LAB 5.4 CONDUCTIVITY: SOLIDS AND SOLUTIONS
BACKGROUND:
Elements may combine in many ways forming an almost infinite variety of compounds.
Examples of compounds include alcohol (propanol), salt (sodium chloride), sugar (sucrose), etc. Each
compound has a chemical formula. For example, sucrose has the formula C12H22O11. Sucrose is
composed of the elements carbon, hydrogen, and oxygen. The periodic table organizes elements into
two major groups, metals and nonmetals. The elements found on the left-hand side and center of the
table are the metals. The elements found on the right-hand side of the table are generally nonmetals.
In this lab you will investigate the conductivity of compounds, both as solids and in solution.
Conductivity refers to the ability of a substance to conduct electricity. A conductivity
meter will be used to determine whether the compound conducts electricity. If the light
bulb on the meter lights up, the compound conducts electricity. If the light bulb does not
light up, the compound does not conduct electricity. A complete circuit is required for
the light bulb to turn on. Therefore, the substance between the electrodes must conduct
electricity. Conductivity requires a flow of charge (an electrical current). To conduct,
there must be (1) charged particles, and (2) the charged particles must be free to move.
Not all compounds in solution will conduct electricity. In this lab you will look for
patterns (trends) to determine the combination of elements that conduct electricity when
dissolved in water.
PURPOSE: To differentiate between ionic and covalent compounds. To construct a model of both
ionic and covalent compounds in solution that accounts for their conductivity.
PRE-LAB QUESTIONS:
1. On the periodic table, use a colored pen to outline and label the location of metal elements and the
location of nonmetal elements.
2. In order to allow a flow of charge and conduct electricity, what two conditions must be true about
the particles of the substance?
PROCEDURES (Teacher Demo):
A. Write a sentence to record observations of the conductivity meter in the solid sugar.
B. Write a sentence to record observations of the conductivity meter in the solid salt.
INTERPRETATIONS:
1. Based on the conditions required for conductivity, explain the conductivity results for the solid
sugar and solid salt.
2. Predict what will happen if the solid sugar and salt are dissolved in separate beakers of water. (i.e.:
will the compounds in solution conduct electricity?) Explain your thinking.
PROCEDURES (Teacher Demo):
C. Copy the following 2 data tables. Be sure to include the title of each table. Leave at least eight
lines for each table.
Table #1: Solutions that do conduct electricity
Name
Formula First
Metal or
Second
Metal or
Element Nonmetal? Element
Nonmetal?
Name
Table #2: Solutions that do not conduct electricity
Formula First
Metal or
Second
Element
Nonmetal? Element
Metal or
Nonmetal?
D. Test the salt solution with the conductivity meter. Record this solution (name and formula) in the
appropriate table. Leave the other columns blank for now.
E. Test the sugar solution with the conductivity meter. Record this solution (name and formula) in the
appropriate table.
F. Use your Periodic Table of Elements to complete the other columns of the data tables.
G. Test a variety of other solutions with the conductivity meter. For each solution tested:
 Record the names and formulas for the solution in the appropriate table.
 Use the periodic table to complete the entire row in the table.
 Attempt to make a prediction before each new solution is tested.
INTERPRETATIONS:
3. What combination of elements (M/NM, M/M, NM/NM) in solution conducted electricity?
4.
What combination of elements in solution did not conduct electricity?
5. COVALENT COMPOUNDS- The combinations that did not conduct electricity in solution were
covalent compounds. A covalent compound is composed of neutral groups of atoms called
molecules. A covalent bond holds together the atoms in a molecule. Attractions between the
molecules hold the molecules in fixed positions in the solid.
a. Copy and complete the following sentence: “Covalent compounds are compounds composed
of ________ and _______ elements.” Hint: Refer back to your data tables.
b. Rubbing alcohol and sugar are both covalent compounds and both form a solution with water.
Think about a diagram of sugar dissolved in water (Lab 5.1). Sketch an alcohol solution and
label the particles.
c. Do molecules have a charge?
d. Are the molecules in a solution free to move?
e. Of the two conditions required for conductivity, which one is not met when a covalent
compound dissolves in water? Hint: refer back to pre-lab #2 and your answers to c and d
above.
6. IONIC COMPOUNDS- The combinations that conducted electricity in solution were ionic
compounds. An ionic compound is composed of positively and negatively charged particles
called ions. Ions are atoms that have acquired a charge. An ionic bond holds the positive and
negative ions together in fixed positions in the solid.
a. Copy and complete the following sentence: “Ionic compounds are compounds composed of
________ and _______ elements.” Refer back to your data tables.
b. Draw an ionic compound as a solid. Show the charges on the ions.
c. When the ionic compound dissolves in water, do the positive and negative ions stay together?
Hint: think about when solid salt was tested compared to a salt solution.
d. Draw an ionic compound in solution (dissolved in water). Label the particles.
e. Based on your picture for “d”, explain why an ionic compound conducts electricity.
7. Compare your pictures of a covalent compound that is dissolved and an ionic compound that is
dissolved.
a. When water molecules collide with the ionic compound do the collisions break the ionic bonds?
Explain.
b. When water molecules collide with the covalent compound do the collisions break the covalent
bonds? Explain.
8. NAMING IONIC COMPOUNDS.
a. What rules appear to be followed in naming ionic compounds? Examine your table of solutions
that conducted electricity to find the patterns.
 Which type of element is listed first in the name?
 Which type of element is listed second in the name?
 How is the name of the second element modified?
b. Use your periodic table and new knowledge about ionic compounds to predict a combination of
elements that will form an ionic compound that was not tested. Name this compound using the
ionic naming rules.
c. Name two additional ionic compounds that were not tested in the lab.
9. NAMING COVALENT COMPOUNDS. How is the naming of covalent compounds different than
the naming of ionic compounds?
10. PREDICTING CONDUCTIVITY.
Complete the table below. Formulas for ionic and covalent compounds have been written in the
first column. Write the name for the compound in the second column. Predict whether it would
conduct electricity if dissolved in water (yes or no?) in the third column. Explain your reasoning
for your prediction in the fourth column.
Formula
Name
Will it
conduct?
Explanation for conductivity results
SiO2
BaI2
MgO
BrCl
CONCLUSION:
Choose one of the compounds listed in the table for question #10.
 For the compound, draw a particle model for the compound dissolved in water.
 Identify the compound as either covalent or ionic and explain your reasoning.
 Explain why the compound will or will not conduct electricity, when it’s dissolved.