Question

why H2S is gas and H2O is liquid

Answer 1

when sulphur is added to Hydrogen it forms H2S whereas oxygen is added to Hydrogen it forms H2O

Answer 2

water exists as a liquid at room temperature with a high boiling point. Sulphur is less electronegative than oxygen, and the S-H bond is much less polar than the O-H bond. Hence, there is no hydrogen bonding in hydrogen sulphide, and it exists as a gas
normally with discrete H2S molecules.

hope it helps u (: