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ENERGY Fruit and vegetable clock Chemical cell Carlo Waldfried Edited by Anne Starace Abstract Energy is an important concept in our everyday lives. This module demonstrates chemical energy being transformed to kinetic and thermal energy. Keywords: energy, conservation of energy, electrolytes, battery, electrode, chemical cell Funded by the National Science Foundation and the University of Nebraska Content Standards K 1 2 3 4 5 6 7 8 4.2.1 8.2.1 4.3.3 8.3.3 History & Process Standards K 1 2 3 4 5 6 7 8 4.6.2 4.7.2 Skills Used/Developed: 2 Energy- chemical cell V 3.0 © University of Nebraska 2002 TABLE OF CONTENTS I. OBJECTIVES...............................................................................................................................4 II. SAFTEY.....................................................................................................................................4 III. LEVEL, TIME REQUIRED AND NUMBER OF PARTICIPANTS.......................................4 IV. LIST OF MATERIALS............................................................................................................4 V. INTRODUCTION .....................................................................................................................5 VI. PROCEDURE...........................................................................................................................7 VII. FREQUENTLY ASKED QUESTIONS…………………………………………………...10 VIII. TROUBLE SHOOTING…………………………………………………………………..10 IX. HANDOUT MASTERS…………………………………………………………………….10 X. REFERENCES………………………………………………………………………………..10 3 Energy- chemical cell V 3.0 © University of Nebraska 2002 I. OBJECTIVES Students will: -understand that food contains chemical energy. -understand that chemical energy can be converted to other forms of energy. -(older students) determine which materials work best in a chemical cell. II. SAFTEY Make sure that no one tries to drink the soda/juice out of the electrolyte cell! Do not give away the fruits/vegetables used for the fruit and vegetable battery. III. LEVEL, TIME REQUIRED AND NUMBER OF PARTICIPANTS LEVEL This activity is appropriate for grades K-12. TIME REQURED Preparation involves buying fruit and fruit juice. This activity takes from 15 - 30 minutes to complete. NUMBER OF PARTICIPANTS About 3 - 10 participants at a time IV. LIST OF MATERIALS fruit and potato clock chemical cell ( plastic cup with different strips of materials) 1.5 - 3 V DC motors light bulb fan (12 V DC, 60 mA) buzzer (24 V DC) patch cords (insulated wires) to buy close to activity time: fruits and/or vegetables (orange, lemon, grapefruit, etc.) can of coke, orange juice 4 Energy- chemical cell V 3.0 © University of Nebraska 2002 V. INTRODUCTION Our world is under constant change, which is possible because there is energy available to be used in making the change. Without energy, the world would be completely static -- no changes could occur. This module explains the different forms of energy and how they can be used to make changes. The principle forms of energy can be categorized as: kinetic energy potential energy chemical energy heat (thermal) energy Although you cannot create or destroy energy (we say that energy is ‘conserved’), energy can be transformed from one type of energy into another type. One of the important characteristics of energy is that it can be used to do work. Work is defined as force multiplied by distance. So basically, moving things is doing work; you must apply a force to make them move a certain distance. The harder you push and/or the farther you move something, the more work you are doing. Often, you cannot actually see energy, but you can measure energy by its ability to do work. The different types of energy have different features and to understand changes between these forms, we have to understand how each type of energy is different than the others. Type of energy kinetic energy potential energy heat or thermal energy description energy of motion energy of position: something that could potentially be pulled by gravity energy due to temperature chemical energy energy stored in chemicals solar energy energy due to the sun example a moving car, a jogger a piledriver, a bungee jumper just before the jump, a ball tossed in the air boiling water, a hot piece of coal a battery, gasoline, food solar cells Energy is constantly being transformed from one form of energy to another. For example, the human body uses food (which contains chemical energy) and converts it in our body into heat (body temperature), kinetic energy (motion), or into a different type of chemical energy - fat. 5 Energy- chemical cell V 3.0 © University of Nebraska 2002 The principle of conservation of energy is the most fundamental principle in the world. Its applications and usages are so common to our everyday life, that often it is not perceived. This module will help participants discover and explore various forms of energy and how they interact. 6 Energy- chemical cell V 3.0 © University of Nebraska 2002 VI. PROCEDURE A. 1. Fruit and Vegetable Clock 2. Chemical Cell Fruit and Vegetable clock: Setup: Place two fruit and/or vegetable items into the clock's trays. Insert two electrodes (black and yellow) into each fruit and/or vegetable. Make sure that each energy source has a black ( zinc) and yellow (copper) electrode for proper operation. Keep extra fruits and vegetables nearby as needed. Execution: The fruit and vegetable clock is in operation. To demonstrate that the clock is powered by the fruits unplug one electrode to discontinue the electrical circuit and watch the clock go blank. 7 Energy- chemical cell V 3.0 © University of Nebraska 2002 Chemical Cell: Chemical cell is just another name for a battery. The term “chemical cell” is more descriptive than “battery” because it tells you it is using chemical energy. Setup: a) Mount two electrodes to the electrode holders of the plastic cup of the chemical cell and b) connect the wires of the electrodes to a light bulb, the buzzer, or the fan. c) Keep a can of coke and/or orange juice nearby. Note that wire must touch the bulb at the side and bottom as shown in the picture above. However, the bulbs in the kit may be placed in wire holders, which make sure the current gets to the side and bottom of the bulb. electrode holder plastic cup electrode electrolyte (coke/juice etc.) 8 Energy- chemical cell V 3.0 © University of Nebraska 2002 Execution: Open the coke can or orange juice container and fill the plastic cup. This will power the buzzer. (The light bulb requires more energy than the buzzer, so the bulb may not work for as many combinations of electrodes and electrolytes as the buzzer. When trying new combinations, test with the buzzer first.) The participants can also see that the coke/fruit juice etc. supplies enough power to run the fan, small light bulbs, etc. For more advanced participants, a voltmeter and ammeter can be connected to the electrodes of the chemical cell for accurate measurements. Participants may try various combinations of electrodes to see which ones produce the brightest light or highest voltage on a voltmeter. The participants will discover that if the same electrodes are used on both ends, no voltage is produced. The following table lists some expected values for various combinations of electrodes that are included in the chemical cell kit, i.e. carbon (C), copper (Cu), lead (Pb), nickel (Ni), iron (Fe), zinc (Zn) and aluminum (Al). ∆V C Cu 0.35 Pb 0.8 0.45 Ni 0.95 0.6 0.1 Fe 1.15 0.8 0.3 0.2 Zn 1.45 1.1 0.6 0.5 0.3 Al 2.4 1.9 1.45 1.3 1.15 Cu Pb Ni Fe Zn 0.8 The actual measured voltages might differ from the values listed in the table, depending for example, on the electrolyte solution (coke, orange juice, etc) used for the experiment. This demonstrates that chemical energy (food) can be converted into kinetic energy (fan) and heat energy (the light bulb will become warm). The human body similarly converts food energy to supporting individual organ systems. These organ systems collectively maintain the human body. 9 Energy- chemical cell V 3.0 © University of Nebraska 2002 Cleanup: Throw away the fruits and vegetables. Empty the plastic cups and rinse. Rinse and clean off the electrodes and return them to the box. VII. Frequently Asked Questions Why doesn’t it work to have two electrodes of the same element? Electrons must flow from electrode to electrode to make a battery or cell. Some materials want to lose electrons and other materials want to gain electrons. If two such materials are allowed to exchange electrons, they will. This movement of electrons is what lights the light bulb. If the electrodes are made of the same material, then they either both want more electrons, or they both want to lose electrons. So, no exchange will be made. VIII. Trouble Shooting IX. Handout Masters See page 10 X. References For more information about chemical cells: http://www.funsci.com/fun3_en/electro/electro.htm For information about energy and work: http://scienceworld.wolfram.com/physics/ (search for energy) 10 Energy- chemical cell V 3.0 © University of Nebraska 2002 Record your observations about the different combinations in the boxes. carbon copper aluminum lead iron zinc nickel carbon copper aluminum lead iron zinc nickel 11 Energy- chemical cell V 3.0 © University of Nebraska 2002 12 Energy- chemical cell V 3.0 © University of Nebraska 2002