Lab: Differences in Ionic and Covalent Compounds
I. Prelab Questions:
1. What kinds of elements generally form ionic compounds?
2. What kinds generally form covalent (molecular) compounds?
3. Based on their formulas, predict whether each of the following is ionic or covalent.
a. __________NaI
b. __________CH4
c. __________CaCl2
d. __________NH3
4. Describe briefly the properties of ionic compounds
5. What is an electrolyte?
6. Describe briefly the purpose of this experiment.
II. Data Table
Substance
Solubility in
methanol
Solubility in
water
Conductivity
(strong/weak/non)
Relative melting
point
Citric Acid
Sodium Chloride
Beeswax
Potassium Iodide
Magnesium
Sulfate
Sucrose
Stearic Acid
Distilled water
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Analysis/ Conclusions/ Synthesis Questions
1. Determine, based on the formula, whether each of the substances used is covalent or ionic.
a. __________Citric acid, H3C6H5O7
b. _____________Stearic Acid, C18H36O2
c. __________Sodium Chloride, NaCl d. __________Calcium Chloride, CaCl2
e.__________ Beeswax, CxHy
f. __________Potassium Iodide, KI
g. __________Sucrose, C12H22O11
h. __________Magnesium Sulfate, MgSO4
2. Look carefully at your data. Do you see any patterns? In the space below, summarize the
results of this experiment.
3. Predict the following, based on the patterns established in this experiment.
a. Is sodium iodide soluble in water? Why/why not?______________________________
________________________________________________________________________
b. Is the relative melting point of NaI high or low? Why/why not?___________________
________________________________________________________________________
c. Is a solution of glucose, C6H12O6 , electrically conductive?_______________________
________________________________________________________________________
4. Why are the melting points of some compounds higher than others?
______________________________________________________________________________
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5. Why did you test the conductivity of distilled water before the solutions were tested?________
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Lab: Differences in Ionic and Covalent Compounds
Introduction:
A compound is defined as a chemical combination of two or more elements. A chemical bond is
the “glue” holding together atoms of different elements. Two types of bonds are ionic and
covalent. Ionic bonds generally occur between a metallic atom and a nonmetallic atom. The
bond results from the transfer of electrons and the attraction between the resulting ions. Covalent
bonding generally occurs between two or more nonmetallic atoms. Covalent bonding involves
the sharing of electrons.
Properties such as melting point, boiling point, solubility, electrical conductivity, color, and odor
can help you distinguish ionic from covalent compounds. As in many areas of chemistry, the
distinctions are not always clear, nor do the distinctions apply to all compounds.
In this experiment, you will observe several properties of some ionic and some covalent
compounds and attempt to recognize patterns among the properties. The patterns you may
recognize are generalizations and may not necessarily apply to all ionic and covalent compounds.
Objectives:
1. Classify compounds as either primarily ionic or primarily covalent from the name and
formula of the compound.
2. Observe and record some properties of several ionic and covalent compounds.
3. Recognize patterns among the properties and distinguish ionic compounds from covalent
compounds.
Procedure:
SAFETY PRECAUTIONS: Wear safety goggles and aprons at all times.
Part 1
1. Place a small sample of each solid (about the size of a grain of rice) in separate wells of a
microplate. Make sure you know which is which by labeling a piece of paper and
keeping it under the microplate.
2. Add methanol to the wells until they are nearly full.
3. Stir each well with a separate toothpick.
4. Observe relative solubilities and record in data table.
5. Repeat steps 1-4, only add water this time instead of methanol.
6. Keep the water solutions for part 2!!
Part 2
1. Fill an extra well in the microplate with plain distilled water. Test the conductivity of the
distilled water and each solution from part 1. Place the gold wires on the conductivity
tester in the solution. If the red light comes on, then the substance in the solution
conducts electricity and is called an electrolyte. The faster the red light blinks, the
stronger the electrolyte. Rinse the wires with distilled water and blot dry with a paper
towel in between each solution.
2. Record observations in data table.
Part 3- PERFORM THIS STEP IN THE FUME HOOD
1. Observe relative melting temperatures of the solids. Use a spatula to place a small
sample of each substance on a piece of aluminum foil. Place the foil on a hot plate. Turn
the heat to medium and begin to heat the samples. Gently hold a thermometer so that the
bulb just rests on the foil. Continue heating until the temperature reaches 135C.
Observe each substance and record which substances have melted. Turn off the hot plate.
Clean up by carefully folding up the aluminum foil (after it is cool of course!) and place
it in the trash and put up materials.
Be sure to clean up microplates and any other materials used and put away in the appropriate
place. Wipe up lab area when finished and throw away trash.