Old Coins Turn To Gold

Research Question: How does zinc affect the colour of the coin?

Hypothesis: İf coin gets boil zinc will change the color of the coin.

Variables:Independent Variable: Dependent Variable: The color of the coinConstant Variable: Type of coin, the heat, environment

Materials:Zn fillings/ 3M NaOH solution/ Copper penny/ tongs/ hot plate/ 100 ml beaker/ 250 ml beaker/ water/ spoon

Procedure:

Part I:

1. Half fill a 250 ml beaker with tap water2. Place half a spoon of zinc fillings in a 100 ml beaker 3. Add 20 ml of 3 M NaOH to the beaker4. Place the beaker on a hot plate. (make sure the liquid does

not boil)5. Carefully place the penny to the beaker6. After the penny is coated remove it from the beaker.7. Put the  penny into the 250 ml beaker and leave it to cool

for about 30 seconds8. After removing the penny refill the beaker with cold

water.

Data:

Penny is coated

Penny is heated

Penny is left to cool

Penny is taken out of the beaker

Turning coin intosilver

No change No change Penny starts to change color

The color of the penny is silver

Penny is being heated

The heating procedure is done

The penny is left to cool

The color starts to change

The color of the penny is now gold

The color of the penny looks like gold

Conclusion:

My hypothesis is right. Zinc has changed the colour of the penny. The penny is gold. I don’t think that it is a real gold just the colour is like gold. Zink has changed the colour of the penny because the zinc metal dissolves and releases electrons that go into the copper and give it a negative charge. The zinc ions in solution now redeposit form a thin layer of zinc metal giving the coin a gold colour.

ImprovementsAs a group we were working very well. Everybody was working on something. Yet we didn’t have enough time to finish it. İf we could have another experiment we should be organized.

References

Instructables. Autodesk, Inc. 08 Oct 2015http://www.instructables.com/id/Turn-Copper-Pennies-into-Silver-and-Gold-Chemistr/

Nuffield foundation. 28 December 2011. Nuffield Foundation. 08 Oct 2015http://www.nuffieldfoundation.org/practical-chemistry/turning-copper-coins-silver-and-gold