How do we Classify Three Unknown Compounds (Ionic/Polar Covalent/ Non-
polar Covalent) Based on Their Properties?
1. INTODUCTION
The various types of intramolecular bonding that can be present in different chemical
compounds allows for these compounds to experience clear differences in their properties
and behavior. These types of bonding include ionic bonding (electrostatic attraction between
nonmetal anions and metal cations), polar covalent bonding (covalent bonding with one atom
being more electronegative than the other, thus “attracting” these electrons more towards
its nucleus and adopting a partial negative charge), non-polar covalent bonding (electrostatic
attraction between a nonmetal atom and a shared pair of electrons), metallic bonding
(electrostatic attraction between the nuclei of metal atoms and delocalized electrons), and
coordinate covalent bonding (electrostatic attraction between a central metal atom and the
electrons donated by another atom/ion). In this lab, we are going to be focusing on the first
three bonding types, determining which of three unknown compounds is ionic, polar covalent
and non-polar covalent.
The properties we will be examining are electrical conductivity, melting time, and solubility in
distilled water and cyclohexane. Cyclohexane (C6H12) is a colorless liquid with a petroleum-
like odor. It is a non-polar covalent substance made of a hexagonal ring of carbon atoms,
each bonded to two other carbon atoms and two hydrogen atoms. Since “like dissolves like”,
we know that the substances that dissolve well in the water are either ionic or polar covalent,
whereas the ones that dissolve better in cyclohexane are non-polar. As for melting time, we
will measure the time taken for each substance to melt (change state from a solid to a liquid).
Ionic compounds have higher melting points than polar compounds, which have a higher
melting point than non-polar ones. This is because ionic bonds are stronger than covalent
bonds (there is being a transfer of electrons in ionic bonding), so it will take much more energy
to break the bond between ions than between atoms that are covalently bonded. Moreover,
ionic compounds are good electrical conductors in their molten state or when dissolved in
water, since their ions are “free to move”, thus able to carry along the electrical charge.
Covalent compounds, on the other hand, do not conduct electricity because no ions are
present to carry the charge. Though we might not reach an accurate conclusion, observing
these properties in the unknown compounds we are presented with will give us an idea which
of them have which type of intramolecular bonding.
Structure of Cyclohexane - pubchem.ncbi.nlm.nih.gov
, 2. METHODOLOGY
Variables
Our dependent variables are the electrical conductivities (mg/L), the melting time for
each substance, and the levels of solubility in water and cyclohexane.
Our independent variables are the three unknown compounds we are experimenting
with.
Here are the controlled variables:
Variable How it will be controlled
1. Amount of unknown substance 1. We will add a small scoop of the
used in each trial substance using a spatula in the
2. Volume of water and water and cyclohexane. We will
cyclohexane also be measuring the melting
3. Temperature of hot plate to melt times for a small scoop of each
the substances substance.
4. Time that the substances were 2. Measuring 20 mL of the solvents
given to melt using a same-size graduated
beaker (50 mL)
3. Setting the hot plate to the same
temperature (350 degrees
Celsius) and using the same one
to melt all of the substances
4. Recording 20 minutes using a
timer, then checking which of the
substances melted the fastest
SOLUBILITY
Materials
Three 50 mL beakers Glass stirring rod Cyclohexane Unknown samples
(A, B and C)
Spatula Distilled water Masking tape Six test tubes
polar Covalent) Based on Their Properties?
1. INTODUCTION
The various types of intramolecular bonding that can be present in different chemical
compounds allows for these compounds to experience clear differences in their properties
and behavior. These types of bonding include ionic bonding (electrostatic attraction between
nonmetal anions and metal cations), polar covalent bonding (covalent bonding with one atom
being more electronegative than the other, thus “attracting” these electrons more towards
its nucleus and adopting a partial negative charge), non-polar covalent bonding (electrostatic
attraction between a nonmetal atom and a shared pair of electrons), metallic bonding
(electrostatic attraction between the nuclei of metal atoms and delocalized electrons), and
coordinate covalent bonding (electrostatic attraction between a central metal atom and the
electrons donated by another atom/ion). In this lab, we are going to be focusing on the first
three bonding types, determining which of three unknown compounds is ionic, polar covalent
and non-polar covalent.
The properties we will be examining are electrical conductivity, melting time, and solubility in
distilled water and cyclohexane. Cyclohexane (C6H12) is a colorless liquid with a petroleum-
like odor. It is a non-polar covalent substance made of a hexagonal ring of carbon atoms,
each bonded to two other carbon atoms and two hydrogen atoms. Since “like dissolves like”,
we know that the substances that dissolve well in the water are either ionic or polar covalent,
whereas the ones that dissolve better in cyclohexane are non-polar. As for melting time, we
will measure the time taken for each substance to melt (change state from a solid to a liquid).
Ionic compounds have higher melting points than polar compounds, which have a higher
melting point than non-polar ones. This is because ionic bonds are stronger than covalent
bonds (there is being a transfer of electrons in ionic bonding), so it will take much more energy
to break the bond between ions than between atoms that are covalently bonded. Moreover,
ionic compounds are good electrical conductors in their molten state or when dissolved in
water, since their ions are “free to move”, thus able to carry along the electrical charge.
Covalent compounds, on the other hand, do not conduct electricity because no ions are
present to carry the charge. Though we might not reach an accurate conclusion, observing
these properties in the unknown compounds we are presented with will give us an idea which
of them have which type of intramolecular bonding.
Structure of Cyclohexane - pubchem.ncbi.nlm.nih.gov
, 2. METHODOLOGY
Variables
Our dependent variables are the electrical conductivities (mg/L), the melting time for
each substance, and the levels of solubility in water and cyclohexane.
Our independent variables are the three unknown compounds we are experimenting
with.
Here are the controlled variables:
Variable How it will be controlled
1. Amount of unknown substance 1. We will add a small scoop of the
used in each trial substance using a spatula in the
2. Volume of water and water and cyclohexane. We will
cyclohexane also be measuring the melting
3. Temperature of hot plate to melt times for a small scoop of each
the substances substance.
4. Time that the substances were 2. Measuring 20 mL of the solvents
given to melt using a same-size graduated
beaker (50 mL)
3. Setting the hot plate to the same
temperature (350 degrees
Celsius) and using the same one
to melt all of the substances
4. Recording 20 minutes using a
timer, then checking which of the
substances melted the fastest
SOLUBILITY
Materials
Three 50 mL beakers Glass stirring rod Cyclohexane Unknown samples
(A, B and C)
Spatula Distilled water Masking tape Six test tubes
