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.
Pour the baking soda into the glass jar and fill about 3/4 full. Swirl to dissolve most of the baking soda and allow the rest to settle at the bottom. Add small amounts of vinegar to start the production of carbon dioxide gas bubbles. Then add several paper clips, raisins, and two-inch pieces of spaghetti and watch.
Carbon dioxide gas collects on the surface of the objects and causes
them to float to the surface. At the surface, the gas bubbles burst, the
object sinks to the bottom, and the process starts again. The gas forms
from the reaction of sodium bicarbonate (baking soda) with acetic acid
(vinegar).
Cut open the diaper and carefully peel
away the cotton-like filling. You will notice that it
feels gritty. Separate the small gritty beads from
the cotton fibers (tweezers and a small kitchen
strainer may help, but are not really necessary).
You should be able to easily get about 1/2 tsp. of
beads, then pour them into a clear glass. Add
about 1/2 cup of water and gently swirl, or pour the
mixture back and forth between two glasses until it
is too thick. (If you are able to get distilled,
deionized water, it works better than hard tap
water.) To "unlock" your gel, sprinkle a little salt on
top and stir it into the gel. When the water is released the now syrupy liquid can be washed down the drain.
The superabsorbent beads are a
co-polymer of poly(acrylamide) and sodium
polyacrylate that can undergo physical changes
quickly and reversibly with water. Other uses for
these polymers are for hydro-mulching plants
(places like Frank's Nursery now sell small bags of
colored gel for this) and removal of water from jet
fuels. Try your experiment again if you like with a
drop of food coloring in the water (yellow fits the
diaper theme nicely).
Kids, you probably already know that iron is
magnetic. In this column, we will demonstrate a
way to prove that there is iron metal in two places
that you have probably not ever realized: a one
dollar bill and a bowl of cereal! You will need a bar
magnet (chemists can use long thin stir bars), a
dollar bill (or $5, $10, $20 - they all work), and a box
of cereal that claims to be high in "reduced" iron
(like Total®).
First we will do the money experiment. Hold
your bill straight down by the very edge of a short
end - a newer bill works best because it will hang
straight. With the other hand, slowly move the bar
magnet lengthwise along the back of the dollar bill
as close as possible without actually touching it.
What happens? There should be at least one
portion of the bill where it actually moves toward
the magnet, or is "attracted". Why is this? Some,
but not all, of the ink used in printing paper money
is deliberately magnetic. This method is used to try
to foil possible counterfeiters, and it also helps aid
in the detection of counterfeit money!
In the second experiment, soak a few cups
of the cereal in a large bowl of water until it is
mushy. Vigorously stir the mixture with a wooden
spoon for five minutes. Then add your bar magnet
and continue stirring, more slowly, for several
minutes. Carefully nudge the magnet around the
bottom of the bowl a few times, then let the mixture
stand for about ten minutes. Slowly pour off the
"mush" and examine your bar magnet. Is it
covered with small black needles and specks?
This is the "reduced" iron (iron metal) that is
actually added to the cereal because it is healthy
for us to have iron in our diets. Chemists will find
this easy to do using a magnetic stir plate, and a
large beaker and stir bar. The more cereal you start
with and the more time you give, the more iron you
will collect!
To one-half cup of cold water add
anywhere from 5 to 10 heaping tablespoons of
household corn starch, one at a time with complete
mixing each time. The amount varies with the
quality of both the water and the cornstarch. You
will know you have the right amount when the
following tests work. Do you notice a difference
between stirring very slowly and stirring faster, or
between slowly lifting the spoon out and quickly
pulling it out? How about putting your finger in
slowly and touching the bottom of the bowl vs.
jamming it in?
The starch mix should act almost like a
solid when confronted with a fast motion. This is
because the long, skinny starch molecules are
very crowded and get tangled up with each other.
When a slower motion is used, the molecules have
enough time to move out of the way of each other
(just like spaghetti!). Disposal: The mix gets
thicker on standing, so immediately after finishing
pour it into a large bowl of water and wash down
the drain with lots of water.
On the paper wet with the table salt (sodium
chloride) solution, you should see small, white,
cubic crystals that increase in size each day.
Sodium chloride salt crystals have a cubic shape.
You should see long, slender, needle-shaped
crystals on the paper wet with the epsom salt
solution. "Epsom salts" is the common name for
this chemical, but it is also called magnesium
sulfate. When epsom salts are packaged, the
needles of magnesium sulfate are first crushed.
By dissolving in water and then allowing for slow
evaporation, the needles and cubes are given the
chance to build in size.
Among other things, there are chemical
compounds called "anthocyanins" in some plants.
These compounds have different colors
depending upon the strength of an acidic or basic
solution. The vinegar (acetic acid) is a weak acid
and the baking soda (sodium bicarbonate) solution
is a weak base. Because of their ability to change
colors, anthocyanins are one kind of indicator for
determining the strength of an acid or base. Your
results should have showed you that radishes, red
cabbage, and grape juice all contain anthocyanins.
They are also present in the petals of red roses.
The major pigment in many green plants is
chlorophyll, while that in carrots is called carotene;
these compounds do not act as indicators. Try
other fruits, vegetables, or plants with your new
chemical testing system!
This activity should help you discover how
water can move up through a plant stem. Many
plants have a series of tube-like cells that bring
water up, and another set that takes nutrients
produced in the leaves down the plant. After 24
hours, the celery without the tubes should be
much more limp than the piece with the tubes
intact. You might also be surprised to see what
happens to a white carnation after being placed in
a glass of water with food coloring for several
hours; try other food colors and make a
multi-colored bouquet! (Hint: cut about 1" off the
bottoms of the of the carnation stems first).
Aluminum foil will begin to decompose in
the presence of many other acidic substances in a
process called oxidation. Acids like to oxidize
obliging metals. Some common acidic foods
include ketchup which has a pH of 3.8 (7 is
neutral), or a cola soda which is even more acidic
with a pH of 2.7. Tell any cooks you know to never
wrap a meatloaf glazed with ketchup or tomato
sauce in aluminum foil for storage. After several
hours the result of this contact is a grayish-black
disgusting mush of aluminum oxide.
Brainteaser: why doesn't a full aluminum
cola can dissolve? Chemistry solves that problem,
too. The inside of the can is coated with a
harmless but effective protective surface made up
of long molecules called polymers (in short, a
plastic coating).
Form a 12-inch circle with a handle out of stiff
wire about the diameter of coat-hanger wire. You
can try an actual coat hanger, but they are often
coated to prevent rusting; this coating prevents
the bubble solution from clinging to the wire. Dip
the wire circle into the bubble solution and bring it
out at an angle so that a film of solution fills the
inside of the circle. Now sweep the wire through
the air to form a large bubble. A twist at the end of
the sweep helps to loosen the bubble from the
wire.
A bubble is really three bubbles in one.
There's an outside layer of water, a middle layer of
soap and glycerin, and an inner layer of water.
When bubbles these big break, they leave a lot of
soap behind. Be prepared to wipe it up (cleaning
the floor at the same time!), or make your bubbles
outside.
The garbage we bury never really goes
away completely. Not much decomposition occurs
because air and moisture - needed by
garbage-chewing microorganisms - are sealed out.
Many landfills become parks, ski hills, and golf
courses. Color some shredded coconut with
green food coloring and sprinkle it over the dirt to
look like grass. Your landfill is now complete and
ready to eat! Dig in!
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Reference: B. Z. Shakhashiri "Chemical
Demonstrations", Vol. 3, chapter 9, p. 368.
Submitted by Kathleen A. Carrado, Ph.D. (with
help from J. Ellefsen-Kuehn).
Argonne National Lab / (708)252-7968
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Reference: From a "Weird Science"
demonstration given by Lee Marek and Bob Lewis
at Nalco on 12/4/90.
Submitted by Kathleen A. Carrado, Ph.D.
Argonne National Lab / (708)252-7968
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Submitted by Kathleen A. Carrado and Henry L.
Crespi
Argonne National Lab / (708)252-7968
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Submitted by Kathleen A. Carrado
Reference: "Chemistry for Every Kid" by Janice
VanCleave, Wiley: NY, 1989.
Argonne National Lab / (708)252-7968
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Submitted by Kathleen A. Carrado, Argonne
National Lab
Reference: Ann Benbow of ACS, Coordinator of
Pre-High School Science Office, who presented
this at the CHEERS/PACTS Workshop on 4/17/93
at W. Aurora H.S.
Kids, as you know, plants need water to live.
Water goes from the root, up the stem, and into
the leaves. Did you ever wonder how the stem is
specially made so that water can travel up it? This
experiment will help you find out. You will need a
glass one-third full of water, blue food coloring,
and a 8-10" stalk of celery that has been freshly cut
on both ends by an adult partner. Notice the small
dots on the narrow end of the celery stalk. Add 5
drops of the food coloring to the water and place
the wide end of the celery in the water. After a few
hours you should see that the little dots on the top
of the celery are now blue. Use a fingernail to start
pulling away one of the blue tubes at the top. Can
you pull it all the way down and remove it totally
from the stalk? Try another experiment with two
new celery stalks. Carefully remove all of the tubes
from only one new stalk and then place them both
in the blue water. Compare them after 24 hours.
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Submitted by Kathleen A. Carrado, Argonne
National Lab
Reference: WonderScience, 7(5), May 1993.
Kids, let's explain why chewing an
aluminum foil spitball can really hurt some people,
while for others it is just a weird piece of gum. The
difference is because some of us have silver
fillings in our teeth. It turns out that aluminum
atoms lose their electrons very easily. In the
presence of our mildly acidic saliva, which acts as a
catalyst, we have what amounts to a crude electric
battery. Electrons flow from the aluminum to the
silver amalgam filling. The current is felt by the
nerves of our teeth and causes a downright
unpleasant zing!
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Submitted by Kathleen A. Carrado, Argonne
National Lab
Reference: (from p. 121 of The Straight Dope by
Cecil Adams, 1984).
Kids, you can make gigantic soap bubbles
with a mixture of liquid soap or detergent, glycerin,
and water. The glycerin is the secret ingredient
that adds strength to the bubble solution. Mix
together 1 part soap with 1 part glycerin and 6 parts
water (distilled water works best). Pour into a large
tray or cookie sheet.
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Submitted by Kathleen A. Carrado, Chair
Elementary Education Committee
Reference: "Mr. Wizard's Supermarket Science",
Don Herbert, 1980, p. 48.
Kids, how much do you know about how
your local landfill actually works? Let's build one of
our own while we learn. A Keebler© ready-made
chocolate pie crust will be our hole in the ground.
Before any trash can go in, a landfill hole is lined
with pipes to remove liquids from garbage and
decomposition. Place Twizzler© licorice whips
along the bottom of the crust for this purpose.
Most real sanitary landfills surround the hole with
an impermeable clay lining to prevent harmful
waste from leaving the area; the foil tin containing
the pie crust can represent this lining. Mix some
"garbage" made of nuts, raisins, M&Ms, etc., into
vanilla pudding to make your trash, and cover the
bottom of the crust. In sanitary landfills, garbage is
covered with dirt each day. Cover your vanilla
pudding garbage with a chocolate pudding dirt
layer. Make as many alternating pudding layers as
you can until the crust is full. Make sure that the
top is a chocolate pudding dirt layer.
Submitted by Kathleen A. Carrado, Chair
Elementary Education Committee
Reference: "Solid Waste Activity Packet for
Teachers", Ill. Dept. of Energy and Natural
Resources, page 70. (Contact person: Kathy
Engelson, Supervisor for School Education,
IDENR, 217-524-5454. Also Jean Dehorn or Carol
Fialkowski, Chicago Academy of Sciences,
312-549-0606 x2014).