If a substance is ionic, then it likely will what?

There are a number of possibilities for the answer to this question, so I will address a few only:
1. Many ionic substances will dissolve completely in water to form an aqueous solution of cations and anions; this solution will conduct electricity. 
2. The substance will have a slightly lower melting point than a mid-level covalent network solid. 
3. The substance will certainly not conduct electricity as a solid. 

Spontaneity tell us the direction of the reaction, but not how fast it goes. gibbs free energy brings together enthalpy, entropy and temperature in one easy formula. g = h - ts. and, finally the sign of delta g is always negative for a spontaneous reaction.