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By Anna Lount and Pamela Ruggier

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By Anna Lount and Pamela Ruggier Powered By Docstoc
					By: Anna Lount and Pamela Ruggiero
C5.2 Chemical Changes
     C5.2A Balance simple chemical equations applying the conservation of matter.
            Conservation of Matter Activities:

                    Background:

                                Foundational background of matter required
                                Foundational background of conservation required

                        Activitiy 1: Sodium Polyacralate + Water
                            Description: Students will take note of the mass of the ‘reactants’ and the ‘products’ in this ‘reaction’.
                        Students will notice an increase in quantity of product; however the masses should remain the same.

                                 Procedures:

                            1.     Take the mass of a 400ml beaker and record
                            2.     Measure 5g of Sodium Polyacralate and place into a beaker
                            3.     Take the mass of a 100ml graduated cylinder and record
                            4.     Measure 50ml of H20 and measure the mass of the water in the graduated cylinder and record
                            5.     Subtract the mass of the graduated cylinder from the mass value above.
                            6.     Add the masses from the following steps: step 1 + step 2 + step 5 = _________
                            7.     Pour the 50ml of H20into the beaker
                            8.     Record observations
                            9.     Take the mass of the substances you see. (including same beaker) and record.

                                 Analysis:

                            10. Compare the mass of the reactants (step 6) to the mass of the products (step 9)

                                       You Tube Demo: http://www.youtube.com/watch?v=bWaivm9XpNg

                        Activity 2: Calcium Chloride + Sodium Bicarbonate + Universal Indicator*
                            Description: Students will observe a chemical reaction (Can also be used for benchmark C5.2C)

                            Procedures:

                            1.  Measure 2g Calcium Chloride
                            2.  Measure 2g of Sodium Bicarbonate
                            3.  Put both substances in a plastic baggy and seal it.
                            4.  Record the total mass (including the baggy).
                            5.  Take the mass of a 10ml graduated cylinder and record
                            6.  Measure 5ml of Universal Indicator* and measure the mass of the Universal Indicator in the
                                graduated cylinder and record
                            7. Subtract the mass of the graduated cylinder from the mass value above.
                            8. Add the masses of the baggy with the CaCl2 and NaCO3 to the mass of the universal indicator
                            9. Open a small section of the bag and add the indicator, then quickly seal the bag.
                            10. Students should observe a color change, an exothermic reaction, and gas being produced.
                            11. Record observations
                            12. Without opening the baggy take the mass.

                                   *
                                    The indicator can be replaced with water and the reaction will still take place, but without a color
                                   change.

                                 Analysis:

                            13. Compare the mass of the reactants (step 8) with the products (step 12).
Balancing simple chemical equations:

       Background:

              Chemical symbols (subscripts, coefficients, etc.)
              Knowledge of Reactants and Products
              What is equality?
              Understand how atoms are rearranged into molecules
              Be able to balance atom survey (changing coefficients)

           Activity 1: Balancing Equations using M&M’s or Colored Marbles
               Description: Students will use M&M’s, or other colored manipulative, as a way of balancing the atoms
           and molecules in a given reaction.

               Procedures:

                  1.   Separate colored M&M’s by their colors.
                  2.   Give the students an unbalanced “M&M reaction” and ask them to balance.
                         Ex: Orange---Orange +           Red---Red               Red---Orange---Red




                  3.   Students will add number of needed molecules
                              Orange---Orange +          Red---Red                   Red---Orange---Red




                                                          Red---Red                     Red---Orange---Red




                  4.   Have students draw their balanced M&M reactions in a notebook.



           Activity 2: Students as Atoms and Molecules
               Description: The purpose of this activity is to get a group of students to organize and reorganize
           themselves as a balanced chemical equation.

               Directions:

                  1.   Give signs with elemental symbols on them to the students. (include addition and yield signs)
                       Each student will represent just one atom.
                  2.   Set the students up in an unbalanced reaction. (Students who are part of a molecule should
                       hold hands or hold a piece of rope between them.)
                                                                                   Cl
                       Ex:
                              Ca        +         Cl               Ca
                                                                                   Cl

                  3.   Have students survey the amount of atoms on each side of the reaction. They should be able
                       to determine how many more students they should have on each side. In this case a student
                       with a Chlorine ion would have to be added to the reactants side.


                                                                                   Cl
                       Ex:
                              Ca        +         Cl               Ca
                                                                                   Cl
                                                                      Cl
                                           *Be sure to produce a generous portion of signs for reactions with larger molecules, or for
                                           extreme coefficient ratios.



         C5.2B Distinguish between chemical and physical changes in terms of the properties of the reactants and
products.

                                 Background

                                Change vs. Properties
                                Physical change (change of state C5.4, size shape, distance)
                                Chemical change (rearrangement of atoms C5.2A)
                                Physical properties (size, shape, distance, density, appearance)
                                Chemical properties (the ability to…)

                             Activities:

                             Activity 1: Calcium Chloride + Sodium Bicarbonate + Universal Indicator:

                             SEE ABOVE – C5.2A

                             Activity 2: PHYSICAL VS CHEMICAL CHANGE INVESTIGATION

Synopsis: Students perform lab activities to determine if a chemical or physical occurs after observing change of
properties of the reactants and the products.

Purpose: To distinguish between chemical and physical changes

Materials: Liquid food dye, eye dropper, 100 mol tap water, 250 mL beaker; baking soda, vinegar; aluminum foil, mini
chocolate bar; liquid food dye, 100 ml beaker and tap water; 1M HCl 50 ml, small nugget metal (Zn, Mg, Al) 100 ml
beaker; 1 M CuSO4 solution 100 mL, aluminum foil, 250 ml beaker, 5cm x 5cm paper, scissors; 3cm x 3 cm piece of
paper; 2 cm x 2 cm square Al foil.



                         Student Observation and Comment Chart

Reactants                Observations                            Physical     Chemical       Comments
                                                                 Change       Change
    1.   drop of food
         dye +
         water
    2. baking soda +
         vinegar
    mini chocolate bar
    + heat from your
    hand
4. HCl + Mg


    5.      CuSO4 +
    Al

   6.    paper
whole
7.   Aluminum foil
Procedure

Student Activities:

    1. Add one drop of liquid food dye into a beaker half filled with tap water. Record the movement of the food dye.
    2. Add vinegar to baking soda. Record what happens.
    3. Take off paper wrap of mini chocolate bar. Place mini chocolate bar inside palm of your hand on till it is melted.
       Place on cool table top. Wait five minutes and open. Record your observations.
    4. Add coiled Mg strip to HCl acid in beaker. Wait five minutes. Record your observations.
    5. Take aluminum foil and crumble it into a ball. The entire ball to CuSO4 solution. Wait 10 – 20 minutes. Record
       your observations
    6. Cut paper into ten pieces. Put the cut pieces of paper back together. Record your observations
    7. Roll aluminum foil into small ball. Then flatten it back out into a square. Record your observations.


Analysis:

    1. Determine what type of change occurred in each of the above activities on record in data chart for each activity
       1 -7.


    2. Explain in terms of physical properties what changed in the comments column for each activity.


    3. Write how physical and chemical changes are alike?




    4. Write how physical and chemical changes are different?




   5. Explain how to distinguish between a physical and a chemical change
Sample student data chart.



                            Data

Reactants                  Observations                           Physical   Chemical   Comments
                                                                  Change     Change
1. liquid food dye + tap   Liquid food dye spreads until the      Yes -                 Change of
water                      water turn color thorough the                                distance between
                           beaker                                                       particles – no
                                                                                        change of
                                                                                        properties
    2.   baking soda +     Gas is given off bubbles                          yes        Change physical
         vinegar                                                                        properties –
                                                                                        bubbles of gas
                                                                                        form
                                                                                        & odor change of
                                                                                        product molecules
3. Mini chocolate bar      The bar softens and melts. When it     Yes                   No change of
                           is cooled, it hardens                                        physical
                                                                                        properties –
                                                                                        returns to original
                                                                                        form
4. HCl + Mg                Bubbles form – gas is given off                   Yes        Change of
                           and metal dissolves                                          physical
                                                                                        properties – goes
                                                                                        into solution
    5. CuSO4 +             Orange material gathers around                    Yes        Solid substance
    Al                     nail, solution becomes clear                                 forms from
                                                                                        combination of Al
                                                                                        and CuSO4
    6. paper               Smaller piece of paper forms.          Yes                   No change of
    whole                  After paper is put back together, it                         physical
                           is like the whole paper                                      properties -
                                                                                        change of size –
                                                                                        shape only
    7.   Aluminum foil     Flat metal forms ball                  Yes                   No change of
                                                                                        physical
                                                                                        properties –
                                                                                        change of shape
                                                                                        only




    Student Analysis Responses



    1. Determine what type of change occurred in each of the above activities on record in data chart for each activity 1
    -7.

         (see above chart)



    2. Explain in terms of physical properties what changed in the comments column for each activity.
       (see above chart)
    3. Write how physical and chemical changes are alike?


In both changes there is some thing different after each change.



    4. Write how physical and chemical changes are different?


Physical change – no change of physical properties - can go back to original form

Chemical change – new properties appear after chemical change – cannot go back to original form



   5. Explain how to distinguish between a physical and a chemical change



A physical change is a change of distance, size, shape of the substance physical properties remain the same. Substance
can return to original form. A chemical change is a change in physical properties. The product molecules are different
from the reactant molecules because the physical properties are different. (Atoms of reactant molecules rearrange into
new product molecules.



Good website for Chemical Demos you may or may not do in class:
http://jchemed.chem.wisc.edu/JCESoft/CCA/pirelli/index.html



        C5.2C Draw pictures to distinguish the relationships between atoms in physical and chemical changes.
                                Background

                               Knowledge of the atom
                               Knowledge of molecules
                               Know chemical vs. physical change



                        Activity 1: SEE DOCUMENT titled: Physical vs. Chemical Change Activity

				
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