by Dr. Kathleen A. Carrado, Argonne National Labs |
Place your solid object on the yellow side of
the architect paper. Let it sit under a bright light for
about five minutes. While waiting, place the rocks
in the jar and have your adult partner add the
ammonia. Make sure the liquid is just below the
surface of the rocks. Cover the jar tightly with the
lid. Remove your solid object from the light and
notice the "imprint" it left on the paper. Open the
jar and carefully place the paper inside, taking care
to not let the paper touch the ammonia. Re-cover
tightly and observe the paper for about 5-10
minutes.
The ammonia fumes will turn the imprint a
deep blue purple color, leaving the rest of the
paper alone. The light has chemically altered the
unprotected surfaces of the paper so that it will no
longer react with the ammonia, which is a chemical
base. Architect paper is a very light-sensitive
material, but your object has protected and
preserved a small portion of it.
When you are finished, have your adult
partner pour the ammonia down the drain and
clean the jar and rocks with warm soapy water.
Take care not to inhale the ammonia fumes at any
point during your experiment.
Bubble gum is a mixture of several
chemicals, but rubber is the most important. A
good bubble gum must be strong enough to
stretch to a thin film without breaking, but still be
soft enough to chew easily. That's a tall order. The
other chemicals in bubble gum - resins, waxes,
fillers, flavors, sugar, humectants, and emulsifiers -
are all there either to provide flavor or to modify
when and by how much the rubber stretches.
Rubber molecules are polymers, which are long
chain-like molecules formed when many smaller
molecules bond together end to end. A natural
polymer called latex, which is from trees, used to
provide the stretchy part of bubble gum. Now
many gum companies use a synthetic, food-grade
version of the same rubber that goes into truck
tires! This polymer is a mixture of styrene and
butadiene and is abbreviated SBR.
Of the 20 or so chemicals in bubble gum,
some dissolve in water and some do not. Most of
the water-insoluble portion of bubble gum is called
"gum base". That's where the rubber is. Some of
the additives in the gum base actually restrict the
size to which the bubbles can be blown on
purpose, so as not to completely alienate parents!
The most intense fragrances and flavorings in fruits
are often essential oils like limonene (which is from
orange and lemon rinds). They are well suited to
gums because they are not water soluble and do
not dissolve out of gum in your mouth. Gum does
seem to lose flavor after a while, but that is usually
because the sugar, which intensifies the fruit
flavor, has dissolved.
Chemists must think of not only how the
gum tastes and how big the bubbles get, but also
how it feels in the mouth. It must soften without
getting gooey, take up water without dissolving,
and keep its flavor for as long as possible. On top
of all that, it must not dry out on store shelves,
should not stick to the wrapper, and be easy to
work with in the factory. Chemists know how to
tweak all the ingredients to make a formulation that
is just right; who knew a simple thing like gum
could be so complicated!
Sugar Gems. Granulated sugar is made up
of ground-up sugar crystals. Have an adult help
you slowly and carefully dissolve 2 cups of sugar
into 3/4 cup of boiling water. Let the solution cool
slightly, and then pour it into paper cups or clear
plastic glasses. Set them aside where they won't
be disturbed. As the water evaporates, crystals of
sugar (sucrose, C12H22O11 ) will begin to form on
the bottom and sides of the cup. Unfortunately,
the faster the water evaporates, the smaller the
crystals will be. Be patient. Crystals the size of
peas will form in a month or so, depending on the
temperature and humidity. You can buy jewelry
settings at a craft store and attach your best gems
singly or in groups. If you want to grow large single
crystals, you'll have to use special techniques
described in books on crystals at the library.
Spice Jewelry. Spices are used by cooks
to add flavor and aroma to foods. No one pays
much attention to their appearance. But some
spices are attractive and can be used as beads in
unusual necklaces or bracelets with a nice smell.
First we will consider cloves, which are dried
flower-buds grown in places like Zanzibar and
Sumatra. The aromatic oil of cloves is called
eugenol (C10H12O2 ). Another good one is allspice,
which is the aromatic dried berry of the pimento.
This also contains eugenol, and is grown in places
like the Indies and South America. Soak whole
cloves (these are round) and allspice (this is
flute-shaped) in water for a day or two until they are
soft. Using a needle threaded with nylon thread or
even dental floss, pierce the spices and run them
onto the thread in your own designed pattern.
The allspice can be pierced either lengthwise
(down the middle of the long axis) or crosswise (to
give a tooth-like appearance). When completed,
the spices will dry back to their original shapes and
will be held firmly on the thread.
You can prove that this droopiness is due to
a gas leak by doing the following test. Get a regular
balloon, a bottle of vanilla extract (or almond or
orange), and a glass of water. Pour two capfuls of
the vanilla into the balloon and then blow it up with
air and tie it. Set the balloon on the glass so that
the knot is under water. Leave this set-up
overnight in a confined space, such as a closed
bathroom or closet. Your nose should then help
you solve the mystery. A balloon's surface has lots
of tiny holes that can be seen only with powerful
magnifiers, and vanilla molecules are small enough
to eventually leak through this surface. Helium
molecules are much smaller than air or vanilla
molecules, and so they leak out even faster.
What can be done to slow this leakage and
make the balloons last longer? A chemist (a "leak
buster") invented a chemical called Hi-Float® to
slow down the leaks. Hi-Float® coats the inside of
balloons with a special stretchy film with very small
holes. It makes it harder for the helium molecules
to leak through the walls of the balloons. Some will
float for as long as 15 days! Now in gift shops they
will often ask you if you want Hi-Float® used in your
balloons. The shiny foil balloons made from
Mylar® are also leak busters. Their surface has
virtually no holes at all so they can stay filled for
several weeks.
The colors of construction paper quickly
disappear with the application of bleach. The trick
is to apply and spread bleach in a manner that will
result in an artistic pattern. Pour a small amount of
bleach into a glass, and then experiment with
different applicators, such as a spoon, brush, and
cotton swab. Spread the bleach around on the
paper by folding, tilting, and blowing through a
straw. A little bit of bleach goes a long way, and
you'll be able to see the patterns almost
immediately. Let your work of art dry before
hanging it up for all to see.
In this case the bleaching action can also be
called an "oxidizing" reaction. You can prove that
oxygen is made from bleach by putting two small
balls of steel wool (of the same size) into two
different glasses. Cover them with equal amounts
of water. Add a tablespoon of vinegar to each
glass, and then to just one of them also add a
tablespoon of bleach. After about half an hour the
steel wool without bleach should be unchanged,
but the ball with the bleach should be very rusty.
Rust is iron (from the steel wool) that has combined
with oxygen in the presence of water. While iron
rusts easily, it happens very quickly here because
the bleach is producing so much oxygen!
[SAFETY NOTES: Do not leave children
unattended while working with bleach. Do not let
the bleach come into contact with skin or eyes; if it
does flush immediately with large amounts of
water. Thoroughly clean or dispose of all materials
that came in contact with bleach.]
The "cold light" given off by living things is called
bioluminescence. Certain kinds of moss glow in
the dark, and rotting tree stumps give off an eerie
light that is called foxfire. Many cases depend on
bacteria. The flashlight fish, for example, lives very
deep in the ocean where it is absolutely dark.
They have sacs of luminous bacteria near their
eyes. The bacteria glow all the time, but the fish
can cover and uncover the sacs with flaps of skin.
They search for food with these lights, blink to
attract other flashlight fish, and confuse their
predators by flashing and then quickly changing
direction.
Bacteria and fireflies make their cold light by mixing
chemicals called luciferin, luciferase, oxygen, and
ATP (adenosine triphosphate). This reaction has
even been developed into a sophisticated medical
test for treating tuberculosis (TB). Saliva samples
taken from TB patients are treated to make
luciferase and then luciferin is added to make them
all glow. Each sample is then exposed to a
different antibiotic until the right one works, the
bacteria are killed, and the glow goes out.
In Light Sticks, a large outer tube is made of
flexible, translucent plastic. Inside is a solution of
oxalate ester and fluorescent dye molecules. Also
inside is a smaller glass tube that contains
hydrogen peroxide. When you bend the stick, the
thin glass tube breaks and allows all of the
chemicals to mix and react. This chemical reaction
provides the energy needed by the real workers in
this process, which are called electrons. It is the
Light Stick chemical system that has been
repackaged to also make glowing bracelets,
necklaces, and earrings. So now you know a little
bit about the science behind the bright lights that
your parents might make you wear at outdoor
sporting events, concerts and fireworks!
First, put a piece of bread and a teaspoon of
water into a ziploc plastic bag, seal it, and let is sit at
room temperature for 3 or 4 days. You'll notice that
the bread is now covered in green mold. Mold is a
furry growth of fungus found on the surfaces of
decaying food or in moist, warm places. A fungus
is a tiny non-flowering plant with no chlorophyll,
roots, stems, or leaves. The fungus could have
gotten onto the bread by a variety of means, such
as transfer from your hands.
Secondly, we'll do a test for microbes that
cause feet to smell bad. Feel smell bad when very
tiny plants or animals grow on our skin. Have an
adult boil 1/2 cup of water. Sprinkle in 4 envelopes
of unflavored gelatin and dissolve it. Pour this into
a clean mayonnaise jar and set it on its side (let the
extra pour out and dispose of it). Put on sneakers
without socks and go play outside. After about 3
hours the gelatin should be hard and your feet
should be smelly. Take a swab and rub it between
all your toes. Carefully brush the gelatin with the
cottin tip in long strokes. Close the jar and put it in
a warm dark place for 4 days.
Inside your shoes it's dark, warm, and damp.
This is perfect for microbes, which will grow and
grow. The mayo jar is similar, and the microbes
survive by eating the gelatin. You'll see grooves in
the gelatin after 4 days showing where the
microbes are living and eating. If you open it, you'll
smell something much worse than smelly feet. It
smells really horrible. Either dispose of the jar
intact or, if you want to save it, fill it with hot water
and then wash with soap and water. DON'T touch
inside the jar at first, and keep washing your hands.
Where does that pressure come from? At the
surface of the water, a column of air weighs 14.7
pounds per square inch, or "one atmosphere".
When you go underwater, you add the weight of
the water to the atmospheric pressure. A 10-meter
(33-foot) column of water also weighs 14.7 pounds
per square inch, so at a depth of 10 meters the
pressure is two atmospheres: half from the water
and half from the air above it. Pressure influences
how divers use air. At ten meters, the increased
pressure means that lungs hold twice as much air
as they do at the surface - and divers breathe air
from their tanks twice as fast. This is why divers can
stay down only a short time, for example, 15
minutes at 50 meters.
"The bends," or decompression sickness, is a
health hazard associated with pressure changes.
The longer you stay down and the deeper you go,
the more nitrogen gas dissolves into your body
tissues. Nitrogen comes from the air we normally
breathe, which is about 80% nitrogen and only
20% oxygen. If you ascend too rapidly, the
dissolved nitrogen comes out of solution too
quickly and forms bubbles in your tissues. You
could experience severe pain in joints, dizziness,
blindness, paralysis, and convulsions.
Divers learn they must ascend slowly, and
sometimes take "decompression stops" on the
way up. This allows the dissolved nitrogen to
come out of the body safely. Sometimes a
hyperbaric chamber has to be used to stabilize a
diver in critical condition. These are chambers in
which patients breathe 100% oxygen at greater
than one atmosphere pressure using a mask.
Flooding the body with pure oxygen helps to
quickly and safely eliminate the nitrogen gas.
Divers can also be certified to use different
mixtures of air in their tanks, which are enriched in
oxygen ("nitrox").
It is between the layers or sheets of a clay that
chemistry can take place. Many molecules are
soaked up into these layers and are either strongly
held or else react to form different molecules. Did
you know that kitty litter is almost 100% clay? The
absorbent properties of clays are obvious here,
and they are especially good at binding up the
smelliest molecules! Clays are sold commercially
as products to help clean up spills, especially oily
spills. You will come into contact with kaolinite clay
many times a day, for it is used as both a paper filler
and paper coating. In fact, the higher quality and
glossier the paper is, the more kaolinite is coating
the surface; and it aids in binding the inks and
dyes. Kaolinite is also the active ingredient in
Kaopectate®, and so clay is even used as a dietary
aid
Very pure clays can be used in a number of
other products around the home. When all the
iron and soil is removed, many pure clays are
actually white. They are then ground into fine
powders and added to many formulations. If you
see "magnesium aluminum silicate" or "bentonite"
or "talc" in the list of ingredients, then you know
that some clay is there. It is an inert, harmless
material and is used in lotions and sunscreens for
example. So, besides your modeling clay and the
clay in your lawn or gardens, take a look around
your home and see how often you come across
clays!
What different kinds of glass are there? Huge
windows are called float glass because of the way they
are made. Since they need to be perfectly flat and
smooth, the molten glass is floated on a layer of molten
metal (often zinc) and is then cooled very slowly. To
visualize this, pour some cooking oil over the back of a
spoon onto water in a clear bowl. See how the oil layer
floats on top? Some other types of glass are made
from other ingredients added to the silica. "Pyrex"
cookware is borosilicate, made with some boron to
withstand quick temperature changes. Lead crystal
incorporates lead to sparkle and make the glass easy to
cut and engrave.
What do you know about glass recycling? Amber
and green glass are separated because a coloring
agent has been added that cannot be removed.
Therefore, brown bottles can only make other brown
bottles. Recycled glass is crushed into pieces called
cullet. Cullet, which melts at a lower temperature, is
mixed with the raw materials silica, soda, and lime. This
process reduces air pollution by 20%, water pollution
by 50%, and saves space in landfills. However, only
about 10% of the glass used in the U.S. is recycled.
References: "Glass" by Jane Chandler and the
"Newton's Apple" web page:
www.ktca.org/newtons.
Kids, in this experiment we will be making
imprints of objects and then coloring them
"chemically" to a beautiful blue-purple (indigo)
shade. You will need a 3-inch square piece of
architect paper, any solid object to imprint (key,
coins, paper cut-out letters, etc.), an empty, clean
peanut butter jar with its lid, 1/2-cup household
ammonia, several small rocks or pebbles to cover
the bottom of the jar to about 2-inches in height,
and a bright light (such as a desk lamp).
-------------
Submitted by Kathleen A. Carrado, Chair
Elementary Education Committee
Reference: Phil Parratore, Wacky Science: A
Cookbook for Elementary Teachers, Kendall-Hunt
Publ., Dubuque, Iowa, 1994, page 76.
Kids, all you really have to do in this
"experiment" is chew your favorite kind of gum for
a while. Think about what you learn here while you
are chewing...
-------------
Submitted by Kathleen A. Carrado, Chair
Elementary Education Committee
Reference: Gail Marsella, ChemMatters, October
1994 (American Chemical Society, 1155 16th St.,
N.W.; Washington, DC 20036).
Kids, in these activities you will be making
some home-grown sugar gems into rings and also
modifying some spices to make necklaces or
bracelets.
-------------
Submitted by Kathleen A. Carrado, Chair
Elementary Education Committee
Reference: Don Herbert, Mr. Wizard's
Supermarket Science Random House (NY) 1980,
p. 22-25.
Kids, today we'll prove that helium leaks out
from regular balloons and what can be done to
stop it. Did you ever buy a balloon bouquet for
someone? You probably know that you can't just
make one yourself, because balloons filled with
normal air don't float like the ones with helium do.
And you may have already learned that this works
because helium gas is lighter, or less dense, than
the gases in regular air (nitrogen and oxygen). So
you have to buy balloons filled with helium. But
the gift shops now know certain tricks. Leaking
helium molecules were a real problem for people
who deliver balloon bouquets to parties. Their
customers used to often complain that the helium
balloons drooped within a day, or even overnight.
-------------
Submitted by Kathleen A. Carrado, Chair of the
Elementary Education Committee
Reference: WonderScience (American Chemical
Society), November 1986.
Kids, people use liquid laundry bleach to
remove unwanted color, in other words stains,
from clothes. This bleach is a 5% solution of
sodium hypochlorite in water. It also removes color
from other materials and we will use this today to
produce some interesting effects. First of all
though, you must do this with an adult partner
because of the care that must be taken when
handling bleach. So get your adult partner, a
bottle of laundry bleach, colored construction
paper, spoons, brushes, cotton swabs, steel wool,
and drinking glasses.
-------------
Submitted by Kathleen A. Carrado, Chair of the
Elementary Education Committee
Reference: Mr. Wizard's Supermarket Science, by
Don Herbert, Random House: NY, 1980, pg. 45.
Kids, you have probably seen a Light
Stick, a plastic tube that is often stored in an
emergency survival kit instead of a flashlight. Once
activated, the Light Stick glows brightly for many
hours. Did you ever wonder how it can do this?
The process is called chemiluminescence.
Fireflies and light sticks make "cold light" from this
chemical reaction that makes light without making
any heat
-------------
Submitted by Kathleen A. Carrado, Chair of the
Elementary Education Committee
Reference: October 1995 issue ofChemMatters, a
publication of the American Chemical Society,
1155 16th St., N.W., Washington, DC 20036.
Kids, our planet is made up of millions of
different species which try to live together. Man is
a species, just as animals like dogs, cats and fish
are. Some species are so small that you can't even
see them. Today you'll learn about fungus and
microbes ("small life")
You can collect microbes from many places,
such as from the drinking fountain, the cafeteria, or
even from fellow classmates at school!
-------------
Submitted by Kathleen A. Carrado, Chair of the
Elementary Education Committee
Reference: The Internet at: Bill Nye, The Science
Guy (http://nyelabs.kcts.org/demo/) and Beakman
& Jax (http://www.nbn.com/youcan/feet/).
How do scuba divers get "the bends", and just
what are they? Kids, you can feel some of the
effects of pressure in a swimming pool. Down just
a few feet underwater your ears begin to hurt. This
is caused by pressure on your eardrums.
-------------
Submitted by: Kathleen A. Carrado, Chair of the
Elementary Education Committee
Reference: The Internet at:
www.ktca.org/newtons (Minnesota's
PBS TV station KTCA produces "Newton's
Apple", a national science program for kids and
adults).
Kids, so what do you know about "clay"? Clays
are layered minerals found naturally in the ground.
Often the layers are much too small to see, but
sometimes the minerals crystallize in big enough
pieces to see them by eye. Two examples are
mica and vermiculite. Did you ever peel apart the
shiny, thin, transparent layers from a piece of mica?
Vermiculite is very similar to mica, and observing
the layers is even made easier by the high
pressure steam is that often used to expand this
clay into fat, swollen chunks that feel cushion-y.
Your parents and teachers may have heard of
vermiculite as the gold-flecked mineral added to
many potting soils. It makes an excellent insulation
material, and is also used as a packing material due
to it's absorbency and cushioning properties. Try
to find a sample at a crafts store, a nursery, or a
hardware store, and peel apart the layers yourself
-------------
Written by: Kathleen A. Carrado, Chair of the
Elementary Education Committee
Kids, what does the word "glass" make you think
of? Glass objects can come in all shapes, sizes, and
colors. List all the objects you come across in one day
that are made out of glass. Where does glass come
from? One example is window glass, also called "soda
lime" glass. It is made mostly from a pure, white sand
called silica. Also added are soda (soda ash or sodium
carbonate) and lime (limestone or calcium carbonate).
Soda ash makes the sand melt more easily and lime
makes the glass hard and waterproof. In a glass factory
furnace, the mixture is heated to 2,500°F for up to a
day. Molten glass is viscous and small bubbles take a
long time to disappear. To visualize this, mix powdered
sugar in a glass of corn syrup and watch how long it
takes for the bubbles to rise.
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Written by: Kathleen A. Carrado, Chair of the
Elementary Education Committee.