Re: HOW MUCH HEAT IS NESSASARY IN ORDER TO GET AN EGG BOILED

>HOW MUCH HEAT IS NESSASARY IN ORDER TO GET AN EGG BOILED?

You could be asking one of two questions:	
Do you want to know at what temperature eggs can be boiled?
  or
Do you really want to know the amount of heat energy necessary to boil one 
standard egg?

Since the first question is easier, I'm going to answer it first. Eggs are 
made of whites and yolks. The soft-boiled egg is prepared by simmering at 
185 degrees Fahrenheit for 5 to 6 minutes. A hard-boiled egg is prepared by 
simmering at that tempreature for 25 to 35 minutes. If you carefully crack 
an egg on a heated frying pan you will see that there is a thin part of the 
white and a thick part of the white. The thin part will coagulate (cook) 
first, not just because it is thinner, but because it has less ovomucin 
which is more resistant to heating than the ovalbumin which is the major 
white protein. The thin part of the egg white begins to cook at 145 deg F 
(63 deg C). All parts of the egg white will be firm at 160 deg F (71 deg 
C). The need for higher temperatures than 160 deg F comes from the desire 
to get the egg cooked in a reasonable time frame. You need the higher 
temprature so that heat will pass throught the shell and the outer 
thickness of the egg into the deeper portions.
The source of this information is a fascinating book, On Food and Cooking, 
by Harold McGee, 1984, Collier Books. He has six pages on the biochemistry 
and biophysics of cooking eggs.

What that book doesn't have is the information necessary to answer the 
second question. In order to calculate the amount of heat energy to cook (I 
will assume you want it soft-boiled) an egg I would need to know the heat 
capacity of the egg white, as well as the extra energy necessary to cause 
the "phase change" from liquid to solid. It is undoubtedly much more 
complex that the simpler process of heating a liquid to boiling. The heat 
capacity of the water-protein solution probably changes over the range of 
tempratures between room temprature and the cooking tempratures. 

If you really wanted to know, you could do an experiment where you took a 
pan of boiling water, put it into a styrofoam container (a picnic cooler 
for instance) and measured the rate of fall of temperature over five 
minutes: 1)when nothing was added, 2)when an egg was added, and 3)when an 
ice cube of known weight was added. Further calculation will be necessary 
at that point:
What you will be doing is making your own bomb calorimeter and determining 
the heat absorbed by the egg during its first five minutes of cooking. The 
three conditions will let you calculate the heat lost by the pan to the 
calorimeter, the heat capacity of the pan-water system, and  finally the 
heat absorbed by the egg.

If you are going to do this experiment: Get your parent's permission, keep 
careful notes of the weight of the ice cube and the temperature changes. 
Send in another question with your results and we'll help you do the 
calculations.