# How to measure (heat) energy used?

Before I start with my question, would like to highlight - the last time I delved into this topic was 13 yrs back during my schooling courses. But the enthusiasm never died.

Coming back to topic - I want to know/understand if there's a way to know the amount of energy (heat energy, i guess!) used to boil an egg?

Ex. if suppose I start boiling an egg in saucepan filled with water, how much heat energy is used in that process. Say, 1.3 Joule of energy.

Also, is there any instrument in market to calculate that?

• There are too many variables associated with your question. How quickly do you want to boil the egg. Do you want a hard boiled egg? A soft boiled egg? What is the minimum temperature of the egg necessary to harden the yolk. What is the specific heats of the egg white and egg yolk How big is the egg? How much water in the saucepan. And I am sure there are more. – Bob D Jul 3 at 14:55

As Bob D has commented, this is very difficult to calculate theoretically. He didn't mention that you need to know the thermal conductivity of the egg's contents – and to make things worse, this conductivity will change as the white and yolk change consistency.

Boiling an egg in a saucepan is, of course, a very wasteful process. Most of the heat supplied goes to making steam or is lost to the surrounding air from the sides of the saucepan.

If you want to know how much heat goes into boiling the egg itself, I think you're better off trying to measure it. A 'steam calorimetry' approach (good nineteenth century Physics) should work... Suspend the egg in a jet of steam at 100 °C (the colourless stuff, not the cloudy stuff that's already starting to condense. Collect the condensate that drips off the egg and, when it has stopped dripping, measure its mass, m, and temperature, $$\theta.$$

Then heat that has gone into egg = $$mL+mc(100°-\theta)$$

in which $$L$$ is the specific latent heat of evaporation of water and $$c$$ is the specific heat capacity of water. The second term will be much smaller than the first.

[For a well known use of this method, see Joly's steam calorimeter.]

• I'll try and do this at home, when I can find time, which won't be for a few weeks. The condensate will continue to drip until all the egg is at 100°C. This will take some time, because of conduction (and at first, perhaps) some convection of heat from the outside to the centre of the egg. By this time, of course, the outer layers of the egg might be over-cooked. Some experimentation will be needed! – Philip Wood Jul 5 at 17:28