Water is an interesting substance, We all know that our life depend on the presence of water around us! It’s the only substance on all of our planet that occurs naturally in solid, liquid and gas forms. Because of its composition it has some unique physical properties.
Let’s start with the world’s most famous molecule, the molecule of water H2O which contains one oxygen atom and two hydrogen atoms connected by covalent bonds. These covalent bonds are made up of a pair of electrons shared between Oxygen and Hydrogen, and they are the reason to the water’s unusual Properties.
Oxygen is more electronegative than hydrogen, this means that the oxygen atom develops a partial negative charge which leaves the hydrogen atoms with a partial positive charge. These partial charges create a positive end and a negative end to the molecule, making it polar. Different polar water molecules can attract each other and stick together, this attraction is called ‘hydrogen bonds’.
Hydrogen bonds give water a boiling point that is about 100oC that’s why water is liquid at room temperature, but other similar molecules like hydrogen sulfide, hydrogen selenide, And hydrogen telluride are all gases. The polar nature of water molecules is also the reason that some substances can dissolve in water while others don’t. For example salt which is made of charged particles can dissolve in water but unlike salt, oil is made of nonpolar particles, which don’t carry any charges, so there’s nothing to attract the polar water molecules to it, this is why water and oil do not mix.
So water’s high boiling point and the way it interacts with different substances are caused by the polar nature of water molecules.