The first scientists who made cold liquids out of gases like hydrogen, nitrogen, and oxygen did so simply because they were trying to understand states of matter and what makes things cold. But over time, people have put those liquids to use in all sorts of modern applications -- as can clearly be seen in the field of medicine.
The ability to create liquid oxygen means hospitals have an easy way to store oxygen for their patients. A single liter of liquid oxygen (around three soda cans’ worth) will expand 862 times when allowed to come to room temperature -- and that will fill some five oxygen tanks. So as long as you keep it cold you can store a huge amount of oxygen in a small space.
Doctors use liquid nitrogen more directly to fight illness. A dab will help remove warts and moles, painlessly freezing them so they fall off. The same principle is used in more serious surgery too. Cryogenic liquids can be used to kill off unhealthy tissues like cancers on the skin. (This is in fact what happens when you get frostbite -- extreme cold kills human tissue. But when a doctor does it, the cold is focused on a sick part of your body.) And new research is even studying how to freeze just a bit of the muscle on the heart to cure arrhythmia.
Doctors also make use of cryogenic temperatures when storing important tissues. A simple freezer destroys live cells because the slow freezing process causes the cells to deform], but liquid nitrogen can flash freeze things like blood and bone marrow for safe long-term storage.
Research the process of how cryogenic liquids are made. Where do we get the oxygen and nitrogen? What process is used to make them cold enough to become liquid? Is this process anything like how your refrigerator makes things cold? Is it anything like how scientists make a Bose-Einstein Condensate?
Hands on Activity
The Advantages of Storing Cold Air
In this activity you will explore how very cold air takes up less space than room temperature air. You will not be actually making the air so cold that it becomes liquid, but the volume change will nevertheless be dramatic. While liquid nitrogen will evaporate long before it could freeze your skin, it is nonetheless a good idea to where rubber gloves when pulling the balloons out at the end of the activity.
A medium-sized Styrofoam container or ice bucket with a hole somewhat smaller than your average inflated balloon
10 to 20 balloons
Fill the Styrofoam container about one-quarter full with liquid nitrogen. Blow up a number of balloons. Do you think that any of the balloons can fit into the container through the small opening? If you could get the balloon through the opening, how many balloons do you think would fit into the bucket?
et a balloon directly on top of the bucket, where it should balance, unable to fit through the hole. . . until the liquid nitrogen begins to chill the air inside the balloon. As the balloon gets colder it will eventually fall into the container. Why do you think this is?
Check out understanding hot and cold, if you need a refresher on what happens to atoms when they get cold.]] Repeat with the next balloon. And the next. Keep going until all the balloons have fallen into the container. Now what do you think about how many balloons could fit inside?
ow that all the balloons are in the bucket, what do you think will happen when you take the balloons out and they warm up again? Try it! Do the balloons look the same as they did before they went in? If a hospital wanted to store large amounts of oxygen, do you think it would make more sense to store it hot or cold?
(Teachers: This can be a particularly fun demonstration for those with some showmanship. One doesn’t have to tell the students that the container has liquid nitrogen in it. The blowing up of balloons can be done almost absentmindedly during a talk -- with a seemingly unendless amount of balloons filling the bucket, like clowns fitting into a car. Then each balloon can be retrieved one at a time -- looking like a flat Frisbee -- and thrown into the audience. As it flies it will re-inflate long before it reaches anyone.)
Thank you to our Underwriters: National Science Foundation, Alfred P. Sloan Foundation.
Credits: 2006 - Design and Development: Devillier Communications and Wood St. Content - Devillier Communcations. All Rights Reserved.