Question

why water freeze at 0°c and boils at 100°c plz explain

Answer 1

We've all been taught that water freezes at 32 degrees Fahrenheit, 0degrees Celsius, 273.15 Kelvin. ... As the temperature of the waterapproaches -55 degrees F, the watermolecules form tetrahedrons, with each molecule loosely bonding to four other molecules.

the boiling point of a substance is the temperature at which the vapor pressure of the liquid equals to the pressure of the gas above it

So at atmospheric pressure if water boils at a temperature of 100 degrees celsius

Answer 2

because water needs some small nucleus and seed of the ice for the molecule.and it is also known as super cooled. but once the super cooled form it will be solid - rock in instant. if it goes below this will happen so it is in 0 degree Celsius.
the boiling part of substance is the temperature at which the vaporize air / pressure of liquid equals to the pressure of gas above it.so it boils at 100 degrees Celsius. at only atmospheric pressure.