1 Unit 3: Reactions

2 Warm Up What makes elements reactive?Which element is more reactive: neon, lithium, or beryllium? An unidentified element has many of the same physical and chemical properties as magnesium and strontium but has a lower atomic mass than either of these elements. What is the most likely identity of this element? A. Sodium B. Beryllium C. Calcium D. Rubidium

3 Today’s Learning ObjectiveDemonstrate that mass is conserved when substances undergo chemical change and that the number and kind of atoms are the same in the reactants and products

4 Block 1 Agenda Warm Up Review Unit 2 Test Conservation of Mass NotesConservation of Mass Lab Conservation of Mass Practice Exit Slip

5 Guiding Questions What are chemical reactions?Why are the same number of atoms of each reactant and product found when a chemical reaction occurs?

6 Chemical Reactions Chemical reactions are taking place all around you and even within you Chemical reaction is a change in which one or more substances are converted into new substances The substances that react are called reactants The new substances produced are called products This relationship can be written as: Produce Reactants Products Give an example of a chemical reaction from your everyday life.

7 Fireworks How It's Made Fireworks

8 Evidence of a Chemical ReactionRelease of a gas Change in temperature Change in color Formation of a precipitate Light or sound are released as a form of energy

9 Keep in Mind Atoms are rearranged in a reaction, but do not disappearSo the total mass of the system and the number of atoms of each element stays the same

10 Law of the Conservation of MassMass cannot be created or destroyed in chemical reactions Matter can be and is changed by the rearrangement of atoms, but the mass cannot change Therefore, the same atoms of matter still exist after a chemical reaction as were present before the reaction Why is it important that mass is conserved in chemical reactions?

11 Exit Slip What is the law of the conservation of mass?If all the reactants in a chemical reaction are completely used, which of the following statements accurately describes the relationship between the reactants and the products? A. The products must have a different physical state than the reactants. B. The total mass of the reactants must equal the total mass of the products. C. The reactants must contain more complex molecules than the products do. D. The density of the reactants must equal the density of the products.

12 Warm Up According to the law of the conservation of mass, how much zinc was present in the zinc carbonate? A. 40 g B. 88 g C. 104 g D. 256 g

13 Today’s Learning ObjectiveUnderstand how to interpret the parts of a chemical equation Be able to identify the 5 types of chemical reactions

14 Block 2 Agenda Warm Up Parts of a Chemical Equation NotesChemical Equations Gizmo Types of Chemical Reactions Notes Exit Slip

15 Guiding Questions What are the parts of a chemical equation?What are the 5 types of chemical reactions and how do you identify them? Why is it important for chemical equations to be balanced and how is this accomplished?

16 Parts of a chemical equationReactants Yield sign Products Coefficients Subscripts Yield Sign Subscripts Image used courtesy of:

17 Symbols Used in Chemical ReactionsMeaning of Symbol (s) A reactant or product in the solid state; also used to indicate a precipitate (l) A reactant or product in the liquid state (g) A reactant or product in the gaseous state (aq) A reactant or product in an aqueous solution (dissolved in water)  or ↔ Used in place of a single arrow to indicate a reversible reaction ↓ Alternative to (s), but used only to indicate a precipitate ↑ Alternative to (g), but used only to indicate a gaseous product Δ → Reactants are heated  Pt Catalyst, in this case platinum, used to increase the rate of the reaction.

18 Writing chemical reactionsDescribing the chemical reaction occurring in the picture: Nickel (II) chloride, dissolved in water, plus sodium hydroxide, dissolved in water, produces solid nickel (II) hydroxide plus sodium chloride, dissolved in water Use a chemical equation with formulas and symbols: NiCl2(aq) + 2NaOH(aq) Ni(OH)2(s) + 2NaCl(aq) Why do we use chemical equations with formulas and symbols?

19 Types of Chemical ReactionsSingle Replacement Double Replacement Synthesis Decomposition Combustion

20 Single Replacement ReactionGeneric Form: A + BY → AY + B Reactants: A is a metal element or diatomic molecule such as chlorine (Cl2) BY is an ionic compound Products: AY is an ionic compound B is a metal element or a diatomic molecule Reaction Mechanism: A and B are elements of the same type (both are metals or both are diatomic non-metals) If A is more reactive than B, the reaction occurs with A replacing B If A is less reactive than B, no reaction can occur

21 Examples of Single Replacement Reactions2 Na(s) + CuCl2(aq) → 2 NaCl(aq) + Cu(s) Sodium is a metal and copper is the metal in the ionic compound Sodium is more reactive than copper, therefore the reaction occurs The sodium replaces the copper ion in the ionic compound and the element copper forms as a precipitate

22 Double Replacement ReactionGeneric Form: AX + BY → AY + BX Reactants: AX is an ionic compound BY is an ionic compound Products: AY is an ionic compound BX is a an ionic compound Reaction Mechanism: A and B are elements of the same type (both are metals ) as are X and Y (both are non-metals) A replaces B and X replaces Y (the ions trade partners) If an insoluble product (precipitate or insoluble gas) is produced, the reaction occurs

23 Examples of Double Replacement ReactionsNa2SO4(aq) + Ba(NO3)2(aq) → 2 NaNO3 (aq) + BaSO4(s) The ions in the two ionic compounds change partners and form two new ionic compounds BaSO4 is not soluble in water BaSO4 is the product of the reaction

24 Synthesis Reaction Generic Form: A + B → AB Reactants: Products:A and B are either elements or simple compounds Products: AB is a complex compound formed from A and B Reaction Mechanism: The atoms of A and B are bonded together to form a single new compound

25 Examples of Synthesis Reactions2 Na + Cl2 → 2 NaCl Sodium atoms and chlorine gas molecules combine to form a single new product Sodium chloride is the product of the reaction Mg + O2 → 2 MgO Magnesium atoms and oxygen gas molecules combine to form a single new product Magnesium oxide is the product of the reaction In a moment, we will also see that this reaction can also be classified as a combustion reaction

26 Decomposition ReactionGeneric Form: AB → A + B Reactants: AB is a complex compound formed from A and B Products: A and B are either elements or simple compounds Reaction Mechanism: The compound AB breaks down into its elements or into simple compounds

27 Examples of Decomposition Reactions2 H2O2 → 2 H2O + O2 Hydrogen peroxide molecules break down to form new products that are simple molecules Water and oxygen gas are the products of the reaction 2 KClO3 → 2 KCl + 3 O2 Potassium chlorate molecules break down when heated to form new products that are simple molecules Potassium chloride and oxygen gas are the products of the reaction

28 Combustion Reaction Generic Form: A + O2 → AO or H2O + CO2 Reactants:A is metal or a hydrocarbon (a compound of hydrogen and carbon) O2 is oxygen gas (we will assume more than enough oxygen is present) Products: If A is a metal, the product is an oxide of the metal If A is a hydrocarbon, the products will be water and carbon dioxide Reaction Mechanism: The reactant is oxidized and produces energy With a metal this reaction is generally slow; with a hydrocarbon the reaction is generally rapid

29 Examples of Combustion ReactionsC2H O2 → 2CO H2O Ethene (also known as acetylene) is a hydrocarbon When O2 is a reactant, the reaction must be combustion The products must be water and carbon dioxide 2 Al + 3 O2 → 2 Al2O3 Aluminum is a metal The product must be an oxide of aluminum – aluminum oxide in this reaction As discussed in the synthesis reaction section, this reaction is both a synthesis and a combustion reaction

30 Review Video CINCH Video: 5 Types of Chemical ReactionsWrite and explain the 5 types of Chemical Reactions

31 Exit Slip When 127 g of copper reacts with 32 g of oxygen gas to form copper (II) oxide, no copper or oxygen is left over. How much copper (II) oxide is produced? A. 32 g B. 95 g C. 127 g D. 159 g What are the parts of a chemical equation?

32 Warm Up Which of these would support the idea that mass is conserved in a reaction that produces a gas as a product? A. Heating the reactants to ensure the reaction occurs in a gaseous state B. Subtracting the mass of the gas from the mass of the solid and liquid products C. Mixing the reactants and measuring their total mass D. Trapping the gas and measuring its mass What type of reaction is A + B AB What type of reaction is AB A + B

33 Today’s Learning ObjectiveBe able to balance chemical equations and demonstrate conservation of mass.

34 Block 3 Agenda Warm Up Review for QuizQuiz 3.1: Conservation of Mass and Parts of a Chemical Equation Balancing Notes Balancing Chemical Equations Gizmo Balancing Practice Exit Slip

35 Guiding Questions How are chemical equations balanced?Why do the number of atoms have to be balanced?

36 Balancing a Chemical ReactionEquations describe chemical reactions showing the reactants and products Since mass must be conserved, the same number of atoms of each element must be present in the products as were in the reactants Individual atoms do not react alone – many atoms react at the same time Atoms are counted using moles The number of moles of each reactant and product must be adjusted to have the same number of atoms on both sides of the reaction That process is known as balancing the reaction Why do we balance chemical equations?

37 How Are Reactions Balanced?It is a process of counting atoms The chemical formula of the compounds or elements cannot be changed – you may not change anything about the reactants or the products themselves Only the coefficients can be changed Changing the number of moles (coefficients), changes the number of atoms of every element in the compound Coefficients (moles) are changed until the same number of each atom are on both sides of the reaction

38 Steps to balancing a chemical equationStep 1: Write a chemical formula for the reactions using formulas and symbols Hydrogen and Oxygen combine to make water H2 (g) + O2 (g) H2O (l) Step 2: Count the atoms in reactants and products Numbers and Kinds of Atoms H2 (g) O2 (g) H2O (l) H 2 O 1

39 Steps to balancing a chemical equationStep 3: Choose coefficients that balance the equation Remember, never change subscripts of a correct formula to balance an equation H2 (g) + O2 (g) H2O (l) 2H2 (g) + O2 (g) H2O (l) Step 4: Check the result to make sure that the balanced reaction is the lowest whole number ratio of the reactants and products

40 Balancing practice Simple balancing using whiteboards1) ____ N2 + ____ H2  ____ NH3 2) ____ KClO3  ____ KCl + ____ O2 3) ____ NaCl + ____ F2  ____ NaF + ____ Cl2 4) ____ H2 + ____ O2  ____ H2O 5) ____ Pb(OH)2 + ____ HCl  ____ H2O + ____ PbCl2 6) ____ AlBr3 + ____ K2SO4  ____ KBr + ____ Al2(SO4)3  7) ____ CH4 + ____ O2  ____ CO2 + ____ H2O 8) ____ C3H8 + ____ O2  ____ CO2 + ____ H2O  9) ____ C8H18 + ____ O2  ____ CO2 + ____ H2O 10) ____ FeCl3 + ____ NaOH  ____ Fe(OH)3 + ____NaCl

41 Exit Slip _______PbO2 ______ PbO + ______ O2What are the coefficients that will balance this chemical equation? A. 2, 1, 1 B. 3, 4, 2 C. 2, 2, 1 D. 4, 3, 2 ___CO(g) + ____O2 (g) ______ CO2 (g) What coefficient values will balance the reaction shown above? A. 2, 2, 1 B. 1, 1, 1 C. 2, 1, 2 D. 1, 2, 2

42 Warm Up K + H2O KOH + H2 What is the coefficient for H2O when the above equation is balanced? A. 1 B. 2 C. 3 D. 4 Which chemical equation supports the law of conservation of mass? A. 2H2O(l) H2 (g) + O2 (g) B. Zn(s) + HCl(aq)  ZnCl2 (aq) + H2 (g) C. Al4C3(s) + H2O(l)  CH4(g) + Al(OH) 3(s) D. CH4 (g) + 2O2 (g) CO2 (g) + 2H2O(g)

43 Today’s Learning ObjectiveAnalyze energy changes that accompany chemical reactions such as those occurring in heat packs, cold packs, and glow sticks and classify them as exothermic or endothermic reactions

44 Guiding Questions What is responsible for the release or absorption of energy when a chemical reaction occurs? How do we determine if a reaction is exothermic or endothermic?

45 Block 4 Agenda Warm Up Review Quiz 3.1 Finish BalancingEnergy Changes Notes Demonstration of Heat Packs, Cold Packs, and Glow Sticks Energy Changes Lab Exit Slip

46 Chemical reactions-energy exchangesA dynamic explosion is an example of a rapid chemical reaction Most chemical reactions proceed more slowly, but all chemical reactions release or absorb energy This energy can take many forms, such as heat, light, sound, or electricity Chemical bonds are the source of this energy Why do chemical bonds contain energy?

47 Chemical reactions-energy exchangesWhen most chemical reactions take place, some chemical bonds in the reactants are broken, which requires energy In order for products to be produced, new bonds must form Bond formation releases energy

48 Exergonic Reactions Less energy is required to break the original bonds than is released when new bonds form Some form of energy, such as light or heat, is given off by the reaction Example: abdomen of a firefly glows as a result of an exergonic reaction that produces visible light

49 Endergonic Reactions Sometimes a chemical reaction requires more energy to break bonds than is released when new ones are formed The energy can be in the form of light, heat, or electricity Example: an electric current passed through water produces hydrogen and oxygen

50 Source of energy being released or absorbedBreaking and formation of bonds Image used courtesy of:

51 Thermal energy absorbedWhen the energy needed to keep a reaction going is in the form of heat, the reaction is called an endothermic reaction Cooking requires the addition of thermal energy to bring about chemical changes in the food Give another example of an endothermic reaction

52 Thermal energy releasedWhen the energy given off in a reaction is primarily in the form of heat, the reaction is called an exothermic reaction The burning of coal and the explosion of dynamite are exothermic reactions Most electricity in the U.S. is produced by burning coal Give another example of an exothermic reaction

53 Every day examples Heat packs Cold packs Glow sticks

54 Exit Slip What is the difference between an exothermic and endothermic chemical reaction? When you activate an instant cold pack, water mixes with a chemical and the pack gets very cold. This is an example of __________________________________________

55 Warm Up Give an example of an exothermic chemical reaction.Give an example of an endothermic chemical reaction. What is the source of energy being released or absorbed when chemical reactions occur?

56 Today’s Learning ObjectiveDescribe types of nuclear reactions such as fission and fusion and their roles in applications such as medicine and energy production

57 Block 5 Agenda Warm Up Review for QuizQuiz 3.2: Balancing and Energy Changes Nuclear Chemistry Notes Nuclear Chemistry Puzzle Exit Slip

58 Guiding Questions What are the different types of nuclear reactions?How do nuclear reactions differ from chemical reactions? What are some everyday applications of nuclear reactions?

59 Nuclear Reactions All nuclear reactions are based on Einstein’s Theory of Relativity At speeds approaching the speed of light energy and light are interchangeable E = mc2 Energy = mass x (speed of light)2 Mass can be converted to energy and vice versa

60 Types of Nuclear ReactionsFission – Splitting of the nucleus into smaller nuclei Fusion – Combining nuclei of light elements into a larger nucleus Radioactive Decay – Spontaneous release of radiation to produce a more stable nucleus Which type of nuclear reaction produces the most energy?

61 Fission Nucleus splits into smaller nuclei when struck by a neutron of sufficient energy Tremendous release of energy When controlled can produce huge amounts of power in nuclear reactors Clean source of energy with no carbon footprint Produces radioactive nuclear waste with long term environmental and health considerations

62 Fission Process

63 Fission and Nuclear Reactors

64 Nuclear energy BrainPop Video (CINCH Nuclear Energy)

65 Fusion Lighter nuclei (such as hydrogen) combined to form heavier nuclei Tremendous release of energy 2H H  He n energy Deuterium Tritium Helium (occurs naturally in water) Powers the sun and stars No practical application to produce usable energy at this time

66 Fusion Process

67 Fusion and solar energyThe nuclei of atoms are positive, so they tend to repel each other When it’s hot enough (millions of degrees Celsius), the kinetic energy of the nuclei can be so great that the nuclei slam into each other and merge The pressure inside the core of the Sun is so great that hydrogen atoms collide and their nuclei fuse together

68 Nuclear Medicine Use of radioisotopes as diagnostic probes in imaging studies Use of radioisotopes in treatment of cancer Iodine-131 used to determine activity of thyroid gland Radiation treatment using cobalt-60, phosphorous-32, gallium-67, and cesium-136 Sodium-24 used to detect constrictions and obstructions in the circulatory system Injections into tumors can destroy the tumor without harming nearby healthy tissue What is another example of nuclear medicine?

69 Nuclear Medicine VideoTargeted Radionuclide Therapy

70 What part of the atom is involved? Outermost electrons Chemical Reactions Nuclear Reactions What part of the atom is involved? Outermost electrons Protons and neutrons in the nucleus How is the reaction started? Atoms are brought closer together with high temperature or pressure, or catalysts, or by increasing concentration of reactants High temperature is required or atoms are bombarded with high-speed particles What is the outcome of the reaction? Atoms form ionic or covalent bonds The number of protons or neutrons in an atom usually changes How much energy is absorbed or released? A small amount A huge amount What are some examples? Burning fossil fuels, digesting food, housecleaning, making medicines, and commercial products Nuclear energy, taking x-rays, treating cancer, irradiating food to sterilize it, the sun generating heat and light

71 Exit Slip What kind of reaction do nuclear power plants use to generate electricity? In nuclear reactions, mass is converted into __________________.

72 Warm Up Do chemical or nuclear reactions release a greater amount of energy? Do fission or fusion reactions release a greater amount of energy? What is powered by fusion reactions? What is powered by fission reactions?

73 Today’s Learning ObjectiveReview Unit 3 Concepts

74 Block 6 Agenda Warm Up Review for QuizQuiz 3.3: Energy Changes and Nuclear Chemistry Review for Unit 3 Test Exit Slip

75 Exit Slip In the procedure shown above, a calcium chloride solution is mixed with a sodium sulfate solution to create the products calcium sulfate precipitate and sodium chloride in solution. What is illustrated by this activity?

76 Warm Up The illustrations show a conservation-of-mass experiment. The solution in the beaker lost mass because — A. materials have less mass at high temperatures B. the mass of the reactants and products was less than 100 g C. sodium sulfate (Na2SO4) is lighter than air D. some of the water molecules turned into gas

77 Today’s Learning ObjectiveDemonstrate level of mastery of Unit 3 concepts

78 Block 7 Agenda Warm Up Review Quiz 3.3 Unit 3 Test Exit Slip

79 Exit Slip Our next Unit is Chemistry Applications. Come up with some every day examples of how chemistry impacts the world we live in.

80 Key Terms Endothermic- accompanied by or requiring the absorption of heat. Exothermic- accompanied by the release of heat. Fission- a nuclear reaction in which a massive nucleus splits into smaller nuclei with the release of energy Fusion- a nuclear reaction in which nuclei combine to form more massive nuclei with the release of energy Nuclear Reactions- a change in the identity or characteristics of an atomic nucleus that results when it is bombarded with an energetic particle, as in fission, fusion, or radioactive decay

81 Key Terms Chemical Change- a change in the chemical composition of a substance to produce a new material with new properties Chemical Equation- a chemical equation is a representation of a chemical reaction where the reactants are on the left hand side and the products on the right hand side Chemical Formula- a representation of a substance using symbols for its constituent elements Chemical Reaction- a process in which one or more substances are changed into others Coefficient- a number placed in front of a term in a chemical equation to indicate how many molecules (or atoms) take part in the reaction Covalent Bond- a chemical bond that involves sharing a pair of electrons between atoms in a molecule.

82 Key Terms Energy Transformation- this refers to energy conversions from one form to another Isotope- forms of the same element that contain equal numbers of protons but different numbers of neutrons in their nuclei Law of Conservation of Mass- law that says that mass cannot be created or destroyed Molecule- a group of atoms bonded together Oxidation Number- represents the number of electrons lost or gained by an atom of that element in the compound Product- a substance produced during a chemical process

83 Key Terms Reactant- a substance that takes part in and undergoes change during a reaction Subscript- a small number placed to the lower right of a symbol in a chemical formula that gives the number of atoms of each element in a molecule of that compound Substance- a particular kind of matter with uniform properties Yield- the amount of product obtained in a chemical reaction