Why Iodine Doesn't Dissolve in Water
Water is polar, while iodine is nonpolar.
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Transcript
Have you ever noticed that oil floats on water? Although water is often called the universal solvent, there are substances that do not dissolve in water.
One substance that does not dissolve well in water is iodine—or more precisely, iodine crystals. That is because iodine and water have opposite polarity.
Water is polar, meaning one side of the water molecule has a small positive charge while the other side of the molecule has a small negative charge.
Iodine is nonpolar. This means the charge of the molecule is evenly distributed.
Polar solvents are able to dissolve polar solutes, as the positively charged parts of the solvents will surround the negatively charged parts of the solute.
But polar solvents cannot dissolve nonpolar molecules.
Similarly, nonpolar solvents are able to dissolve nonpolar solutes but cannot dissolve polar solutes.
Watch what happens when iodine (a polar solute) is placed in both a polar solvent, water, and a nonpolar solvent, cyclohexane.
The iodine dissolves in the nonpolar cyclohexane because both substances are nonpolar.
But it does not dissolve in the water because the water is polar, while the iodine is nonpolar.
One substance that does not dissolve well in water is iodine—or more precisely, iodine crystals. That is because iodine and water have opposite polarity.
Water is polar, meaning one side of the water molecule has a small positive charge while the other side of the molecule has a small negative charge.
Iodine is nonpolar. This means the charge of the molecule is evenly distributed.
Polar solvents are able to dissolve polar solutes, as the positively charged parts of the solvents will surround the negatively charged parts of the solute.
But polar solvents cannot dissolve nonpolar molecules.
Similarly, nonpolar solvents are able to dissolve nonpolar solutes but cannot dissolve polar solutes.
Watch what happens when iodine (a polar solute) is placed in both a polar solvent, water, and a nonpolar solvent, cyclohexane.
The iodine dissolves in the nonpolar cyclohexane because both substances are nonpolar.
But it does not dissolve in the water because the water is polar, while the iodine is nonpolar.