Mystery Powder Crime Scene Inves by fjzhangweiqun


									Mystery Powder Crime Scene Investigation                        Name: ________________________________ Per: ____

Key Chemistry Concepts:

    •    Chemical changes, or chemical reactions, are changes that result in the production of a new substance. Bonds in the
         reactants break and different ones form in the products. When you burn a log in a fireplace, you are carrying out a chemical
         reaction that releases carbon. When you light your Bunsen burner in lab, you are carrying out a chemical reaction of methane
         and oxygen that produces water and carbon dioxide. Possible evidence for chemical change: gas (bubbles) produced –
         sometimes smelly!, color change, heat released or absorbed, a solid forms.

    •    Physical changes are those changes that do not result in the production of a new substance (no new bonds are formed). If
         you melt a block of ice, you still have H2O at the end of the change. If you break a bottle, you still have glass. Painting a
         piece of wood will not make it stop being wood. Some common examples of physical changes are: melting, freezing,
         condensing, breaking, crushing, cutting, and bending.

The Investigation

At 2:09 pm, the police are called to a secluded, wooded area where a body has been found. At the scene, the Crime Scene
Investigators determine that the victim, a male about 35 years old, was fatally stabbed. Based on a lack of a blood pool under the
body, they also conclude that the victim was not killed at the scene but was moved to this location. Using information found in the
victim’s wallet, they determine his name to be Joseph Carruthers. After thoroughly investigating the scene, they send his body to the
crime lab for further research.

Through subsequent phone investigation, they determine Joseph worked as a local truck driver for Williamsburg Trucking and that he
delivered chemicals to various production plants in the area. Through microscopic analysis of his clothing, they find a white powder
on his shirt and the soles of his shoes. Joseph’s employer states that Joseph delivers the various chemicals but is not allowed to unload
the truck or enter the production facilities based on his work contract. To obtain a search warrant to search suspected plants where the
crime may have occurred, the crime lab must determine what the white powder is.

As the newest member of the CSI team, you have been asked to follow the procedures below to learn how to tell the various powders
apart, then test the unknown powder to determine which plant to obtain the search warrant for.


Procedures for determining the properties of known powders (be sure to note if each change is a chemical or a physical change and the
evidence for how you know):

         1.   Observe each powder with a magnifying glass. Try to record as many details as possible regarding the crystal form,
              shape, color, etc… of the substance.
         2.   Obtain a VERY SMALL sample of the powder to be tested and place on a small square of aluminum foil. Using forceps,
              place the foil on a hotplate and observe for a few minutes. Discard the remains in the trash can. Record results.
         3.   Place a VERY SMALL sample of each powder into 6 clean wells of a well-plate. Add 2-3 drops of water to each.
              Record results.
         4.   Place a VERY SMALL sample of each powder into 6 clean wells of a well-plate. Add 2-3 drops of iodine solution to
              each. Record results.
         5.   Place a VERY SMALL sample of each powder into 6 clean wells of a well-plate. Add 2-3 drops of lead nitrate solution
              to each. Record results.
         6.   Place a VERY SMALL sample of each powder into 6 clean wells of a well-plate. Add 2-3 drops of vinegar to each.
              Record results.

Procedures for identifying the unknown powder:

         Obtain an unknown powder and record its number in the data table. Develop your own procedures for identifying which
         powder it is. Record your detailed procedures—you’ll need to write these in your conclusion later.
                                                                       indicate physical (P) or chemical (C) change
                                                                       and record your evidence in the large box.
                                      Mystery Powder Data Table

    Test           Magnifying Glass         Heat      Water        Iodine        Lead nitrate            Vinegar
  Substance                                                       Solution




Potassium iodide


  Baking Soda


Questions to consider:

   1. What is the identity of the unknown powder? _________________________
      Describe the data from your lab that supports your conclusion:

   2. Describe the positive test for each known powder: (For example: what happens when vinegar is added
      to baking soda?)
      Starch: _____________________________________________________________________________
      Salt: _______________________________________________________________________________
      Sugar: _____________________________________________________________________________
      Potassium iodide: ____________________________________________________________________
      Plaster: _____________________________________________________________________________
      Baking Soda: ________________________________________________________________________

   3. Which tests described in #2 above show evidence of a chemical change? Describe the evidence to
      support your answers.

   4. The positive test for potassium iodide (KI) involves lead nitrate Pb(NO3)2. Write the chemical equation
      (reactants, products, phase symbols, etc) for the chemical reaction that occurs. Solid potassium iodide
      and lead nitrate dissolved in water are the reactants. The products are potassium nitrate (KNO3) which
      dissolves in water and lead iodide (PbI2) which is a yellow solid.

      Challenge: Can you balance the reaction using coefficients?
5. Circle all the statements below that are evidence of a chemical change:

        1. Burning of a building
        2. Adding sugar to lemonade
        3. Water changing to steam
        4. Rusting of iron
        5. Fluffy egg whites
        6. Leaves changing color
        7. Milk turning sour
        8. H2 (g) + 3 N2 (g)       2 NH3 (g)
        9. Churning of milk into butter
       10. Baking rolls
       11. Ripening of tomatoes
       12. A stick broken into small pieces
       13. Growing vegetables
       14. Formation of a gas bubble
       15. Disappearance of color
       16. Making ice cream
       17. Using hot water to expand a metal cup
       18. Mg (s)         Mg (l)
       19. Digestion of food
       20. Popcorn popping
       21. Freezing water

6. Which plant should the search warrant be secured for? _______________________________________

   Production plants that Joseph delivered to:

   CandyLand Candy Company – manufactures sugar-free chewy candy using starch
   Redstone Pretzel Company – manufactures pretzels covered with salt (sodium chloride)
   Fritz’z Soda Company – manufactures sugar-containing beverages
   PerPlex Company – manufactures thyroid medicine containing potassium iodide
   Yardlines Statues – manufactures garden statues using plaster (calcium carbonate/calcium sulfate)
   Burp-X Company – manufactures antacids using baking soda (sodium bicarbonate)

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