Power to Go SCIENCE TOPICS PROCESS SKILLS VOCABULARY

Transcription

1 SIDE DISPLAY Power to Go Visitors observe an electrochemical cell constructed from a small jar containing zinc and copper strips immersed in separate solutions. The strips are connected to a motor that turns a small fan. OBJECTIVES: Visitors observe that chemical reactions can produce electricity. They infer that electrically charged particles exist in solutions and they make a connection between chemistry and common batteries. SCIENCE TOPICS PROCESS SKILLS VOCABULARY Electrochemistry Electricity Chemical Reaction Properties of Ions Observing Inferring Atom Chemical Reaction Gas Electrochemical Electron Ion Solution Unit 2 Chemical Reactions U2.85

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3 Power to Go Watch a chemical reaction make electricity. Please explore this display with your eyes only. How does the fan turn? The fan is connected to a small motor that is powered by electricity from a chemical reaction. What gives it the power to go? The zinc reacts with the sodium sulfate solution, releasing free electrons. These electrons move through the wire and the fan motor to the copper rod. Ions in both solutions complete the electrical circuit. The chemical reactions produce enough electricity to power the fan motor. What else is inside the jar? If you look very carefully, you may see tiny bubbles of hydrogen (H 2 ) gas coming off the zinc OMSI

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5 Side Display: Power to Go Operating Guide See Materials Prep for more details (with amounts to have on hand) Small baby-food jars (or small beakers) (keep five on hand) One-holed stoppers (size 7) (keep five on hand) Zinc foil strips 6 in. long (15 cm) (keep several on hand) Copper foil strips 6 in. long (15 cm) (keep several on hand) One spool of dialysis tubing Wire leads with alligator clips One small motor/fan, similar to those in toy construction sets One clamp and ringstand 1.0M CuSO 4 (copper sulfate) solution (500 ml reserve) 0.5M Na 2 SO 4 (sodium sulfate) solution (500 ml reserve) Steel wool (keep three to four pieces on hand) Plastic pipette Setup/Takedown Procedures Resealable plastic sandwich bags (keep four boxes on hand) Clamp the motor to the ring stand so that the fan rotates freely. Cut the metal strips to fit the jars, allowing 1 in. extra (total length approximately 6 in.). Store the metal in resealable plastic sandwich bags labeled Copper and Zinc, respectively. Cut the dialysis tubing (6 in.) and hold under water until flexible. Tie a knot in the bottom to make a bag. Store in labeled reseal able plastic sandwich bag. Hold a dialysis bag under water until it s flexible. Place the dialysis bag in a jar. Use the pipette to partially fill bag with CuSO 4 (copper sulfate) solution. Insert a shiny copper metal strip and fill the rest of the bag with CuSO 4 solution. Insert the clean zinc strip into the jar. Fill the jar with Na 2 SO 4 (sodium sulfate) solution. Insert a stopper so the metal strips and dialysis bag are held in place. Connect the metal strips to the motor using wire leads with alligator clips. Unit 1 The Nature of Matter U1.87

6 Side Display: Power to Go Operating Guide Remove the metal strips; clean and store them in resealable plastic sandwich bags. Discard all solutions in sink. Rinse the dialysis tubing and place it into a resealable plastic sandwich bag. Rinse the jars and stoppers. Cu (copper) is reduced at the cathode (-); Zn (zinc) is oxidized at the anode (+) (see picture). Zinc is an electron source. The length of the zinc strips is important; it should be the same as the length of the copper strips. Left over short strips that are in good condition can be used for Build A Battery. Each baby-food jar produces approximately 1.5+ volts. Results will vary with condition of metals and solution concentration. One baby-food jar will run the small motor for one hour or more. Stoppers need holes to let out H 2 (hydrogen) gas and O 2 (oxygen) gas from electrolysis. Six baby-food jars may be connected together in series to run a small 9-volt radio or toy with few movements. This uses the same principle as the Build A Battery experiment, except there is more voltage in this display. Electrolysis is present in this display. Compare different types of batteries: Battery type Used in cathode (-) anode (+) dry cell flashlight graphite rod with MnO 2 (manganese dioxide), NH 4CI (ammonium chloride) C paste Zn (zinc) cup alkaline watch MnO 2 (manganese dioxide) + conductor Zn (zinc) powder +KOH lead car PbO 2 (lead dioxide) in H 2SO 4 (sulfuric acid) Pb (lead) in H 2SO 4 (sulfuric acid) U2.88 Unit 2 Chemical Reactions

7 Side Display: Power to Go Operating Guide CuSO 4 (copper sulfate) and Na 2 SO 4 (sodium sulfate) are hazardous substances; follow handling and disposal instructions in Materials Prep. Consult Material Safety Data Sheets (MSDS) for additional information. To prepare 1.0M CuSO 4 (copper sulfate) solution: Wear protective eyewear, chemical safety gloves, and lab coat. Dissolve 125 g CuSO 4 5H 2 O in 500 ml dh 2 O (deionized water). To prepare 0.5 Na 2 SO 4 (sodium sulfate) solution: Wear protective eyewear, chemical safety gloves, and lab coat. Dissolve 35.5 g Na 2 SO 4 in 500 ml dh 2 O (deionized water). Unit 1 The Nature of Matter U1.89

8 U2.90 Unit 2 Chemical Reactions