Shedding Light on Ions
Context: This lesson was done in an eighth grade classroom. Previously, students learned about atoms, elements, ions, and ionic bonds. Students have also constructed conductivity testers and practiced using them. This lab activity had a time constraint of 45 minutes with a class discussion the next day. However, this lab would benefit from additional class time.
Objective: Students are investigating which compounds produce ions in solution. Compounds that separate into ions in solution will conduct electricity and light up the light bulb.
Materials: 6V battery, light bulb and socket, 3 wires with alligator clips, copper electrode, zinc electrode, graduated cylinders #1-6, compounds to test (table salt, distilled water, tap water, sugar, baking soda, rubbing alcohol, vinegar, hydrogen peroxide, etc).
Students will begin the lab at a specific station. They should make observations about their initial compounds and take notes in a table (student created or teacher provided). Students should now create a conductivity tester and use it to test their compounds. Before moving on to the next station, students should deconstruct the conductivity tester enough to be safe. Based on their prior knowledge and observations, students should match their compounds to the name and formula written on the board. Students then rotate to the next station and repeat.
After the lab, students can analyze the following:
How could they tell which solutions were ionic?
Why were tap and distilled water tested?
Is sucrose (table sugar) is made up of ions? What evidence can be used to reach the conclusion?
Why do the ionic compounds light up the light bulb?
Conductivity tester:
A. Use a wire with alligator clips to connect the positive terminal of the battery to a lamp socket
B. Connect one end of a second wire to the negative terminal of the battery
C. Connect one end of a third wire to the negative terminal of the lamp socket
D. You will connect both loose wires to your electrodes
E. DO NOT LET THE ELECTRODES OR WIRES TOUCH
Extension: In the future, I could provide my students with the chemical formulas for the compounds and challenge them to figure out the common name. Students can make predictions before we begin, generating a list of expectations on the board.
Context: This lesson was done in an eighth grade classroom. Previously, students learned about atoms, elements, ions, and ionic bonds. Students have also constructed conductivity testers and practiced using them. This lab activity had a time constraint of 45 minutes with a class discussion the next day. However, this lab would benefit from additional class time.
Objective: Students are investigating which compounds produce ions in solution. Compounds that separate into ions in solution will conduct electricity and light up the light bulb.
Materials: 6V battery, light bulb and socket, 3 wires with alligator clips, copper electrode, zinc electrode, graduated cylinders #1-6, compounds to test (table salt, distilled water, tap water, sugar, baking soda, rubbing alcohol, vinegar, hydrogen peroxide, etc).
Students will begin the lab at a specific station. They should make observations about their initial compounds and take notes in a table (student created or teacher provided). Students should now create a conductivity tester and use it to test their compounds. Before moving on to the next station, students should deconstruct the conductivity tester enough to be safe. Based on their prior knowledge and observations, students should match their compounds to the name and formula written on the board. Students then rotate to the next station and repeat.
After the lab, students can analyze the following:
How could they tell which solutions were ionic?
Why were tap and distilled water tested?
Is sucrose (table sugar) is made up of ions? What evidence can be used to reach the conclusion?
Why do the ionic compounds light up the light bulb?
Conductivity tester:
A. Use a wire with alligator clips to connect the positive terminal of the battery to a lamp socket
B. Connect one end of a second wire to the negative terminal of the battery
C. Connect one end of a third wire to the negative terminal of the lamp socket
D. You will connect both loose wires to your electrodes
E. DO NOT LET THE ELECTRODES OR WIRES TOUCH
Extension: In the future, I could provide my students with the chemical formulas for the compounds and challenge them to figure out the common name. Students can make predictions before we begin, generating a list of expectations on the board.