DRY ICE
Background
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 commonly 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 convert to
its frozen form and easy to handle using insulated gloves. Dry Ice changes directly from a solid to a gas sublimation- in normal atmospheric conditions without going through a wet liquid stage.
Experiments
Screaming Metal
THE EXPERIMENT: When metal is placed against dry ice, the metal will usually make a loud screaming
noise. You can create the loud screaming noise at home using a spoon against the dry ice. Also, you can
put water in the spoon and see how the water freezes right when the spoon touches the Dry Ice. Careful
that the spoon doesn't get too cold. The spoon can get cold enough to give you frostbite in this
experiment.
WHAT IS HAPPENING: The reason it makes the noise is because when the warm metal bar touches the
dry ice, it vaporizes a little of the dry ice which makes a puff of gas. The puff of gas pushes the bar
up...but as soon as the bar goes up, it falls back down. This happens over and over again really fast which
make the screaming noise. A spoon left against the dry ice will dig a hole in the ice. Do you know why?
Magic Balloon
RIDDLE: What gets smaller, but gets a thousand times bigger?
Fill a large balloon with some pieces of dry ice using a funnel. (Remember to wear gloves). You can
even add some warm water to the balloon. Tie off the balloon and you will see the balloon look as if it is
blowing itself up. If you put enough dry ice in the balloon, the balloon will pop. This is supposed to
happen, BUT DO BE CAREFUL. Stand far away from the balloon when it is about to pop.
WHAT IS HAPPENING: When regular ice melts, it goes from being a solid to a liquid and
drips all over. In thes experiment, dry ice doesn't really melt, but it does get smaller. The Carbon
Dioxide undergoes what is known as a phase change. The dry ice goes from a solid state, straight
to a gaseous state, (which is technically called sublimation, rather than melting). AND.....A
LITTLE DRY ICE MAKES A LOT OF GAS. When you put the dry ice in the balloon, as it
"sublimates" it eventually will probably build up enough pressure inside the balloon to make the
balloon pop.
Spooky Fog
THE EXPERIMENT: Add a piece of dry ice into a cup of warm water and you will see the dry ice
making bubbles and creating a very interesting fog. If you add a large piece of dry ice into a large
container of hot water in a box you will get a box of fog.
WHAT IS HAPPENING: Why is the dry ice making bubbles? Is it changing from a solid into a
gas? You've seen water boil before. In this case, is the water or the dry ice boiling? Why would
the water hitch-hike in the Carbon Dioxide gas and make fog? It turns out water molecules are
very happy jumping into the Cabon Dioxide and once they are there, the water molecules get
cold and combine together to make fog....kind of like the fog you see on a cold day.