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					     Golf Ball Lab


What is the minimum amount of salt
 needed to make a golf ball float?
Determine the minimum amount of salt needed
   to make a golf ball float in 100 mL water.

Weigh out 50.0 g of NaCl
Add 5 g additions of salt to the water, dissolve, check to see if ball floats.
Continue with this method of successive additions until ball floats.
Re-weigh remaining salt and subtract this amount from 50.0 g to determine
the amount of salt needed.
Finally, repeat…begin 5 g less salt and add 1 g increments to narrow range.


           Trial          Salt (g)            Total         Float /Sink
             1              5.0 g             5.0 g             Sink
             2              5.0 g            10.0 g             Sink
             3              5.0 g            15.0 g             Sink
             4              5.0 g            20.0 g             Sink
             5              5.0 g            25.0 g            Float
        Theorize, but Verify
            …We must trust in nothing but
         facts. These are presented to us
         by nature and cannot deceive. We
         ought in every instance to submit
         our reasoning to the test
         of experiment. It is especially
         necessary to guard against the
         extravagances of imagination which
         incline to step beyond the bounds
         of truth.

              Antoine Laurent Lavoisier, 1743 - 1794



Jaffe, New World of Chemistry, 1955, page 1
 Theory Guides, Laboratory Decides!
Density of water = 1.0 g/mL

Need to determine density of a golf ball.
        mass =______ g (electronic balance)
        volume = ______ mL (water displacement method) or formula?

Density of golf ball cannot be made to decrease. Therefore, you need to
increase the density of the water by dissolving salt into the water.

Limiting Factor: accurate determination of volume of golf ball

Solubility Curve of salt in water.
          Water has a limit to how much salt can be dissolved.
Saturation – point at which the solution is full and cannot hold anymore solute.
Packing of NaCl Ions




     Electron Microscope
     Photograph of NaCl
Dissolving of Salt in Water

      Na+
      ions                   Water molecules




                       Cl-
                      ions




   NaCl(s) + H2O  Na+(aq) + Cl-(aq)
                                              Dissolving of NaCl
                                                           H         H

                                                               O

                                                               Na+

                                       +                                     +
                                              +
                                                         hydrated ions
                         -      +        -                               +   -
                          +      -                                       -
                                                               Cl-




Timberlake, Chemistry 7th Edition, page 287
     Interstitial Spaces and Particle Size

                                                      Interstitial spaces
                                           (holes in water where substances dissolve)



100 mL
                                                                                    Easy
                                       Parking at school if you arrive at 7:00 AM = _____
                                                                                     Hard
                                       Parking at school if you arrive at 7:45 AM = _____


         More available spaces if you arrive early. Salt dissolves quicker when you
         begin because there are more available spaces to 'park'.

         Analogy: Compact car is easier to park than SUV.
         Theory: Crush salt to make particles smaller (increase surface area)
                 …it will dissolve more rapidly.                                        STIR
                        100 mL of water = 100 g        density of water= 1.00 g/mL

                        You determine the density of golf ball to be 1.18 g/mL

                          Add 19 g salt to 100 g water = 119 g salt + water
                            Volume remains100 mL (saltwater)

                               Density =     Mass                    119 g
                                            volume         or       100 mL

                                        Density (saltwater) = 1.19 g/mL

If golf ball doesn’t float, add 2 g additions of salt until it floats.

   Add 3.0 mL water,stir…float                  119 g      x g salt
   Add 3.0 mL water,stir…float                           
                                            100 mL  6 mL 100 mL
   Add 3.0 mL water,stir…sink
Goals and Objectives:
  a. Given materials and problem, formulate and test a hypothesis to
     determine if a golf ball can float in salt water.
  b. Collect accurate data and compare own data to other class
     data. Evaluate own results.

Investigation Procedure:
   a. Design an experiment to accurately determine how dense salt water
      must be in order for a golf ball to float. Use metric units. Be sure to
      control as many variables as possible.
   b. Write down the procedure that you and your partner(s) are going to use
      prior to lab day. Record any researched facts that may be useful in
      knowing before conducting your experiment.
   c. Carefully run your experiment, make observations and record your
      measurements in a data table. Use grams and milliliters in your
      measurements. Include a calculation column in your data table.
   d. Critique your own procedure, discuss and compare your process with
      another group, then modify your own steps as needed.
   e. Repeat your experiment to check for accuracy, if time allows.
Discussion Questions for Understanding:

a. How did you determine the density of your golf ball?
b. Why does a golf ball normally sink to the bottom of a pond at the golf course?
c. What variables were difficult or impossible for you to control during this
         experiment?
   How much salt can be dissolved in 100 mL of water? (saturated)
      effect of temperature on solubility
   Surface area of salt may affect rate of dissolving (may need to crush salt finely)
d. What variables may have changed as time went on that could have affected
         the outcome of your results?
e. Did you improve the accuracy of your results after conferring with another
         group?
f. Describe your sources of error.
         (Human error and faulty equipment are unacceptable answers)
 Materials:
   electronic balance                  100 mL & 500 mL graduated cylinder
   mortar / pestle                     glass stirring rod
   golf ball                           salt (Kosher, iodized table salt, table salt)
   250 mL beaker
Extension:
  a. Research the manufacturing of golf balls to determine why they sink in
     pond water.
  b. Research to determine which body of salt water in the world would float a
     golf ball the highest.
Lab Report : (10 - 12 point font two page maximum length)
     Background / problem
     Hypothesis (if...then)
     Procedure (protocol)
     Data (table, graph)
     Analysis
     Conclusions / Future directions (limitations)
            Sample calculations - appendix

Do not use references to yourself or others in your writing of a lab report
         (except for citing past research).
OR
Poster (25 words or less) A picture is worth 1000 words!
                                                                                                                                      Solubility vs. Temperature for Solids
                                                                                                                                140
                                                                                                                                          KI
                                                                                                                                130

                                                                                                                                120

                                                                                                                                110              NaNO3                  gases

             Solubility


                                                                                       Solubility (grams of solute/100 g H2O)
                                                                                                                                                                        solids
                                                                                                                                100
                                                                                                                                                                KNO3

              Table                                                                                                             90

                                                                                                                                80
                                                                                                                                                HCl               NH4Cl
             shows the dependence                                                                                               70

          of solubility on temperature                                                                                          60              NH3                    KCl
                                                                                                                                50

                                                                                                                                40

                                                                                                                                30
                                                                                                                                                         NaCl     KClO3
                                                                                                                                20

                                                                                                                                10
                                                                                                                                                          SO2

                                                                                                                                      0   10 20 30 40 50 60 70 80 90 100
LeMay Jr, Beall, Robblee, Brower, Chemistry Connections to Our Changing World , 1996, page 517
                 Teacher Notes
Some golf balls will NOT float in a saturated solution of salt water.
Their mass is too great.
The maximum density of salt water is ~1.36 g/mL. The solution is saturated.

The limiting factor is determining an accurate volume for the golf ball.
My students use a 250 mL graduated cylinder.
Anything smaller and the golf ball won’t fit.
Each line is 5 mL (students often think it goes by 10 mL increments).

				
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