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What About Batteries?

Description of Activity

Title: What About Batteries?
Overview: Working in small groups (2-4 students) students will investigate electrical voltage and build a battery that produces a measurable and reproducible voltage. This laboratory exercise should take two or three fifty-minute lab periods. This time frame will allow students to try and possibly fail a few times before arriving at a solution.
Materials: This is not intended to be a complete list of materials. You may add or delete any items that you feel may be helpful or useful in the lab. Encourage students to bring other materials from home which they feel they may be improve their battery.

Skill Development Activity: (suggested materials for each group)

a lemon
2 strips each of Al, Zn, Sn, Mg,
2 pennies
2 nails
alligator clip jumpers and insulated wires
a voltmeter
a plastic cup
water

Inquiry Lab Activity: (Students may choose to use only the materials above. Other suggested materials that the teacher make available are listed below.)

strips or wires of other metals (copper, lead, nichrome, iron, aluminum, etc.)
graphite electrodes
0.10 M solutions of various salts
dilute hydrochloric acid solutions

Background

An electric current is produced as electrons move through a conductor. A chemical reaction can provide the energy necessary to induce the flow of electron. In a typical dry cell or battery, electrical energy is produced by the interaction of two different metals (electrodes) in the presence of a conducting agent (electrolyte). The basic requirement for the two electrodes is that they have a significant difference in activity. Zinc and graphite are commonly used. The voltaic cell is designed so that the electrons being transferred in a redox reaction do so indirectly through an external circuit (voltmeter and leads, the circuitry of a toy, etc.). The two half reactions of the redox reaction must somehow be separated but provided with an electrolyte as a bridge between them in order to complete the circuit.

The first electric cell is believed to have been developed by an Italian scientist, Alessandro Volta, in the late 1790's. His cell, known as the voltaic pile, consisted of a stack of zinc and silver disks separated by cardboard disks moistened in a salt solution. One can get similar results with copper pennies, filter paper and aluminum foil. We measure the electrical force that sends electrons around a circuit in "volts" in Volta's honor.

Teaching and Learning Strategies

Prerequisite instruction:

Students will need instruction on the function, use and limitations of a voltmeter. A CBL with voltage probes makes a suitable voltmeter.

In order to keep this exercise an experience in inquiry, offer as little information to students as possible. This activity can be successful if students just know how to use a voltmeter. Using a CBL with voltage probes allow students to investigate potential differences quite rapidly.

Encourage the students to bring materials from home to supplement the materials provided. There are so many possible combinations of materials that work, encourage your students to be creative and leave the discovery totally up to them.

This lab and assessment could also be related to half-cell reactions.

Safe Operating Procedures

Safety goggles and lab apron should be worn at all times in the laboratory. Dispose of all materials in an appropriate manner.

Skills Development Lab

Demonstrate the use of a voltmeter. Give the students the supplies and equipment listed above (a lemon, 2 strips each of Al, Zn, Sn, Mg, 2 pennies, 2 nails, 2 alligator clip jumpers, a voltmeter, a plastic cup, and water). Ask the students to build something that creates the most voltage. Students must keep a log of each trial attempted while trying to produce voltage. A table describing the design, parts, and voltages is an appropriate method of tracking and reporting results.

Skills Development Lab Assessment of Learning:

Based on the observations which you recorded:

1. What 2 things are necessary to produce voltage?
2. What metals produce the most voltage?
3. How is voltage output between metals related to electronegativity?

Invitation to Learn

Using what you learned in the previous activity, construct a battery or voltaic cell that produces the greatest voltage or the greatest amperage. Try different constructions until you build a battery that has measurable voltage and can be reproduced.

Assessment of Learning:

Suggested Evaluation Tools

The formal written lab report is, of course, an acceptable evaluation tool. In addition to any data tables developed students should address the following questions:

1. Draw a diagram of the battery built by your group. What voltage did you measure?
2. Compare the construction of your battery to a commercial battery that you would purchase from the store? In order to answer this question, students should research commercial batteries and their components.
3. What is the purpose of each component of your battery? (In other words, what part does each play in making your battery work?)

Alternative Evaluation Tools

Alternatives to the written report may include the following:

Guided Tour:
When all the groups have completed this experience, set aside time for a tour of each group's project. Allow each group to explain how their battery works to the class.

Contest:
You may wish to offer a reward for the group of students with the battery that produces the most voltage, or the most creative battery or the battery with the cheapest materials, or the one that produces a voltage for the longest period of time. You may wish to invite your administrator or other staff member to help in judging winners.

Journal Writing:
You may wish to have the students keep a journal of what they did in the process of coming up with a working battery including those trials that failed. Have them review their journal and write a paragraph about why their attempts succeeded or failed. Another option would be to have the groups trade journals and write the same paragraph about their peer's work.

If time or teacher choice permits further investigations, students could investigate the effects of concentrations, temperature etc. on cell voltage.

1. To achieve the greatest voltage, which of the following must be true?

A. The two metals (electrodes) must be as similar as possible.
B. The two metals (electrodes) must be as different as possible.
C. The voltage depends on the composition of the salt bridge (lemon, potato, etc.).
D. Voltage is impossible to predict without completing the experiment.

2. A salt bridge (lemon, potato, etc.) is used in a voltaic cell (battery) to:

A. Allow current to flow through the cell.
B. Prevent charge build-up in the half cells.
C. Prevent direct reaction between the two electrodes.
D. All of the above.

All rights reserved except those which may be granted under Sections 107 and 108 of the Copyright Revision Act of 1976. This document may be freely distributed in its entirety for non-profit purposes provided that the copyright notice is not removed. If you have questions concerning proper use of this material, or if you are interested in obtaining permission, contact the Curriculum Section Reception Desk at 801-538-7698.

This document was submitted for posting to the Internet by the State Science Specialist. Any questions concerning content should be directed to that individual.

Updated September 25 1997 by Michelle Dumas