CHEMICAL AND PHYSICAL CHANGE EXPERIMENT

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CHEMICAL AND PHYSICAL CHANGE EXPERIMENT Powered By Docstoc
					                                                                 Mr. Toburen

February 15, 2011                                                Class Period 3       Clicker Number 24


                                  Chemical And Physical Change Experiment




I. Problem:

        What is the difference between a chemical change and a physical change?            What are some of the

characteristics of a physical change as opposed to a chemical change? What are some indicators that distinguish a

physical change from a chemical change?



II. Background Information:

        Understanding the properties of matter is an essential tool to understanding and predicting reactions.

This experiment demonstrates the physical and chemical properties of elements, compounds and mixtures and

illustrates their interactions with one another. Physical and chemical interactions are taking place every day. The

observations made in this lab guide understanding of those reactions taking place in the environment and in the

lab.

        Indicators of Chemical reactions taking place can be observed through color changes, gas bubbles

forming, precipitates forming, temperature changes and the variable dispersion of light2. The dispersion of light

through a substance is also know as the Tyndall effect and can be measured to tell the difference between a

homogeneous or heterogeneous mixture.

        A physical change is manifest by the lack of a color change or gas bubbles, no precipitates forming, no

temperature difference and no discernable change in the dispersion of light through the mixture that was not a

property of either of the two being combined in the mixture. A change in number of pieces for instance, one piece

of paper being divided into two, or a change in size, a powder absorbing a fluid might be examples of a physical

change having occurred.
III. Hypothesis

        The following is a table of predictions for the 4 parts of the lab:

                   Test                     Type of Change

Part 1: KI and Pb(NO3)2                     Physical

Part 3: Sodium polyacrylate and water       Physical

Part 7: Mg metal and acid                   Chemical

Part 8: Gatorade® and water                 Physical




IV. Test the Hypothesis

        Part 1

                  8 drops of aqueous KI were placed in a clean test tube. To it about 8 drops of Pb(NO3)2 was

added. Observations were recorded. The test tube was cleaned well with water.

        Part 3

                  A scoopula was used to obtain a small serving of sodium polyacrylate, which was placed in an

evaporating dish. An excess of deionized water was added to the evaporating dish. Observations were recorded

and per instructions the products were discarded in the trash.

        Part 7

                  A small piece of magnesium metal was obtained and placed in a cleaned test tube. Three drops

of solution B were added and observations were recorded. The metal was discarded in the trash.

        Part 8

                  A small scoop of Gatorade® powder was added to a clean test tube and a few drops of water were

added to the same tube. Results were recorded and the solution was discarded down the drain.




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V. Observations

                                    Table #1: Physical Chemical Change Results

              Test                        Indicators                          Observations                         Type of

                                                                                                                   Change

Part 1: KI and Pb(NO3)2             Color, precipitate        A yellow precipitate formed                       Chemical

Part 3: Sodium polyacrylate         Swelling                  The sodium polyacrylate got bigger                Physical

and water                                                     absorbing the water

Part 7: Mg metal and acid           Bubbles and               The metal bubbled and gave off some               Chemical

                                    temperature               heat

Part *: Gatorade® and water         No change                 The two mixed well with no chemical               Physical

                                                              indicators




VI. Draw Conclusions:

         This experiment evaluated the physical and chemical changes associated with differing compounds, elements and

mixtures. Through this experiment it became clear when a chemical reaction was taking place. The color changed in part 1

with the formation of a precipitate. In part 3 there were bubbles as the chemical indicator. While the physical changes were

not as obvious, the lack of the chemical indicators provided the necessary clues as to which reaction was taking place.

         This experiment illustrated the applicability of the indicators in accurately discerning physical changes from

chemical changes and provides a method in determining whether these changes exist without testing each and every sample.

         This experiment investigated physical and chemical changes associated with KI and Pb(NO 3)2, sodium

polyacrylate and water, magnesium metal and acid and Gatorade ® with water. It was found that KI in Pb(NO3)2

and magnesium metal in acid were chemical changes whereas the Gatorade® with water and sodium polyacrylate

in water were physical changes




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