by Dr. Kathleen A. Carrado, Argonne National Labs |
Please note: All chemicals and experiments can entail an element of risk, and no experiments should be performed without proper adult supervision.
Kids, do you have a pair of safety goggles from a chemistry kit or a science fair? You can even buy a cheap pair at a hardware store. These goggles serve a necessary safety function, but everyone knows how unattractive they are (okay, "nerdy"). One way to jazz them up is to tint the frames in a variety of colors. Use a packaged fabric dye (such as Rit) that can be found in grocery stores. Make up the dye solution according to the directions on the package, and have your adult partner keep it warm on the stove. The goggles are put in here for a few minutes until you have the tint you like. There is some beautiful chemistry involved in the dyeing process. The poly(vinyl chloride) frames become tinted while the polycarbonate lenses are not colored. One package of dye will in fact tint dozens of goggles.
Did you know that these dyes are used by optical supply companies to tint regular eyeglasses? The dyes are azo and anthraquinone compounds that produce no skin irritation, and are neither caustic nor toxic. If you get some dye on your skin flush with water; any staining is harmless. Get creative and tint your goggles to match clothing or to match a holiday, like orange and black for Halloween.
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Submitted by Kathleen A. Carrado, Chair
Elementary Education Committee
Reference: J. W. Hill and C. A. Harmes, J. Chem.
Ed. 1993, 70(9), 779.
Printing presses use rubber rollers to pick up ink and apply it to the surface of paper. Because of the chemicals that make up rubber, it has a way of picking up ink and then releasing the ink to paper. Rubber works because of the unique interactions between molecules in rubber and the molecules in ink and paper. So why can an eraser rub out pencil marks from paper? Because the attraction between rubber and graphite (pencil lead) is stronger than that between paper and graphite.
Now let's make our own rubber stamps. Cut out a 5 cm square of cardboard. Draw a line down the middle of a rectangular pink school eraser. Now draw a simple shape (star or heart) on both the cardboard and on one-half of the eraser using a ball point pen. Fill in the shapes with a lot of ink to make them dark. Press the shapes down hard on a piece of white paper. Which one prints better? On the other half of the eraser draw a simple picture such as a flower or tree using red, blue and green ball point pens. See how many good clear prints you can make on your paper without re-inking the eraser.
Use another eraser to make a stamp of
your name. To have your name come our correctly
when you print it, you have to write it backwards on
the eraser. Add some designs around your name
using different colors; be creative and have fun!
Kids, let's learn how fossils are formed and
preserved. Use fresh play dough that is soft and
pack it into an empty margarine tub until the tub is
half full. Make sure the surface is very smooth.
Coat a twig, shell, or chicken bone with a thin film of
vegetable oil. Press it into the play dough to make
a clear, deep imprint. Remove the item and throw it
away. Let the play dough harden for a day or two in
order to make your special mold fossil.
Coat your hard mold fossil lightly with more
oil. Measure 1 cup plaster of Paris and 1/2 cup
water and mix them together. (Be sure to follow all
precautions on the plaster of Paris label). Pour the
mixture on top of the mold fossil and let it dry.
Carefully separate the plaster piece and notice
your new cast fossil, which has the outward shape
of the original item. The play dough represents
the soft mud of ancient times. Plants and animals
made imprints in the mud. If nothing collected in
the prints, the mud dried and made a mold fossil. If
sediments filled the imprint, a sedimentary rock
formed with the resulting cast fossil.
Plaster of Paris is made by grinding a clear,
shiny crystal called gypsum (calcium sulfate,
CaSO4 .2H2O) into a powder. The powder is
heated to dry out all the moisture. This dry powder
changes back into a solid when water is added, but
it never looks clear and shiny again. Some heat is
given off during this phase change!
Place one unopened can of diet cola and
one unopened can of regular cola (do not use
bottles) in a large container of water, such as a 5
gallon aquarium or a regular pail. Make sure no air
is trapped under the cans. Using the glass
container makes a nice visual demonstration for a
large group such as your classroom. Both cans
occupy the same volume (they are the same size),
but they weigh different amounts because of the
extra 18 grams or so (about 2/3 ounce) of sugar in
the regular soda.
Fill a clear plastic cup 2/3 full of water and
place a straw on an angle all the way in. Use an
eyedropper to carefully drip some regular cola
through the straw and into the bottom of the water
cup. Do not stir the liquids, and notice where the
cola stays. Now repeat the procedure using the
diet cola, a new cup and straw, and a rinsed
eyedropper. Does this one behave differently
from the regular soda, and do you think it has
anything to do with what the cans of soda did
earlier? Now let's drink to density with what soda is
left in the cans!
If your adult partner has special access to the
following chemicals, a great slime can be made.
Add a drop of food coloring to a 4% PVA solution
in water in a styrofoam cup. Add an equal volume
of 4% borax (Na2B4O7 .H20), and stir the gel with a
wooden tongue depressor or ice cream bar stick.
Commercial Slime (Mattel) is made by crosslinking
guar gum with borax. A polyvinyl alcohol/sodium
borate "slime kit" (AP1829) can be obtained from
Flinn Scientific, Inc., P.O. Box 219, Batavia, IL
60510 for $2.85. (Sorry, only school order forms
or teachers using school letterhead can be used to
order from Flinn). "Natural Wonders" (a store in
Fox Valley Mall) also sells something called
"Professor Wacko's Slime Chemistry Kit" for
$29.95.
Your slime can be kneaded into an elastic,
semi-rigid glob that has highly physical properties.
If the gel is simply suspended from your hand, it will
flow and stretch. It can also be stretched by slowly
pulling, but it will break if pulled quickly. When
placed in a container the gel assumes the shape of
the container. Similarly, it will flow into a film on a
flat surface. Because of these physical properties,
slime is one example of what is called a
non-Newtonian fluid.
Well, go ahead and squish away! Read the
references below for lots more info.
Light the candle and drip some wax onto
the cardboard square. Blow out the candle and
position it in the hot wax until it stands alone. Place
the candle on its base inside the jar. Spread the
baking soda around the base of the candle. Light
the candle again, using tongs to hold the match.
Carefully pour the vinegar down the side of the jar.
What do you see happening?
The reaction between vinegar (weak
acetic acid solution in water, HC2H3O2 ) and baking
soda (sodium bicarbonate, NaHCO3 ) produces
carbon dioxide gas (CO2 ). The candle cannot
continue to burn in a carbon dioxide atmosphere
because fires needs oxygen to burn, so the flame
is extinguished! This activity is a variation of the
common baking soda-vinegar volcano.
(1) A major athletic shoe company is
recycling rubber from the soles of defective shoes
into an ingredient used in the surfaces of running
tracks and basketball courts.
Fill one jar half way with steel wool. Add
enough vinegar to cover the steel wool and close
the jar. Write IRON ACETATE on the side of the
glass. You will have to be patient and let this jar
stand undisturbed for five days. Then pour one
tablespoon of your liquid Iron Acetate into the
second jar. Add one tablespoon of household
ammonia and stir. What happens? A dark green,
glutinous material forms immediately.
The iron in the steel wool combines with
the vinegar (weak acetic acid) to produce iron
acetate. The active component of household
ammonia is a compound called ammonium
hydroxide. A chemical reaction occurs as soon as
these two liquids combine. So, ammonium
hydroxide + iron acetate make ammonium acetate
+ iron hydroxide. Note that what happens is really
just an exchange of materials. The same
ingredients of ammonium, iron, hydroxide, and
acetate are present, but their recombination
produces a totally different product. In fact, two
liquids (solutions of iron acetate and ammonium
hydroxide) have reacted to form a new phase -
your gel!
(Safety concerns are typical: no eating, wash any
skin contact with water, and dispose of materials
down the sink with water.)
Cut two one-inch squares from a piece of
white bread. Put one square in your mouth and
chew it about 30 times, making an effort to mix as
much saliva as possible with the bread. When the
bread is nice and mushy, spit it out onto a piece of
wax paper. Put the other dry piece of bread onto a
separate piece of wax paper. Add four drops of
tincture of iodine to each bread sample. What
happens? The unchewed bread turns a dark
blue-purple color. The chewed up bread-saliva
mixture does not turn dark.
Why? The starch in the bread combines with
iodine to form iodine-starch molecules, which are
blue-purple in color. Chewing the bread mixes it
with saliva. This is where the chemical reaction
occurred in your mouth: the large starch
molecules were changed into completely different,
smaller, sugar molecules. Sugar does not react
with iodine in the same way that starch does.
Chemists can use iodine as an "indicator" for
starch. Try testing for starch in other foods, like a
cracker, a piece of dry cereal, or a cookie!
(Safety Tip: Do not eat anything that has the
iodine in it).
Both Gack and Slime are examples of what
are called non-Newtonian fluids. Your gack can be
kneaded into an elastic, semi-rigid glob that has
dramatic physical properties. If the gack is simply
suspended from your hand, it will flow and stretch.
It can also be stretched by slowly pulling, but it will
break if pulled quickly. When placed in a container
the gack assumes the shape of the container.
Similarly, it will flow into a film on a flat surface.
This recipe can be easily scaled up to
make large quantities of gack. If you want to have
enough for all your classmates, for example,
two-liter pop bottles can be used to make the two
solutions ahead of time. Then use a dishpan to mix
the ingredients. It is easiest to simply use your
hands to mix up the gack; if you choose this
method wear playtex gloves.
(Safety Tip: Do not eat any of your experiments).
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Submitted by Kathleen A. Carrado, Chair
Elementary Education Committee
Reference: "Wonderscience", 1993, 7(8), p.5.
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Submitted by Kathleen A. Carrado, Chair
Elementary Education Committee
References: "WonderScience", 1993, 8(1); J.
VanCleave Earth Science for Every Kid, 1991, p.
48; J. VanCleave Chemistry for Every Kid, 1989,
p. 144.
Kids, did you ever notice at your summer
family picnics that all the cans of diet soda float on
top in a cooler of ice water, while regular sodas
have to be fished from the bottom of the freezing
cold water? It is obvious that the densities of the
two are quite different. Density is a property used
by chemists to help identify substances. It is the
amount of mass in a particular volume of a
substance.
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Submitted by Kathleen A. Carrado, Chair
Elementary Education Committee
References: J. Chem. Ed. 1986, 63, 515 and
WonderScience 1993, 7(6).
Kids, you all know what Slime is, right? Did
you know that you can make your own slime at
home? Slime is made by reacting just two
compounds or ingredients. One is a long chain
molecule, a polymer called polyvinyl alcohol (PVA).
This is crosslinked with a simple solution of borax
(sodium borate). Crosslinking means that the long
chains are joined to each other at a few points
along the chain. Such a process makes the
molecules so heavy that they are no longer soluble
in water, and a gel begins to form.
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Submitted by Kathleen A. Carrado, Chair
Elementary Education Committee
References: (1) J. Chem. Ed. 1986, 63, 57; (2)
J. Chem. Ed. 1993, 70, 893; (3) Chemical
Demonstrations: A Sourcebook for Teachers,
ACS, Washington, D.C. 1987, 2, 95.
Kids, can you guess what carbon dioxide
gas will do to the flame from a candle? Here is how
to check your guess. You will need a wide-mouth
bottle or jar (or a 250 ml beaker), 3-4 teaspoons of
baking soda, 1/4 cup vinegar, a birthday candle, a
square of cardboard that will fit inside the jar,
matches, and tongs.
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Submitted by Kathleen A. Carrado, Chair
Elementary Education Committee
Kids, while you were enjoying the outdoors
this summer, we hope that you were on the
lookout for recreational products made from
recycled materials. If not, try it during your free time
this fall! Here are just a few examples.
(2) A company in
Oregon is using recycled materials to make
lightweight hiking shoes that are sold through mail
order outlets. These shoes contain materials left
over from making coffee filters, wetsuits and
gaskets, as well as recycled tires, plastic milk jugs,
ground-up shoe soles, and old magazines.
(3) A
nature walkway was made on a small wetlands area
near a high school in Schoharie County, NY. This
nature walk was built entirely of commercially
available recycled pressed lumber, which is made
from used grocery bags, stretch film, sawdust, and
wooden pallets.
(4) Did you know that some of the
latest playground equipment is being made from
assorted plastic waste? This waste is mixed with
carbon black, then melted and pressed into a
variety of shapes including even picnic tables. The
easily pressed recycled material is made into
playground equipment, and the rest is used as
plastic groundcover chips instead of sand or wood
chips.
(5) Another major manufacturer has
developed a fiber made completely from recycled
plastic soft drink bottles (made of PET or
polyethylene terephthalate). Fabrics made from
this fiber are beginning to be used by clothing
manufacturers. For example, one women's
sweater contains the PET from 25 soda bottles!
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Submitted by Kathleen A. Carrado, Chair
Elementary Education Committee
Reference:The Conservationist: NY's
Environmental Magazine, 48(5&6), 1994, 62.
Kids, our purpose in this experiment is to
make a green, jelly-like blob from mixing two
liquids. One liquid is made by dissolving steel
wool. You will need vinegar, steel wool (pure - no
soap), household ammonia, and 2 small baby food
jars.
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Submitted by Kathleen A. Carrado, Chair
Elementary Education Committee
Reference: Janice VanCleave's "Chemistry for
Every Kid" 1989, p.102.
Kids, did you know that chemical reactions
are going on all the time right in your mouth,
especially when you chew? Let's see what
happens to starch in our mouths.
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Submitted by Kathleen A. Carrado, Chair
Elementary Education Committee
Reference: Janice VanCleave's "Chemistry for
Every Kid" 1989, p.108.
Kids, a while back we learned how to make
slime in this column. Now it is time to make GACK,
a similar material that is made from easy-to-find
ingredients. In one container mix 4 oz. Elmer's
glue (water-soluble) with 4 oz. water, and set it
aside. In another container, mix 1/2 cup of water
with one teaspoon borax (which is sodium borate)
and stir. Mix the two solutions and add a few drops
of food coloring for effect. Mix very well until you
have a solid mass.
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Submitted by Kathleen A. Carrado, Chair
Elementary Education Committee