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Sublime a good time with dry ice

This article appeared in the October 21, 2011 edition of the Davis Enterprise

Article For:    The Davis Enterprise
Sublime a good time with dry ice

By Lisa Justice
Special to the Enterprise

As Halloween approaches, families will be looking for fun and spooky activities and decorations.  Dry ice is a popular choice for its appearance of billowing smoke, good for turning a bucket of water into a witch’s brew or an otherwise unassuming porch into a foggy and forbidding lair.

Let’s take a look at dry ice and what makes it so great for easy special effects at home.

The regular ice that most of us are familiar with is frozen water made of hydrogen and oxygen (H2O).  Dry ice is made of carbon dioxide (CO2), what we exhale when we breathe. 

Carbon dioxide exists as a solid (not a liquid or a gas) at much lower temperatures than water (approximately -109.3ºF).  This makes dry ice an excellent substance for keeping things very cold.  One use for dry ice is in ice cream trucks.

Dry ice appears to give off smoke or fog as it warms up and the carbon dioxide stops being a solid and returns to being a gas.  Dry ice is special because as it transitions from a solid to a gas, it does not pass through a liquid phase.  This process is known as sublimation.

Water ice has to melt into a liquid form before it evaporates into gas.  Dry ice sublimes directly back into a gas.  And that sublimation process makes dry ice such an eerie special effect.

Adding dry ice to water can help speed up the sublimation process and produce more visible carbon dioxide gas more quickly.  But adding dry ice to a cup of water will create other effects as well.

Breathing out is one place in our daily lives that we encounter carbon dioxide.  But those little bubbles of gas in your favorite soda are also made of carbon dioxide.  That’s what makes soda a carbonated beverage—it has carbon dioxide added.

So if you added a piece of dry ice (solid carbon dioxide) to a cup of water, what do you think will happen?  The dry ice will sublime.  The solid piece of dry ice will disappear as the carbon dioxide becomes gas.

Some of that gas you will see billowing out of the cup.  But once the dry ice has fully sublimed, take a sip of the water and see if anything has changed.

Be careful handling dry ice or drinking from a cup that has dry ice in it.  Dry ice is so cold that it can hurt your skin.  Always wear gloves when handling dry ice and never let dry ice touch your skin or tongue.

Dry ice is available at many grocery stores and can be a source of some great chemistry fun.  But use your dry ice soon after purchasing it.  Most home freezers aren’t cold enough to keep dry ice for very long.

Try the experiment of adding a piece of dry ice to water and then visit us on Facebook to share your results and observations.

Explorit’s coming events:

• Explorit’s newest Exhibition, “Forces of Nature” is open the first Weekend of every month from 1:00 to 5:00 p.m.  This exhibition welcomes the public back to our 3141 5th Street Nature Center and will feature some of the best of Explorit’s past exhibits.
 

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Explorit Science Center is located at 3141 5th St. and is open to the public every first Saturday and Sunday of the month.  For more information call (530) 756-0191 or visit http://www.explorit.org, or “like” us on Facebook.


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