"Mining an Ore"

Teresa Granito                 Von Steuben Metropolitan Science Center
                               5039 Kimball
                               Chicago IL 60625
                               312-534-5100   MR#51

Objectives:

The high school students will be able to: 
     1.  calculate percentages
     2.  read chemical formulas
     3.  determine the molar mass of a compound
     4.  differentiate between an ore and a mineral
     5.  calculate the percent composition of a mineral in an ore
     6.  determine which ore has the greatest percentage of mineral
     7.  do a Performance Assessment activity to demonstrate mastery

Materials needed:

     1.  "ore" = two brands of chocolate chip cookies (2 per lab group)
     2.  "mining tools" =  paper clip, forceps, etc.
     3.  balance
     4.  periodic table

Strategy:

Part I  (calculating percentages)

Remove a "precious mineral" from an "ore".  The "ore" will be the chocolate chip 
cookie and the "mineral" will be the chocolate chips.  The object is to 
determine which "ore" has the greatest percentage of "mineral". 

     1.  find the mass of a cookie 
     2.  separate chips from cookie using "mining tools"
     3.  find mass of chips
     4.  determine the percentage of chips in the cookie:
           mass of chips 
           mass of cookie  x   100%  =  percent of chips in cookie
     5.  repeat with second cookie
     6.  compare results

Part II (percent composition of an ore)                       
 
     Define
     1.  chemical formula
     2.  molar mass
     3.  mass number
     4.  periodic table of elements
     Do some example problems with students:
     5.  What is the percent composition of Ag in AgS?
         Ag = 1 x 108g = 108g            108gAg
          S = 1 x  32g =  32g           140gAgS  x 100 = 77% Ag in AgS
                         140g 

     Data Chart         
          ORE       MASS OF    MASS OF    PERCENT OF    PERCENT OF
                      ORE      MINERAL    MINERAL       WASTE
     --------------------------------------------------------------------  
         Al2O3 
         CaSO4
 
Performance Assessment:

     Because of your superior mining ability you have been awarded your choice 
     of one of two mining locations.  One site, located in Mexico, is rich in 
     Chalcopyrite (CuFeS2).  The other site, located in Russia, is rich in 
     Chalcocite (Cu2S).  

     Which location would you choose to mine?  Explain all aspects of your 
     decision. 
                               DIG AWAY!
Scoring Rubric
                 DEMONSTRATED COMPETENCE

For 6 points:    The response is exemplary.
                 - an explanation that is complete
                 - molar masses and percent composition calculated precisely
                 - all aspects of decision looked at completely
                 - more than one explanation that is complete and correct
                 - well thought out answer

For 5 points:    The calculations are correct and the response is clear.  Not 
                 all aspects taken into consideration. 

For 4 points:    The calculations are correct, but the explanation lacks 
                 clarity. 

                 SATISFACTORY RESPONSE

For 3 points:    The response indicates a partial solution.  Perhaps the molar 
                 masses are correct, but the percentages are done incorrectly, 
                 or vise versa. 

                 INADEQUATE RESPONSE

For 2 points:    The response indicates a partial solution.  Or, the response 
                 indicates the student may understand the solution, but the 
                 explanation is incoherent. 

For 1 point:     The response is incorrect, but it shows evidence of 
                 mathematical and logical reasoning.  A mathematical explanation 
                 is developed.  The explanation, however, does not address the 
                 crux of the problem or the essence of the solution.  

For 0 points:    The student leaves a blank page or writes, "I don't Know."