1. Names:____________________________________________________________________________
Date:___________________ Per:__________________
COMPARING IONIC and COVALENT COMPOUNDS
Purpose:
• To compare physical properties of ionic and covalent compounds
• To determine whether an unknown substance is ionic or covalent
• To build a conductivity tester
• Identify conductors and insulators
Background:
Why does electricity only flow through the copper on a circuit board? Simple! Copper, like most metals, is a
conductor of electricity. That means that electricity can easily flow through it, as opposed to an insulator which
is a material that electricity does not easily flow through, like rubber or plastic. And then there are
semiconductors, but we’ll save them for a different episode.
So why does electricity flow easily through conductors? Well, that is a little more complicated to explain.
Basically, think of electricity as energy that flows through electrons. [Reminder: electrons are the tiny,
negatively charged subatomic particles that orbit around the nucleus of the atom.] Some of the outermost
electrons of metal atoms aren’t strongly attracted to the nucleus. This creates a sort of “cloud” of electrons that
easily move around, thereby easily allowing them to transfer energy.
In order for electricity to flow through a circuit, the circuit must be a complete loop – from the battery, to a
device, then back to the battery, through a conducive material. This is called a “closed circuit.” The two open
alligator clips act as a type of switch, controlling when the circuit is open or closed. When a conductive material
is placed between the two clips, the circuit is complete and electricity can flow.
By the way, it is important to connect the buzzer as I described above. It is like a one-way street – electricity
can only flow one direction through it. Connect it the other way and it won’t work! There are several devices
like this, just like there are some that can electricity flow through either direction (like a light bulb).
Pre-lab Questions:
1) Based on what you’ve learned about electronegativity differences and bond types, predict which group of
elements (A-C), (D-F) or (G, H) are ionic and which are covalent and which are metallic. Explain your
reasoning for each choice
2) Outline the procedure.
Materials: SOLIDS LIQUIDS
Lab burner sodium chloride (A) Isopropyl alcohol (I)
Conductivity apparatus potassium iodide (B) Vinegar (5% acetic acid) (J)
Scoopula or spoons baking soda (C) De-ionized water (K)
Deflagrating spoon/aluminum foil sugar (D) Tap water (L)
Watch glass/paper camphor (E)
Beaker /cups Aspirin (F) OTHER
Paper clip (G) Unknown solid
Aluminum strips (H)
Safety precautions:
Safety goggles must be worn. Use caution when heating compounds. Follow instructions for the conductivity
meter.

2. Names:____________________________________________________________________________
Date:___________________ Per:__________________
PROCEDURE:
1) Complete a chart for your observations. And GIVE IT A TITLE.
2) Collect a small pea size sample of each compound
Observations/Physical Properties
3) Try to detect if any substances have an odor by using the wafting method.
4) Determine whether each substance seems hard or soft. Do this by rubbing a small
sample of each between your fingers. Try to crush a few crystals of each. Place
each compound in the watch glass at a time and use a scoopula to crush them.
Melting Point
5) Light the burner. Place a small sample of substance A into a deflagrating spoon
and a small sample of substance D into the other. Record the one that melts first
as low and the other as high. You do not need to melt the higher one. Repeat
with substances B and E, C and F.
6) Repeat step 5 with your unknown.
Conductivity
7) Make a solution of each solid compound using distilled water in separate beakers. (Use the
same solid samples and add ______mL of DI water).
8) Test the conductivity of each solution, including your unknown.
Let’s build a conductivity tester so you can test substances to see how conductive they are!
What You Need:
3 alligator clip wires
An LED light bulb 60mA or a 12VDC buzzer
a 9V battery
What to Do:
1. Connect one wire to the negative (-) terminal of the battery.
2. Connect the other end of the wire to a wire on the LED (the black wire on the buzzer), making
sure the metal on the clip is grabbing the exposed metal of the wire.
3. Connect a second wire to the positive (+) terminal of the battery
4. Connect a third wire to the other wire on the LED (or the red wire on the buzzer), making sure
the metal on the clip is grabbing the exposed metal of the wire.
5. To test the circuit, touch the two empty alligator clips together. What happens?? (note as
observations).
6. Place a material between the two clips to test them. Or, you can immerse the two ends into
liquids to see how conductive liquids are.
7. In the space below, draw a picture of the conductivity tester you created.
Figure 1 creating a closed circuit

3. Names:____________________________________________________________________________
Date:___________________ Per:__________________
TITLE:___________________________________________________________________________________
Substance Type of Observations Melting Conductivity
bond Point (High or (yes or no)
Low) As a solid? In solution?
A. Sodium Chloride
NaCl
B. Potassium Iodide
KI
C. Baking soda
NaHCO3
D. Sugar
C12H22O11
E. Camphor
C10H16O
F. Acetylsalicylic
acid (Aspirin)
C9H8O4
G. Paper clip
H. Aluminum strips
I. Isopropyl alcohol
N/A
C3H8O
J. Vinegar
N/A
CH3COOH
K. De-ionized water
N/A
H2O
L. Tap water
N/A
H2O
M. Unknown
Post-Lab Questions:
1. Compare the physical properties of ionic and covalent substances.
2. What is the number of your unknown? Is it ionic or covalent? How do you know?
3. Intermolecular forces exist between molecules or ions. Based on this lab, which do you think are
stronger, intermolecular forces between covalent compounds or intermolecular forces between ions?
4. Which type of substance conducted electricity when dissolved in water? What is the difference between
ionic and covalent substances that causes this?
5. List the solids that were good conductors of electricity.
6. List the liquids that were good conductors of electricity.
7. Which solutions are electrolytes? List them in order from strong to weak.
8. Which liquids were nonconductors of electricity?
9. Why is de-ionized water not an electrolyte? What must be done to de-ionized water to conduct
electricity?
10. Based on what you know about electrical conduction explain why some of the substances did not
conduct electricity.
11. Compare the conductivity of solid NaCl and the solution of NaCl. Explain the difference.
12. Which type(s) of bonds resulted in electrical conduction and which type(s) of bonds did not. Explain
why ionic compounds (i.e., salts and bases) in the solid phase do not conduct an electric current, but in
the liquid state and in aqueous solution, these same compounds act as electrolytes.