OBSERVING A CHEMICAL REACTION (REACTION IN A BAG)

PURPOSE:  To learn how to make careful observations during a laboratory experiment and to illustrate several common indicators of a chemical reaction

MATERIALS:  zip lock bag, sodium bicarbonate, calcium chloride, teaspoon, dropper pipet, balance, phenol red solution

PROCEDURE:
          PART ONE
          1.)
  Open a zip lock bag.  Add about 1 spoonful of sodium bicarbonate to the bag.

2.)     Completely fill a plastic pipet with phenol red solution.  (Pay close attention to your instructor’s demonstration of this technique.)

3.)  Place the filled dropper pipet inside the zip lock bag and seal it completely.

4.)  Fold the zip lock bag in thirds.

5.)  Place your zip lock bag and all of its contents on the balance.  Record the mass on your
      paper.

6.)  Unfold the zip lock bag and squeeze the phenol red solution into the sodium bicarbonate. 
      (Be sure to empty the dropper pipet of all of the phenol red.)  Record your observations.

7.)  Place the zip lock bag on the balance again.  Record this mass on your paper.

8.)  Pour the contents of your zip lock bag in the beaker that is labeled “WASTE – PART 1”. 
      Rinse your bag and dry it thoroughly.  You will use it again for Parts 2 and 3.

PART TWO
1.)  Open a zip lock bag.  Add about 1 spoonful of calcium chloride to the bag.

2.)     Repeat steps 2 – 7 from Part One.

3.)  Pour the contents of your zip lock bag in the beaker that is labeled “WASTE – PART 2”. 
      Rinse your bag and dry it thoroughly.  You will use it again for Part 3.

PART THREE
1.)  Open a zip lock bag.  Add about 1 spoonful each of sodium bicarbonate and calcium
      chloride to the bag.

2.)     Repeat steps 2 – 7 from Part One.

3.)  Pour the contents of your zip lock bag in the beaker that is labeled “WASTE – PART 3”.
      Rinse your bag and dry it thoroughly.  

4.)  Clean up your lab station and return to your seat.


DATA TABLE:

TRIAL

OBSERVATIONS

MASS BEFORE

MASS AFTER

sodium bicarbonate

 

 

 

 

calcium chloride

 

 

 

 

sodium bicarbonate & calcium chloride




 

 

CONCLUSIONS:
1.)  Did your observations agree with the Law of Conservation of Mass?  Explain.

 

2.)  Write a paragraph (that means complete sentences!) summarizing how chemists know when a
      chemical change occurs.

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