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					Chemical or Physical Change?                                     Name: ____________________________________

Chemistry studies changes in matter. In this experiment, you will investigate two
different interactions of matter, make observations and determine if each is a physical
or chemical change. A large difference in temperature before verses after a change
tells a scientist that a chemical change (or reaction) has occurred. An endothermic
reaction takes heat in from its environment. An exothermic reaction gives heat off to
its environment. Other evidence will also be used to determine if a change is physical
or chemical and eventually you will manipulate (or change) matter for your own
purposes as a chemist.

1) Define physical change: ___________________________________________________


2) Define chemical change: __________________________________________________


3) Will the container holding an endothermic reaction feel hot or cold?

4) Will the container holding an exothermic reaction feel hot or cold?

5) Other that temperature change, what would be evidence that something is a physical change?




6) Other that temperature change, what would be evidence that something is a chemical change?




Part A: Salt (NaCl) & H2O
     Step                      Procedures                                 Comments, Observations, Errors and Data
                   Add 100mL of tap water into a beaker
                   Measure the temperature of the H2O
       1


                                                                Temp H2O:
                      Add 1 level spoonful of NaCl to the
                       H2O
      2               Stir until you see a change
                      Measure the temperature of the H2O
                       and NaCl
                                                                Temp H2O & NaCl mixed:
                      Wait and observe for three (3) minutes
                      Measure the temperature of the H2O2
                       and yeast after 3 minutes
      3


                                                                Temp H2O & NaCl mixed:
Part B: Yeast and Hydrogen Peroxide (H2O2)
     Step                     Procedures                                  Comments, Observations, Errors and Data
                 Add 25.0 ml of H2O2 into beaker
                 Measure the temperature of the H2O2
       1

                                                                   Temp H2O2:
                     Add ½ of a level spoonful of yeast to
                      the H2O2
       2             Stir until you see a change
                     Measure the temperature of the H2O2
                      and yeast                                    Temp H2O2 & yeast mixed:
                     Wait and observe for three (3) minutes
                     Measure the temperature of the H2O2
       3              and yeast after 3 minutes

                                                                   Temp H2O2 & yeast mixed:

Analysis
1) Use the formula (Tafter salt added – Tbefore salt added = ΔT) to calculate the temperature difference (ΔT) of the change you
observed in Part A.




2) Was the ΔT in Part A large to give evidence of a chemical change? Yes or No


3) Use 2 pieces of evidence to explain if the change observed in Part A was chemical or physical.




4) Use the formula (Tafter sat added – Tbefore salt added = ΔT) to calculate the temperature difference (ΔT) of the change you
observed in Part B.




5) Was the ΔT in Part B large to give evidence of a chemical change? Yes or No


6) Use 2 pieces of evidence to explain if the change observed in Part B was chemical or physical.

				
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posted:12/30/2011
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