Properties of Ionic and Molecular Compounds

Essential Question: What properties can be used to distinguish ionic compounds from molecular compounds?

Safety: Be careful when handling hot objects.

Always wear your safety goggles.

Materials:

Ionic Compounds:NaClLiClKBrNH4NO3

Molecular Compounds:C6H12O6StarchCriscoSalicylic Acid

Other:Hot plate(2) 100mL beakers

(2) Aluminum BoatsGlass Stirring Rod

Stop WatchConductivity Tester

Procedure for Melting Point(Red Tape):

  1. Gather your materials. You will need a hot plate, 2 aluminum boats, 2 scoopulas, and a stop watch.
  2. Set the hot plate to 300°C. The hot plate will need 3-5 minutes to warm up before you can conduct the experiment.
  3. Place 1 scoop of the ionic compound you are assigned into an aluminum boat. Place 1 scoop of the molecular compound into the other aluminum boat.
  4. Place the boats onto the hot plate. (Yes, you can heat them both at the same time.) Begin timing.
  5. Observe the compounds for 3 minutes. Note when and if the compounds begin to melt.
  6. When you’re finished, the aluminum boat and everything inside it can be thrown away. USE A POTHOLDER, IT WILL BE HOT!

Procedure for Solubility and Conductivity (Green Tape)

  1. Obtain your materials. You will need (2) 100mL beakers, 2 scoopulas, a glass stirring rod, and a conductivity tester.
  2. Place 1 scoop of the ionic compound you are assigned into a beaker. Place 1 scoop of the molecular compound into the other beaker.
  3. Fill the beaker with ~80mL of water. Stir for about 1 minute. Record on the data table whether or not the material dissolved.
  4. Plug in your conductivity tester. Place the tester into each beaker.Record whether or not the solution conducts electricity (The bulb will light up if it does).

Data Tables:

Melting Point:

Group / Ionic / Yes/No / Molecular / Yes/No
A-red / NaCl / C6H12O6
B-red / LiCl / Crisco
C-red / KBr / Starch

Solubility:

Group / Ionic / Yes/No / Molecular / Yes/No
A-green / NH4NO3 / Crisco
B-green / NaCl / Starch
C-green / LiCl / Salicylic Acid

Conductivity

Group / Ionic / Yes/No / Molecular / Yes/No
A-green / NH4NO3 / Crisco
B-green / NaCl / Starch
C-green / LiCl / Salicylic Acid

Questions:

  1. Did you notice a difference in the melting points of ionic and molecular compounds? If yes, what was it?
  1. Based on differences of their melting points, which do you think has stronger bonds?
  1. Was there any difference in the solubility of ionic and molecular compounds in water? If yes, what was it?
  1. Was there any difference in the conductivity of ionic and molecular compounds? If yes, what was the difference?
  1. List the properties of ionic and molecular compounds.