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charles' law

1/29/2014

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I am devoting a few entries to the laws related to the action of gases.  The next relationship is Charles' Law, the relationship of volume and temperature:

Volume / Temperature = Volume / Temperature

This is a direct relationship -- this link describes quite a bit:
http://en.wikipedia.org/wiki/Charles%27s_law
Click on the animation to the right to view a full-sized animation.

CAUTION: There cannot be any negative or zero values for temperature, so this relationship must be solved using Kelvins!

Remember, absolute zero is -273 degrees Celsius -- it's the temperature at which particle motion stops.

Kelvin temperature = Celsius temperature + 273

Here's one example of a laboratory:

My classes put ice in the cool water bath, and didn't take their finger off the stopper until a minute or two had passed.  Many times, when their finger was removed, the water shot up when rushing into the flask.  It wasn't fun for the student holding the flask, but the result was fun to see!

I had access to large, plastic buckets in one school which made it easier to submerge the flask in the cold water bath.  I didn't put glass medicine dropper valves in the stoppers, we just put our fingers of the hole in the stopper.

Here's a stopper size chart for several sizes of Erlenmeyer flask (just ignore the Product Numbers):
http://www.phytotechlab.com/pdf/FlaskStopperGuide.pdf

You can make a graph and extrapolate to absolute zero.  My students only had two points and many would miss -273 degrees Celsius, but it was exciting when we got close!

I found a simple laboratory procedure:
http://www.newwestinghouse.org/ourpages/auto/2011/5/4/41324522/Charles_s%20Law%20Lab.pdf

Here is a video of a sample mathematical solution for Charles' Law:
http://www.kentchemistry.com/links/GasLaws/charles.htm

And here is a worksheet of 5 problems with answers:
http://mmsphyschem.com/chuckL.pdf

Please let me know about your experiences, ask if you have any questions or if you have ideas for other topics for this blog.

And, check out my lab book "Chemistry on a Budget"  at:
http://www.amazon.com/Chemistry-Budget-Marjorie-R-Heesemann/dp/0578129159/ref=sr_1_1?s=books&ie=UTF8&qid=1389410170&sr=1-1&keywords=chemistry+on+a+budget

I hope you're having a good week!
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    Marjorie R. Heesemann is a chemistry teacher with 15 years of experience who is now working to develop resources for the Chemistry classroom.

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