Question

Why is sodium chloride soluble in water but not kerosene oil?

Answer 1

This so because both the solutes are different types. NaCl dissolves because it goes in the intermolecular space as being a solid crystals, but as the density matters in liquids, due to the densities of the liquids as oil is less denser than water it always floats and so it doesn't goes in the intemolcular spaces of water.

Answer 2

Sodium chloride is an ionic molecule. There exists electronegativity difference between Sodium and Chlorine, which gives polarity to the molecule. Thus sodium chloride is polar molecule.
Generally polar molecules will soluble in polar solvents and insoluble in non-polar solvents. Non-polar molecules will soluble in non-polar solvents and insoluble in polar solvents.
As sodium chloride is polar molecule it will be soluble in polar solvents like water. And insoluble in kerosene (as it is non-polar solvent).