why are fats solid and oils liquid at room temperature? Give a brief explain regarding saturated and unsaturated, and Van der waals forces if possible others ...

because fats are saturated and oils are unsaturated

Explanation:

Saturated fatty acids (fats) contains maximum amount of hydrogen

and all carbons have sigma (single) bond between each other

the fats are solid because of the presence of intermolecular bonds called van der Waals forces.

Van der Waals forces' is a general term used to define the attraction of intermolecular forces between molecules

The unsaturated fatty acids have double and triple bonds. Because of it the van der Waals forces are less effective and the unsaturatd fatty acid (oil) is a liquid at room temperature.