What is meant by "evaporation to dryness"?

Nov 22, 2016

I think you mean $\text{evaporation to dryness..........}$
$\text{Evaporation to dryness}$ occurs when a still pot (or a kettle) is left at reflux (at boiling point) in other, and all the water is (or other liquid) is evaporated from the kettle or pot.
Of course, even with non-flammable solvents, such a phenomenon is dangerous. When we distil water, the temperature of the kettle can get no higher than $100$ ""^@C, i.e. the normal boiling point water. Once the kettle is dry, it can get a whole lot hotter than $100$ ""^@C.