SCIENCE - SCHOOL PROJECTS
Dry Ice is frozen carbon dioxide, a normal part of our earth's atmosphere.
It is the gas that we exhale during breathing and the gas that
plants use in photosynthesis. It is also the same gas added to
water to make soda water. Dry Ice is particularly useful for freezing,
and keeping things frozen because of its very cold temperature:
-109.3°F or -78.5°C. Dry Ice is widely used because it
is simple to freeze and easy to handle using
insulated gloves. Dry Ice changes directly from a solid to a gas
-sublimating - in normal atmospheric conditions without going through
a wet liquid stage. For more information on carbon dioxide see:
HOW DRY ICE IS MADE
first step in making dry ice is to compress carbon dioxide gas until
it liquefies, at the same time removing the excess heat. The C02
gas will liquefy at a pressure of approximately 870 pounds per square
inch at room temperature. Next, the pressure is reduced over the
liquid carbon dioxide by sending it through an expansion valve into an empty chamber. The liquid will flash, with some turning into gas causing the
remainder to cool. As the
temperature drops to -109.3°F, the temperature of frozen CO2,
some of it will freeze into snow. This dry ice snow is then
compressed together under a large press to form blocks or extruded into various sized pellets. Dry Ice is
much heavier than traditional ice, weighing about double.
DRY ICE MAKERS
Dry Ice machines are available in all sizes and use liquid CO2. Hand held ones make soft Dry Ice that dissipates
commercial machines use hydraulic presses to compress the Dry Ice snow
with up to 60 Tons of pressure. It can produce a 55 pound block in under 60
Latent Heat of Vaporization
241 BTU/LB 0°F
-109.3°F or -78.5°C
Solubility in H20
79FT³ CO2 GAS/FT³
( when H2O is at 32°F )
-69°F 75.1 PSIA
0.015 Centipoises @32°F
0.14 Centipoises @0°F
A pound of Dry Ice will sublimate
into 8.3 cubic feet of carbon dioxide gas.
DOT Shipping Class:
ORM-A UN-1845 Pkg. Group III Class Nonflammable Gas UN2187
Dry Ice can
add the right touch to the typical school volcano. The "smoke" will come out the
top and flow down the sides for several minutes. Inside the volcano must be a
container to hold hot water. If hot water is not immediately available use a
thermos to store it. The hotter the water is (nearly boiling if under adult
supervision) the better. The bottom must be sealed tightly. Otherwise Dry Ice
fog will leak out the bottom. Use putty or some other sealant. At the time of
eruption, use gloves and put small pieces of Dry Ice into the hot water. The
volcano will bubble and "smoke" for several minutes.
An easy to make cloud chamber
can be used to observe Alpha or Beta particles. Use a clear Pyrex or Corning
shallow glass container that will not break in a freezer. Cover the bottom
inside of the dish with black felt or black paper. Cut a piece of cardboard
larger than the top of the dish. Pour alcohol on one side of the cardboard.
Place the cardboard on the dish with the wet side down. Heat the top cardboard
with your hand or something else warm such as an iron. Place the dish on a slab of Dry Ice. The
alcohol will form a cloud. Shine a light through the side of the dish to observe
vapor trails. Some natural vapor trails can be seen in time although you may
have to put alcohol on the cardboard several times. Place an alpha ray source
such as an old fashion illuminated watch dial or a Coleman lantern mantel inside
to see more ion trails in the cloud chamber. Use a light source such as a bright
flashlight to see the cloud tracks better.
hydrogen carbonate (NaHCO3), also called Sodium
bicarbonate, bicarbonate of soda, and baking soda, is an important chemical.
Hundred of thousands of tons are produced each year for use in baking and in
producing other chemicals. One way to make this compound at home or in the
school chemistry laboratory is to use Dry Ice, salt, ammonium carbonate, and
can make a miniature comet and watch as it sublimates--just like a real comet
being heated by the Sun! Make sure you have adult supervision. The materials you
will need are Dry Ice (solid carbon dioxide), a large bowl, a garbage bag,
several smaller plastic bags, gloves, a hammer, water, sand, and a few drops of
ammonia. Buy about 3 pounds of Dry Ice. Be very careful in handling Dry Ice, and
always wear gloves. Solid carbon dioxide is much colder than ice, and if it
touches your skin it will hurt as if you had been burned by fire. Use a plastic
garbage bag to line a bowl big enough to hold a quart of water. Put two cups of
water into the lined bowl. Add a couple spoonfuls of sand. Sprinkle in a few
drops of ammonia and stir the mixture well. Wearing gloves, wrap the dry ice in
several plastic bags. Use a hammer to pound the dry ice into small pieces. When
the dry ice is crushed add about two cups of it while stirring your comet
"soup". Keep stirring while the dry ice freezes the water. When the mixture is
almost completely frozen, lift it up using the plastic liner of your bowl and
shape the wrapped mixture into a ball. When the "comet" is frozen and can hold
its shape on its own, unwrap it and set it somewhere you can watch it. The dry
ice will sublimate into a gas. You may see jets of carbon dioxide shoot from
your comet. After a while, your comet will shrink and become pitted, like a
comet that has been eroded by the Sun. (Based on a Recipe by Dennis Schatz,
Pacific Science Center, Seattle, WA.)
project developed by UC Berkeley is called "Make a Comet in the Classroom"
"DRY ICE INVESTIGATIONS" ** A Teachers Guide
revolves around the intriguing nature of dry ice and the incessant curiosity it
provokes in all those who have the opportunity to interact with it. Whenever
science (especially chemistry) is depicted on film or television, you can almost
guarantee that you'll see dry ice bubbling away in a colorful liquid. Music
videos, scary movies, theatrical plays, and Halloween frequently feature its
eerie heavy fog slowly and silently creeping across a surface. Although it is
perhaps the ultimate symbol of "fun science," students rarely have the
opportunity to explore it themselves in science class, most likely because many
teachers often don't know where to get it, don't know what to do with it, and
are intimidated by safety issues. This guide hopes to deal thoroughly with all
these issues, and to build on the wondrous appeal of dry ice to provide a highly
memorable and powerful science learning experience."
**One of the best science books for grades 6-8 is called "Dry Ice
Investigations" from LHS Gems, UC Berkeley, (ISBN: 0-924886-15-3) available
through Amazon.com and other suppliers.
OTHER SITES FOR COOL PROJECTS
Anthony Cody has
developed "Cody's Science Education Zone" featuring "Dry Ice: Simply Sublime".
This includes teacher lesson plans and projects for Grades 4-10.
Brian Rich's "The
Saturday Scientist" has lots of fun projects including a singing spoon and
popping film cans.
The San Francisco Exploratorium has a on line list of over 100 science experiments. One of them:
"Bubble Suspension" uses dry ice to form a cold thick atmosphere of CO2 for soap
bubbles to float on. Eventually the CO2 will diffuse into the soap bubble by osmosis and the bubble will land on the dry ice. Some bubbles actually freeze and
Exploratorium: Science Snacks
Jane Hoffman's Backyard Scientist series is recognized by the National
Science Foundation as a unique teaching resource. Her books and kits
include dry ice and are used by home, private and public schools as a
curriculum resource. All The Backyard Scientist books have received
the Award of Merit from "Curriculum Product News" magazine (now
The Backyard Scientist:
Science for Kids
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