Place your pre-1982 copper penny in an watch glass and heat with a mixture that first turns it silver, then suddenly turns it “gold” when the penny is then heated on a hot plate.
Caution: Wear safety goggles and gloves and do the reaction in the fume hood with the sash down. Note step 10: special disposal.
Place approximately 2 g of zinc in an watch glass.
Add enough NaOH solution to cover the zinc and fill the dish about one-third.
Place the dish on a hot plate and heat until the solution is near boiling.
Prepare a copper penny (pre-1982) by cleaning it thoroughly with a light abrasive (steel wool pads work well).
Using crucible tongs or tweezers, place the cleaned penny in the mixture in the dish.
Leave the penny in the dish for 3-4 min. You will be able to tell when the silver coating is complete.
Remove the penny, rinse it, and blot dry with paper towels. (Do not rub!) Remove particles of zinc.
Using crucible tongs or tweezers, place the coated penny on the hot plate. The gold color appears immediately.
When the gold color forms, remove the coin, rinse it, and dry it with paper towels.
Special disposal procedures: Do not discard the waste zinc in the trash container. When zinc dries, it forms a powder that may spontaneously ignite. Rinse the NaOH-zinc mixture several times with water. Then add the solid to a beaker that contains 200 mL of 1 M
. When all of the solid dissolves, flush the zinc sulfate solution down the drain.
The golden penny experiment.
Your TA will set this up for you by putting 8 g of 30 mesh zinc in the bottom of a 400-mL beaker. It is best to weigh-out the zinc in a watch glass and pour the zinc into a tilted 400-mL beaker so as to keep the zinc on one side of the beaker. Use a spatula and tilt and tap the beaker on the bench top in order to get all the granular zinc to cover about half the bottom of the beaker (one-half not covered: see Figure 5). Carefully pour 200 mL of 1 NaOH down the side of the beaker, being careful not to disturb the distribution of zinc. Use a stirring rod or spatula to clear any remaining granules so that half of the beaker bottom is completely free of zinc granules. Place the beaker on a hot plate in the fume hood and turn the hot plate to medium heat. The solution should be heated to about 80-90
; if it is heated to boiling the distribution of zinc granules will be disturbed. Continually monitor and check the temperature to keep it in this range.
20-25min.
While waiting for the solution to heat, buff six copper pennies with steel wool until they are shiny. Wash them with deionized water and dry. Solder 10-cm lengths of 20-gauge copper wire to two of the pennies, overlapping the wire and penny about 2 to 3 mm from the edge. Solder the free end of one of the copper wires to a 5 x 100 mm strip of zinc metal, as shown in Figure 5. Clean any rosin off the soldered joints with steel wool, and rinse with water.
Figure 2
When soldering, place the penny on a ceramic fiber square, with the end of a copper wire overlapping the penny 2-3 mm. Ask a partner to apply pressure to the wire to hold it in place while you are soldering the joint -use a rubber stopper as before to do this.
Four arrangements of copper pennies in the golden penny experiment.
Questions & Answers
A golfer on a fairway is 70 m away from the green, which sits below the level of the fairway by 20 m. If the golfer hits the ball at an angle of 40° with an initial speed of 20 m/s, how close to the green does she come?
A mouse of mass 200 g falls 100 m down a vertical mine shaft and lands at the bottom with a speed of 8.0 m/s. During its fall, how much work is done on the mouse by air resistance
Chemistry is a branch of science that deals with the study of matter,it composition,it structure and the changes it undergoes
Adjei
please, I'm a physics student and I need help in physics
Adjanou
chemistry could also be understood like the sexual attraction/repulsion of the male and female elements. the reaction varies depending on the energy differences of each given gender. + masculine -female.
Pedro
A ball is thrown straight up.it passes a 2.0m high window 7.50 m off the ground on it path up and takes 1.30 s to go past the window.what was the ball initial velocity
2. A sled plus passenger with total mass 50 kg is pulled 20 m across the snow (0.20) at constant velocity by a force directed 25° above the horizontal. Calculate (a) the work of the applied force, (b) the work of friction, and (c) the total work.
you have been hired as an espert witness in a court case involving an automobile accident. the accident involved car A of mass 1500kg which crashed into stationary car B of mass 1100kg. the driver of car A applied his brakes 15 m before he skidded and crashed into car B. after the collision, car A s
can someone explain to me, an ignorant high school student, why the trend of the graph doesn't follow the fact that the higher frequency a sound wave is, the more power it is, hence, making me think the phons output would follow this general trend?
Nevermind i just realied that the graph is the phons output for a person with normal hearing and not just the phons output of the sound waves power, I should read the entire thing next time
Joseph
Follow up question, does anyone know where I can find a graph that accuretly depicts the actual relative "power" output of sound over its frequency instead of just humans hearing
Joseph
"Generation of electrical energy from sound energy | IEEE Conference Publication | IEEE Xplore" ***ieeexplore.ieee.org/document/7150687?reload=true
A string is 3.00 m long with a mass of 5.00 g. The string is held taut with a tension of 500.00 N applied to the string. A pulse is sent down the string. How long does it take the pulse to travel the 3.00 m of the string?
