THE ACIDS: Striking it Rich Lab

Questions:

1.
a.Compare the color of the three coins- untreated(the control), heated in the zinc chloride solution only, and heated in the zinc chloride solution and then on a hot plate.
b. Do the treated coins appear to be composed of metals other than copper? If so, explain.

a. The untreated control coin is copper-colored and shiny, while the coin heated in the zinc chloride solution only has silver blotches. The coin heated after being in the zinc chloride solution is now gold where the silver blotches were.
b. Because the coins formed alloys that resembled different forms of brass, we know the coins are also made of zinc.

2. If someone claimed that a precious metal was produced in this investigation, how would you decide whether the claim was correct?

Due to the law of conservation of matter, matter is neither created or destroyed. A coin composed of copper and zinc could not react to produce a prescious metal, but simply combine to form an alloy, brass.

3. Identify at least two practical uses for metallic changes similar to those you observed in this investigation.

Alloys like brass, bronze, and steel are stronger than the elements that compose them. These alloys are widely used for every day items.

4.
a. What happened to the copper atoms originally present in the treated pennies? Provide evidence to support your conclusion.
b. Do you think the treated pennies could be converted back to ordinary coins? If so, what procedures would you use to accomplish this?

a. The silver coin that had been treated with only the gently bubbling zinc chloride solution formed a less-combined alloy of copper and zinc, brass, than the gold coin that had been treated with the gently bubbling zinc solution and the hot plate. The atoms of copper and zinc combined in different proportions with each procedure.
b. We don’t believe the treated pennies could be converted back to ordinary coins, at least not in our classroom.