Pre-AP Chemistry Unit 4 Topic 1 Chemical Bonds
LAB-Comparing Ionic and Covalent Compounds
TEKS
C. 7 D Describe the nature of metallic bonding and apply the theory to explain metallic properties such
as thermal and electrical conductivity, malleability, and ductility.
KUD
The chemical and physical properties of compounds are determined by the nature of bond.
Metallic properties (luster, ductility, malleability, & conductivity) are a result of electron behavior.
The strength of a bond is determined by the amount of energy it holds.
Atoms undergo interactions to become stable.
The properties of a substance are a product of valence electron interactions and the energy in the bonds
they form.
Materials
1 gram of a six different substances
50 mL of distilled water
Conductivity meter
Magnifying lens
Index card
Hot plate
Aluminum foil
Small test tube
Stopper
LAB-Comparing Ionic and Comparing Compounds Student Pages
Teacher Procedure (Expected students answers are shown in italics.)
Pre-lab Activities
1. Distribute Lab Student Pages to each student at least one day in advance.
2. Instruct students to complete the Prelab Assignment in their lab book before coming to class on
lab day. Prelab Assignment includes:
 Background Questions
 Safety
 Chemical Inventory
 Purpose
 Procedure
 Data and Observations Table
Teacher Lab Setup
1. Prepare each lab station with the materials listed above.
Warm-up
1. Utilize a relevant question or suitable warm-up activity to allow time for you to check the Pre-Lab
assignment.
2. Use this time to also convey to students any changes to the lab or special instructions necessary
to facilitate student time in the lab.
3. Ask some students these questions: (Student answers will vary. Encourage some class discussion
at this point)
a. Who can describe the difference in electron behavior between ionic and covalent
bonding? In ionic bonding, electrons are transferred. In covalent bonding, electrons are
shared.
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Pre-AP Chemistry Unit 4 Topic 1 Chemical Bonds
b. How is metallic bonding different? Electrons are not tied to one atom, they are free-
moving throughout the metal sample.
Lab
1. Send student groups to assigned lab station to start the activity.
2. As students are working the teacher should be circulating though the room to ensure that
students are on task and following the lab procedure. Ask the following questions:
a. What substances did conduct electricity? Metals and dissolved ionic substances.
b. Which substances are flexible and can be shaped? Metals. Help students see that even
though wax is soft, it is not malleable in the same way metals are.
3. At the end of the experiment, give instructions to students regarding final clean-up of the lab
tables. Remind students to wash their hands before leaving the lab area. Briefly check each
station to ensure students have not removed equipment or chemicals from the lab area.
4. Instruct students to return to their seats. Lead a classroom discussion on their observations.
a. What properties did metals have? Conduct electricity and heat, flexible.
b. What properties did all the substances have in common? They are all solids at room
c.
temperature.
What type of substance was hardest and least flexible? Ionic. Why? Because the lattice
energy in ionic bonds are so strong, the crystals are held tightly together.
5. Explain to students that they will complete the lab for homework, including Conclusion & Error
Analysis.
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Pre-AP Chemistry Unit 4 Topic 1 Chemical Bonds
LAB- Comparing Ionic and Covalent Compounds -Student Page
Pre-Lab/Background Questions
1. Answer the following questions with the terms “electrons, “protons,” “sharing,” and
“transferring,” and “sea of electrons.”
a. What does “ionic bonding” mean?
b. What does “covalent bonding” mean?
c. What does “metallic bonding” mean?
Background
It is said that opposites attract. It is true in chemistry, as well. Positive charges in the nuclei of atoms are
attracted to the negatively charged electrons of surrounding atoms. When the nuclei of two atoms are
attracted to the same electrons, the atoms become involved in a chemical bond, forming a new chemical
substance. The forces of attraction are between atoms within a molecule, therefore the attractions are
known as intramolecular forces.
If one electron from each of the atoms is shared between the two atoms, then a covalent bond exists.
Some atoms, however, are more electronegative (have a greater tendency to gain an electron). These
atoms with greater electronegativity are able to possess the electron more often. Even though it is being
shared, it is being shared unequally. This results in the negative charge of the electron being stronger on
the side of the atom with the greater electronegativity. The result is a polar covalent bond. If the two
atoms have similar electronegativities, then the charge is equally distributed between the two atoms in a
non-polar covalent bond.
Some atoms are so electronegative that they no longer share the electron, but take it completely from
another atom. This causes both atoms to become ions. Ions are atoms with a charge. When ions of
opposite charges are attracted, they form ionic bonds. Instead of electrons being shared, it is the
electrostatic forces of attraction that hold ions together in ionic compounds, much like magnets sticking
to one another.
Atoms of a molecule are often attracted to the electrons of a neighboring molecule and result in
intermolecular forces. These attractions are weaker than intramolecular forces. Intermolecular forces hold
molecules together in solid and liquid states.
The types of forces holding atoms and molecules together cause substances to have different physical
properties. By investigating the different physical properties, inferences can be made about the type of
bonding taking place at the molecular level.
Purpose: To examine the physical properties of several compounds to determine if they are ionic or
covalent.
Safety: Wear goggles and lab apron.
Chemicals: paraffin wax, sodium chloride, aluminum, sucrose, calcium chloride, copper
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Pre-AP Chemistry Unit 4 Topic 1 Chemical Bonds
LAB-Comparing Ionic and Covalent Compounds-Student Pages
Procedure
1. Dissolve about 1 gram of a substance in 50 mL of distilled water. Do not use tap water. Test for
conductivity with the conductivity meter. Record your results. Repeat with other compounds.
2. Examine each compound with a magnifying lens. Record whether or not it appears to have a
repeating crystalline structure or if it appears amorphous.
3. Determine if the compound is hard or not by taking a very small amount and attempting to crush it
between an index card and the lab table. If the crystal shapes are unchanged, the compound is hard.
Wipe off the lab table with a wet paper towel when you are done with all six compounds. Record
data.
4. Turn the hot plate on the lowest setting. Place a square of aluminum foil on the hot plate. Put a tiny
amount of each substance on the foil and watch to see which ones melt. After about five minutes,
record which ones seem to have a low melting point and which ones have a higher melting point.
Throw away the foil.
5. Test the water solubility of each compound by putting a small amount in a test tube, adding ½ a test
tube of water, stoppering, and shaking hard for 30 seconds to see if it will dissolve. You may use
your thumb to stopper it, but wash your hands soon after. Record S for soluble and I for insoluble.
Data:
Draw a chart that will contain information for 5 tests on 6 different compounds. Record your
observations in the table.
Questions
1. Why is it important to label the test tubes and aluminum dishes?
2. Explain the types of bonds that are being overcome during the melting of ionic and covalent
molecular compounds.
3. Conductivity of distilled water (µS/cm):
4. What does conductivity indicate about the molecular structure of a compound?
5. Use what you know about bond types to explain why spoons are never made with ionic or polar
molecular compounds.
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Pre-AP Chemistry Unit 4 Topic 1 Chemical Bonds
LAB-Comparing Ionic and Covalent Compounds-Student Pages
Conclusion:
Write a conclusion about which compounds are ionic and which ones are covalent. Give your reasons for
each one! Do your own work.
Analysis Questions
1. How can you determine if an unknown substance is an ionic compound or a molecular covalent
compound (either polar or non-polar)?
2. What properties are the same for ionic and molecular covalent compounds (either polar or nonpolar)?
3. What is the difference between an ionic bond and a molecular covalent compound?
4. What properties can be used to determine if a molecular covalent compound is polar or non-polar?
Synthesis Questions
1. What are the two main chemical components of air? Predict the type of bonding for each. Explain
your reasoning.
2. Odor is another physical property that can be tested. Which type of compounds (ionic or molecular
covalent) would you expect to have a stronger odor? Why?
3. Oil does not dissolve in water. Based on this observation, would you classify oil as a non-polar
covalent, polar covalent, or ionic compound? Explain.
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