Water is a liquid while many heavier molecules like [math]CO_2 [/math],[math] O_2 [/math]and [math]N_2 [/math]are gases. Why? Water molecules are sticky. read more
So, at room temperature water's molecules are strongly attached to each other through Hydrogen bonding.While the molecules of H2S are weakly attached to each other so they are converted into gaseous state.Hence H20 is a liquid while H2S is gas at room temperature. read more
Due to Cl's lower electronegativity and larger size, it cannot undergo hydrogen bonding, so the dipole interactions between the HCl molecules are not strong enough to keep that molecule as a liquid at room temperature, while the HF is, even though the molecular weight is less. read more