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Bubble nucleation, needed for boiling, slows exponentially with the height of a free energy barrier ΔG*. This barrier comes from the free energy penalty of forming the surface of the growing nucleus.
As the temperature approaches 100C, more and more molecules of water have enough energy to leave the water surface as a vapor.At 100C, there are so many water molecules in the bulk of the liquid that have enough energy to become a vapor that any initial pocket of gas will be joined by other molecules, so that the bubble of vapor grows, rises to the surface, and this is seen as boiling.
in my opinion causes happen before the consequence. But in this case the cause (temperature) happens at the same time as the consequence (vapor pressure).
What do you mean with a pocket of gas?
You say two different things. First you say that (1) before reaching 100C, the vapor molecules will leave the bulk. Later you say (2) AT 100C there are many water molecules that have enough energy to become a vapor. Which one is right?
add a pinch of salt or sugar to the superheated water.
Will the water molecule break the IMF during the increasement or after the increasement, at the moment when the energy (temperature) reached the next level (i.e. reaching 90.0002C)?Let's say in example: an increase from 90.0001 will break 20 water molecules from their IMF while an increase from 99.9999 to 100C will break alot more water molecules from their IMF? And thus the vapor pressure reaching the external pressure.
There are a few seemingly simple points about this (which are actually very complicated, once you think about it for a while):A tiny increase in the temperature of the water will lead to a disequilibrium, where now slightly more water molecules are leaving the liquid for the gas phase. This will continue until the pressure of gaseous water increases to the point where they are back in equilibrium (with now a slightly higher fraction of all total water molecules in gas state than when it was slightly cooler).