If the engine has been running and is hot, shutting off the ignition allows the water in the water jacket to continue to be heated. Therefore, until the engine cools down below boiling temperature, it will continue to heat the water.
Boiling is prevented by a couple of things; anti-freeze (which raises the boiling temperature) and the radiator cap (because water boils at a higher temperature when under pressure).
If your car is overheating, you should not remove the radiator cap (until the vehicle is cool), you can be severely burned as the pressure drops rapidly, boiling the liquid and forcing it out of the radiator!
when water boils it evaporates in to air
saltwater boils the fastest
You would add coolant (not water) to the vehicle's reservoir when it is off and cooled down. Fill it to the cold line.
cold water does.
when water boils it simply evapourates and broke steamy particles
Water boils at 100 degrees Celsius
The water that boils fasteris fresh water because salthas an effect on water.
Steam condences into water, water freezes in to ice, ice melts into water, water boils to steam
fresh water
Water boils at 100 degrees Celsium at sea level (1 atm).
Fresh water under atmospheric pressure boils at 100 C or at 212 F
at normal atmospheric temperature (in plains) it boils at 100oC