Here suggested strategies are presented within
the context of Informed Design, a pedagogical model
for teachers. The FOCUS
components are: Focus
discussion on the problem context, Organize
for informed design, Coordinate
student progress, Unite
the class in thinking about what has been accomplished,
and Sum up progress
on the learning goals.
PERIODS 1-2: Focusing Discussion on the Problem
Context
THE PROBLEM. In
order to focus and engage your students, explain
to the class that a group of elementary school children
needs their help. The children are planning a weekend
hike during which they must carry everything, including
their food and clothing. They are concerned about
the heavy load each person will have to carry. Unable
to think of ways to substantially reduce the weight
of their backpacks, they have turned to your class
for advice. Ask the following question: "How can
the load in the backpacks be reduced? After providing
"wait time" for the class to think, elicit and record
(on chalkboard, flip chart or overhead projector
acetate) a number of weight-reduction ideas and
briefly examine the feasibility of each with the
class. If the class fails to mention food dehydration,
lead them in that direction by asking for examples
of the foods astronauts have used. They should respond
with examples of dehydrated foodstuffs such as soup,
juice, cocoa, chicken dishes, fruits and vegetables.
Tell the group that they are going to focus on
dehydration as a way to reduce the load in the backpacks
and then describe the design challenge. Distribute
Handout #1, the Introductory Packet, and refer students
to the design challenge.
Have students put aside the Introductory Packet
until the following period.
Display for the class a plate of fresh apple slices
and a plate of dehydrated slices of the same variety
and size of apples. Have students compare and contrast
the contents of the two plates. Ask "KWL" questions
to find out what the students do know, what they
want to know, and what they need to learn for the
following questions: "How and why do apples become
dehydrated under natural conditions?" and "Why and
how do humans choose to dehydrate them?" Use these
questions to discover naive conceptions individual
students hold about food preservation and dehydration.
THE CHALLENGE.
Redirect students to the Introductory Packet.
As you go through the packet's contents together,
present the challenge in a manner that will motivate
them. Discuss briefly the Here's What You Will Do,
Problem Context, and Materials Needed sections.
PERIODS 3 - 5: Organizing For Informed Design
INFORMED DESIGN.
Elicit from students what they know about good
design and who engages in design. Ask for examples
of good design and poor design.
Tell the class that completing a series of KSBs
will help prepare them for addressing the design
challenge they face. Then introduce Handout #2,
KSB TI: The Informed Design Cycle, and provide time
to read it.
The information in KSB TI should be referred to
often as groups work on the design challenge. The
informed design loop can be particularly useful
to the students as they chart their progress using
a Design Journal (or Design Activity Folio). Like
professional engineers, they will find themselves
using the loop in an iterative way rather than in
a linear way. Discuss the informed design cycle
and stress that although design is normally informed
by the designer's current knowledge, completion
typically requires access to new knowledge. Discuss
the need to research what solutions exist to solve
this design challenge, and how reaching an optimal
design solution requires meeting specifications,
working within constraints and making trade-offs.
STUDENT REQUIREMENTS.
Discuss the student requirements (Introductory Packet)
after determining whether you will expect the students
to use the Design Activity Folio (DAF) or the Design
Journal. Help students see that either of these
devices allows them to document progress as they
complete literature searches, factor investigations
and Knowledge and Skill Builders (KSBs). Describe
the requirement that each student submit a Design
Report and each group make a class presentation
at the conclusion of the module. Explain that the
report and the presentation will be based on information
recorded in the Design Journal or DAF. Alert them
that they are expected to deliver multimedia presentations
that detail their design process and results. Help
them see that such a presentation summarizes work
completed in research, collecting and analyzing
data, developing models, improving design and making
refinements. Describe multiple forms of media (e.g.,
presentation software, color overheads, videos and
computer animation) that they might use to enhance
their presentations. Assure them that when classmates
ask probing questions and challenge group findings
at the end of presentations, they are mirroring
proceedings that are common at science conferences.
ASSIGNING GROUPS.
Talk with some of the students ahead of time
to see how experienced they are at working in cooperative
groups. Assign small working groups: three is ideal.
Monitor groups throughout the module.
PERIODS 6 -16: Coordinating
Student Progress
COORDINATE WORK BY INDIVIDUALS.
Plan opportunities within this module for students
to revisit their initial understandings by providing
experiences with new phenomena that contradict their
stated perceptions. Unless individuals get to actively
process such contradictions, they may fail to grasp
the new concepts and then may revert to their naive
conceptions.
Help individual students make the connection between
carefully documenting information as they proceed
and well-written reports and presentations at the
end. Note that a student displaying unacceptable
behavior may be doing so because other members of
the group do not value what he/she says. Get to
know the strengths of such a student and try assigning
roles for all members of his or her group. Give
the student a role that features a personal strength
and inform the group ahead of time that this person
is known to do that task well.
Suggest that individual students pursue their own
investigations of different topics related to dehydration.
Some possible topics include how commercial dehydrators
are made; the factors influencing the speed of dehydration;
microbes and spoilage; the relationship between
temperature and drying time; and how to preserve
nutrient values.
As the work becomes more technical and cerebral,
some students will begin to complain that they are
doing all the work while others loaf. Citing examples
from your own experience, explain to such individuals
that the best way to learn something is to teach
it to others. Remind the group that it is essential
that all members of a cooperative group understand
all ideas and steps along the way. Conduct frequent
oral checks to see that each student has adequate
understanding before the group moves on in its work.
GROUP RESEARCH AND INVESTIGATION
THROUGH KSBS. Have
students complete Handout #3, KSB T2: Dehydration
Techniques. If your class has prior knowledge of
the mathematics in KSB M1, then you can save time
by proceeding directly to Handout #6, KSB S1: Factor
Investigation. Otherwise, complete KSB M1: Mathematical
Comparison of Relationships and/or KSB M2: Banana
Data prior to KSB S1.
KSB S1 has students explore factors that affect
dehydration and allows them to practice using some
of the equipment/materials they may choose to use
later in completing the design challenge. This activity
gives students concrete evidence that there are
design factors to consider such as the thickness
of apple slices. KSB SI calls for the use of materials
(apples, slicing tool, fan, heat source [such as
a 120w bulb], wire mesh, scale and graph paper or
spreadsheets [computer optional]) to address a research
question ("How does the thickness of a foodstuff
such as an apple affect the rate of drying?").
Here are acceptable responses to the Develop Your
Understanding section of KSB S1:
1. A new title might be: "The effect of thickness
on drying time. "
2. One possibility is: "If the thickness increases,
then the drying time will increase proportionately."
3. The variable that is purposefully changed by
the experimenter is: "the apple thickness."
4. Each test should be conducted at least three
times. The way around this is to pool data from
several experimenters using the same conditions.
5. The variable that responds is: "the drying time
of the apple slices."
6. All other factors should remain the same and
have a fixed value (e.g., the amount of heat from
the lamp or the fan speed). All variables should
be kept constant except the independent and dependent
variables.
7. The control is the standard for comparing effects
(e.g., an apple slice that is purposely prevented
from drying by heat or airflow).
8. The independent variable (apple thickness), by
convention, is placed in the left-hand column of
the table, the dependent variable in the right-hand
column.
9. Answers will vary. Some will notice the nonlinear
relationship; others will express ideas for optimizing
the design.
10. Answers will vary.
OPTIONAL MATHEMATICS KSBS.
Some student groups would benefit from an activity
that involves the analysis of data for both linear
and nonlinear relationships; if so, they should
complete Handout #4, KSB M1: Mathematical Comparison
of Relationships, prior to KSB S1. In Part A of
KSB M1, the data plots reveal a linear relationship.
In Part B, the data 16 plots reveal a nonlinear
relationship.
Materials needed in Part B include graph paper
or spreadsheets (computer optional), safety goggles,
+100°C thermometer, a heating source, a water
source, and a poorly insulated container. Be aware
that it would save time in Part B if the container
chosen (cup, beaker, etc.) was not well insulated.
Heat transfer from the container to the environment
will be faster and the overall cooling time will
be reduced.
The desired response to the Develop Your Understanding
item in Part B ("Should you be taking measurements
at the same time interval throughout the cooling
process?") is: "Since the form of the data is similar
to dehydration, Y = Yfinal+
Yinitial-xt, the more rapid temperature change in the
beginning of the cooling process suggests more frequent
readings than toward the end, when the temperature
change is slower."
Most student groups are likely to need help seeing
the value of using dimensionless data during analyses
and therefore would benefit from completing Handout
#5, KSB M2: Banana Data, prior to attempting KSB
S1 but after KSB Ml. KSB M2: Banana Data helps students
see how converting to dimensionless data enhances
data analysis. The effect of the drying of fruit
is nonlinear and follows a process of y = A + Be-xt.
When students plot the data, the y ordinates for
the different banana thicknesses have different
values, making it difficult to compare data with
different banana thickness. The y ordinates become
dimensionless numbers between 1 and 0 for all thicknesses
and the slice drying times can be more readily compared.
SEEKING ADDITIONAL FACTORS
AFFECTING DEHYDRATION. After debriefing
on the factor investigations (KSB S1), conduct some
small group discussions on additional factors that
might affect fruit dehydration. Prompt the students
to further investigate the process of dehydration
through the use of experts, print sources, the World
Wide Web and/or additional factor investigations.
Present students with Handouts #7 - #9, KSBs S2:
Dehydration, Microbes, and Spoilage; S3: Humidity;
and S4: Appearance Changes. Help them decide the
type and extent of their investigations.
Materials needed for KSB S4: Appearance Changes
include: apple
slices, dissecting microscope (3-D scope), and one
or more chemical preservatives such as ascorbic
acid, citric acid, lemon juice, salt water or sodium
bisulfite.
One efficient way for a class to investigate dehydration
extensively is to have different groups cover different
investigations and share findings later on. Here
are samples of Internet sources that students might
locate:
1. Sources on drying foodstuffs:
http://www.ag.uiuc.edu/vista/html_pubs/DRYING/
dryfood.html
2. A NASA site with an alternative
dehydration activity: http://spacelink.msfc.nasa.gov
(Use "Space Food and Nutrition" link and then "Dehydrating
Food for Space Flight" link.)
Work with groups of students, monitor overall progress,
and see that student work proceeds in an orderly
and timely way. If things are not going well within
a group, help group members find another way to
obtain the knowledge or skills they need. Individual
tutoring, peer teaching, teacher lecturing and using
outside resources and/or instructional technology
might come into play at your discretion.
SHARING. Convene
the large group one or more times to share results
of individual and group investigations. Invite students
to listen critically to one another and facilitate
a discussion of how this knowledge can be used to
inform their design of a dehydration system. Continue
to work as a facilitator as students work in their
groups to create alternative designs. Check to see
that each group understands that its solution must
address the specifications and constraints and the
conditions needed to dehydrate apples. Remind each
group to make decisions and select design components
based upon their investigations and their understanding
and application of MST principles. You might want
the groups to develop a rating system to determine
which alternative design is preferred.
PLANNING AND CONSTRUCTING.
Continue to work as a facilitator as groups
select their preferred alternative and develop plans
for construction. Facilitate a discussion of trade-offs
that are made in the search for an optimal design
solution. Encourage groups to identify and model
functional design elements and construct their working
prototype.
TESTING. Bring
students together as a large group and discuss ways
in which each group might test their design. Facilitate
small group development of testing and evaluation
procedures.
Bring the entire group together to compare results.
Encourage student groups to carefully review the
work of other groups to glean ideas that might inform
a redesign. When redesign is discussed, continue
to direct students' attention to how the understanding
and application of MST concepts can guide improvements.
PERIODS
17 - 22: Unite the class in thinking about what
has been accomplished
DESIGN REPORT. The
reports are one of the major opportunities for you
to determine whether individuals have attained your
goals for this module. Continue to work as facilitator
as groups document their progress and share results.
Explain that each student must submit a Design Report.
Assist individuals in structuring and writing their
Design Reports. The Design Report should include
a discussion of redesign with justifications for
the redesign decisions. Remind students that the
report should include a response to the hiking club
issue described in the Introductory Packet. Provide
students with Design Report guidelines. As you introduced
this module, you told students that careful documentation
in the Design Journal leads to a well-written final
report later on. For individuals who have trouble
writing, check their documentation frequently along
the way to ensure that they will have a source of
information adequate to generate a report.
GROUP PRESENTATIONS. Discuss
with the class what is considered proper and expected
deportment during group presentations. Address the
need to use a variety of media to support the presentation.
During the group presentations to the class, encourage
students (through example) to ask appropriate questions
and provide constructive feedback to the presenters.
