[kimixa]

I thought everyone did the experiment of leaving a saucer of water out and seeing it evaporates over time, despite being significantly lower than 100c.

And "Steam" is wooly term for high enough density of water vapor that you see condensation - often caused by higher temperatures in the majority of cases people experience it in day to day life. So it doesn't really have a precise definition. At what temperature point does "mist" become "steam?" What %age of the volume of air needs to be water vapor? If you lowered the pressure water "boils" at a lower temperature - is that still steam?

[at_a_remove]

That first question, it is 100C at STP. Second question, enough to make you have a second or third degree burn. Third question, yes.