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.
Into a bowl add 1 cup heavy whipping cream, 1 cup half & half, 1/3 cup sugar, 1 egg, and 1 teaspoon vanilla extract. After whisking for a few minutes, pour half of the mixture into a sandwich-size ziploc baggie and seal. Into a gallon-size ziploc baggie add four good handfuls of rock salt and eight good handfuls of crushed ice. Seal this baggie and gently shake the ice-salt mixture around until a good amount of water is formed. Rock salt is a chunkier version of common table salt (sodium chloride), but it is not clean enough to eat. Place the sandwich baggie into the gallon-size baggie and seal. Mix it around so that the smaller baggie is in contact with the cold water as much as possible. The material in the little bag should thicken in 10-15 minutes. When it is thick enough, take the small baggie out of the large one and scoop the contents into a cup for your very own edible treat.
The milk solution becomes thicker because it is freezing. When a liquid freezes it turns into a solid form. The salt-ice mixture should feel very cold, and though it will be hard to feel a difference, it is colder than the ice by itself. The experiment would take much longer if you used ice alone. The ice would melt quickly and need to be replaced often. So, how do you make the ice colder? The trick is adding the salt. It is a well-known phenomenon to chemists that a solution, such as salt-water, will freeze at a lower temperature than a pure liquid, such as water. So your salt-ice water solution is colder than just ice water alone. The same principle is being used when salt is sprinkled on icy roads in the wintertime.
The ice-salt baggie will in fact get so cold that
you should wear gloves or use a towel. Try
another experiment with the remaining unfrozen
cream mixture. Add a few teaspoons of preserves
for flavor, or some food coloring for looks. You can
even try fooling around with the ingredients a little
bit and use some chocolate milk!
Use blunt end scissors to cut 3 strips from
a cone-type coffee filter that are about 10 cm long
and 3 cm wide. Using a pencil, write at the end of
each strip the name of one candy. Pour about 1/4
cup of water into a clear plastic cup. Wet one end
of a cotton swab and gently wet one side of a
candy. Gently rub the candy's wet candy coating
onto its filter strip. Make the dark dot on the paper
about 2 cm from the unwritten end, in the center.
Do not use the dirty end of the cotton swab again.
Repeat this procedure for the other two candies,
using a clean cotton swab each time. When they
are dry, carefully place the strips in the cup of water
so that only the very end of each strip touches the
water. The end with the writing can be folded over
the rim of the cup to keep the strip in place. Be
sure the colored dots are above the surface of the
water, otherwise all the coloring will simply wash
out in the solution.
Observe each strip as the water moves up
the paper through the dots. What do you notice
happening? Let the water rise nearly to the rim of
the cup (this happens naturally by capillary action),
then remove the strips and let them air dry. Is the
brown color on the candies a mixture of other
colors? Compare the colors used for each type of
candy, and see in what ways they are the same or
different. Each color is a different pigment
molecule. Because of the different shape, weight,
size, and electric charges on different pigment
molecules, they will bind to the paper in slightly
different ways. This is how they can separate.
Check the ingredients on the candy wrappers to
see whether the colors you observed were actually
used to color the candies!
Cover a work area with paper towels. Label 3
clear 8 oz plastic cups as "water", "water and
plaster", and "soapy water". Pour 1/2 cup warm
water into each cup. Add about 1/4 teaspoon of
plaster of paris powder to the cup labeled "water
and plaster". Stir thoroughly with a plastic straw.
Grate 1-2 tablespoons of soap from a bar of soap.
Put about 1 tablespoon into the "soapy water"
labeled cup. Stir thoroughly with a new straw. Add
1 tablespoon of your soapy water to the "water"
and "water and plaster" cups. Do not stir right
away, and observe what happens closely. Is there
a difference? What do you see happening in one
of the cups? Now stir each cup with a separate
straw. Do they still look different? Next use a new
clean straw to blow gently into each cup. Do you
notice a difference in the bubbling? What do you
think is the reason? It will help you to know that
plaster of paris is a chemical compound called
calcium sulfate (made from gypsum).
[Safety Tip: Please be sure to blow into the
liquids. Do not suck the liquid into the straws at all.]
Pop exactly 1/4 cup of fresh popcorn in a
hot air popcorn popper, and then do the same with
the dried kernels. Measure the volume of each of
your results. Some kitchens have large glass
measuring cups than can be used for this, or else
just use similar sized bowls or drinking cups and
"eyeball it".
The fresh popcorn should produce a
larger volume of popped corn. Popcorn is mostly
starch and water. As the kernel is heated, the
water inside turns to steam. So much steam
pressure can build up inside the kernel that the
outer layer finally cannot hold it back and the kernel
explodes. The starch expands into the familiar
white substance that we have all come to know as
popcorn. So now can you guess why the dried
kernels resulted in a lower volume? Most of their
moisture was evaporated beforehand, slowly and
intentionally, so that there was not enough left to
explode the kernel as much.
If you like, you can try different brands of
popcorn to see which one gives the highest
volume of product. Also try popping old and fresh
popcorn of the same brand. Cleaning up from this
experiment can be summed up in one word:
Enjoy!
You will need a can of Scotchguard® spray,
facial tissue, 2 clear plastic cups, 2 rubber bands,
and water. You will also need proper ventilation
because of the Scotchguard® spray fumes.
Open one tissue and drape over one of the
cups. Push the center of the tissue slightly into
the cup, forming a pocket. Secure it to the cup
with a rubber band. Slowly pour some water into
this pocket and observe what happens. Now spray
a new tissue with Scotchguard®, let it dry, and
repeat the experiment. What happens? Does this
tissue cause different behavior?
Why does this happen? The spray forms a
coating over the surface of the tissue. The coating
is so smooth that any holes present are smaller
even than tiny water molecules. Therefore water is
not allowed to penetrate through the tissue. You
can try this same test on different materials, such
as pieces of scrap fabric.
The old-fashioned white kind of peanuts
are made of Styrofoam, which is an expanded
version of a polymer called polystyrene. The
newer kind is called Ecofoam and it is made from
corn starch. The most obvious difference
between them in terms of chemical properties is
that Ecofoam will dissolve in water while Styrofoam
will not. Just put a foam peanut in a cup of water
and wait a few minutes. The warmer the water the
faster the Ecofoam will dissolve. Can you think of a
way to take advantage of this difference for a
useful purpose? Of course the answer is fairly
obvious. Ecofoam was deliberately made as an
alternative to Styrofoam because it will quickly
degrade in the environment. It is therefore a more
ecologically- and environmentally-friendly
packaging peanut. (Can you see that Ecofoam
would not make a very good beverage container,
however?)
If you have an adult partner that has
access to acetone (the active ingredient in many
nail polish removers), they can show you that
Styrofoam will "melt" in acetone while Ecofoam will
not. This could therefore be one way to reduce
the space that Styrofoam products take up as
waste.
{SAFETY NOTE: Please leave the handling of any
acetone only to an adult].
With your adult partner, turn on a hose and
make a fine spray using a nozzle or your thumb.
Move so that you are looking at the water with the
sun behind you. Spray harder or softer and higher
or lower until you see a rainbow. Try changing your
position so that the sun hits your water from a
different angle. Or try having your partner spray
the water while you view from different angles and
distances. If you are successful, note the order of
the colors.
Light is an electromagnetic wave of energy.
Some electromagnetic waves have higher
energies than others. The whole range is called
the electromagnetic spectrum. Waves in this
spectrum include X-rays, microwaves, radio waves,
visible light, and others. The waves of visible light,
which is what we can see, are in the middle of this
spectrum. Their energies are lower than those of
X-rays, but higher than those of microwaves and
radio waves. The colors appear in order according
to their energy. From the lowest energy to the
highest energy the colors appear as
red, orange,
yellow, green, blue, indigo, and violet.
With your partner in a dark room, crunch
the mint with your teeth with your mouth open.
Your partner should see sparks of light generated
when you bite on the candy. Reverse the roles so
that you can see the sparks in your partner's
mouth. If your partner is an adult, have them hit the
candy with a hammer on a hard surface to observe
the same quality of sparks.
What is going on here? When the candy is
crushed, the friction of unlike charges (positive
and negative, or + and -) causes loose particles
called electrons to start a series of interactions
between the nitrogen in the air, sugar, and candy
molecules. This type of light is called triboluminescence.
Place 1 tablespoon of bubble solution in the
plastic bag. Close the bag almost completely,
leaving just enough room to slip the straw into the
bag. Gently blow through the straw to fill the bag
with bubbles. Now study the bubbles that formed.
Are the sides of the bubbles curved or flat? How
do their sizes and shapes compare? Do most of
them have the same number of sides?
How thick is a soap bubble? The film is one
of the thinnest things that we can see without
using a magnifying glass. It is about 5000 times
thinner than a human hair! What's inside the
bubbles? It is always a gas, and most have ordinary
air inside. The bubbles that you blow contain more
carbon dioxide because this is a gas that we
exhale. Bubbles in soda pop are filled with carbon
dioxide, and those in boiling water are filled with
vaporized water or steam.
[Since different detergents have different
bubble-making abilities, you may have to
experiment by using different amounts of
detergent, water, and sugar until you get the
nicest, longest-lasting bubbles.]
Taste begins with an ion or molecule
docking in receptors on the tongue or palate. The
substances that trigger sweet and bitter tastes are
usually large, complex organic molecules that fit
these receptors like keys in a lock. In contrast,
salty and sour tastes are triggered by tiny positive
ions. SLS is one of the most widely used
detergent molecules. It is a large organic molecule
found in toothpaste, laundry detergents, and
specialty detergents such as Woolite®. The
reason why some of you won't notice the taste
effect of SLS is because you may be insensitive to
the bitter tastes of compounds called
phenylthiourea and propylthiouracil, and less
sensitive to bitter flavors such as caffeine,
potassium chloride, and certain preservatives.
These people have failed to inherit a gene from
their parents that makes them sensitive to bitter
tastes. Some people have inherited the gene
from just one parent, and they experience the
bitterness effect to a lesser degree.
-------------
Submitted by Kathleen A. Carrado, Chair
Elementary Education Committee
References: Chemical & Engineering News
10/31/94, p. 48; Downer's Grove Friends of the
Gifted and Talented: "Weird Science" Program,
Fall 1994.
Kids, there are many different ways to
separate the components of a mixture. This time
we will separate the substances used to color
candy by using a technique called chromatography. The candy you will need is the brown color of M&Ms©, Reeses's pieces©, and Skittles©.
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Submitted by Kathleen A. Carrado, Chair
Elementary Education Committee
Reference: WonderScience, volume 8, number 8,
December 1994.
Kids, you may have heard that the chemical
element CALCIUM is very important for strong
bones and teeth. Terrific sources of calcium in our
diets include milk, broccoli, salmon and sardines.
Along with bones and teeth, calcium is also a major
part of things like cement, seashells, limestone,
chalk, marble, eggshells, and de-icer for icy roads.
Sometimes when water flows over limestone or
other materials with a lot of calcium in them, the
calcium gets into the water. Water that contains a
lot of calcium or other minerals is called HARD
WATER. One characteristic of hard water is that it
makes a soap scum when mixed with soap. It also
makes a soap solution much less bubbly. But
don't just take our word for it, let's check it out!
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Submitted by Kathleen A. Carrado, Chair
Elementary Education Committee
Reference: WonderScience 10/94, volume 8(6).
Kids, have you ever wondered exactly
what's behind the popping of popcorn? Here we
will demonstrate that both heat and the moisture
inside popcorn kernels are necessary for making a
perfect bowl of popcorn. You will first need to have
an adult partner dry out 1/4 cup of popcorn kernels
by placing a single layer on a tray in an oven at 190
degrees overnight.
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Submitted by Kathleen A. Carrado, Chair
Elementary Education Committee
Reference: Phil Parratore inWacky Science: A
Cookbook for Elementary Teachers, Kendall/Hunt
Publishing Co. (Dubuque, Iowa), 1994, page 104.
Kids, did you ever spill something on your
furniture or carpet and be surprised when it was
easy to clean up without leaving a stain? Some
fabrics are treated with a very thin coating that
repels liquids somewhat. In this experiment you
will test such a coating by studying the absorbency
of tissues both with and without a water repellent
substance.
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Submitted by Kathleen A. Carrado, Chair
Elementary Education Committee
Reference: Phil Parratore inWacky Science: A
Cookbook for Elementary Teachers, Kendall/Hunt
Publishing Co. (Dubuque, Iowa), 1994, page 112.
Kids, have you ever seen the packaging
peanuts that are made of foam? Have you ever
noticed two different kinds of these peanuts? One
kind is bright white and sort of S-shaped, while the
others are not so white and not so curved. In this
experiment we will find out the differences
between the two types.
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Submitted by Kathleen A. Carrado, Chair
Elementary Education Committee
Reference: Steven D. Gammon, J. Chem. Ed.
1994, 71, 1077.
Kids, why does the light from the sun make
rainbows some of the time but not all of the time? It
is because raindrops in the air can break up the
sun's light into the different colors of light that we
can see in a rainbow. You may have seen a
rainbow on a day when the sun came out while rain
was still falling. You may also have seen one at a
waterfall where the water splashed up into a mist,
or even in the water from a lawn sprinkler on a
sunny day. In this activity, you can try making your
own rainbow show! All you need is an adult
partner, a garden hose, and a sunny day.
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Submitted by Kathleen A. Carrado, Chair
Elementary Education Committee
Reference: WonderScience 1995, vol. 9,
number 4.
Kids, did you have any idea that crushing
certain lifesavers in your mouth can set off sparks?
This experiment will demonstrate how light can be
given off by a simple chemical reaction. All you
need is a roll of wintergreen mint Life Savers®
with the green-speckled centers, a very dark room,
and a partner.
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Submitted by Kathleen A. Carrado, Chair
Elementary Education Committee
Reference: Wacky Science: A Cookbook for
Elementary Teachers by Phil Parratore, 1994,
Kendall-Hall Publishing Co., Iowa, page 77.
Kids, did you ever wonder what a turtle shell,
a bee's honeycomb, a soccer ball, a chicken wire
fence, and a bag full of bubbles have in common?
All you will need to find out is a quart size zip-lock
bag, a plastic straw, and a bubble solution. To
make the bubble solution, mix 4 parts of water to 1
part of liquid detergent. For example, measure 1
cup of water and add 1/4 cup of detergent. Add
the detergent to the water, and stir gently. Adding
about 1/2 teaspoon of sugar makes longer lasting
bubbles.
You'll find that many of the bubbles inside
your bag should have six-sides, which makes them
hexagons. Many hexagon shapes can be found in
nature. Spider webs, some insect's eyes, and
certain plant stems are based on this shape.
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Submitted by Kathleen A. Carrado, Chair
Elementary Education Committee
Reference: WonderScience , vol. 9, no. 1,
January 1995. (call 1-800-333-9511 for
subscription information to WonderScience).
Kids, does orange juice taste awfully bitter
to you right after brushing your teeth? If so, you
are one of about 2/3 of the population who has a
taste gene on your tongue that allows you to
detect certain bitter compounds. The other 1/3 of
you lacks this gene. When one of you who has the
gene brushes your teeth with a toothpaste that
contains sodium lauryl sulfate (or SLS), you notice
this bitterness effect. SLS reduces the sweet
taste of sucrose (sugar) and at the same time
strengthens the bitterness of citric acid
(responsible for the sour and bitter taste of orange
juice) by about ten times! If you would like to see if
you inherited this gene or not, select a toothpaste
that contains SLS in the list of ingredients. Take a
sip of orange juice and note the relative strength of
the sweet, sour, and bitter tastes. Rinse your
mouth with water, then vigorously brush your teeth
with the toothpaste. Rinse with water again, then
taste the orange juice again. Are the relative
intensities of the tastes very different now?
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Submitted by Kathleen A. Carrado, Chair
Elementary Education Committee
Reference: P. DeCristofaro,ChemMatters,
published by the American Chemical Society
(Washington, DC), 1995, vol. 13, no. 2, pg. 14.