How to measure specific latent heat of vaporization.

In a well insulated pot (tle taller the pot is, the more accurate the result is), pour in some water and put a heater with the water, mersure the energy used by the heater by a electricity meter. add a slide with a hole on it also in order to keep the environment in 1 atm and to prevent water spirt out. put the setup(beaker and heater) onto a electric balance and switch on the heater.
After water is boiled, lower the power of the heater in order to minize the chance of weight of setup as gas bubbles from the water really affect the weight.
Then, measure both the readings of the electric meter and the electric balance for several times (use a camera to record those if you want accuracy). Plot a graph about energy supplied to the heater against weight of the whole setup. As E=ml, latent heat=E/m, therefore latent heat is the change of energy/ chance of mass of water (shows in the mass of setup). the value you want can be found by measuring the slope of the graph you plotted.

2008-06-11 06:25:57 補充：
Water traps the heat? How?

2008-06-13 20:12:06 補充：
I think you should read my suggestion again. As I said, the experment starts with water boiling, i.e. temperature of water is 100℃. However, what your idea is about water will absorb heat to raise its temperature, this is quite impossible to say as water is just boiling!

2008-06-13 20:12:23 補充：
And all of the heat it absorded is used as transferring water into steam!
Also, what you suggested at last is not a good idea. You know, when water level is low, heat loss to the air is more serious and water absorbs heat to raise temperature before it boils also!

2008-06-13 20:12:38 補充：
What I have mentioned is about recording the energy producing steam (only producing steam) and Its relationship between mass of water!

2008-06-13 20:12:42 補充：
The slope is exactly what you want if the experiment is in perfect environment (flask is well insulated, pressure is at 1 atm, the meters you use have not much error, water is pure and all heat is absorbed by water).

2008-06-14 22:45:51 補充：
total weight loss is both the water vaporized by the energy absorbed from the input and by the heat in the water? So you mean water temperature drops during the expt? Or why don't you try this expt to prove that I'm wrong?

2008-06-15 16:49:27 補充：
I don't care what is happening below the boiling point, why do you just focusing on things before the expt starts?

2008-06-15 22:44:21 補充：
Come on...... Read the expt instruction again and again, also study about the machanism of vapourization please......
This "extra weight loss" won't be counted by you......