BAGGIE SCIENCE

Submitted by:Judith Holt-Mohar, Odell Elementary, Hood River, OR
Endorsed by: These lesson plans are the result of the work of the teachers who have attended the Columbia Education Center's Summer Workshop. CEC is a consortium of teacher from 14 western states dedicated to improving the quality of education in the rural, western, United States, and particularly the quality of math and science Education. CEC uses Big Sky Telegraph as the hub of their telecommunications network that allows the participating teachers to stay in contact with their trainers and peers that they have met at the Workshops.
Date: May 1994

Grade Level: Appropriate for grades 3-5.

                       
OVERVIEW:  This activity introduces students to the idea of
chemical reactions.  As student teams work together the excitement
mounts as they watch changes occur when the chemicals inside their
zip-lock bag are mixed.  The bag gets hot, inflates with gas, the
bubbling contents change color and the liquid turns cold, all
within a matter of minutes.  The task then becomes one of
designing and conducting a series of experiments to determine
which variables produce the different reactions.
  
PURPOSE:  This activity teaches students to observe, experiment,
and make inferences.

OBJECTIVES:  Students will be able to:

     Observe changes and design experiments to explain
     observations.

ACTIVITIES:  Tell students they will be doing an activity
involving a chemical reaction and then designing some experiments
of their own.  For the first part of the activity they will need
to observe very carefully.  Give teams of students 5-10 minutes to
use all their senses EXCEPT TASTING to write down observations
such as "looks like small styrofoam moth balls" or "has a strong
odor".  Write down observations on the right side of the
worksheet.

Demonstrate procedure outlined on Chemical Reactions sheet, but
don't spill the bromothymol blue.  Discuss leveling off teaspoon
to get consistent measurement.  Tell students the reactions will
happen quickly so they will have to concentrate and watch closely. 
Write down reactions on the bottom of the worksheet.

WARNING!!  Excitement is high!  Students are amazed at the
reaction.  They will want to repeat the experiment 3-4 times to
validate the sequence of reactions.  At the end of class period
gather students back together and list reactions on the board. 
Reactions should include:

                          turns blue
                          turns green
                          turns yellow
                          gets cold
                          gets hot
                          forms gas

During this session students will design and test experiments to
determine which variables caused the different reactions. 
Summarize the results from the last session.  Ask students what
they think caused the fizz and bubbles?  What caused it to get
hot?  What caused the gas to form?  Note that three things went
into the baggie, two dry chemicals and one fluid.  Ask them how
they could design experiments to test the variables.  List ideas
and discuss.

Select one of the students' ideas and show them how to write it
down.  For example, "If you mix everything but the baking soda, it
will get hot."

CaCl2 + bromo blue -> hot
 
Challenge students to design experiments by combining 2 variables
and recording results.  Which reactions are dependent on the
combinations of all 3 variables?  Gather the class together at the
end of the session to go over the results.



RESOURCES:  The following quantities are enough to conduct each
activity 2-3 times with a group of 30 students.

 1.  1.5 lbs. sodium bicarbonate (baking soda).

 2.  3 lbs. calcium chloride - purchase at chemical supply house,
     at some hardware stores (ask for "road salt"), or borrow from
     local high school.

 3.  Bromothymol blue - concentrate to make 1 gallon.

 4.  5-6 plastic zip-lock bags per student team.

 5.  5-6 plastic vials per team - go to the photo store and ask
     for the clear plastic 35 mm film containers.

For each team set up a tray with:

 1.  Calcium chloride - CaCl2
 2.  Sodium Bicarbonate - NaHCO3
 3.  Bromothymol Blue
 4.  10 ml graduated cylinder

TYING IT ALL TOGETHER:  Adapted from Chemical Reactions, GEMS,;
Lawrence Hall of Science, U of Calif., Berkeley, CA and article
"The Baggie Problems", Scott Bowler, Catlin Gabel School,
Portland, OR.