Each new school year offers endless
possibilities for igniting student interest in science. The
principles students study in your classroom touch every aspect of
their lives. Seeing the science involved in everything from a
rainbow to a rock concert can be rewarding and enjoyable; having an
understanding of the underlying physical principles behind these
phenomena serves to heighten these experiences even more. Such
consciousness-raising can enrich your students’ lives just as an
appreciation of art and music can expand their horizons.
Science students have an opportunity to interrogate nature directly
through experimentation. As science teachers, we should take full
advantage of this aspect of our discipline and allow students as
many hands-on experiences as possible. While the laboratory is the
traditional arena for such inquiry-based activities, a host of
alternative venues exist.
The following activities are, for the most part, to be performed
outside the classroom. They are intended to provide students with an
awareness, appreciation, and understanding of the myriad phenomena
that surround them.
Mentos & Diet Coke You may have
seen this clip before, if not you're in for a treat. Chemistry,
pressure & fluids and a flair that, if nothing else, is fun to
Watch the Video
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Now that you have seen seen the Diet
Coke and Mentos geyser video, here's the science behind the reaction. When a Mentos mint is dropped in a 2-liter
bottle of Diet Coke, a tremendous amount of carbon dioxide gas is
released in an instant, resulting in an eruption of soda. Most
students and teachers speculate that the effect is caused by a
chemical reaction between the mint and the carbon dioxide-rich soda.
However, based on research findings, this explanation is not
correct. As it turns out, the root cause of the reaction is
physical, not chemical.
Diet Coke is supersaturated with carbon dioxide gas. Supersaturated
solutions contain more dissolved material than could be dissolved by
the solvent under normal conditions. At the elevated pressure found
in a Coke bottle, much more carbon dioxide can dissolve than at
Scratches on the surface of a Mentos mint can serve as nucleation
sites, places where the carbon dioxide gas can form bubbles. Since
there are so many of these sites on a Mentos, the gas comes out of
solution extremely rapidly. The effect is magnified by the fact that
a Mentos is denser than Coke. As it sinks, it comes into contact
with liquid from the top to the bottom of the bottle. The sudden
increase in pressure that results from the rapid release of gas
forces the soda out of the bottle.
The question is: will other sodas and other candies produce similar
results? This is where experimentation comes in. While a wide range
of combinations have been tried, most of which can be seen in
Internet videos, having students do a series of controlled
experiments could teach them much about how science is done.
Controlling variables, making measurements of geyser height,
recording, sharing and analyzing data, and drawing conclusions can
all be done either in school or at home.
1. Taking the Science
Classroom into the World
The world outside the classroom provides
endless possibilities for discovering and understanding nature’s
laws. Through experiments and exploratory activities performed in
non-traditional settings, students of all ages can be made aware of
the beauty and wonders of science. Furthermore, such experiences
make evident the examples and applications of science in everyday
Measuring the Moon:
From CoolStuff #10 Indirect Measurement
The key concept is that students will use the concept of similar
triangles to indirectly measure the diameter of the moon. This activity can be done in the classroom, if
the moon happens to be visible from your windows, or it can be done at
home by each student.
You may find this hard to believe, but you can
measure the diameter of the moon from the comfort of your home.
The equipment needed includes an index card, a pin, two strips of opaque
tape (masking or electrical tape works well), and a centimeter ruler.
Oh, and one other thing, you’ll need to know
that the moon is 3 x 105 km from earth.
When the moon is full, place the two strips of
tape 2cm apart on a windowpane facing the moon. After making a
pinhole in the index card, observe the moon through the pinhole and two
strips of tape. Back away from the window until the moon appears
to just fill the space between the two strips of tape. Measure the
distance from the card to the window. Using the proportionality of sides
that exists for similar triangles (see figure above), calculate the
diameter of the moon.
2. Science to Go:
Doing Science with Family and Friends
Why not let your students share the fun
and excitement of science with their family and friends? Using
simple and safe materials, students may do a wide variety of science
experiments at the kitchen table or in the backyard.
The benefits of at-home science
activities are many. They increase the time students are thinking
about and doing science. Since many of the explorations focus on
counterintuitive phenomena, students delight in sharing unexpected
outcomes with others. Needless to say, parents love seeing what
their children are doing in school.
More Mint Magic
Can you identify this eerie-looking
object? If you guessed UFO, you’d be wrong. It’s a Wint-O-Green
Lifesaver being crushed with a pair of pliers in a dark room.
Referred to as the “electric Life Saver effect” by some people, the
phenomenon was first observed over 400 years ago.
Photo courtesy of Lewis Kozlosky
Officially known as triboluminescence,
the luminescent effect is the result of a two-step process. First,
the crushing of the mint causes some the positive and negative
particles in the sugar crystal to separate. As these charged
particles recombine, they may collide with nitrogen molecules in the
surrounding air. Energized by the collision, the nitrogen molecules
emit both visible and ultraviolet light. However, the visible light
produced is of low intensity and difficult to see. This is where the
wintergreen comes in. The ultraviolet light causes the methyl
salicylate in the wintergreen flavoring to fluoresce with a blue
glow. Once your eyes have adjusted, this light is bright enough to
be seen in a very dark room.
Students can experiment with a variety
of mints to see which work and which don’t. Among other things, they
will find that both pink Necco wafers and wintergreen Certs produce
results similar to those obtained with Wint-O-Green Lifesavers. Both
of these mints contain sugar and wintergreen. (Note: Students love
to see their mouths light up as they crush the Lifesavers between
their teeth. This procedure is not recommended since it could
necessitate a trip to the dentist.)
Quite often the materials needed to investigate physical phenomena
at home may be found in the kitchen or workshop. When more
specialized equipment is needed, create a "Lab in a Bag" by packing
required materials in a plastic food-storage bag. Using the “Lab in
the Bag” approach, students take home simple materials relating to a
given concept in Zip-Loc® bags. Everything needed to investigate
phenomena ranging from electromagnetic radiation to Newton’s Laws is
contained in a single plastic bag.
Prior to presenting the students with
their first activity, send a letter home to parents explaining the
purpose and nature of the activities. The letter might also inform
parents that their child will receive credit upon the return of a
signed sheet indicating the parents’ or guardians’ involvement in
Lab in a Bag:
From CoolStuff #20 Take Home Science
Construct a Kaleidoscope
Click here for details on assorted mirrors
This activity is a hands-down favorite of our students! This “Lab in
a Bag” includes three 1”X 6” mirrors and an instruction sheet. The
sheet describes kaleidoscope construction and offers suggestions for
creating a variety of objects to be viewed through the scope. The
sheet also provides a brief explanation of image formation by the
kaleidoscope and a history of the device. The resulting
kaleidoscopes are absolutely stunning! Students often give their
finished kaleidoscopes to family members and friends as gifts.
The mirrors used are cut from standard mirror tile available at any
hardware or home supply store. You may cut the mirrors at home using
a glass cutting tool; however, many hardware stores will cut the
glass for free when they learn of your mission.
The simplest kaleidoscope is constructed by simply taping the three
mirrors together with masking or electrical tape. The mirrors are
placed face down and the tape is applied over small gaps left
between the mirrors. These spaces allow the mirror assembly to be
folded into a triangular shape. Without the gaps, the mirrors will
When no object is permanently attached
to the far end of the three-mirror system, the device is called a
teleidoscope. View your world through the teleidoscope and be
amazed! Everything seen through the teleidoscope is transformed into
a beautiful, multi-faceted pattern. Attaching an object such as a
decorated ping pong ball or test tube containing water and colored
beads to the end of mirror system formally turns your teleidoscope
into a kaleidoscope.
3. Physics on
Science is too interesting to keep it
cloistered in the classroom! For almost 30 years, we have been
sharing the wonders of nature with others in our school through the
use of display cases and exhibits located outside the classroom.
While doing science in the hallway or other non-traditional settings
may seem a bit unorthodox, this form of informal education beckons
members of the entire school community to learn just how interesting
and enjoyable science can be.
Our first involvement in hallway science displays occurred when we
realized that the primary use of our school’s display cases was to
store and display trophies. Many cases were not used at all. It
occurred to us that we might be able to use these showcases as
extensions of the classroom. Our very first effort revealed that a
science showcase attracts both science students and non-students
alike. In fact, we learned that the display case is an excellent way
of introducing non-science students to the wonders of the various
scientific disciplines. Students often spend their passing periods
trying to understand some phenomenon that to them seems paradoxical
or a violation of common sense.
Interactivity is the key to a good display. Doing, not just looking
and reading, engages both hands and minds. Furthermore, the more
open-ended an activity, the better. Individuals should be able to
view the apparatus as a vehicle of discovery and feel free to ask,
“what will happen if I do this or that.” As you’ll see, even
displays behind glass can be interactive.
The following examples of hallway exhibits and display cases have
been very popular with our students. While inexpensive and simple to
build and use, they have provided hundreds of students of all ages
with a great deal of pleasure and perhaps a desire to learn more
about the wonderful world in which they live. Hopefully, these
exhibits will get you thinking about ways of decking your halls with
Pipes of Pan:
From CoolStuff #15 Hallway Science
A trip to the carpet store was the genesis of the giant ambient
noise resonators or Pipes of Pan, as they are sometimes called.
Eight carpet tubes mounted on a plywood base became the basis for a
rather strange musical instrument. Based on the principle of
resonance, the air in each tube vibrates with a frequency determined
by the length of the tube. The background noise in a room contains
virtually all audible frequencies, and is capable of creating
resonant vibrations in each of the tubes.
We simply put our Pipes of Pan in our school’s central hallway and
allow people to explore. A sheet with suggestions for use and a
brief explanation of the apparatus is provided. Needless to say, the
unusual musical instrument is almost always in use.
As is seen in the photograph, a person placing their ear near the
end of one of the tubes hears a definite pitch. Moving from one tube
to the next in succession, the listener hears a musical scale. Some
people try to play a simple tune by rapidly jumping from one tube to
To make your own Pipes of Pan, ask your local carpet installer for
carpet tubes. The carpet tubes should have a combined length of at
least 8 m (roughly 24 ft). This length allows for loss that will
occur during cutting. The tubes should be cut to the lengths in the
chart below. The chart also shows the corresponding note and
resonant frequency for each tube. The tubes may be painted
(optional) and attached to a sheet of plywood with small bolts. The
tubes may also be simply placed on a tabletop with end stops to
For ready-made sound tubes, check out
This Exploratorium-inspired exhibit is visual ambiguity set in motion.
As you stare at the shadow of a slowly rotating cube, you notice that it
mysteriously appears to reverse its direction of rotation. A quick check
of the actual cube reveals that its motion is unchanging. What gives?
Rotational ambiguity arises when the three-dimensional cube is
compressed to a two-dimensional projection, removing important visual
cues. Finding either direction of rotation equally acceptable, the mind
perceives the cube to rotate in one direction, then the other.
As the photo indicates, the exhibit is very simple. A cube fashioned
from balsa or soda straws is suspended from a slow turning motor. A
slide projector is used to form a shadow of the cube on a translucent
screen. Our screen is made of muslin. PVC pipe may be used to form the
support for the screen and the motor, but ring stands also work quite
well. Two ring stands support the muslin screen while a third ring stand
and clamp hold up the motor and cube assembly.
This device may be modified slightly for Halloween. Replacing the cube
with a dangling plastic skeleton adds an additional creepy element to an
already eerie display.
The sky offers a wide variety of
stunning optical effects. Among them are red
sunsets, rainbows, halos, glories, and coronas. Common optical
phenomena are often due to the interaction of light from the sun
or moon with the atmosphere, clouds, water, or dust and other
particulates. Some of these phenomena can be seen almost every
day; others are once in a lifetime sights. The next issue of
CoolStuff will examine examples of atmospheric optical phenomena
and how they may be demonstrated in the classroom.
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