I did an experiment on salt and ice, it came out that Iodized salt melted ice faster than sea/table salt. Why?

Question

The salts used were Iodized salt, Lite Salt (it's a salt with Potassium chloride and Iodine combined) Sea salt and table salt.
Iodized salt melted the ice cube faster than all the others..but why?

Answer 1

What was your methodology? For example, were you careful to use the same amount of each salt? Were the grains the same size for each of the salts? Did you distribute the salt over the surface of the ice evenly for each run? Were all ice cubes the same temparature and the same dimensions? These are just some factors that will affect your results.

Ice melts when salted because of a phenomenon called freezing point depression (which is one of the colligative properties of a solution). Solutions of water tend to freeze at lower temperatures as the ionic concentration of solution increases.

If you start with equal masses of pure "table" salt (NaCl), iodized salt (NaCl + NaI), "lite" salt (NaCl + KCl), and sea salt (a complex mixture of mostly Na+, Cl-, SO4--, Mg++, Ca++, and K+) the pure "table" salt will produce the highest concentration of ions and therefore the lowest freezing point. This is because all of the other examples contain heavier ions, which means fewer moles per unit mass.

Another factor that will determine how fast the ice melts is the solubility of the salt. Calcium salts, for example, are less soluble and therefore dissolve more slowly. More soluble salts will tend to form solutions more quickly, and therefore produce faster melting.

My guess as to why the iodized salt melted ice fastest in your experiment is that you didn't carefully control all variables in the experiment. If you repeat it, making sure that you follow EXACTLY the same procedure for each salt, my guess is that pure NaCl will produce the fastest melting.

EDIT: Upon further study, NaI has the highest solubility of the salts involved. But the amount of NaI in iodized salt is very low, so I don't think it will enter solution substantially faster than pure NaCl.

Answer 2

This is called a colligative property.

As you add impurities to the solute, there are more particles to disrupt the crystal formation of the ice. So it melts faster.

Also the boiling point will be a bit higher.

Answer 3

maybe because it is more crystalized.