Question

Why are ionic compounds soluble in water?

Answer 1

You can look up here something about ionic bonding.

But, except that, here is a simple answer:

When ionic bonds form, one atom becomes positively charged (+), and the other one becomes negatively charged (-).

Water is a covalent polar compound (it has positive and negative poles). Also, ionic compound tend to form complex lattice networks and structures (see the picture).

When the salt is put in water, the water is pulling `Na^+` on one side and `Cl^-` on the other side. The water molecules can pull hard enough to eventually break each salt molecule away from the lattice, dissolving the crystal structure.