Richardson Chemistry
Unit 8: Properties of Ionic and Covalent Compounds Lab
Class Set – Do Not Take
Introduction
A compound is defined as a chemical combination of two or more elements. A chemical bond is the “glue” holding the atoms together. 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
one or more electrons from the metallic atom to the nonmetallic atom, resulting in a charge difference. The positively charged metal ion is then
attracted to the negatively charged nonmetallic ion. 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 a scientist to classify a compound as ionic
or covalent. However, the distinctions are not always clear, nor do the distinctions apply to all compounds.
The salt and sugar on your kitchen table both dissolve easily in water, but there is an important difference. Salt is an ionic compound. Like all ionic
compounds, it produces ions when it dissolves (or dissociates). The ions are free to move in the solution, so the solution conducts electricity.
Key Vocabulary: A solution is a homogenous mixture of two or more substance. In such a mixture, a solute is a substance dissolved in another
substance, which is called the solvent.
The more ions in a solution, the better it conducts electricity. If something produces a large amount of ions it is called a strong electrolyte. If
something produces a small amount of ions, it is called a weak electrolyte. Covalent compounds do not conduct electricity when dissolved
because they do not produce ions. If something produces no ions, it is called a nonelectrolyte.
The purpose of this experiment is to 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
●
Identify physical and chemical properties of ionic and covalent compounds.
Materials
Goggles (Required for Part 1)
Spatula
Methanol
Distilled Water
Toothpicks
Conductivity Tester
Chemicals
The chemicals used in this lab are unknowns labeled A, B, C, D, E, F. The chemicals used in this lab should be handled with
care. Try not to spill anything, but if you do, wipe your spill with paper towel and place in the trash. Avoid skin contact and
ingestion. Please wash your hands before leaving the lab.
Procedure
Part 1: Melting Point – Remember to follow all safety protocol for using hot plates and BE CAREFUL!
1. Put on your goggles.
2. Get an aluminum foil tray and draw 6 wedge shapes on it. Label the wedges A, B, C, D, E, & F. (This may already be done for you.)
3. Using a spatula, place a SMALL grain-of-rice sized sample of each substance in the appropriate wedge of your foil.
4. Place the foil on a hot plate and turn it on high.
5. After a few minutes, observe each section and record on a chart, which substances have melted and in which order.
6. Turn off the hot plate.
Part 2: Solubility in Water – DO NOT DUMP THE CUPS. YOU WILL NEED THEM FOR PART 4.
1. Thoroughly clean and dry the 12 small plastic cups.
2. Label the cups A, B, C, D, E, & F.
3. Line up the cups side by side.
4. Using a spatula, place a SMALL grain-of-rice sized sample of each substance in the appropriate cup.
5. Fill each cup to a little less than the half way mark with distilled water. Stir with a toothpick and observe the relative solubility of each of the
solids. Record observations in the data table.
Part 3: Solubility in Methanol - DO NOT DUMP THE CUPS. YOU WILL NEED THEM FOR PART 4.
1. Repeat steps 1-4 above.
2. Fill each cup to a little less than the half way mark with methanol. Stir with a toothpick and observe the relative solubility of each of the
solids. Record observations in the data table.
Part 4: Conductivity
1. Pour the contents of cups from Part 3 into the cups from Part 2 and use a toothpick to mix the solutions.
2. Test the resulting solutions with the conductivity tester. Record observations in the data table.
3. Wash your cups with soap and water to remove all chemicals. Wash your hands thoroughly with soap and water. Wipe down your lab table
with a wet paper towel.
Richardson Chemistry
Unit 8: Properties of Ionic and Covalent Compounds Lab
Name:____________________________________________
This is your copy to write on and turn in.
Data:
Use the words completely, partially, or not at all to describe the extent to which the substance melted, dissolved, or conducted electricity.
Substance
Physical Appearance
Melts
(Yes or No)
Order of
Melting
(Rank 1-6)
Dissolves in
water
Dissolves in
Methanol
Conductivity
A
B
C
D
E
F
Analysis & Conclusion:
1. Look carefully at your results. Do you see any patterns? Summarize the results by circling the correct answer below..
Property
Ionic
Covalent
Melting Point
High / Low (Circle One)
High / Low (Circle One)
Dissolves in Water
Always / Somewhat / Never (Circle One)
Always / Somewhat / Never (Circle One)
Dissolves in Methanol
Always / Somewhat / Never (Circle One)
Always / Somewhat / Never (Circle One)
Conductivity
Strong / Weak / None (Circle One)
Strong / Weak / None (Circle One)
3. Predict the following, based on patterns established in this experiment:
a. What would you expect the solubility of sodium iodide (ionic) in water to be?
b. What would you expect the relative melting point of sodium iodide to be?
c. What would you expect the conductivity of a glucose (glucose) solution to be?
4. Explain why ionic compounds are strong conductors of electricity when dissolved in water and why covalent compounds are poor or nonconductors of electricity? What differences between these two types of compounds results in their different electrical conductivity.