Module 4; Ionic vs. Covalent Compounds
Introduction
In this experiment you will test properties (melting temperature, solubility in water, and electrical
conductivity of water solution) of substances which contain ionic bonds and substances which contain
covalent bonds. You will use the results of your tests to identify differences between ionic and
covalent substances. First, read the following information from your textbook and complete the table
below:
Chemical bonds
Chemical Bonds are the attractive forces that hold atoms together. There are three basic types of bonds.
Ionic bond is the electrostatic attraction between ions, in ionic compounds, after losing or gaining
electrons among atoms. These usually occur between a metal and a nonmetal. Covalent bond is the sharing of
electrons among atoms and usually occurs between two non-metals. (The third kind of bond is a metallic
bond which is not covered in CHEM 1405).
Ionic Compounds
An ionic compound contains positively charged cations, usually made from metals which tend to lose
electrons, and negatively charged anions, usually made from nonmetals which end to gain electrons. In
some cases, ion charges can be determined by locating the element on a periodic table. Ionic compounds
typically form when a metal atom donates an electron to become a cation and a non-metal atom accepts
that electron to form an anion. The cation and the anion are held together via electrostatic attraction. The
metal cation and non-metal anion must combine in a whole number ratio that results in a neutral
compound.
Molecular Compounds
Compounds that exist as discrete molecules containing only non-metals are termed molecular
compounds. Water (H2O), carbon dioxide (CO2), and ammonia (NH3) are molecular compounds
that are common in everyday life. These are very different from ionic compounds like sodium
chloride (NaCl) and silver nitrate (AgNO3). In a molecular compound, two atoms within the
compound share electrons in the form of a covalent bond.
IONIC COMPOUNDS COVALENT COMPOUNDS
(or MOLECULAR COMPOUNDS)
Sodium chloride (NaCl), Water (H2O), Carbon dioxide (CO2)
Two Examples
Calcium carbonate (CaCO3)
Type of elements low electronegativity, high nonmetal elements, high
involved electronegativity. electronegativity
ionic bonding. covalent bonding
Type of bonding involved
In ionic compounds, the This type of bonding involves the
Description of bonding bonding involves the transfer sharing of electrons between atoms
involved of electrons from one atom to to form a stable molecular structure.
another, resulting in the Unlike ionic compounds, which
formation of positively charged involve the transfer of electrons from
cations and negatively one atom to another, covalent
, charged anions compounds share electrons between
atoms to achieve a stable electron
configuration.
Procedure
You will observe three experiments in the assigned YouTube video. The link for the video is:
https://youtu.be/VGXvCyPkTS8 (There is no sound/speaking initially in this video for observations.
You will just watch it. But then there is speaking when the three tests are run.) Also notice that you will
need to use your cell phone timer to record melting times.
1) While you are watching the video, complete the data table on the following page.
2) Also, while you are watching the video, answer the following questions about the procedure used
in the experiment:
a) In the solubility experiments, why does the scientist swirl the beaker?
- When conducting solubility experiments, a scientist may swirl the beaker to increase the rate at
which the solute dissolves in the solvent
b) In the solubility experiments, why does the scientist use the same amount of compound for
each trial (0.05 moles) and the same amount of water (50 mL)? (Notice that in the melting
point experiment he used 1.0 g for each trial).
- Using the same amount of compound and solvent in solubility experiments is important for
ensuring consistency and accuracy in the results
c) Before the conductivity tests are run, what does the scientist show you is required to light the
light bulb?
- Before conducting the conductivity tests, the scientist may demonstrate what is required to
light the light bulb. This demonstration is meant to show the basic principle of how electrical
circuits work.
d) In the conductivity experiment, the scientist tests water by itself as a control. Why?
- In the conductivity experiment, the scientist may test water by itself as a control to establish a
baseline for comparison with the conductivity of other substances being tested. By testing the
conductivity of water by itself, the scientist can establish a baseline value for the expected
conductivity of a non-conductive substance.
e) In the melting point experiments, what important tips did the scientist explain about using a
Bunsen burner?
Introduction
In this experiment you will test properties (melting temperature, solubility in water, and electrical
conductivity of water solution) of substances which contain ionic bonds and substances which contain
covalent bonds. You will use the results of your tests to identify differences between ionic and
covalent substances. First, read the following information from your textbook and complete the table
below:
Chemical bonds
Chemical Bonds are the attractive forces that hold atoms together. There are three basic types of bonds.
Ionic bond is the electrostatic attraction between ions, in ionic compounds, after losing or gaining
electrons among atoms. These usually occur between a metal and a nonmetal. Covalent bond is the sharing of
electrons among atoms and usually occurs between two non-metals. (The third kind of bond is a metallic
bond which is not covered in CHEM 1405).
Ionic Compounds
An ionic compound contains positively charged cations, usually made from metals which tend to lose
electrons, and negatively charged anions, usually made from nonmetals which end to gain electrons. In
some cases, ion charges can be determined by locating the element on a periodic table. Ionic compounds
typically form when a metal atom donates an electron to become a cation and a non-metal atom accepts
that electron to form an anion. The cation and the anion are held together via electrostatic attraction. The
metal cation and non-metal anion must combine in a whole number ratio that results in a neutral
compound.
Molecular Compounds
Compounds that exist as discrete molecules containing only non-metals are termed molecular
compounds. Water (H2O), carbon dioxide (CO2), and ammonia (NH3) are molecular compounds
that are common in everyday life. These are very different from ionic compounds like sodium
chloride (NaCl) and silver nitrate (AgNO3). In a molecular compound, two atoms within the
compound share electrons in the form of a covalent bond.
IONIC COMPOUNDS COVALENT COMPOUNDS
(or MOLECULAR COMPOUNDS)
Sodium chloride (NaCl), Water (H2O), Carbon dioxide (CO2)
Two Examples
Calcium carbonate (CaCO3)
Type of elements low electronegativity, high nonmetal elements, high
involved electronegativity. electronegativity
ionic bonding. covalent bonding
Type of bonding involved
In ionic compounds, the This type of bonding involves the
Description of bonding bonding involves the transfer sharing of electrons between atoms
involved of electrons from one atom to to form a stable molecular structure.
another, resulting in the Unlike ionic compounds, which
formation of positively charged involve the transfer of electrons from
cations and negatively one atom to another, covalent
, charged anions compounds share electrons between
atoms to achieve a stable electron
configuration.
Procedure
You will observe three experiments in the assigned YouTube video. The link for the video is:
https://youtu.be/VGXvCyPkTS8 (There is no sound/speaking initially in this video for observations.
You will just watch it. But then there is speaking when the three tests are run.) Also notice that you will
need to use your cell phone timer to record melting times.
1) While you are watching the video, complete the data table on the following page.
2) Also, while you are watching the video, answer the following questions about the procedure used
in the experiment:
a) In the solubility experiments, why does the scientist swirl the beaker?
- When conducting solubility experiments, a scientist may swirl the beaker to increase the rate at
which the solute dissolves in the solvent
b) In the solubility experiments, why does the scientist use the same amount of compound for
each trial (0.05 moles) and the same amount of water (50 mL)? (Notice that in the melting
point experiment he used 1.0 g for each trial).
- Using the same amount of compound and solvent in solubility experiments is important for
ensuring consistency and accuracy in the results
c) Before the conductivity tests are run, what does the scientist show you is required to light the
light bulb?
- Before conducting the conductivity tests, the scientist may demonstrate what is required to
light the light bulb. This demonstration is meant to show the basic principle of how electrical
circuits work.
d) In the conductivity experiment, the scientist tests water by itself as a control. Why?
- In the conductivity experiment, the scientist may test water by itself as a control to establish a
baseline for comparison with the conductivity of other substances being tested. By testing the
conductivity of water by itself, the scientist can establish a baseline value for the expected
conductivity of a non-conductive substance.
e) In the melting point experiments, what important tips did the scientist explain about using a
Bunsen burner?
