Ionic vs. Covalent Properties
Objective: To
measure and observe the properties of various compounds in order to group them
into categories of ionic and covalent.
After grouping the compounds, to analyze which of the properties were
most and least helpful to organizing the compounds.
Background:
Chemical compounds are
combinations of atoms held together by chemical bonds. These chemical bonds are
two basic types: ionic and covalent. Ionic bonds result when one or more
electrons from one atom or a group of atoms are transferred to another atom.
Positive and negative ions are formed. In covalent compounds, the electrons are
shared by the bonded atoms.
The
physical properties of a substance such as melting point, solubility, and
conductivity tell us a lot about the type of bond in a compound. In this
laboratory, you will conduct tests on the properties and collect data enabling
you to classify compounds as ionic or covalent.
Pre-Lab Questions:
1. Explain
ionic bonding and covalent bonding in terms of the electrons in each type of
bond.
2. Explain the
differences in properties between ionic and covalent compounds.
Procedure:
Make complete observations for each step and record in your data table.
1. Data Table
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Compound:
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Description:
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Melting Point:
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Solubility with ethanol:
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Solubility with water:
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Conductivity:
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Calcium
chloride
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Sucrose
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Potassium
iodide
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Copper sulfate
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Citric acid
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Salicylic
acid
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A. Melting Point
1. Measure 1 g of each compound and
place in an aluminum foil boat.
2. Heat over a candle for a two (2)
minutes and record how it reacts to the heat and notice the amount of time to
record a change in the substance if there is one.
3. If a substance melts, remove it
immediately.
4. Record data to which substances
melt and do not and any other details.
B. Solubility with Ethanol
1. Place 0.3 g of each compound and
place in a test tube.
2. Add 10 drops of ethanol to each
test tube.
3. Shake it for approximately 2
minutes.
4. Record the observations in the
data table and repeat for remaining compounds.
C. Solubility with water
1. Repeat steps 1-4 from above for
solubility with ethanol but use water instead of ethanol.
2. Pour your liquid into a well of
your testing tray after you have finished shaking it.
D. Conductivity
1. Place your wires of the
conductivity into your substance.
2. Make sure that your wires do not
cross.
3. Record if the lightbulb lights up
and how brightly.
Post-Lab Questions:
1. Using each
of the properties that you tested separate the compounds into two groups:
A. Melting point
--Compounds that melted and compounds
that did not melt
B. Solubility with ethanol
--Compounds that dissolved in ethanol
and compounds that did not dissolve
C. Solubility with water
--Compounds that dissolved in water
and compounds that did not dissolve
D. Conductivity
--Compounds that conducted
electricity and those that did not conduct
2. Separate
the compounds into two groups: Ionic and covalent
*(Hint: if not sure, look at the elements that
are in the compounds)
3. Describe
the general physical properties that you observed for ionic compounds.
4. Describe
the general physical properties that you observed for covalent compounds.
5. Using your
data which physical property best separated your compounds into ionic and
covalent?
6. Using your
data which physical property was least helpful to separate your compounds,
explain why.
7. List the
physical properties you would expect these compounds to have:
a.
acetic acid HC2H3O2
b.
methane CH4
c.
magnesium oxide MgO
As a global Contract Research Organization (CRO), headquartered in New York, USA, Alfa Chemistry has served the pharmaceutical and biotechnology industries for eight years. 1-butyl-2,3-dimethylimidazolium dodecylsulfonate
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