustion D.single replacement E.double replacement

50. A.A B.B C.C D.D Exit Pass The following equation is what type of reaction? 2. CO (g) + O 2 (g)  CO 2 (g) A.decomposition B.synthesis C.combustion D.single replacement E.double replacement

51. A.A B.B C.C D.D Section Assessment The following equation is what type of reaction? 3. NaNO 3 (s)  NaNO 2 (s) + O 2 (g) A.decomposition B.synthesis C.combustion D.single replacement E.double replacement

52. So what do I really have to be able to do? Identify what type of reaction a chemical equations is. Predict if a single replacement reaction will happen and what the products would be. Predict the products of a double replacement reaction.

54. Replacement Reactions (cont.) Key Concept 15:

55. Types of Chemical Reactions Write a balanced chemical equation for each double-replacement reactions BaCl 2 (aq) + K 2 CO 3 (aq) (a precipitate of barium carbonate is formed) FeS (s) + HCl (aq)(Hydrogen sulfide gas is formed) Get out your practice problems.

56. Solution Everyday definition Answer to a problem A type of liquid Chemistry Solution- uniform mixture that can contain solid, liquid, or gases Solution = Homogenous mixture They are synonyms

57. How a solution is made? Solution consist of a solvent and solute. Key Concept 16: Solvent- the substance that dissolves the solute to form a solution; most plentiful substance in the solution. Key Concept 17: Solute- one or more substance dissolved in a solution. Dissociation

58. Solubility is physical properties. – Physical properties are those properties that can be observed or measured without affecting the composition of the sample. Solubility is the maximum quantity of a substance that may be dissolved in another. The maximum amount of solute that may be dissolved in a solvent. Solubility

59. Effect of Temperature on Solubility Solubility depends on temperature of most solids increases as temperature increases of gases decreases as temperature increases What is sodium chlorides solubility? – Water: 359 g/L – Ammonia: 21.5 g/L – Methanol: 14.9 g/L

60. 59 Soluble and Insoluble Salts Ionic compounds that dissolve in water are soluble salts do not dissolve in water are insoluble salts

61. Key Concept 18: Quick DR Visual Lead (II) NitrateSodium Chloride Pb(NO 3 ) 2 NaCl 1.How do I make an solution? 2.What is the solvent and the solute? 3.What happens during dissociation? 4.What happens in a double replacement reaction? Pb(NO 3 ) 2 (aq) + 2NaCl(aq)  PbCl 2 (s) + 2NaNO 3 (aq)

62. This Week’s plan of attack Today- Complete last three station (if you an your partner get done, work on practice problems) Tuesday- Start Double Replacement Lab Wed- (35 min classes) Complete three more stations Thursday- Finish Double Replacement Lab (due Friday) Friday- Acid and Bases

63. Part 1: (2.5 pts) Purpose: To determine whether or not a reaction occurs and to predict the products of a reaction. Determining Solubility to Solve Double Replacement Reaction (70 pts)

64. (7.5 pts) Safety: We are working with acids; gloves, goggles, and aprons must be worn properly at all times. All chemicals must be disposed of in specified waste beakers in the fume hoods. These chemicals are toxic and will harm the environment if not disposed of properly. Do not eat, drink, or apply the chemicals to skin. Many of these chemicals are highly corrosive and in addition to being toxic, they will burn your skin and muscle tissue. Ouch! If any of the chemicals get on your skin/eyes you MUST wash exposed area for 15 minutes in eye wash/shower. Determining Solubility to Solve Double Replacement Reaction

65. (10 pts) Data Table and Results Determining Solubility to Solve Double Replacement Reaction Beginning Nitrate HCl added H 2 SO 4 added NaOH added LiNO 3 KNO 3 Mg(NO 3 ) 2 Ca(NO 3 ) 2 Co(NO 3 ) 2 Cu(NO 3 ) 2 AgNO 3 Pb(NO 3 ) 2

66. (10 pts) Part 2- 1.All nitrate salts are __________. 2.Most salts containing ______ and ________ cations are soluble. 3.All cations from ______________ are soluble. In addition NH 4 +1 salts are soluble. 4.Salts with halogen anions are usually _____________. 5.Most sulfate salts are __________. Exceptions include the cations __________ and ____________. 6.Hydroxides are usually ___________ except those containing cations from __________. Determining Solubility to Solve Double Replacement Reaction

67. (20 pts) Part 3- 1-11 You will need to answer the questions by predicting products of the double replacement reaction. (20 pts) Part 4- Using solubility tables and charts Determining Solubility to Solve Double Replacement Reaction

69. pH less than 7 Neutralizes bases Acids increase H + cation concentration in water. Key Concept 19: What is an Acid?

70. Key Concept 20: What is an Acid?

71. HCl- hydrochloric- stomach acid H 2 SO 4 - sulfuric acid - car batteries HNO 3 – nitric acid - explosives HC 2 H 3 O 2 - acetic acid - vinegar H 2 CO 3 -carbonic acid – sodas H 3 PO 4 - phosphoric acid -flavorings Common Acid

72. pH greater than 7 Neutralizes acids Forms OH - ions in solution Key Concept 21: What is an Base?

73. NaOH- sodium hydroxide (LYE) soaps, drain cleaner Mg (OH) 2 - magnesium hydroxide-antacids Al(OH) 3 -aluminum hydroxide-antacids, deodorants NH 4 OH-ammonium hydroxide- “ammonia” Common Bases

74. Key Concept 22 : What is an Base?

75. Acids and Bases Common acids include HCl, HNO 3, and H 2 SO 4 Common bases include NaOH, LiOH, and KOH Key Concept 23: Predict the products of these acid-base rxns: HCl + NaOH  HNO 3 + LiOH  H 2 SO 4 + KOH  Do we notice any patterns?

76. Acid and Bases All double replacement reactions produce either water, a precipitate, or a gas.

77. Acids and Bases Because the reaction is a type of double- replacement reaction, H + and OH - always form a product of H 2 O and the other ionic compound is always a salt. Key Concept 24:The products of a reaction between acids and bases are always a salt and water.

78. Acids and Bases The question becomes how much of the solution is water, and how much is acid/base? If the ratio of acid/base to the amount of water is high, then the solution is considered to be strongly acidic or strongly basic. Key Concept 25 : The strength of a solution can be quantified in two ways: pH and Molarity.

79. Acids and Bases pH is typically on a scale of 1-14, however there can be pH values outside of that range. Key Concept 26: A pH of 7 is considered to be completely neutral, non-acidic and non-basic. – Any solution with pH < 7 is considered acidic. – Any solution with pH > 7 is considered basic.

81. Digestion-process by which foods are broken down into simpler substances. Mechanical digestion-physical process in which food is torn apart (mouth) Chemical digestion- chemical reactions in which large molecules are broken down into smaller molecules. (stomach and small intestines) Digestion and pH

82. Mouth-pH around 7. Saliva contains amylase, an enzyme which begins to break carbohydrates into sugars. Stomach- pH around 2. Proteins are broken down into amino acids by the enzyme pepsin. Small intestine-pH around 8. Most digestion ends. Small molecules move to bloodstream toward cells that use them Digestion and pH

83. Acids and Bases In biology and chemistry we can use indicators to approximate a solution’s pH. Key Concept 27: Indicators are chemicals that show different colors above and below the indicator’s pH constant. The color and the pH range it changes colors at vary for different indicators. The most common indicator, phenolphthalein, turns pink in basic solutions (pH > 7) and clear in acidic solutions (pH < 7).

84. Acids and Bases

85. Natural Acids and Bases Indicators

86. Acids and Bases An acid’s or base’s strength can also be measured in terms of “Molarity”. Key Concept 28:Molarity is a measure of the concentration in terms of moles of acid/base per liter of water. Molarity can be expressed with a capital “M” or as a conversion factor: X mol = 1 liter Molarity has a wider range of application than pH, especially in chemistry. Molarity is also required to calculate pH.

87. Acids and Bases Three chemicals were made with the following procedures: – 3.0 mol HCl in 1 liter of water. – 5.5 mol NaOH in 1 liter of water. – 4.0 mol HNO 3 in 2 liters of water. Which is the strongest Acid? (5) 3.0 mol HCl 1 liter 5.5 mol NaOH 1 liter 4.0 mol HNO 3 2 liters = 3.0 M HCl = 5.5 M NaOH = 2.0 M HNO 3 3.0 M HCl is the strongest Acid

88. Acids and Bases Three chemicals were made with the following procedures: – 2.7 mol H 2 SO 4 in 2 liters of water. – 1 mol NaOH in 0.5 liters of water. – 6.6 mol LiOH in 6 liters of water. Which is the strongest base? 2.7 mol HCl 2 liter 1 mol NaOH 0.5 liter 6.6 mol HNO 3 6 liters = 1.35 M H 2 SO 4 = 2.0 M NaOH = 1.1 M LiOH 2.0 M NaOH is the strongest Base

90. Practice What ions are responsible for a acidic solution?

91. Practice What ions are responsible for a basic solution?

92. Practice What is the general conversion factor for Molarity?

93. Practice How does an indicator help us estimate pH?

94. Practice What are the products when an acid react with a base?