Physical Properties of Ionic Compounds
Recall: Ionic compounds are compounds made up of two oppositely charged ions, a cation and an anion.
Take a look through your kitchen and you’ll probably find two seasonings that look very much alike: salt and sugar. However similar these two may look, chemically, they are entirely different beings. Salt (NaCl) is an ionic compound whereas sugar (C12H22O11) is a molecular compound. You can observe some differences in their properties with a few simple tests. First, heat up a pan on the stove and sprinkle some salt into it. No matter how hot you heat the pan, the salt will not melt due to the high melting points of ionic compounds. However if you were to heat sugar, you would notice melting very early on. Another property of ionic compounds is that they always form crystals. While sugar does form crystals as well, not all molecular compounds do. Next, let’s observe what happens when you dissolve them in water. If you were to make two separate solutions, one of sugar-water and one of salt-water, you would find that you are only able to run an electrical current through the salt-water solution. This is because ionic compounds are able to conduct electricity when dissolved in water. While these two common seasonings may be different chemically, they both sure taste great in your food!
1. Think to the molecular structure of ionic compounds. What allows them to form crystals?
2. Think to the molecular structure of ionic compounds. What allows them to conduct electricity when in solution?
3. Find some more ionic compounds in your house and think about what common properties of ions they hold.