Ouch - Hot Pizza!

When eating pizza the recently with my family, my wife and I burned the roof of our mouth's as so many people do.  The next time we had pizza we waited several minutes before chowing down.  While waiting my son was asking why the crust did not feel hot while the cheese was very steamy even after several minutes.  A great question!

I immediately proceeded in giving some long-winded explanation to an 8-year old about the heat capacity of cheese being higher than the heat capacity of the crust.  Of course I had to explain that heat capacity (C) is amount of heat energy (q) needed to raise the temperature (Δ T) of a specific amount of substance (mass, m).

The formula:  q = C × m × (Δ T)

The higher the Heat Capacity the longer it stays hot.  In addition, bread is a good insulator so it transfers heat very slowly while mozzarella cheese being a better conductor transfers heat faster.

After after giving this explanation I asked my son if he understood, to which he replied, "Oh I got it, the crust has lots of holes in it like bread or bubbles which means it won't get as hot".  His explanation is essentially correct (replace get as hot with hold as much heat) and is simpler to understand than mine.  The crust is much less dense than the cheese, thus the same volume of cheese can hold a lot more heat than the same volume of crust.  In think I will run explanations through him from know on.

Believe it or not, others have studied this topic.  For more information checkout: The Thermodynamics of Pizza from ChemPRIME.

Am I Joking?

I just got done making a big stink about why we need to use the Metric System and my choice for Featured Scientist of the Month is Daniel Fahrenheit.  Actually Fahrenheit was a brilliant dedicated scientist who understood the need to develop a universal scale for thermometers.  See post below...

SEPTEMBER 2012

Daniel Fahrenheit (1686-1736) was born into a German merchant family in Gdansk, Poland.  He was a scientist who is best known for making the modern day alcohol thermometer and mercury thermometer.  His parents died from eating poisonous mushroomswhen he was fifteen.  After spending time in foster homes, apprenticeships, and studying natural science, Fahrenheit become a  glassblower making barometers and thermometers. 

Early thermometers had arbitrary scales and he as well as Isaac Newton years earlier recognized that thermometers based on materials that change at certain temperatures would make them reproducible.  Newton was not a thermometer maker and did a couple of other things anyway.  Fahrenheit choose a mixture of ice, water, and ammonium chloride (a salt) for zero.  He used 32 degrees for the freezing point of water and 96 degrees for body temperature.  The funny numbers come from his original idea of have a 12-point scale where zero, four, and twelve are the three constants.  He then separated each point by eight gradations.  The result, multiply each constant by eight: 4 X 8 = 32, 12 X 8 = 96.  Body temperature is normally measured at 98.6 degrees but he was close.

sources:

John Lienhard: http://inventors.about.com/gi/o.htm?zi=1/XJ&zTi=1&sdn=inventors&cdn=money&tm=6&f=10&su=p284.13.342.ip_&tt=2&bt=0&bts=0&zu=http%3A//www.uh.edu/engines/epi1300.htm 

wikipedia: http://en.wikipedia.org/wiki/Daniel_Gabriel_Fahrenheit 

Unfortunately Fahrenheit's constants were not as simple as the constants Anders Celsius chose for for his scale who used the freezing point and boiling point of pure water.  

Also, for those interested in the where the following conversion formulas comes from:

        F to C where C = (F-32)*5/9     

        C to F where F = C*9/5+32

Notice the difference between 0 and 100 (100) on the Celsius scale and their corresponding Fahrenheit temperatures 32 and 212 (180).  The ratio is 100 to 180 which reduces to 5 to 9.  Whether it is 5/9 or 9/5 and if you have to add or subtract 32 depends on which scale your looking for.