how do you know if a solution is a good conductor and why?

Question

how do you know that salt is a good conductor (heat and electricity) and why!

Answer 1

If the substance dissolve in the solution stays molecular, conductivity is low or nil. If it breaks up into ions, conductivity is high.
Ions are particles (atoms or parts of molecules) that give of their outer, unbalanced electrons. When ions form compounds, they have Ionic bonds, not covalent. This means electrons are not shared evenly but are more localized. Think salt (NaCl) The sodium and chlorine each have one unbalance electron. Sodium wants to give its electron up, chlorine wants to take one in. This is due to the fact chlorine is more electronegative than sodium. They seek the state of: Na+ and Cl-. When driven together to crystalize, they bond. But the ideal state is ionic. They are not molecules but rather ionic solids. When they hit water, they become ionic, and give off heat. And they tend to try to stay in solution, as a function of the electronegativity.
Sugar is a molecule and does not break apart in solution. Really, what happenes is that particles of sugar are blended into the water, like chocolate in chocolate chip ice cream. Only, this happens at the molecular level. Since these molecules have no charge, they don't carry electrons between electrode. And, they don't release much heat when they dissolve or have a major effect on freezing points. They share elecrons more evenly, for the most part, when they are solids and are true molecules. However, because of the oxygen, they are polar, so there is some clumping. Again, this has to do with electronegativity.
Water, interestingly, is partly ionic. In the H2O, there is a low concentration of H+ and OH- ions. Water partially is ionic and will conduct electricity.
To answer your question, how to know the conductance of a solution, just run a current through it. The more current (lower resistance) they better the the conductance. Also, the more readily something dissolves spontaneously, the more heat it gives out when doing so, the greater the change in freezing and boiling points all indicate conductance.

Answer 2

current is movement of electrons into a metallic cable.

but

a solution of a salt contains ions H+ OH- (for the water) and Cation+ and Anion-.
All of them are charged, so they can be actracted to the cathode or anode.
So a solution can close a circuit and conduct electricity.

Heat conducibility and capacity depends only from water properties:
Water has the second highest specific heat capacity of any known chemical compound, after ammonia, as well as a high heat of vaporization (40.65 kJ mol-1), both of which are a result of the extensive hydrogen bonding between its molecules. These two unusual properties allow water to moderate Earth's climate by buffering large swings in temperature.
http://en.wikipedia.org/wiki/Water#Heat_capacity_and_heat_of_vaporization

Have fun

Answer 3

Ionic bonds. Salt is highly ionic.