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Turn Me on.... with a Clean, Green Machine
Grades 9-12

Overview

Batteries or chemical cells could be to energy what the microchip is to computers. The first electric battery was invented by Alessandro Volta in 1794. Today, these chemical generators power computers, cars and your cellular telephone. Pollution could all but disappear by our using this clean, green machine. So could our reliance on smelly oil. Batteries are so common today, but very few students understand the basic ideas of electrochemistry - how batteries work. This lesson, in two parts, teaches students the basic concepts of electrochemistry, then applies them to the building of a super energy cell.
ITV Series
ELECTRICITY # 4 "Current Electricity"
ELECTROCHEMISTRY #1 & 4 "Building Blocks..." & "Commercial Electrochemical Cells"

Note: ELECTROCHEMISTRY, not currently on the ASSET schedule, is available from TVOntario, 1140 Kildaire Farm Rd., Cary, NC 27511, phone 800-331-9566.
Learning Objectives
Students will be able to:
Materials
Per group (2-3 students):

To make a balloon circuit: To make a chemical cell: For the class: To make a lime cell: To make a wet (chemical) cell: * Located at the end of the lesson.

Vocabulary:


Pre-Viewing Activities
Part I: The Human Circuit!
TEACHER: "Here's a simple 'voltaic cell' with almost one full volt of electricity: A lime with two nails! I need a volunteer to test the potential of our lime." Ask the student to place the wires against his or her tongue. "What can you sense -- feel or taste?" Option: The teacher may decide to either demonstrate the live cell, or direct the students to prepare and test the lime.

TEACHER: "The slight tingle you feel and the metallic taste that you sense results from a motion of electric charge through your tongue. This is 'current electricity.' It is created by the 'voltaic cell' - - a simple battery."

TEACHER: "Turn to Activity Sheet 1, The Human Circuit. On the back side of the paper, sketch the complete path along which the current electricity flows from the lime through the copper nail into the tongue and then out through the zinc nail and back to the lime. Your sketch must show a complete path from one terminal of the lime to the other terminal. The road map of electricity you have just sketched is called a 'circuit.' Your wet tongue is a part of the circuit -- a human circuit."

TEACHER: "Allessandro Volta invented the first electric battery about two hundred years ago, in the year 1794. Volta called his invention a 'voltaic pile' or the chemical cell. Later on, you will make a 'cell.' He found that when he connected cells (like lime cells) in series (in a row), the potential adds up to give large jolts of electricity called voltage. The more cells, the more juice. In physics terms, the more voltaic cells, the more current electricity. In the lesson today, we will explore the concepts of current electricity and voltage by building circuits and batteries." OBJECTIVE 1.

The teacher instructs the students to refer to Activity Sheet 2, Making the Circuit, during the next part of the lesson. Students are to write their answers to the questions, based on information from the video, on a clean sheet of paper or on the back of the activity sheet.
Focus Viewing
It is very important to give students a focus for viewing. This helps them focus their attention on the lesson objectives. This way students learn that video is not solely for their entertainment.

TEACHER: "Think about a battery as a chemical cell which produces a continuous flow of charge." Point to the lime cell and Volta's pile. "Let's watch a video to determine the reason for the flow of charge -- the secret to its success."
Viewing Activities
Video: CONCEPTS IN ELECTRICITY #4 "Current Electricity"

Making the Circuit:
START the video at the point you hear the words "for a continuous flow of charge you need a source like a flashlight battery," and you see a flashlight battery on the screen.
PAUSE the video after you hear the words "we call these two charged parts electrodes," and you see a diagram of a battery showing the positive and negative terminals.

TEACHER: "What is the secret to a battery's success?" (The chemical reaction that takes place in the battery.) "What happens to the outer zinc layer of the battery during the chemical reaction?" (The zinc layer becomes negatively charged. Point to the zinc outer layer. It is called the negative electrode.) "What happens to the graphite rod in the middle?" (It acquires a positive charge by losing negative charges, and is called the positive electrode. Point to the graphite rod.) "Sketch the battery and label the following: the zinc layer, the graphite rod, the positive electrode, and the negative electrode."

The teacher places a transparency over the battery on the TV monitor. Make the sketch of the battery on the transparency. Replay the video segment so that students can verify their reponses. Place the transparency on the overhead, and check student's sketches for the correct labels.

TEACHER: "Now, what if you connected the two materials called electrodes with a conducting wire? Watch the video carefully and be able to tell me what will happen." OBJECTIVE 2.

RESUME video.
PAUSE video after you hear the sentence: "Current electricity is the name given to this continuous flow of charge," and you see the label "current electricity" on the screen.

TEACHER: "What will happen if you connect them with a wire?" (Charges or electrons will flow through the wire from the zinc to the graphite rod.) "On your sketch, show the direction of the flow of electric charge with an arrow. Which way does current electricity flow through a circuit?" (Current flows from the negative terminal through the wire to the positive terminal of the battery.) "Define 'current electricity.'" (The continuous flow of electric charge.) "So, because of this chemical reaction, a battery makes a steady flow of electric charge called current electricity." Write "current" on the chalkboard. OBJECTIVE 3. "Watch the video very carefully, and be able to define "simple circuit" and illustrate all the parts of the "simple circuit" on your sketch."

RESUME video.
PAUSE video after you hear the words, "If a gap is introduced in the circuit, the flow of charge stops immediately," and you see the bulb light up.

TEACHER: "What is a simple circuit?" (The complete path or loop around which current flows.) "On your sketch of the battery, show the direction of current electricity (electric charge) with an arrow. Label the parts of the simple circuit." Allow students one to two minutes to complete the task. Give a volunteer the transparency, and ask him or her to complete the sketch on the transparency.

TEACHER: "What are the parts of a simple circuit?" (A source of energy, such as a battery, and a conducting material (a wire, a load, a light bulb). "A flashlight battery is a chemical cell, and is a source of chemical energy." Show some examples of chemical energy, such as a lime cell and a flashlight battery. "Watch the video carefully to observe the reason the bulb lights up."
RESUME video.

STOP video after you hear the definition for direct current.

TEACHER: "What is the source of light in the bulb?" (Chemical energy inside the cell is transformed into electrical energy. In turn, electrical energy in the wire is transformed into light and heat in the bulb.) "Identify the form of energy produced in the battery, the wire, and in the light bulb. Label them on your sketch. Why is this circuit said to illustrate direct current?" (The electric charge continually flows in one direction.) "Scientists call this type of circuit a direct current circuit, or simply a DC circuit."
Post-Viewing Activities
The Big Bang:
TEACHER: "Let's make a 'DC circuit' to test your understanding of current electricity and circuits. You will need the following materials: Activity Sheet 3, "The Big Bang," 1 balloon, transparent tape, aluminum foil ribbon, 1 popsicle stick, 2 batteries, steel wool, 4 paper clips, and 2 rubber bands."

The teacher provides students with the 4-step method, as outlined on Activity Sheet 3, "The Big Bang." Allow students 10 to 15 minutes to construct their circuits.

TEACHER: "Let's analyze the events leading up to the 'big bang.' Rank the following statements in the proper order to explain why the balloon pops." The teacher may write these events on the chalkboard or present them on a transparency. TEACHER: "Make a sketch of your balloon circuit, and be able to describe the complete pathway of electric charge." Allow students two to three minutes to sketch their circuits. "We need a volunteer to draw his or her sketch on the chalkboard. What is the source of energy that caused the wire to get hot and pop the balloon?" (Chemical energy inside the batteries is transformed into electrical energy, which is passed along the electric charges through the ribbon to the steel wire. Because the path through the very thin wire resists the flow of electric charges, the charges transform some electrical energy into heat energy. The heat melts the skin of the balloon, and it pops with a big bang!)

The students will need the Assessment page.

TEACHER: "Illustrate the path of current electricity through the DC circuit on your sketch. In your group, take two to three minutes to write a description of the complete pathway. Make certain that your description includes all parts of the circuit. And, use the vocabulary that we learned while viewing the video. Be prepared to share your description with the whole class."

The teacher writes the vocabulary words on the board or on a transparency for the students. The teacher may use the students' paragraphs as an assessment. (Chemical energy is produced in the battery by a chemical reaction that causes a flow of electric charge. The electric charge or current flows from the negative electrode of the battery through the conducting wire -- the aluminum ribbon as electrical energy. When electric charges move across the gap through the thin steel wire called the load, some energy is transformed into heat. To complete the simple circuit, the current electricity flows around the balloon through the aluminum ribbon into the switch -- the popsicle stick. Electric charge moves out of the switch, and then through the second battery to the positive electrode of the first battery. Electric charge has flowed in one direction only around the loop or simple circuit.) "The pathway through which electric charges flow in your circuit is called a complete ______?" (DC circuit.) OBJECTIVE 4.

Note: The teacher may list the terms on the chalkboard and match the part of the circuit with the form of energy for a graphic summarization of the main concepts.
Pre-Viewing Activities
Part II: The Chemical Cell
Video: ELECTROCHEMISTRY #1 "Building Blocks of Electrochemistry"

The teacher sets up the demonstration of a wet (chemical) cell. Students will need Activity Sheet 4, Voltaic Cells. They are to place their sketches on the back side of the activity sheet.

TEACHER: "Volta found that if you dip two different metals in a chemical bath, a difference in potential will appear between them. He called the potential difference 'voltage.' This means that charge wants to flow from one metal terminal to the other. What would happen if you connected the terminals with an aluminum ribbon?" (A charge or current would flow through it.) "A modern flashlight battery is actually a single chemical cell, and it works on the same chemical principles of the first electric battery. Look at Activity Sheet 4, Voltaic Cells. You will answer the questions on a sheet of paper."

TEACHER: "Let's watch a video to learn about how the first electric battery was invented and discover the two principles of chemical cells. Listen carefully to Galvani's discovery."
Viewing Activities
Video: ELECTROCHEMISTRY #4 "Commercial Electrochemical Cells"

Volta's Pile:
START the video after the words, "although the laboratory models work completely differently from today's modern batteries, they work on the same chemical principles," and the picture of a flashlight battery.
PAUSE video at the point you see a portrait of Volta.

TEACHER: "What did Galvani discover in the year 1786?" (He discovered that a freshly dissected frog's leg twitched whenever it came in contact at the same time with different metals, such as zinc and silver. It did not twitch when the metals were the same.) "The first chemical principle of a battery was accidentally discovered by Galvani: When a chemical cell is made from two different metals (electrodes), current electricity flows through the cell (the frog's leg). Listen carefully to the video, and be able to tell me how Volta constructed the first electric battery, based in part on Galvani's work."

RESUME video.

STOP video at the point you see Volta's pile turn on the light.

TEACHER: "What does one find in Volta's pile?" (Volta's pile was constructed from zinc and silver disks separated by cardboard soaked in salt water.) "Volta discovered the second principle, that batteries consist of a conducting solution, or electrolytes such as salt water. Make a sketch of Volta's pile and label the following parts: electrodes, electrolyte, and the number of cells."

The students will need this sketch for the lab in the Post-Viewing Activity of the lesson. Ask a volunteer to put his or her sketch on the chalkboard. Allow students 2 to 3 minutes to complete the task.

TEACHER: "How many cells are there in Volta's pile?" (Two.) OBJECTIVE 5.
Post-Viewing Activities
Voltaic Cells:
TEACHER: "Go to Activity Sheet 4, Voltaic Cells. Let's make a chemical cell - - the prototype battery using the two principles of a chemical cell. Review Activity Sheet 4. Here's how to build a cell. Obtain the following materials: 4 different kinds of metal strips, cardboard strips, 1 cup of vinegar, and a multimeter. Follow the steps to construct a chemical cell. Measure the voltage of the cells using a voltmeter." Allow students 10 to 15 minutes to build their cells and then compile the voltage data to analyze.

TEACHER: "Construct a table with four columns: 'Electrodes,' 'Number of cells,' 'Electrolyte,' 'Voltage.'" Ask students to record their data on the chalkboard, and analyze the data for the different groups. "How would you explain the observed differences?" (The differences in voltages are related to the kind of metal electrodes.) "Which cell has the most potential?" (The copper and zinc cell.) OBJECTIVE 6.

Assessment:
TEACHER: "Obtain a flashlight battery, and observe the information on the label. Record the voltage and contents of the battery. Make a sketch of the inside of the battery and label the following: electrodes, electrolyte, and voltage." (A single dry cell has a voltage range of 1.25 - 1.50, depending upon the size of the battery.) "How does the voltage of Volta's pile compare with that of commercial dry cells, for example the voltage of a single flashlight battery? If the voltage of a car battery is 12 volts, how many cells do you think there are in a car battery?" (There are six cells; two volts times six cells equals twelve volts.)
Action Plan
Extensions
History And Science:
  1. Research the Italian scientist Alessandro Volta. Write a report on his life, and the events that led him to become a great scientist and inventor.

  2. Research the variety of batteries that were built through history. Compare the voltage output of regular Leclanche cells and modified Leclanche, super energy cells.
Art and Science:
  1. Design and construct a chemical generator -- a battery. Test the battery using a small bulb lamp.
Math and Science:
  1. Students measure the current and voltage produced by building wet cells using different electrodes. Compile the data as a whole class, and compute the average and the range of the data. Compare their values to that of commercial batteries.

  2. In experimenting with the Voltaic Cell, students could alter the strength of the salt water to determine the effects on the voltage of the cell.
Careers in Science, Math and Related Technologies:
  1. Research careers in electricity and electronics, including the automotive industry and the electric car.
Other ASSET Courses on Careers in Science: Computer Software: Alternate Videos: Laserdisc:
Worksheet
Click here to view the first worksheet associated with this lesson.

Click here to view the second worksheet associated with this lesson.

Click here to view the third worksheet associated with this lesson.

Click here to view the fourth worksheet associated with this lesson.

Click here to view the fifth worksheet associated with this lesson.

Master Teacher: Steve Martin

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