Sunday, May 20, 2012

Thermite vs. a Hamburger

The thermite reaction releases 852 kilojoules (kJ) of energy whereas a hamburger typically has only 600 Calories (Big Mac has ~600 Calories).  Looks like thermite wins!  Good  news for summer grilling.  Either way I am having a burger tonight!

However, a calorie is defined as the amount of energy need to raise the temperature of 1 gram of water 1 degree Celsius.  In the food business, for some reason, they use Calories, notice the capital 'C', therefore 1 Calorie = 1 kilocalories = 1000 calories.  Are we in the clear yet since it is 852 kJ vs. 600  Calories?  Not really as 1 calorie = 4.2 Joules or 1 Cal = 4.2 kJ which means the 600 Cal must by multiplied by 4.2 in order to convert this to kJ.  When we do this the the 600 Cal is equivalent to 2520 kJ.

The thermite reaction is shown below.  It is a reaction between powdered aluminum and iron powdered iron III oxide (rust).  To get the reaction to occur it must be heated to around 2200 degrees Celsius which is why an ignition reaction must first be used.  I used a mixture of potassium chlorate and sucrose plus a few drops of sulfuric acid.

Video 1) Thermite Ignitor (KClO3 + Sucrose + Sulfuric Acid)

Video 2) Thermite

The good thing about having the AP Chem Test first is it leaves more time at the end of the year to perform neat demos.

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