Introduction

In this hands-on investigation, students build simple batteries and explore the chemistry that makes them work! They begin by building a simple battery that uses cola as the electrolyte to light an LED diode before conducting a controlled experiment to investigate how a different electrolyte solution affects electrical output and overall battery performance. By measuring voltage, comparing performance, and analyzing their results, students experience electrochemistry in action while connecting their findings to the science behind real-world batteries.

Student Objectives

Students will be able to

• Explain the role of an electrolyte in an electrochemical cell.
• Build and test a simple battery using zinc and copper electrodes.
• Measure voltage using a multimeter.
• Conduct a controlled investigation and compare results across different electrolyte solutions.
• Analyze how electrolyte composition affects battery performance.
• Use evidence to explain how electrolyte composition affects battery performance.

Materials

Per Student Group

• Student Handout
• Optional: Biology Extension
• ~280 mL of cola
• 4 copper electrode strips
• 4 zinc electrode strips
• 4 small paper or plastic cups
• 5 pairs of alligator clips
• 100 mL measuring beaker
• Sticky tape (e.g. clear, electrical, masking)
• 1 digital multimeter
• 2-3 LED diodes
• Safety goggles
• Paper towels

Materials, continued

Electrolyte solution options for controlled experiment section (each student group chooses 1 and will need ~280 mL)

• Vinegar
• Salt solution (1 tsp salt dissolved in 70 mL of water)
• Energy or sports drink

Safety Guidelines

Students should

• Wear safety goggles.
• Never taste electrolyte solutions.
• Handle metal strips carefully.
• Handle electrolyte solutions carefully and avoid spills.
• Wash hands after the lab.

Procedure:

Note 1: Students should be familiar with basic circuit construction. A recommended lab to familiarize students with series and parallel circuits is the Play-Doh Circuits Hands-On. If needed, review the student procedure beforehand and model multimeter use for students before they start the experiment.

Note 2: Depending on class period length, this investigation can be conducted in one class period or over two class periods. In Part 1, all students use cola to build a simple battery and familiarize themselves with the set-up. In Part 2, students choose an electrolyte and conduct a controlled experiment.

Part 1: Build a Battery with Cola

In this section, students work in groups to learn how a battery works using cola as the electrolyte.

Optional Introduction: Background Information

• Provide students with the Background Information section of the Student Handout, which begins with a section that introduces the key concepts of electrolytes and ion movement, anode vs. cathode, oxidation and reduction, and voltage and current.

Building a Battery Using Cola as an Electrolyte

• Divide the students into groups of 2-3 and provide them with Part 1 of the Student Handout.
• Provide each group with the materials they will need to build the electrolyte cells, and provide instruction on the basic use of a multimeter, if needed (clear instructions are provided in the Student Guide).
• Go over safety guidelines with students and emphasize the importance of avoiding spills and handling electrodes carefully.
• Instruct students to carefully follow the directions in the Student Guide. Carefully monitor student progress.

Part 2: Conduct a Controlled Experiment

In this section, each group will test a different electrolyte, and compare results with other groups.

• Provide student groups with Part 2 of the Student Handout.
• Tell students that the only variable that is changing between groups is the electrolyte solution. Everything else, including electrode materials, volume of solution, cup size, wiring, LED diode, etc. should be kept constant.
• Following the directions in the Student Handout, students will repeat the battery construction steps in Part 1 using their new electrolyte.
• Once all groups are completed, combine all class data into one table or visual. Suggested: Create a table on the classroom board where each group can input their data.
• Instruct student groups to complete the post-lab reflection questions. Then conduct a class discussion to go over student responses and observations.

Note: Students often believe that the liquid creates electricity. Emphasize that:

• The chemical reaction occurs between zinc and copper. 
• The electrolyte allows ions to move.
• The electrolyte completes the circuit.