PROPERTIES LAB:
Activity 3: Pre-lab predictions:
1. Using your existing understanding of ionic and covalent compounds, rank each type of
compound in terms of the following properties (1 being best, 3 the worst):
Ionic
Polar
Covalent
Non-Polar
Covalent
a. Solubility (dissolving) in water:
____1_____
___2______
___3____
b. Melting at low temperature:
____3____
___2_____
___1_____
c.
____1_____
___2_____
___3_____
____1____
___3_____
___3_____
Property
Being hard and brittle:
d. Conducting electricity when dissolved:
Activity 4: Draw pictures that illustrate the structure of each of the following types of compounds
(choose an appropriate compound for each type):
Molecular Polar
Molecular Non-polar
Ionic compounds:
Covalent Compounds:
Covalent Compounds:
Crystal Lattice:
Lewis structure
Lewis structure
showing polar
showing non-polar
molecule
molecule
Initial Analysis Questions
What are the properties can help you determine if an unknown
substance is an ionic compound or a molecular covalent compound (either
polar or non-polar)? Support your statements using observations from
this lab.
A.
1. Substances that dissolve in water, conduct electricity, and have a high melting point are ionic
compounds. These properties were displayed by the ionic compound tested, NaCl.
2. Substances that do not dissolve in water, do not conduct electricity, and have low melting points are
non-polar molecular covalent compounds. These properties were displayed by the non-polar wax
that was tested.
3. Polar covalent molecules will behave similarly to non-polar EXCEPT they will dissolve in water and
tend to be harder. Polar sucrose molecules behaved this way in this lab.
What observed properties were the same for some ionic and molecular
covalent compounds?
B.
1.
Both may be hard and granular, and both may be soluble in water.
C.
What is the difference between an ionic bond and an ionic compound?
Ionic bonds exist between two oppositely charged atoms (ions). Ionic compounds are an entire 3D network
(crystal lattice structure) of ionic bonding between many atoms.
What properties can be used to determine if a covalent compound is
polar or non-polar?
D.
Polar covalent molecules will have higher melting points and will be soluble in water while non-polar
covalent molecules will have low melting points and will not be soluble in water. Non-polar molecules will
also tend to be more waxy and soft, while polar compounds can appear granular and harder.