Penny for your Thoughts


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Experiment Category: 


Copper-plate metal objects by placing them in a jar with pennies and vinegar.

What You Need: 

  • One small jar with lid
  • Vinegar
  • One tablespoon of salt
  • 15 Pennies (or other copper items, e.g. copper wire)
  • A steel paper clip (or other small iron-containing object, e.g. nail)

To Do and Observe: 

1. Put 15 pennies into a jar. What do the pennies look like?

2. Add 1 level tablespoon of salt to the jar.

3. Add about ¼ cup vinegar (acetic acid) - add more if you need to cover the pennies.

4. Close the lid tightly!

5. Swirl the pennies in the jar 15 times. Try to leave the pennies showing on top of the salt when you are done swirling.

6. Open the jar and add a paper clip (or nail). What does the paper clip (or nail) look like?

7. Put the lid back on tightly.

8. Look at the jar after about 15 minutes. How do the pennies look? What does the paper clip (or nail) look like?

9. Look at the pennies every 30 to 60 minutes. What does the paper clip (or nail) look like now?

What's Going On: 

Vinegar is an acid (acetic acid). Acids are reactive and corrosive. In this activity the acid, together with the abrasive salt, cleaned the pennies. Some copper from the surface of the pennies was loosened along with the dirt. The copper dissolved into the vinegar as copper ions (electrically charged copper atoms). When the acid (vinegar) reacted with the iron in the nail or paper clip, the copper ions in the vinegar solution \"traded places\" with the iron. The copper was deposited on the nail or paper clip, and iron ions were released into the solution. In the end, the paper clip (or nail) was coated with copper. If the jars sit for 1 to 5 days, grayish clumps may be visible in the solution. This is the iron that came off the paper clip (or nail). Metals form a class of chemicals with similar physical properties. They are solid at room temperature, except for mercury. Most are hard and shiny. They can be molded into different shapes. They are strong, because they are made of tiny crystals held together by strong metallic bonds. Metals also have similar chemical properties. They all form positively charged ions in chemical reactions. They carry heat and electricity, because their electrons are able to move around easily. Copper metal is a particularly good conductor of electricity. That is why copper is often used in electrical wiring.

Parent/Teacher Tips: 

Electroplate! You\’ll need two wire leads, a small jar, salt, ½ teaspoon measuring spoon, a battery (a 6-volt lantern battery works well), a metal object to be plated, a copper object (coiled wire, penny or strip). Connect lead #1 (an insulated wire with alligator clips at each end) to the negative terminal of a battery. Attach the other end of lead #1 to a metal object that you wish to plate, e.g. a key or a nickel. Connect lead #2 to the positive terminal of your battery. Attach the other end of lead #2 to a clean, bare coil of copper wire, a clean penny, or a clean strip of copper. Fill a small jar with water. Add ½ teaspoon of salt and stir the solution. Place the metal object to be plated and the copper object attached to lead #2 in the water. Do not let the two metal objects touch! Observe the solutions while the electroplating is taking place. The metal object attached to the negative terminal of the battery should become plated with metal from the object (copper) at the positive terminal of the battery. You should be able to see other evidence of chemical reactions, such as tiny gas bubbles. Carefully rinse the solutions down the drain with ample water when you’re done.