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States of Matter

How many states of matter are there? Well, you have likely heard of solid, liquid and gas states, and maybe plasma as well, but in reality, there are more states still. The reason these are not so obvious to most of us is that they tend to require conditions that we don't normally experience directly in everyday life, such as extremely cold temperatures. The following is a chart of some known or suspected states of matter as of late 2009.

http://www.publicdomainpictures.net/view-image.php?image=8917&picture=states-of-matter


Temperature in eVTemperatures and Scales

Let's consider for a moment the scales that are used to measure temperature. Most people are familiar with degrees centigrade, and if you live in the US, you are probably familiar with the Fahrenheit scale. There is another scale that is less common in everyday use, but is often used by scientists that is called the Kelvin scale.

In degrees centigrade, 0 degrees signifies the temperature at which water freezes at sea level (or 1 atmosphere of pressure). In the Kelvin scale, 0 degrees, also called "absolute zero", signifies the temperature at which all motion, even at the subatomic scale, stops. The study of the physics of the very cold is also called cryogenics.


Bose-Einstein Condensation

When you hear of condensation, you might think of water vapour from a kettle condensing on a cool surface, or perhaps cloud formation in the atmosphere. When the molecules in the gas get colder, they move around less and take up less space. This causes water vapour to condense into a lower energy state and become liquid water. This is exactly what Bose-Einstein condensation is about, but at a much colder level.

The specific atomic description of a substance achieving Bose-Einstein condensation is that every atom reaches the same energy state at the same time. In quantum terms, all electron pairs adopt the same wave function. This happens at very low temperatures-just a few billionths of a degree Kelvin. When this is achieved, some very strange properties emerge.

Early experiments used helium to try and achieve this because helium stays gaseous until it reaches a little more than two degrees Kelvin. At this point, it takes on the characteristics of a superfluid, and approaches Bose-Einstein condensation. More recently, rubidium, sodium and lithium have been used to successfully achieve Bose-Einstein condensation. In 2001, Cornell, Wieman and Ketterle won the Nobel prize in physics for their work on the problem.

Here you can view a Nova excerpt about the quest for absolute zero http://youtu.be/y7xp_hHbDUs or see the full-length program here: http://www.youtube.com/watch?v=y2jSv8PDDwA

Superfluids

One result of the study of very cold temperatures is the discovery of a new state of matter called a superfluid. Superfluids have some bizarre characteristics, such as having the ability to flow through solid matter and zero viscosity among others.

Here is an older BBC video that demonstrates these: http://youtu.be/2Z6UJbwxBZI Here's a more modern BBC version of the same experiment: http://youtu.be/9FudzqfpLLs

Superconductors

Superconductors are metals or oxides that, when cooled to very low temperatures, have the property of zero electrical resistance and a reduced interior magnetic field. There are two types of superconductors: type I and type II. Type I work at the lowest of temperatures (7.1 degrees Kelvin and lower, depending on the material) and include metals and metalloids, and type II work at higher temperatures (at or below 130 degrees Kelvin, depending on the material) and include alloys and complex oxide ceramics. These are the ones you will see in popular science demonstrations.

How do they work?

When an electron moves between ionized atoms, there is a slight attraction because the ions are slightly positively charged and the electron is negatively charged. This causes the atoms on either side to move a bit towards the electron. This action creates Cooper pairs, which have the property of being superconductors.

Here is an excellent demonstration of quantum levitation & suspension of a type II superconductor http://youtu.be/VyOtIsnG71U

The Formation of Cooper Pairs

Here is a demonstration comparing electrons flowing through ions in high and low temperatures http://www.supraconductivite.fr/en/index.php?p=supra-explication-cooper-more
Some interesting properties of superconductors are the Meissner effect, in which all magnetic forces are repelled by the superconducting material, and vortex pinning (flux trapping effect) in which, for higher temperature superconductors (called type II superconductors), magnetic forces are pushed through the material and as a result form tunnel-like paths.

Quantum levitation using both the Meissner effect and vortex pinning are shown here: http://www.supraconductivite.fr/en/index.php?p=supra-explication-cooper-more#supra-levitation
and here: http://youtu.be/Z4XEQVnIFmQ

But Wait! Physics Gets Even Weirder Still!

Recently, physicists were able to create a negative Kelvin temperature state. If you're like me, you may be wondering how this could be possible, and if you're as old as or older than I am, you may be envisioning Kurt Vonnegut's infamous "ice nine". While headlines everywhere read about the breaking of the thermodynamic laws of physics, it would seem that this is a misunderstanding of the way thermodynamics defines temperature.

Since I am not a physicist, I will point you to this excellent article that explains it much better than I can. http://www.zmescience.com/science/physics/lower-than-zero-temperature-07012013/ and here is another explanation of what "below absolute zero" really means: http://www.youtube.com/watch?v=yTeBUpR17Rw&list=FLoxcjq-8xIDTYp3uz647V5A&index=31

Cold Dry Ice Tricks You Can Do At Home

While most of us would be challenged to find a cheap and reliable source of liquid nitrogen for home use, we can find sources of dry ice. Many party suppliers as well as medical supply companies will sell dry ice to the public. Be certain to follow proper handling procedures as dry ice can give severe burns and may explode if stored in a sealed container. You can also make dry ice yourself with a fire extinguisher. Here is an "Instructables" clip to show you how. A word of warning however: the video shows someone handling dry ice with bare hands--unless you want frostbite, you should be advised that this is not a good idea! http://www.instructables.com/id/How-to-Make-Dry-Ice-With-a-Fire-Extinguisher/

Although it isn't as cold as liquid nitrogen, and as such cannot turn materials into superconductors (none that have been discovered yet, anyhow), there are many interesting explorations possible, such as making a spoon scream, levitating pennies, making homemade ice cream, making mini-rockets and much more. If you follow this link to the Lemonade advanced science page, you can find lots of fun and interesting ways to explore the various properties of dry ice.

Click here to watch Veritasium's video on the making of solid nitrogen and the condensation of carbon dioxide from the atmosphere into dry ice.

Interacting Photons

Recently, scientists in the U.S. were able to use gases cooled to just above absolute zero to cause two photons to interact and become a molecule. Although not quite a light sabre nor a holodeck, the ability to make such molecules may lead to breakthroughs in quantum computing. More about this can be found at this Physics World link.




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