Task 1 - Building a Wet Cell

Transcription

1 The following instructional plan is part of a GaDOE collection of Unit Frameworks, Performance Tasks, examples of Student Work, and Teacher Commentary. Many more GaDOE approved instructional plans are available by using the Search Standards feature located on GeorgiaStandards.Org. Task 1 - Building a Wet Cell Standards (Content and Characteristics): S8P5. Students will recognize characteristics of gravity, electricity, and magnetism as major kinds of forces acting in nature. b. Demonstrate the advantages and disadvantages of series and parallel circuits and how they transfer energy. c. Investigate and explain that electric currents and magnets can exert force on each other. S8P2. Students will be familiar with the forms and transformations of energy. a. Explain energy transformation in terms of the Law of Conservation of Energy. b. Explain the relationship between potential and kinetic energy. c. Compare and contrast the different forms of energy (heat, light, electricity, mechanical motion, sound) and their characteristics. S8CS2. Students will use standard safety practices for all classroom laboratory and field investigations. a. Follow correct procedures for use of scientific apparatus. b. Demonstrate appropriate techniques in all laboratory situations. c. Follow correct protocol for identifying and reporting safety problems and violations. S8CS4. Students will use tools and instruments for observing, measuring, and manipulating equipment and materials in scientific activities utilizing safe laboratory procedures. a. Use appropriate technology to store and retrieve scientific information in topical, alphabetical, numerical, and keyword files, and create simple files. b. Use appropriate tools and units for measuring objects and/or substances. c. Learn and use standard safety practices when conducting scientific investigations. S8CS5. Students will use the ideas of system, model, change, and scale in exploring scientific and technological matters. a. Observe and explain how parts can be related to other parts in a system such as the role of simple machines in complex machines. b. Understand that different models (such as physical replicas, pictures, and analogies) can be used to represent the same thing. S8CS6. Students will communicate scientific ideas and activities clearly. (a,b,c) a. Write clear, step-by-step instructions for conducting scientific investigations, operating a piece of equipment, or following a procedure. b. Write for scientific purposes incorporating information from a circle, bar, or line graph, data tables, diagrams, and symbols. c. Organize scientific information in appropriate tables, charts, and graphs, and identify relationships they reveal. JULY 2008 Page 1 of 5

2 Enduring Understandings: Electricity is a general term used to refer to the presence and/or flow of electrical charges. It is usually associated with the movement or position of those charges. A wet cell or dry cell can be used to produce electricity through a chemical reaction. Insulators are poor conductors and resist charge movement while conductors are poor insulators and tend to allow charges to easily move. Closed circuits allow current flow while open circuits do not have an unbroken path for current movement. Essential Questions: How is electricity produced and used? How are insulators and conductors used in the movement of charges? How is static electricity different from regular electricity? JULY 2008 Page 2 of 5

3 ADMINISTRATION PROCEDURES Outcome / Performance Expectations: General Teacher Instructions: Students will build a wet cell that creates about 1 volt of potential difference. There is also the possibility of connecting several cells together into a battery and increasing the voltage. Students will clip a strip of zinc to one side of beaker (inside) and a strip of copper to the other side using alligator clips. Begin by using a 250 ml beaker and filling with about 200 ml of water. Using alligator clips and wire, connect the zinc and copper strips to different leads of a multimeter or voltmeter to detect a potential difference (voltage). Replace the water with grape juice then lemon juice, and then vinegar and record the variations in voltage. Students can try other acidic solutions to see if they increase the voltage. Also, the size of the metal strips can be altered to check for difference. This cell will not produce enough voltage to light a bulb. However, if you hook a small digital clock to it, it should produce enough voltage to make the clock work. Also, a small Light emitting diode (LED) can potentially function on this level of voltage. The voltage can also be increased by connecting several cells in serried by connecting the zinc from one to the copper in the next. If enough cells are hooked together, a very small flashlight bulb may be lit. Substitute other metals such as iron nails, lead, and tin to see if results change. Materials Needed: Safety Precautions: Task with Student Directions: A simple voltmeter can be used to check the voltage. However, a digital multimeter would allow testing a much smaller voltage more accurately. There are many low cost multimeters available in common stores or auto parts stores. The following materials are needed: Per student or group: ml beaker, 1 strip zinc metal 1 strip copper metal 2 lengths of insulated wire preferably with alligator clip connectors 1 multimeter to detect voltage or a voltmeter several acidic solutions (grape juice, lemon juice, vinegar) Also for expansion: LED, small digital clock Glass breakage is always a possibility when using beakers. Be sure not to use concentrated acids. Obtain the following materials: ml beaker, 1 strip zinc metal 1 strip copper metal (and other metals your teacher provides) 2 lengths of insulated wire preferably with alligator clip connectors 1 multimeter to detect voltage or a voltmeter several acidic solutions (grape juice, lemon juice, vinegar) small LED digital clock JULY 2008 Page 3 of 5

4 Place a strip of zinc into the beaker and use an alligator clip connected to a wire to hold it in place against the side of the beaker as shown below. Place a strip of copper on the other side of the beaker using the same procedure. Copper strip Alligator clips holding metal to beaker Zinc strip Acidic solution beaker Voltmeter Or multitester Create a data table that shows each combination of metals and the resulting voltage from the cell as well as other observations you may make. If provided, attach a small LED or digital clock to your cell to see if you can actually power them with your cell. JULY 2008 Page 4 of 5

5 Resources: Homework / Extension: Attach your cell in series with other groups to see what results you get. To connect in series, connect the wire from your zinc to their copper and the wire from your copper to their zinc while their wires are still connected to a meter or bulb. You can also connect in parallel with the other groups cell by hooking your zinc to theirs and your copper to theirs and observe the results. How does this experiment relate to an actual battery you may purchase in the store? Describe how the energy was transformed. Have students hook LED s to the cells or small digital clocks. Have students research other devices that require small voltage that could be powered by these cells Have students experiment with larger pieces of metal and more solution volume to see if they can increase the current. JULY 2008 Page 5 of 5