Tuesday, November 13, 2012

ThermoDynamic Bread!

Hey guys!

A lot of you have probably noticed that if you put 1 object in the microwave for X amount of time, then the temperature of the object goes up by some amount, however if you put two of the same objects for the same amount of time then each object will be individually less hot than in the first case. To me this was always an obvious fact that I learned from my early teenage years heating up tortillas in the microwave (I use tortillas as the example because it's funny cause I'm Latino).

At MIT I have learned that this is not an obvious fact for some people, one time during my junior year I had an argument with a freshman on the subject. He was convinced that if we put two sandwiches in the microwave for the same time as one, all three sandwiches will end up with the same temperature. I quickly tried to correct him but he gave me some stupid explanation on how the air will not heat up as much of you put two things instead of one thus making the efficiency higher blah blah blah... I tried to appeal to his inner scientist/engineer and talked about the first law of thermodynamics applied to microwaves but that did not work so then i just made fun of him which made him get kinda mad (sounds like I was being mean, but HEY! he asked for it! never mess with the FIRST LAW)

A couple of weeks ago I had the same argument with a friend who argued that formation of standing waves blah blah blah and that the temperature rise under the two conditions would be the same. (this case he was arguing that putting two Maruchan soups will heat each up the same as just putting one in. I tried to give my Thermo First Law speech AGAIN but it did not work so I was forced to do some late night experimenting: please enjoy!

 BAM! SCIENCE! I was right yet again, the single piece of bread exhibited a temp. rise that was 1.6 times greater than the two pieces of bread. However the question now is, why isn't that a factor 2? (half the mass means double temp. change for a same heat energy influx). That got me thinking on how the efficiency of the microwave varied with the properties of the food you cooked. (granted, the experimental set-up could be a total failure, thus I will be trying to repeat it in the next couple of days with cups of water instead of bread).

I started exploring the internets for answers I found some people that pretty much agreed with me (click here to see). Then some more people here. After this basic research it was obvious that the food properties (composition and geometry) and a lot to do with the linearity of the heating times, which adds an unknown for cooks in knowing how long to heat up things for. Interestingly fact: microwaves were initially unpopular because they were so "unpredictable" as far as heating times are concerned. (link to wikipedia microwave page

I will be conducting some more experiments of my own to check out how valid the linearity of heating times holds for things like water, bread and other random things.

Keep posted for the results! If you have any other "scientific experiments" or kitchen science questions that need to be answered please let me know and I'll do my best to address them in this blog!


  1. Pretty cool idea! I won't argue with your result, but your method was somewhat unorthodox. You didn't even measure the starting temperature, maybe the first toast was hotter to begin with. And the position certainly does matter, so I'm not quite convinced with the experiment :P

  2. we did measure the temp (but not on tape) and yes I agree with you this is probably the crappiest experiment ever