Sour Power, by Brenda Bradford

Louisiana Curriculum Framework Content Strand / Physical Science / Grade Level / 6-8
Objective:
The Learners Will:
  • Model a battery using a lemon, zinc wire, and cooper wire
  • Design and construct series circuits using lemon batteries
  • Describe the behavior of series circuits
  • Measure the voltage generated by a single lemon
  • Measure the electrical energy of lemon batteries series in volts

Teacher Information

Benchmarks (see Reference 1)
SI-M-A2; SI-M-A3; SI-M-A4; SI-M-A5;
SI-E-A7; SI-MB3; SI-H-A1; SI-H-A3;
PS-H-G2; SI-M-A8; PS-H-F1 / Time Frame
2 or 3 60- minute class periods
Applications
Electrical engineering, Urban Planner, Physicist, Plant operator, and Electrician / Student Groupings
Cooperative pairs
Possible Obstacles to Student Learning
Lack of prior background on electrolysis, serial and parallel circuits, understanding statistics, linear regression, and lack of use of the technology
Opportunities for Assessment
  1. Cooperative laboratory reports: students will write a laboratory report for both the exploration and application activities
  2. Questioning during Concept Development
  3. Students will graph and analyze data using technology
  4. Students will link calculators to computers and print graphs and tables
  5. Mid-term and/or Final Exam: students are held accountable for the manipulation of the equipment in a laboratory practicum.

Lesson Procedure
Exploration: Students will be given a set of materials:
  • CBL System, TI-82- Ti-83 graphing calculators containing the CHEMBIO program, TI voltage leads, Lemon, Zinc metal wire or steel paper clip, 18-gauge cooper wire, Sheet of coarse sandpaper
Students will be asked to make a lemon battery and measure voltage of one battery and compare it to the voltage of lemon batteries in series. Each student in the group will be responsible for a written lab report.
Concept Development Questions with anticipated responses:
  • What do we mean by series circuit? Name some things that are wired in series circuits. In a series circuit, the current has only one path it can travel along. The parts of a series circuit are wired one after another; the amount of current is the same through every part. When any part of a series circuit is disconnected, no current flows through the circuit. This is called an open circuit. A string of Christmas tree lights is an example of series circuits.
  • Predict whether or not a lemon battery can be a source of electricity. Explain your answer.
  • What is the purpose for using zinc and cooper wire?
  • What happens when you link lemon batteries in series?
  • What would it be like if all lights and electrical devices in your home were wired in series and you turned off a light? All the other lights in your home would go off. When you unplug one electrical device on a series circuit or turn off its switch, you are opening the circuit and breaking the path of the current.
Integration of Technology: At this point, students would test the lemon battery using the CBL, graphing calculator, TI voltage lead and computer. See laboratory procedure in student handout.
Concept Application: Students will discuss in their cooperative pairs the different voltages of lemon battery pairing. Students will discuss information collected from data and analyze graphs.
Extensions:
  • TLW - compare parallel circuits (branching out) to series circuit (straight path)
  • TLW - compare lemon battery to dry cell battery
  • Students may use a penny and a dime instead of cooper and zinc they may also try other metals, such as paper clips and brass tacks. Students may try to use other fruits. They may even try to light up a light bulb with a fruit battery.


Attachments
1. Student Handout
2. Assessment Rubrics
3. Sample Data
3. References

SOUR POWER


Objective: This activity is designed to model a battery using a lemon and Zinc and Copper wires. We will design a lemon battery. Batteries contain a chemical called an electrolyte, which allows a chemical reaction to occur between the electrodes, that creates electricity. Lemon juice will act as an electrolyte. This activity will demonstrate how the energy in a circuit is affected as you place successive lemon batteries in a series. In a series circuit, the current has only one path it can travel along. A string of Christmas tree lights is an example of series circuits. The parts of a series circuit are wired one after another; the amount of current is the same through every part. When any part of a series circuit is disconnected, no current flows through the circuit. This is called an open circuit. In a series, the total electrical energy is the sum of the individual energies of each lemon battery. In this activity you will place several batteries in a series and measure the electrical energy of the series in volts. The learner will measure the voltage generated by lemons. Fruits contain substances such as ascorbic acid, citric acid and NADH (chemical that generates cellular energy). Under certain circumstances these chemicals act as electrolytes and then undergo electrolysis. Electrolysis means a chemical change produced by electric current passing through an electrolyte. The electrons flow from the cathode through the electrolytes to the anode. The cathode is the negative electrode, which could be the copper wire, and the anode is the positive electrode, which could be the zinc wire. This process generates electricity just the same way as a voltaic battery.
Voltage is measured in volts. Voltage is the force or pressure that causes a current to flow in a circuit. A circuit is a path that goes from the positive force to the negative force. Current is measured in AMPERES (amps.) Copper is a good conductor and has free electrons of the outer ring that fly off constantly. Electrons from atoms near by fill in the holes. There are millions of electrons moving in all directions at the same time. When voltage is applied across a conductor, it drives the free electrons away from the negative force to the positive force. An amp is the number of electrons going past a certain point in one second. The learner will measure, record, and graph voltage.
Materials:
CBL System
TI-83 Plus graphing calculators containing the CHEMBIO program
TI voltage leads
Lemons
Zinc metal wire or steel paper clip
18-gauge cooper wire
Sheet of coarse sandpaper
Assistance from a lab partner
Procedure:
Part I (Without the calculator)
  1. Squeeze the lemon gently with hands. But don’t rupture the lemon skin. Insert a 2-1/2 cm piece of zinc wire and a 2-1/2 cm piece of cooper wire into opposite sides of the lemon.
  2. Connect the voltage leads into Channel 1 on the CBL. Turn on the CBL.
  3. Use the multimeter on the CBL by pressing the MODE key. The CBL will be reading in volts.
  1. Place the lemon battery on the lab table. Touch the voltage leads to opposite ends of each wire of this first lemon battery. If the voltage reading on the CBL is a negative number, switch the leads of the battery. Measure the voltage and record the scores on a data table as voltage of one lemon battery.
  2. Place another lemon battery in line with the first lemon battery, so that the positive end of the first lemon battery touches the negative end of the second lemon battery.
  3. Touch the voltage leads to the ends of the series of lemon batteries. Record this reading as 2 lemon batteries
  4. Repeat these steps until you have recorded data for 4 batteries in a series.
  5. Answer the question for Part I before going on to Part II

Answer Questions for Part I

  1. Make a Table to Record Voltage and Number of lemon batteries used. Be sure to name and label table.
Table 1 Voltage Reading
Voltage Reading / Number of Lemon Batteries
  1. Draw a graph of your results on the grid below. Be sure to name and label your graph.

  1. Based on the data collected for Part I, predict the voltage of a series of batteries containing 9 batteries. Show on the graph how you obtained your answer.
  1. For this activity, lemon batteries were used. Each lemon battery is claimed to have a voltage of 0.67V. The combined voltage of two lemon batteries determined mathematically is 1.34 V. How does this voltage compare to the actual voltage of connecting two lemon batteries? Explain.
Part II (with calculator) Create a Scatter Plot of the data
A scatter plot is a plot of the values of Y versus the corresponding values of X:
Vertical axis: Variable Y – usually the response variable.
Horizontal axis: variable X- usually some variable we suspect may be related to the response.
  1. Turn the calculator on. Press STAT, then 1 (EDIT).
  2. Clear the data lists L1 and L2, by using the arrow [, , , ] keys to get to a list name and then press CLEAR and ENTER
  3. Enter the independent variable’s data list in L1 (Horizontal Axis). Enter the dependent variable’s data list into L2 (Vertical Axis)
  4. Press 2nd STAT PLOT, then press 1 (Plot1… On) and turn the plot on by pressing ENTER.
  5. Use the Arrow keys to select the scatter plot (the first plot type) and press ENTER.
  6. Xlist should be L1, and Ylist should be L2.
  7. Select a data Mark and press GRAPH.
  8. To auto-scale the scatter diagram, press ZOOM 9 (ZoomStat). [Try pressing (TRACE) and using the arrow keys]
  9. To change to appropriate scaling parameters, press WINDOW, Adjust the values as necessary (whole numbers).

Part III (with calculator and CBL)

  1. Connect the voltage leads to Channel 1 in the CBL, and then use a black link cable to connect the CBL to your graphing calculator. Press the cable into each device firmly.
  2. Turn on both devices. Press APPS on your calculator and select CHEMBIO. Press ENTER until you see the Main Menu.
  3. Choose 1: SET UP PROBES.
  4. Press 1 as the number of probes then press ENTER
  5. Press 5 to select voltage
  6. Press 1 to indicate lowest channel then press ENTER
  7. Select 2: COLLECT DATA, then choose 3: TRIGGER PROMPT. You are now ready to collect data.
  8. Place one lemon battery on lab table. Touch the voltage leads to the first lemon battery. If the voltage reading on the CBL screen is a negative number, switch the leads of the battery. When the voltage reading on the screen of the CBL stabilizes, press TRIGGER on the CBL. When prompted for a value enter 1 for the number of batteries used. Press Enter. You should record your data from the CBL by hand into a data table although the calculator will store it in a list for you.
  9. Place another lemon battery in line with the first battery, so that the positive end of the new battery touches the negative end of the other battery. Choose 1:MORE DATA
  10. Touch the voltage leads to the ends of the series of batteries. When the voltage reading on the CBL is stable, press TRIGGER ON the CBL. When prompted for a value, enter 2 for the number of lemon batteries used. Press ENTER.
  11. Repeat steps 9 & 10, adding one lemon battery at a time, until you have placed all of the batteries in a series and collected 4 data points. When you are prompted to enter a value, you are entering the number of lemon batteries that you have in your circuit.
  12. When you are finished collecting data, select 2: STOP AND GRAPH. View the graph, keep pressing ENTER until you see the MAIN MENU.
  13. At the MAIN MENU, SELECT 4 fit curve.
  14. Choose 1 LINEAR L1, L2. The equation “y= ax + b” appears. Below are the values for the variables a (slope) and b (y-intercept). You should record the equation with your data table in the proper form
Example: On Calculator screen you will see: Y = ax + b; a = 5; b = -2
For this example, you would record: y = 5x - 2
  1. Press ENTER. Choose 1:SCALE TO DATA. The graph appears with the best-fit line drawn.
  2. If you press TRACE, you may use the arrow keys to skip between measured points. The corresponding X & Y values are given at the bottom of the screen.
  3. If you are interested in seeing the voltage of 2.68 lemon batteries while tracing, press the up arrow once and move the cursor left or right until the X at the bottom says 2.68 approximately. The corresponding Y value will be the predicted value for 2.68 lemon batteries.
  4. Do not clear your screen. You will be prompted to print in the analysis questions.
Answer the Questions for Part III
4. Print your best-fit graph using TI Graph Link
  1. Compare and contrast the graphs for questions 1 and 4.
  2. a) Based on the equation derived from the data collected for Part III, predict the voltage of a series of batteries containing 9 lemon batteries. (Hint) Substitute (for the x in the equation and solve for y)
b) Compare this answer to the answer to question #2
c) Explain the results.

Assessment Rubrics

Lab Report: Sour Power
Teacher name: Brenda Bradford
Student Name ______
CATEGORY / 4 / 3 / 2 / 1
Participation / Used time well in lab and focused attention on the experiment. / Used time pretty well. Stayed focused on the experiment most of the time. / Did the lab but did not appear very interested. Focus was lost on several occasions. / Participation was minimal OR student was hostile about participating.
Analysis / The relationship between the variables is discussed and trends/patterns logically analyzed. Predictions are made about what might happen if part of the lab were changed or how the experimental design could be changed. / The relationship between the variables is discussed and trends/patterns logically analyzed. / The relationship between the variables is discussed but no patterns, trends or predictions are made based on the data. / The relationship between the variables is not discussed.
Scientific Concepts / Report illustrates an accurate and thorough understanding of scientific concepts underlying the lab. / Report illustrates an accurate understanding of most scientific concepts underlying the lab. / Report illustrates a limited understanding of scientific concepts underlying the lab. / Report illustrates inaccurate understanding of scientific concepts underlying the lab.
Data / Professional looking and accurate representation of the data in tables and/or graphs. Graphs and tables are labeled and titled. / Accurate representation of the data in tables and/or graphs. Graphs and tables are labeled and titled. / Accurate representation of the data in written form, but no graphs or tables is presented. / Data are not shown OR are inaccurate.
Experimental Hypothesis / Hypothesized relationship between the variables and the predicted results is clear and reasonable based on what has been studied. / Hypothesized relationship between the variables and the predicted results is reasonable based on general knowledge and observations. / Hypothesized relationship between the variables and the predicted results has been stated, but appears to be based on flawed logic. / No hypothesis has been stated.
SAMPLE DATA
Table 1. Lemon Battery Voltages
Number of Lemons / Voltage
1 / 0.604
2 / 1.141
3 / 1.638
4 / 2.210


References

Louisiana Department of Education (1997). Louisiana Science Framework, Retrieved December 13, 2001, from the Louisiana Department of Education website.

LaSIP Nicholls State University Summer 2002, Dr. Judy Chauvin and The LaSIP Staff.

Parker, S. Simple Chemistry (London: Kingfisher, 1990).

Microsoft Encarta World English Dictionary © 2001

“Batteries 101 Weird Science”

“Batteries, The Lemon Battery”

“Make a Battery Using a Lemon”

“Lemon Power, Lemons Are Stronger than You Think!” www.eecs.umich.edu

“Shock Them All”

“Lemon Cells Revisited – The Lemon-Powered Calculator, by

“What other fruits can make a “lemon battery?” www.van.hep.uiuc.edu

“Voltage, Current & Resistance Explained”

“Current” “Resistance” and “Voltage”

“The Energy Story, Chapter 2: What is Electricity?” www.energy.ca.gov/education

Water Quality with CBL, Robyn Johnson, Scott Holman, Dan Holmquist, Vernier Software, Portland, OR, 1999.

Acknowledgments

I would like to thank the Department of Physical Sciences, the LaSIP Staff, and a special thanks to Dr. Judy Chauvin of Nicholls State University, Thibodaux, Louisiana, for their assistance, courtesy, and time during the LaSIP program.