[confusious says (OP)]

Hi everyone, I just want to know how salt actually melts snow and ice, what is the chemical action or reaction going on?

[evan_au]

Salt is mostly Sodium Chloride (Na⁺Cl^-), mixed with some other ionic solids like Magnesium Chloride (MgCl₂).

Water (H₂O) is a "polar" molecule, with a slight negative charge on the Oxygen end, and a slight positive charge on the Hydrogen end.

When water mixes with salt, about 8 water molecules surround the positive Na⁺ ion, with the negative oxygen side facing inwards.
Similarly, about 6 water molecules surround the negative Cl^- ion, with the positive hydrogen side facing inwards.

Water is more strongly attracted by these Na⁺ and Cl^- ions than it is by other water molecules, so the salt water does not tend to form ice crystals until lower temperatures than fresh water.

A strong solution of salt can decrease the melting point of water by as much as 20C; more dilute solutions are enough to prevent ice forming on the road when the temperature drops slightly below 0C/32F.

See: http://en.wikipedia.org/wiki/Sodium_chloride#Road_salt

[lightarrow]

Hi everyone, I just want to know how salt actually melts snow and ice, what is the chemical action or reaction going on?

For a reaction to happen, the Gibbs free energy G have to decrease, that is Delta G < 0.
At constant temperature Delta G is = Delta H - T Delta S
where H is the enthalpy and S the entropy. The melting of snow/ice is an endothermic process, that is Delta H > 0. But the dissolution of salt in water increases the system entropy S, so Delta S > 0. If this Delta S is high enough, given a certain temperature, the entire process can have negative Delta G, as in this case, so the reaction is "spontaneous" that is, "happens".