Ionic compounds split into ions; molecular ones stay whole

0:00Salt and sugar both dissolve in water. Do they dissolve the same way?

0:05Water molecules are polar: the oxygen end is slightly negative, delta minus, and the hydrogen ends slightly positive, delta plus.

0:16Salt, sodium chloride, is an ionic compound: a lattice of positive sodium ions and negative chloride ions.

0:25Water molecules turn their oxygen ends toward sodium ions and their hydrogen ends toward chloride ions.

0:32They pull the ions out of the crystal and surround each one. This is called dissociation.

0:39This is not melting. Salt melts at 801 degrees Celsius, but water pulls it apart at room temperature.

0:48Sugar, C twelve H twenty-two O eleven, is a molecular compound, made of neutral molecules.

0:56Water pulls sugar molecules off the crystal, but each one stays whole. No ions form.

1:03To test for ions, we put two metal electrodes, wired to a battery and a bulb, in each solution.

1:10In salt water, moving ions carry charge, so the bulb lights. Salt is an electrolyte: its solution conducts.

1:19In sugar water there are no ions, so the bulb stays dark. Sugar is a nonelectrolyte.

1:27Polar water dissolves many ionic and polar substances. This rule of thumb is called like dissolves like.

1:35Cooking oil is nonpolar, so it does not dissolve in water. It floats in a separate layer.

1:42So ionic compounds split into ions when they dissolve; molecular compounds stay whole.