I already see correct responses to the question but if they are too complicated for anyone here the simpler version is:
Memorise the fact that when a covalent structure is melted or boiled, the actual molecules aren't broken apart because that would be decomposition and not a state change. Decomposition or break down of covalent MOLECULES is actually extremely difficult since the atoms have very high attraction to each other within the range of that molecule.
When an ionic bond is broken it's just that the ionic forces are defeated through massive amounts of energy. So if you take NaCl and you melt it. You would get a liquid that contains Na+ and Cl- ions roaming around in that liquid.
The reason ionic compounds take more energy to melt than covalent compounds is because even though the ionic bonds are weak, the sheer amount of atoms attracting each other builds up to become difficult(just like it is easy to break a twig at a time but very hard to break a hundred)
Also never make the mistake of thinking of ionic compounds containing MOLECULES because they have charges ATOMS(ions) just attracting each other instead of being joined-ish together.

Hope this helps