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!

The math tends to be pretty simple. One challenge for students can be the use of different pressure and volume units so that they don't cancel.   Students should be aware of different standard pressures depending on the measurement system:

1 atm = 760 mmHg =  760 Torr = 29.92 inHg  =  14.696 psi =  101.3 kPa

Also, volume units can be changed, even though milliliters is the most typical measurement students will encounter.

Including units in their work and being sure the units cancel is always important!

Here's an example of a solved problem:
http://chemistry.about.com/cs/workedproblems/a/bl011804.htm

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

Have a good week!

This lab is a classic and hopefully a roll of magnesium ribbon is available in your department.  I've worked in departments where the grams per centimeter had been measured, so a small length of magnesium ribbon could be used.  However, if the ribbon sample must be massed, a much longer sample of magnesium ribbon may need to be used (depending on the balance available) -- and you may have crumple it up to fit into the crucible.

This again uses the crucible/clay triangle/clamp/ring stand setup:

Safety: Laboratory goggles and an apron are to be worn by students.   Notice that the crucible is glowing red from the Bunsen burner flame.  This is a very hot setup, and it takes time for the crucible to cool down.  I've told this tale here before, but I've had students touch this set-up while it was still hot, flinch and knock it over.  Bring the back of your hand close to the setup to see if it's still warm.

Here's one lab that you might find useful:
http://stahlchem.wikispaces.com/file/view/MgO+aca+09.PDF

Now I'm a fan of the "less is more" approach, but it's difficult to find lab procedures that are brief for this experiment.

One concept that can be applied here is that of determining the empirical formula for the magnesium oxide formed.    An empirical formula is the lowest whole number ratio of the elements in a compound.  All ionic compounds (metal/nonmetal compounds) are empirical formulas (for example, CaCl2 ) but some molecular formulas can be reduced to an empirical formula -- e.g C2H4 can be reduced to CH2.

Mass data can be collected, converted to moles, the lowest ratio calculated, then reduce to a whole number ratio.  Phew, that's a lot of steps! Let's break that down:

1) collect mass data -- 80 g C and 20 g G

2) convert to moles

 80 g C  x 1 mole C / 12 g C = 6.7 mol C

20 g H x 1 mole H / 1 g H = 20 mol H

3) calculate the lowest mole ratio-- by dividing both values by the smallest number

            6.7 mol C / 6.7  =  1 mol C

            20 mol H / 6.7 = 2.99 mol H

4)  Get a whole number ratio by (a) rounding off the numbers or (b) multiplying the ratios by 2 or 3, then r.

Rounding off works well in this case:

1 mol C             2.99 mol H rounds to 3 mol H

So the empirical formula in this case is CH3 !

I hope this lab works out well for you.  Please ask if you have any questions or ideas for other topics

Check out my lab book "Chemistry on a Budget" !
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

A decomposition reaction can easily be performed by heating sodium hydrogen carbonate  (aka sodium bicarbonate or baking soda):

                                                    2 NaHCO3 -->  Na2CO3  +  H2O  +  CO2

The carbon dioxide and water leave the system as a gas.  I have performed this reaction in a crucible in a clay-triangle on a ring-stand and over a Bunsen burner, but I lost a lot of product with the rapid release of the gases.  I could actually see the stream of white powder leaving the system when performing this lab. 

I never tried to use a cooler setting on the Bunsen burner by closing off some of the air vents.  This would result in a flame that is more yellow than blue.  If you end up trying this, write and let me know!I started performing this lab by heating the crucibles in an laboratory oven. 

Remember that the crucible gets very hot!  I've had a few students touch the crucible, flinch and knock over the entire setup.  Be careful! Remind students to detect the heat with the back of their hand, and to use their crucible tongs!

The results can be very good and lead to some good values to work with stoichiometrically.

The Theoretical Yield can be calculated based on the mass of sodium hydrogen carbonate:

# grams NaHCO3 x 1 mol NaHCO3/84 g NaHCO3  = # mol NaHCO3

# mol NaHCO3 x  1 mol Na2CO3 / 2 mol NaHCO3  = # mol Na2CO3

# mol Na2CO3 x  106 g Na2CO3 / 1 mol Na2CO3  =  # gramsNa2CO3

I separated these 3 calculations to aid students in focusing on what is happening and not get lost in the calculations.  Of course, these 3 calculations can be put together:

# grams NaHCO3 x 1 mol NaHCO3/84 g NaHCO3  x  1 mol Na2CO3 / 2 mol NaHCO3  x  106 g Na2CO3 / 1 mol Na2CO3  =  # gramsNa2CO3

Then the lab measurements can be used to calculate an Actual Yield.

These values can then be used to calculate a Percent Error.

                    (experimental value) − (true value)
% error  =  ―――――――――――――  × 100
                                       true value

The absolute value is typically reported (negative symbols are not included).

Here is one lab procedure you could use:
http://phs.princetonk12.org/teachers/FOV2-0001F947/AccelChem/Labs/A19Lab-DecompBakeSoda.pdf

Please write if you have any questions or comments!

Happy Saturday!  I'm starting my revised writing schedule of Saturday, Tuesday, Thursday.  I'd love to hear your comments / questions!

There are several chemical reactions that are good experiences for high school chemistry students, and I'm going to focus on a few through the month of January.

A nice looking experiment is the single replacement reaction between copper wire and silver nitrate solution. 

The materials may already be in your science department -- you might have a little trouble obtaining silver nitrate crystals or solution.

Here is link to a brief YouTube video showing the lab:
http://www.youtube.com/watch?v=PNaZqnFwIIQ

There are several variations available on the Internet -- here's one that I like:
http://www.e-bookspdf.org/view/aHR0cDovL3FzaWIuZmlsZXMud29yZHByZXNzLmNvbS8yMDEwLzEwL2NvcHBlcl9hbmRfc2lsdmVyX25pdHJhdGVsYWIucGRm/VGhlIFNpbHZlciBOaXRyYXRlL2NvcHBlciBSZWFjdGlvbg==

Let me know how about your experiences with this lab!

Welcome to my blog!  All of this is new, so bear with me as there may be some problems/ challenges/changes along the way. 

If you are teaching, you're about  halfway through the school year -- congratulations!  If you are going to graduate and start looking for a teaching job, good luck!  It's a big challenge, but you can do it! 

I'd love to hear from you -- until then it might seem a little random while I try to put useful information up.  I might be writing just M/W/F until I think that schedule needs to change.

Hmmm, it's Wednesday -- for a lot of you it's the end of the marking period, so you're grading or getting that last test in, so I'll let you keep at it.  Bye for now!