There are different temperature scales. The temperature scale of International System of Units is Kelvin, but it is used mostly in laboratories, not in real life. In Europe, the most used temperature scale is Celsius, it can be calculated by subtracting 273 from the Kelvin temperature. Celsius was made to satisfy the need to have the freezing point of water at 0. Since most complex molecules, including the living ones are made partially with hydrogen and oxygen atoms, which is water, the water freezing point is very important.
Other important temperature scale is Fahrenheit which is used mainly in United States. The formula for converting from Celsius to Fahrenheit is more complex. The value in Fahrenheit can be obtained by multiply Celsius value by 1.8 and then add 32. Water freezing point is at 32 Fahrenheit. The best way to get the conversion done is to use an online temperature converter
I will explain what happens when water freezes and boils. The water is containing 2 atoms of hydrogen and one atom of oxygen. In a normal fluid state, the water molecules are walking around and playing, exercising an attraction force one to another. The speed of the molecules is depending on the temperature. Sometimes, some water molecules, hitting others gain some extra speed which will counter the attraction force between them and those molecules will get up in the air, which is the phenomenon of vaporization. When the temperature is getting hotter and hotter, the speed of the molecules will increase until it will be very hard for them to stay one near each other and the speed of vaporization will be very high. This happens when the water reaches 100 degrees, the phenomenon that we call water boil.
At that temperature, the number of molecules is so high that so many of them are leaving, taking with them a great amount of energy, leaving the water behind colder.
When the temperature drops approaching 0 degrees, the water molecules are loosing speed, the attraction between them is growing and finally, they crystallize and forming ice. We all know that the water volume is rising when freezing. This happens because the hydrogen atoms are exercising a great attraction making the water molecules to be arranged in a specific position, leaving small spaces between them, and this making the volume to be higher while the number of molecules is the same.
The speed of atoms and molecules depends on temperature on all elements, but they are not having the same speed at the same temperature as water. For example, the titanium melts at 1668 degree Celsius, that is the temperature when their atoms are starting to lower the attraction between them.