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.