Question

Why is water a liquid at room temperature and pressure? Please be concise.

Answer 1

Because water is insufficiently volatile at room temperature and pressure to exist as a gas...........

Explanation:

Was that concise enuff? Well, here, I am going to expand the answer. Water is a highly unusual molecule. It is VERY small, and has very low molecular mass. Nevertheless, it exists as a room temperature liquid. Why? Because hydrogen bonding exists BETWEEN water molecules, and this acts as a potent intermolecular force.

And the propensity for hydrogen bonding results from the polarity of the water molecule, which we could represent as `""^(delta+)H-stackrel(delta-)O-H^(delta+)` - in solution these dipoles align appropriately, and this is a potent intermolecular force.

You should compare the normal boiling of water to that of other small molecules, `HF`, `HCl`, `NH_3`, `CH_4` etc. What do you find?