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Separation of a Mixture - DOC

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									                                     Separation of a Mixture
                                        Chemistry I Lab


Discussion:
       Mixtures are combinations of elements and/or compounds and can be either heterogeneous or
       homogeneous. Two characteristics of mixtures are that the materials retain their own properties
       and that the mixture can be separated by simple physical means. Some simple physical
       separation techniques are decantation, distillation, filtration and chromatography.

Purpose:
       In this lab you will separate a mixture of sand and salt to determine the percentage of each in the
       mixture.


Procedure:
      1. Put on your goggles.
      2. Press the tare/rezero button on the balance so that it reads zero grams.
      3. Place an evaporating dish on the balance and record its mass on the data table.
      4. Add one spoonful of the salt/sand mixture into the evaporating dish and record the mass on the
      data table.
      5. Remove the evaporating dish from the balance and add 10 ml of water to it.
      6. With a stirring rod, carefully stir the mixture in the evaporating dish.
      7. Carefully decant the bulk of the water, being careful not to let any of the solid materials leave
      the dish.
      8. Add another 10 ml of water and repeat steps 5 and 6.
      9. Add another 10 ml of water and repeat steps 5 and 6.
      10. At this point all of the salt should have been removed.
      11. Place the evaporating dish on the hot plate and begin warming it. Allow it to warm until all
      of the water has evaporated.
      12. Carefully remove the evaporating dish from the hot plate with tongs.
      13. Allow it to cool for 5 minutes; then find its mass and record it on the data table.
      14. Clean out the evaporating dish.

Data:
              Letter on the Sample Bottle for your Salt/Sand
              Mixture
              Mass of Evap. Dish

              Mass of Evap. Dish + Salt/Sand Mixture

              Mass of Evap. Dish + Sand only
Calculations:
1. Find the mass of the salt/sand mixture            2. Find the mass of the sand that remained at the
   used in the experiment.                              end of the experiment.




3. Calculate the percentage of salt in the original mixture. Give your answer to the nearest tenth.




Questions (Answer these questions in complete sentences.)

1. Is the salt/sand mixture heterogeneous or homogeneous? Why do you say so?




2. What could have caused you to get a percentage for the salt that was not correct? Give specific
answers other than “I could have messed up.”
      a)


       b)


       c)


       d)

3. Take one of the ideas in number 2 and propose a method for correcting that problem.

								
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