Students will design two different solar ovens to learn about heat transfer.
- mixing bowl or salad bowl (wooden bowls are good because they are
often rounded without the flat bottom usually found in plastic or glass
- aluminum foil
- doubled-sided tape
- 20 cm x 35 cm sheet of flexible cardboard
- 1 m of string
- long forks or skewers
Background for Teachers
It's possible to fry an egg on a sidewalk, but you need a very
hot, sunny day and the cooking process takes a while. Using a solar oven
is more efficient. You've probably taken a magnifying glass and focused
sunlight through it to burn paper. The curved reflector in a solar oven
does about the same thing, concentrating all the sunlight that strikes
it into a very hot spot near the center of the oven. The efficiency of
an oven made from a bowl is affected by the size and shape of the bowl;
a continuous curve shape will focus the parallel rays of sunlight better.
Both homemade solar ovens will be affected by how smoothly you're able
to apply the aluminum foil. Be aware of things you can't control, like
the movement of the sun. (You can tell the sun is moving by watching the
oven's shadow.) As the sun moves, so does the oven's "hot spot",
so adjust the oven accordingly. Ideally, the reflector should point directly
at the sun at all times.
Intended Learning Outcomes
1-Use science process and thinking
2-Manifest scientific attitudes and interests
4-Communicate effectively using science language and reasoning
- Never look directly at the sun or at reflected, focused sunlight.
It can damage your eyes permanently.
- Design One: Line the inside of a large bowl with aluminum foil, shiny
side up. Use several small pieces of double-sided tape to secure the
foil. Press the foil close to the bowl and make it as smooth as possible.
- Design Two: Cover one side of a sheet of cardboard with aluminum foil,
shiny side up, securing the foil with double-sided tape. Bend the cardboard
into a semicircle, with the foil on the inside of the curve. Wrap a
length of string twice around the cardboard semicircle and knot the
string at the back.
- Face both ovens into the sun. You may want to prop up and angle the
cookers by making a base with Plasticine. Find each oven's "hot
spot", the spot where the sun's reflected rays crisscross. Different
ovens have different hot spots. To find the bowl oven's hot spot, slowly
put you open hand into the bowl until you feel the hot spot; don't
hold your hand in the hot spot! You'll probably find the cardboard
oven's hot spot near the middle of the string, closer to the foil.
- Put marshmallows on the end of long skewers and hold a marshmallow
in each oven's hot spot. Which oven cooks a marshmallow the fastest?
Can you alter an oven to make it work better (e.g. change curve of cardboard)?
Have students go home and recreate their own solar oven. Retest their new ovens and compare results with ovens made in class.
The following rubric could be used or adapted for grading this activity.
You will be assessing each student's progress on an ongoing basis. Use
the response levels to help you evaluate the student's growth toward the
Key Scientific Concepts, the Communication Characteristics and Learning
- Accomplishes the purposes of the question, task or concept.
- Partially accomplishes the purposes of the question, task or concept.
- Shows fragmented understanding; uses vague scientific communication.
Key Scientific Concepts to Discover:
- Heat travels across space from the sun to Earth by radiation.
- Heat energy transfers through Earth's atmosphere.
- How complete were the student's recordings?
- Did the student's drawings make sense?
- Did the student's recordings reflect awareness of Key Scientific Concepts?
- Did the student show perseverance and attention to detail when working
on the tasks?
- Did the student show awareness of science process as they worked on
This lesson is part of the Sixth Grade Science Teacher Resource Book (TRB3)
http://www.usoe.org/curr/science/core/6th/TRB6/. The TRB3 is designed to be
your textbook in teaching science curriculum to your students. This book covers
all the objectives of each standard and benchmark. If taught efficiently, a student
should do well on the End-of-Level (CRT) tests. The TRB3 is designed for
teachers who know very little about science, as well as for teachers who have a
broad understanding of science.