Why is hydrogen sulphide gas at room temperature whereas water is a liquid boiling at 100 oC?

Answer 1

This is due to a phenomenon called Hydrogen Bonding.
Certain elements have a crush on hydrogen, if you like, and theyre just three elements.
Oxygen, Nitrogen and Fluorine.
These three are perfect candidates due to their small size, and high elctron affinity.

Of these F>N>O in terms of hydrogen bond strength.

in H-O-H, the oxygen atom attracts a hydrogen atom, NOT OF THE SAME MOLECULE, but the nearby one. Its not a bond, but just an attractive force, called Van der Vaal's.

Because it pulls them nearer, the molecules consume less space, and when molecules come closer, they become liquid(or solid)

This is the only reason why H2o is liquid, while others are not.

other examples are HF, where F forms the hydrogen bond.

Hope i helped.

Answer 2

Water is just an extremely odd substance because of the strength and nature of the intermolecular forces of attraction between water molecules. This results from the high electronegativity of oxygen and the very polar nature of the H-O covalent bonds. The electronegativity of S is much lower than O, so the H-S covalent bonds are much less polar, leading to much weaker intermolecular forces of attraction.