Saturday, February 16, 2013

What Does Colored Ice Have To Do With Uranium?

Nothing!  Unless you are in Iran and the ice is glowing.  The following pictures were from my son's latest experiment, Making Neat Looking Colored Ice, which he did during the blizzard.  It kept him busy for a little while as well.  The procedure was quite simple: 1) fill cups with water, 2) add a few drops of food coloring, 3) stir, 4) set outside to freeze, 5) remove from cup.  The results speak for themselves, cool looking ice structures that resemble a lava lamp that has been frozen.  BTW, these are upside down from when they were made.  NEAT!

The ice structures show some interesting features upon closer examination.  Most of the food coloring seems to have been concentrated into a ball shaped structure that has been surrounded by uncolored ice.  You can also see bubble zones in the clear ice which eventually get absorbed by a third zone of ice that mixed with food coloring.  I am not certain when this region crystallized.
I kept the geochemical jargon to a minimum.

So Why the Title?
It turns out the pure water crystallized first concentrating the food coloring into a ball which was the last region to crystallize.

What happened here also mimics what happens when when minerals (crystallize) form from a melt deep inside Earth.  As magma solidifies upon cooling, remaining melt changes composition.  The result is a pluton (solidified magma body) with regions of different composition.

Suppose a magma body containing iron (Fe), magnesium (Mg), potassium (K), uranium (U), and silcica (SiO2) solidifies, the first minerals to form will soak up most the Fe and Mg along with some silica.  Uranium is a large element that prefers to be in a melt.  When the rest of the magma finally solidifies it will have a higher concentration of K, U, and silica.  It so happens that granite represents later stage crystallization, thus is higher in U concentration when compared with most other rocks.  This was a very simplistic explanation. 

Relating this back to the Colored Ice model:  The red food coloring would represent the uranium and potassium.  The clear ice would represent the zone where crystallization of the Fe and Mg takes place.

Why Was All This On My Mind?
Someone in my son's cub scout troop was concerned about his granite counter top having radon (Rn) gas.  Since granite has a higher U concentration and Rn is daughter product of U when it decays, most anything granite does emit Rn gas.

Oh No!  Should you rip out the counter tops or sell the house?
No!  Although concentrations of Rn may be higher than background levels they are not high enough for any concern as you don't have enough granite.  Some houses, however, that have granite for bedrock should get there basements checked for radon as that is a potential hazard especially since there is minimum ventilation.

FYI - I have granite counter tops in my bathrooms.

Sunday, February 10, 2013

How Many Gallons of Water Did You Shovel?

My answer to Mike Sirowich's (Physics Teacher Extraordinaire at SHS) Physics Tweet from 2/9/13 (SHScatphysics) regarding how many gallons of water did you shovel came out to be 6355 gallons.  The solution takes in many assumptions of course.  On average a little over 2 feet of snow fell in our driveway.  Also, I have an irregular shaped driveway that is 190 ft long and varying widths.

The approximate dimensions that I removed was as follows:
130 x 7.5 = 975 ft2  
28 x 60. = 1680 ft2
       The total area = 2655 ft2  

Now to add the third dimension and the most varied assumption, the snow to water conversion.  Online I found two common conversions: 1 inch water to 10 inches of snow and the more common  1 inch water to 6.25 inches of snow.  It really depends on the type of snow that falls.  My son's experiments came up with 1 inch of water to 5 inches of snow which is more inline with the 1 to 6.25 conversion so I will use that as the conversion factor.

1) Convert snow to water: 24 in of snow/6.25 = 3.84 in of water
2) Convert inches of water to feet: 3.84 in of water/12 = 0.32 ft of water

            3) Calculate volume:  2655 x 0.32 = 849.6 ft3

Finally convert the volume from cubic feet to gallons (1 cubic foot = 7.48 gal):

849.6 ft3 x 7.48 gal = 6355 gallons of water

In science (as well as the rest of the world) we use the Metric System so (1 gal = 3.78 L):  
24,022 L

Friday, February 1, 2013

Only fitting that that I select a scientist who was instrumental on my next topic.  Gilbert Newton Lewis was born in Weymouth, MA on October 23, 1875.  Lewis entered the University of Nebraska at age 13 and transferred to Harvard in 1894 where he received a BS degree in Chemistry and then a Ph.D. at age 24.  He went to work for Wilhelm Ostwald and Walther Nernst in Germany and then spent time in the Philippines with the Bureau of Weights.  Later returned to Massachusetts where he was appointed to a professorship at  Massachusetts Institute of Technology (MIT).  In 1912 he obtained a professorship with the University of California at Berkeley where he remained for the rest of his life.

In 1916 he published a paper “The Atom and the Molecule” where he describes his theory of bonding where there are eight electrons in the outer orbit of an atom and the electrons are represented with dots (Lewis Dot Structures).  In addition, he developed new classifications for acids and bases and performed photochemical experiments.  Another distinction for Lewis was that coined the term “photon” although he intended for it to be structural unit rather than one quantum of light energy.  Very few people have been nominated for Nobel Prizes but Lewis is the only one who could say they have been nominated 35 times never to win.  A chemist to the end, Lewis died in his laboratory in 1946.

Gilbert Newton Lewis
wikipedia: Gilbert N. Lewis