EXPERIMENTAL DESIGN LESSON
PLAN
ÊÊÊÊÊÊÊÊÊÊÊ This
is a general biology class mainly composed of 14 or 15 year olds.Ê The class is ethnically diverse and a
mixture of males and females.Ê Many
students may not be interested in science.Ê
Hence, a hands-on activity is more appropriate for such a population, as
they would likely tune out, or not understand, a lecture.Ê A lab or exploratory activity is also better
for the concrete operational stage students to get them engaged in science and
experimental design.
á
Sliced
dill pickles (like those on hamburgers; without the ridges), should all be
approximately the same size diameter and thickness.
á
Smooth,
washable vertical surface (e.g. sheet of plexiglass or dry-erase board)
á
ÎPickle
modifiersâ: Water, oil, ketchup, windex, toothpicks, tape
Exploratory
Phase:
On vertical smooth surface,
mark a starting line at the top and divide into ãlanesä for appropriate number
of students.Ê Have students place their
pickle on the start line and race them for a set number of minutes.Ê Pickles slide on their own, no student
interference or aid is allowed.Ê Measure
how far pickle slides (in cm) at the end of the set amount of time.
At end of that time period,
instruct students to remove their pickle and make a change to it using your
provided ãpickle modifiers.äÊ The pickle
must still slide down the surface, so the sliding surface should be
smooth.Ê No other rules or limitations
should be given.Ê Allow 2-3 minutes for
this.Ê Then have students place their
pickles at the start line again and race them for the set amount of
minutes.Ê Measure how far pickle slides
at the end of the set amount of time.
Students should write their
data on a data table on an overhead so that the class can see the results and
how changes to the pickles affected the distance they slid.
Invention
phase:
This next phase is conducted as a class discussion with the following guiding questions.Ê The instructor should write answers, especially those pertinent to the objectives, on the board or overhead.
-
What
did you do to your slice of pickle?
-
What
changed when you did that?
-
Make
a list of modifications made, and another list of what changed.Ê Be aware of dependent variable answers here.
-
Ask
what other words can be used for change and make a list.Ê Among the list of words should be
vary/varied.Ê Explain why change =
varied or variable in science.
-
What
are the things you changed on your own, or independently?Ê Point out that things you change are the
independent variables.
-
What
were the effects of your changes?Ê Point
out these resultant changes as dependent variables.
-
What
things were the same for everybodyâs pickle slice?Ê Point out that these are called constants.
-
What
things should have remained constants, but were not (e.g. amount of ketchup
used, etc.)?Ê Point out idea of ãloose
constants.ä
-
How
do you know if something has changed?Ê
How do you know if the oil on your pickle changed the pickle?Ê Answer should be comparing it to a pickle
with nothing on it.Ê Point out idea of a
control.
-
End
with a small lecture on what a hypothesis is and explain that a rationale needs
to be given for the hypothesis.Ê
Hypothesis:Ê If independent variable, then dependent variable.Ê Rationale is the Îbecause...â statement that
would follow the hypothesis.
Application
phase:Ê
Split students into small
groups of 3-4.Ê Give the following
problem:Ê What brand of gasoline is best
for automobiles?
ÊÊÊÊÊÊÊÊÊÊÊ Ask
what are the independent variable, dependent variable, constants, control,
plausible hypothesis, and a rationale for it.Ê
Groups discuss and write down answers to turn in.
ÊÊÊÊÊÊÊÊÊÊÊ These
are some potential answers from students:
ÊÊÊÊÊÊÊÊÊÊÊ -independent
variable: brand of gas
ÊÊÊÊÊÊÊÊÊÊÊ -dependent
variable: miles per gallon, emissions, engine cleanliness, etc.
ÊÊÊÊÊÊÊÊÊÊÊ -control:
an outside standard (one type of gas)
-constants: same car,
driving conditions, weather, driver, amount of gas, octane, speed, etc.
ÊÊÊÊÊÊÊÊÊÊÊ -should
include some information on repeated and random trials
ÊÊÊÊÊÊÊÊÊÊÊ -hypothesis
and rationale should be plausible and follow aforementioned format
ÊÊÊÊÊÊÊÊÊÊÊ At
the very end, provide a class discussion of the following problem to see if
students understand experimental design concepts.Ê This can also be used for further application/review.
Hot Solutions lab procedure:
150
mL
beaker of plastic cup
Thermometer
Scoop or plastic spoon
Safety goggles
Calcium chloride
Stopwatch
Water
Before students complete lab, ask them questions
about independent variables, dependent variables, constants, controls,
etc.Ê Ask them what hypothesis they
would use and why.Ê
After students complete the lab, ask them what
things they could do to improve the experiment.Ê List should include things like:
ÊÊÊÊÊÊÊÊÊÊÊ Standardize
scoop amount
ÊÊÊÊÊÊÊÊÊÊÊ Use
graduated cylinder to measure water
ÊÊÊÊÊÊÊÊÊÊÊ Use
a consistent measure of time
ÊÊÊÊÊÊÊÊÊÊÊ Take
more time readings
ÊÊÊÊÊÊÊÊÊÊÊ Put
the cups on a standard surface
ÊÊÊÊÊÊÊÊÊÊÊ Keep
hands off the cup (could influence temperature)
ÊÊÊÊÊÊÊÊÊÊÊ Standardize
the thermometer
Finally, to determine if students really understand
what independent variable, dependent variable, constants, and control mean,
give each student a written example of an experiment and have them identify
each of these elements.Ê Also have them
suggest improvements for the experiment.Ê
Once they have done this, have them formulate a hypothesis and give
their rationale for using it to make sure that they understand the concept of
hypothesis.