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Chemical Reactions

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					Chemical Reactions

Table of Contents
Observing Chemical Change


Describing Chemical Reactions


Controlling Chemical Reactions


Fire and Fire Safety
Chemical Reactions - Observing Chemical Change

          Properties and Changes in Matter
   Matter can undergo both physical change and
   chemical change.
Chemical Reactions - Observing Chemical Change


             Energy in Chemical Changes
                              A student places two substances
                              in a flask and measures the
                              temperature once per minute
                              while the substances react. The
                              student plots the time and
                              temperature data and creates
                              the graph at left.
Chemical Reactions - Observing Chemical Change


             Energy in Chemical Changes
                              Reading Graphs:

                                What was the temperature in
                                the flask at 4 minutes? When
                                was the first time the
                                temperature was at 6ºC?

                                At 4 minutes the temperature
                                in the flask was about 23ºC.
                                The first time the temperature
                                was 6ºC was at about 7
                                minutes.
Chemical Reactions - Observing Chemical Change


             Energy in Chemical Changes
                              Calculating:

                                How many degrees did the
                                temperature drop between
                                2 minutes and 5 minutes?


                                20ºC
Chemical Reactions - Observing Chemical Change


             Energy in Chemical Changes
                              Interpreting Data:

                                Is the reaction endothermic or
                                exothermic? Explain.




                                The reaction was
                                endothermic; it absorbed
                                thermal energy from the
                                reaction mixture, causing the
                                temperature to drop.
Chemical Reactions - Observing Chemical Change


             Energy in Chemical Changes
                              Inferring:

                                At what temperature did the
                                reaction stop? How can you
                                tell?


                                The reaction stopped at about
                                2ºC. You can tell because
                                that is the lowest temperature
                                reached.
Chemical Reactions - Observing Chemical Change


             Energy in Chemical Changes
                              Drawing Conclusions:
                                Suppose the temperature in
                                the flask increased instead of
                                decreased as the reaction
                                occurred. In terms of energy,
                                what kind of reaction would it
                                be? Explain.
                                If the temperature increased,
                                the reaction would be
                                exothermic; an exothermic
                                reaction is one in which
                                energy is released.
Chemical Reactions - Observing Chemical Change


                     Asking Questions
   Before you read, preview the red headings. In a graphic
   organizer like the one below, ask a what or how question for
   each heading. As you read, write answers to your questions.
                  Properties and Changes of Matter
       Question                     Answer
       What are physical           Physical properties are
       properties of matter?       characteristics that can be
                                   observed without changing
                                   one substance into another.
       What is the evidence for    The evidence for chemical
       chemical reactions?         reactions is the formation of
                                   new substances and
                                   changes in energy.
Chemical Reactions - Observing Chemical Change

              Links on Chemical Changes




      Click the SciLinks button for links on chemical changes.
Chemical Reactions




         End of Section:
           Observing
           Chemical
            Change
Chemical Reactions

                     Noggin Knockers
Chemical Reactions

                     Learning Objectives
  1. Apply the principle of the conservation of mass to chemical
     reactions (in other words, balance chemical equations
     correctly).



  2. Identify what a chemical equation contains (with an example).



  3. Explain what a balanced chemical equation must show.



  4. Identify the 4 main types of chemical reactions. (Just synthesis
     reactions today)
Chemical Reactions

     Conservation of Mass Demo (with Lab Write-up)
   Goal- Determine if mass was conserved (remained constant)
   for the reaction of copper (II) sulfate with sodium hydroxide
   to form copper (II) hydroxide: Cu(OH)2.

   Data: Mass before = ?
         Mass After = ?

   Conclusion: Was mass conserved? How do you know?
Chemical Reactions - Describing Chemical Reactions

                  Conservation of Mass
    The principle of conservation of mass states that in a
    chemical reaction, the total mass of the reactants must
    equal the total mass of the products. This is why we must
    balance chemical equations (because mass is conserved)!
Chemical Reactions

             Conservation of Mass Review

   For the reaction A + B     AB, which masses are equal?

     1.   Mass of A = Mass of B
     2.   Mass of B = Mass of AB
     3.   Mass of A = Mass of AB
     4.   Mass of A + Mass of B = Mass of AB
Chemical Reactions - Observing Chemical Change

          Properties and Changes in Matter
   Chemical reactions occur when bonds break and new bonds
   form.
Chemical Reactions - Describing Chemical Reactions

             Describing Chemical Reactions
    Cellular phone messages make use of symbols and
    abbreviations to express ideas in shorter form. Similarly,
    chemists often use chemical equations in place of words.
Chemical Reactions - Describing Chemical Reactions

            What Are Chemical Equations?
    Chemical equations use chemical formulas and other
    symbols instead of words to summarize a reaction.
Chemical Reactions - Describing Chemical Reactions

                     Chemical Formulas
  The formula of a compound identifies
  the elements in the compound and the
  ratios in which their atoms are present.
Chemical Reactions - Describing Chemical Reactions


            Balancing Chemical Equations
                               Magnesium metal (Mg) reacts
                               with oxygen gas (O2), forming
                               magnesium oxide (MgO). To
                               write a balanced equation for
                               this reaction, first write the
                               equation using the formulas of
                               the reactants and products, then
                               count the number of atoms of
                               each element.
Chemical Reactions - Describing Chemical Reactions

             Balancing Chemical Equations
    To describe a reaction accurately, a chemical equation must
    show the same number of each type of atom on both sides of
    the equation (due to the principle of the conservation of
    matter).
Chemical Reactions

            Synthesis Reaction Experiment
Goals: Observe and write the balanced chemical equations for 2
synthesis reactions, and identify a synthesis reaction.
Procedure: Given verbally. Do NOT touch the penny, tongs, or
burner after heating! Only put a pre-1982 penny in the flame!
Results: Observations of the penny after heating (but before you
place it in the water) and after placing the penny in the water.
Conclusion: Write the balanced equations for both reactions and
describe the characteristics of a synthesis reaction. (Products: Red
= Cu2O, Dull black = CuO)
Chemical Reactions

                     Synthesis Reaction
Multiple (more than 1) reactants
combining to form 1 product.

Example: Copper metal combining
with oxygen gas to form copper (II)
oxide…

     2Cu + O2        2CuO
Chemical Reactions

                 Synthesis Reaction Review
        Identify all of the following chemical equations that
        represent a synthesis reaction:
   1.   Mg + O2        2MgO
   2.   AB      A+B
   3.   A+B       AB
   4.   A + BC        AC + B
   5.   CuCl2 + Al        AlCl3 + Cu
Chemical Reactions

                     Noggin Knockers
Chemical Reactions

               Ratios in Chemical Equations


                                                     +    Energy




 There’s a 2 to 1 ratio of hydrogen gas (H2) to oxygen gas (O2) that
 produces 2 water molecules (H2O).

           What’s the ratio of oxygen gas (O2) to water (H2O)?
                                  1 to 2
Chemical Reactions

           Balancing Chemical Equations
   Balancing Chemical Equations:
     Balance the equation for the reaction of sodium metal
     (Na) with oxygen gas (O2), forming sodium oxide (Na2O).
Chemical Reactions

      Balancing Chemical Equations for Synthesis
    Reactions (Describe the 1st one in words & include
          the number of each atom or molecule)
   Na +   Cl2        NaCl




   P +    Cl2         PCl3




   N2 +    H2        NH3
Chemical Reactions

                     Noggin Knockers
Chemical Reactions

                    Learning Objectives
  1. Apply the principle of the conservation of mass (in
     other words, balance chemical equations correctly).


  2. Identify what a chemical equation contains (with an
     example).


  3. Explain what a balanced chemical equation must show.


  4. Identify the 4 main types of chemical reactions. Just
     decomposition today!
Chemical Reactions

                Decomposition Reactions
   Goals: Observe and write the balanced chemical equations
   for 2 decomposition reactions (one from the demo), and
   identify this type of reaction.

   Procedure: Heat up a piece of chalk (CaCO3) in the burner
   flame for at least 5 minutes. Then place the chalk in the cup
   with water and observe what happens.

   Results: Observations of the chalk after heating (but before
   you place it in the water) and after placing the chalk in the
   water.

   Conclusions: Write the balanced equations for both
   reactions (one is from the demo) and describe the
   characteristics of a decomposition reaction.
Chemical Reactions

     Balancing Equations (Decomposition Reactions)
Chemical Reactions

                Decomposition Reactions
  Only 1 reactant, but
  multiple products
    (more than 1).

     XY      X+Y
Chemical Reactions

        Balancing Chemical Equations (Decomposition):
          Describe the last one in words & include the
          number of each molecule- Ion chart on p. 23
   1.        HgO         Hg +      O2




   2.        KClO3        KCl +         O2




   3.        NaHCO3         Na2CO3 +         H 2O +   CO2
Chemical Reactions

          How can you tell if a chemical reaction is a
                 decomposition reaction?
    A.   If there’s 2 or more products.
    B.   If there’s 2 or more reactants.
    C.   If there’s only 1 reactant.
    D.   If there’s only 1 product.
Chemical Reactions

     Why are synthesis and decomposition reactions
                considered opposites?
   A. They both have only one reactant.
   B. Synthesis reactions have 2 products while decomposition
      reactions have only 1 product.
   C. They’re not opposites.
   D. Synthesis reactions have only 1 product while
      decomposition reactions have only 1 reactant.
Chemical Reactions

    Which of the following represents a decomposition
                         reaction?
   A.   A+B     AB
   B.   AB     A+B
   C.   AB + C    AC + B
   D.   AB + CD    AD + BC
Chemical Reactions

      Which of the following shows 2 molecules of
     hydrogen peroxide (H2O2) breaking down into 2
    molecules of water and 1 molecule of oxygen gas
                          (O2)?

   A.   2H2O + O2     2H2O2
   B.   2H2O2     2H2O + O2
   C.   H2O2     H2O + O2
   D.   H2O + O2     H2O2
Chemical Reactions

             Single Replacement Reactions
   Goals: Observe and write the balanced chemical equations
   for 3 single replacement reactions (from the experiment,
   demo, and video), and identify this type of reaction.

   Procedure: Clean the nail with a paper towel, then place the
   iron nail into the blue solution of copper (II) sulfate. Take it
   out after a few seconds.

   Results: Observations of the nail before and after placing it
   in the copper (II) sulfate solution.

   Conclusions: Write the balanced equations for all 3
   reactions (including one from the demo and one from the
   video) and describe the characteristics of a single
   replacement reaction.
Chemical Reactions

                Balancing Equations
Experiment:




Demo:




Video:
Chemical Reactions

            Single Replacement Reaction
   One element (or type of atom) replaces another in a
   compound.
                      XY + Z       XZ + Y
   Analogy:
Chemical Reactions

          For a single replacement reaction…
   A.   Two types of atoms switch places between compounds.
   B.   One type of atom replaces another in a compound.
   C.   There are always 2 reactants and 1 product.
   D.   There is only one reactant.
Chemical Reactions

          Which of the following represents a single
                    replacement reaction?
   A.   AB     A+B
   B.   AB + CD   AD + BC
   C.   AB + C   AC + B
   D.   A+B     AB
Chemical Reactions

     Which of following only shows copper (Cu) being
                  replaced by silver (Ag)?
   A.   2Ag + CuSO4      Ag2SO4 + Cu
   B.   Ag + Cu    AgCu
   C.   CuCl2    Cu + Cl2
   D.   CuSO4 + 2AgNO3     Cu(NO3)2 + Ag2SO4
Chemical Reactions

                     Noggin Knockers
Chemical Reactions

               Double Replacement Reactions
 Goals: Observe and write the balanced chemical equations for 6 double
 replacement reactions (5 from the lab and 1 from the video), and identify this
 type of reaction.

 Procedure: Place 3-5 drops of the following solutions in their own well (in the
 chem. plate): Magnesium sulfate (MgSO4), Nickel chloride (NiCl2), Copper (II)
 sulfate (CuSO4), Iron (III) chloride (FeCl3), & Cobalt chloride (CoCl2). Then
 add 3-5 drops of the sodium silicate solution (Na2SiO3) to form metal silicates
 and stir with the clean end of a toothpick. Disposal- scoop out solids and put
 them in the trash and wipe the plate clean. WASH hands immediately if you get
 any chemical on them!

 Results: Observations of each reaction in terms of what formed. You may want
 to write down your observations under the chemical formula for the compound
 that formed in the equation for each reaction.
                                Example: Al2(SiO3)3
                                            white
 Conclusions: Write the balanced equations for all reactions (including one from
 the video) and describe the characteristics of a double replacement reaction.
Chemical Reactions

     Balancing Equations (Silicate ion = SiO3-2)
   Na2SiO3 +   MgSO4    MgSiO3 +       Na2SO4


   Na2SiO3 +   FeCl3    Fe2(SiO3)3 +     NaCl


   Na2SiO3 +   CuSO4    CuSiO3 +        Na2SO4


   Na2SiO3 +   NiCl2   NiSiO3 +        NaCl


   Na2SiO3 +   CoCl2    CoSiO3 +       NaCl
Chemical Reactions

       Double Replacement Reaction (Video)
Chemical Reactions - Describing Chemical Reactions

            Classifying Chemical Reactions
    Double Replacement reactions involve 2 types of atoms (or
    groups of atoms) switching places in different compounds.

                     AB + CD       AD + BC
Chemical Reactions

        For a double replacement reaction…
  A. Two types of atoms or groups of atoms switch places
     between compounds.
  B. One type of atom replaces another in a compound.
  C. There are always 2 reactants and 1 product.
  D. There is only one reactant.
Chemical Reactions

         Which of the following represents a double
                   replacement reaction?
   A.   AB     A+B
   B.   AB + CD   AD + BC
   C.   AB + C   AC + B
   D.   A+B     AB
Chemical Reactions

        Which of the following is a double replacement
                           reaction?
   A.   2Ag + CuSO4      Ag2SO4 + Cu
   B.   Ag + Cu    AgCu
   C.   CuCl2    Cu + Cl2
   D.   CuSO4 + 2AgNO3     Cu(NO3)2 + Ag2SO4
Chemical Reactions

          For a single replacement reaction…
   A.   Two types of atoms switch places between compounds.
   B.   One type of atom replaces another in a compound.
   C.   There are always 2 reactants and 1 product.
   D.   There is only one reactant.
Chemical Reactions

          Which of the following represents a single
                    replacement reaction?
   A.   AB     A+B
   B.   AB + CD   AD + BC
   C.   AB + C   AC + B
   D.   A+B     AB
Chemical Reactions

     Which of following only shows copper (Cu) being
                  replaced by silver (Ag)?
   A.   2Ag + CuSO4      Ag2SO4 + Cu
   B.   Ag + Cu    AgCu
   C.   CuCl2    Cu + Cl2
   D.   CuSO4 + 2AgNO3     Cu(NO3)2 + Ag2SO4
Chemical Reactions

     Combustion Reactions (Balance for Extra Credit)
   Film Canister Rocket (Combustion of methanol):

                   CH4O + O2       CO2 + H2O

   Ping Pong Popper (Combustion of ethanol):

                   C2H6O + O2      CO2 + H2O


   Whoosh Bottle (Combustion of Isopropyl alcohol):

                   C3H8O + O2      CO2 + H2O
Chemical Reactions - Describing Chemical Reactions


                           Building Vocabulary
    Using a word in a sentence helps you think about how best
    to explain the word. After you read the section, reread the
    paragraphs that contain definitions of Key Terms. Use the
    information you have learned to write a meaningful sentence
    using each Key Term.
   Key Terms:               Examples:
    chemical equation
    closed system           A chemical system, matter is not allowed to enter or
                            In a closed equation is a short, easy way to show a
    replacement             Replacement is the process in which one element
                            chemical reaction.
                            leave.
                            replaces another in a compound or two elements in
    reactant
    coefficient               substance is number places.
                            different compounds trade in beginning equation
                            A coefficientyouahave at the a chemicalof a reaction is
                            a reactant.
                            telling you how many atoms or molecules of a reactant
    product                 ornew substance produced in a reaction is a product.
                            A product take part in the reaction.
    synthesis
    conservation of mass    Synthesis means combining two or more a chemical
                            Conservation of mass means that duringelements or
                            compounds to make a more complex substance.
                            reaction, matter is not created or destroyed.
    open system
    decomposition           In an open system, matter can enter from or escape
                            Decomposition means breaking down compounds
                            to the surroundings.
                            into simpler products.
Chemical Reactions




         End of Section:
           Describing
           Chemical
           Reactions
Chemical Reactions

                    Learning Objective
   Describe how the following affect the rate of a chemical
   reaction…
                          •Temperature

                          •Surface Area

                        •Using a catalyst

                       •Using an inhibitor

                         •Concentration
Chemical Reactions - Controlling Chemical Reactions

                   Energy and Reactions
    All chemical reactions need a certain amount of activation
    energy to get things started.
Chemical Reactions - Controlling Chemical Reactions

                  Energy and Reactions
    Both exothermic and endothermic reactions need energy
    to get started.
Chemical Reactions - Controlling Chemical Reactions


                  Relating Cause and Effect
    As you read, identify the factors that can cause the rate of a
    chemical reaction to increase. Write the information in a
    graphic organizer like the one below.
           Causes
  Increase in surface area

                                                     Effect
  Increase in temperature
                                            Increased rate of reaction
  Increase in concentration
  of reactants

  Use of a catalyst
Chemical Reactions - Controlling Chemical Reactions

              Rates of Chemical Reactions
                   The cells in your body (as in all living
                   things) contain biological catalysts called
                   enzymes. At the end of a reaction, an
                   enzyme molecule is unchanged.
Chemical Reactions

     Homework- p. 63: 1a, 2b, 3a, 3b, 3c, 4, & 5
   1a- Formulas- number of each type of atom, arrow means “yields”
   or “produces”. Plus sign- what’s reacting together and/or what 2
   substances are produced b/c they separate the substances in the
   equation.
   2b- 250 g (Mass of reactants = Mass of the products)
   3a- Synthesis, Decomposition, Replacement (Single & Double)
   3b- 2 products minimum
   3c- Synthesis (1 product)

   4- 2Fe2O3 + 3C       4Fe + 3CO2



   5- 2SO2 + O2       2SO3
Chemical Reactions

                   Homework- p. 71: 2a
   2a- Speed up a reaction- increase temperature, increase
   surface area, increase concentration of the reactants, or add
   a catalyst; slow down a reaction- decrease temperature,
   decrease surface area, decrease concentration of the
   reactants; add an inhibitor.
Chemical Reactions

                     Data Sharing Lab




    Click the PHSchool.com button for an activity about sharing
     data for the Skills Lab Temperature and Enzyme Activity.
Chemical Reactions - Controlling Chemical Reactions

       Exothermic and Endothermic Reactions




     Click the Video button to watch a movie about exothermic
                    and endothermic reactions.
Chemical Reactions




         End of Section:
           Controlling
            Chemical
           Reactions
Chemical Reactions - Fire and Fire Safety

                             Understanding Fire
                             Three things are necessary to
                             start and maintain a fire–fuel,
                             oxygen, and heat.
Chemical Reactions - Fire and Fire Safety

                             Understanding Fire
                             The fire triangle can be controlled
                             in the grill. If any part of the fire
                             triangle is missing, the fire will
                             not continue.
Chemical Reactions - Fire and Fire Safety

                     Home Fire Safety
                                            If you know how to
                                            prevent fires in your
                                            home and what to do
                                            if a fire starts, you are
                                            better prepared to
                                            take action.
Chemical Reactions - Fire and Fire Safety


                   Using Prior Knowledge
    Before you read, write what you know about fire safety in a
    graphic organizer like the one below. As you read, write what
    you learn.
                              What You Know
       1. A fire needs fuel to burn.
       2. A fire need oxygen to burn.
       3. All homes should have smoke detectors.

                             What You Learned
       1. Fire is a result of a combustion reaction.
       2. The most deadly fires start with cigarettes.
       3. Baking soda can be used to put out small fires.
Chemical Reactions - Fire and Fire Safety

                    Links on Fire Safety




          Click the SciLinks button for links on fire safety.
Chemical Reactions




         End of Section:
          Fire and Fire
             Safety
Chemical Reactions

                           Graphic Organizer
                        Chemical
                        reactions

               can be                are written as


 Endothermic            Exothermic
  reactions                                    Equations
                         reactions
                                                              balanced with


           which require                      written using           Coefficients

           Activation
            energy               Chemical                 Arrows and
                                 symbols                  plus signs
Chemical Reactions




       End of Section:
      Graphic Organizer

				
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