# Coca-Cola Mystery

## Hypothesis:

I think that when I put the pennies in the cola the copper will come off. The chemicals in the cola will make the copper turn into air bubbles, and the pennies will be silver. The pennies will be smooth with no pictures on them.

## Research

The history of the penny

From 1783 to 1837 the penny was pure copper

From 1837 to 1857 the penny was made of bronze (95% copper and 5% tin and zinc)

From 1857 to 1863 the penny was 88% copper and 12% nickel, giving the penny a white appearance

From 1864 to 1962 the penny was back to bronze

In 1943, the penny was made of zinc-coated steel, because of the war effort needing the copper

In 1962, the penny was made of 95% copper and 5% zinc

In 1982, the penny's makeup changed to 97.5% zinc and 2.5% copper

All this information is from the US MInt's website

The reason that the penny was changed to mostly zinc is because the value of a penny sank until the copper contained in it was worth more than a penny.

This information came from a book called The Elements, by Theodore Gray

Coca-cola is acidic because the carbon dioxide gas used to preserve it dissolves in the solution and forms carbonic acid. The pH ranges from 2.5 to 4.2.

This information comes from ask.com "why is coke acidic?"

## Procedure

1 Pick out 5 different aged pennies

2 Put them in order by year

3 Put the pennies in a container

4 Put 10 oz of Coca-cola in the container

5 Wait for 2 hours

6 Check the pennies for changes

7 Write down what you see

8 Repeat steps 5 through 7 for 24 hours

9 After 24 hours take pennies out of cola

10 Write down final appearance of pennies

## Observation

9:30 am

all coins went in the cola

11:30 am

1973-no change

1977-no change

1978-no change

2000-no change

2013-no change

1:30 pm

1973-color has change penny looks older

1977-color changed looks darker

1978-no change

2000-no change

2013-no change

3:30 pm

1973-color is darker

1977-color is darker

1978-no change

2000-no change

2013-no change

5:30 pm

1973-color is darker

1977-no change

1978-no change

2000-no change

2013-no change

7:30 pm

1973-color is lighter

1977-color is lighter

1978-color is dark looks dirty

2000-no change

2013-no change

9:30 pm

1973-no change

1977-color is lighter

1978-still dark, looks rusty

2000-no change

2013-no change

11:30 pm

1973-color is lighter but penny is dull looking

1977-color is lighter

1978-penny is dirty and rusty looking

2000-penny is darker

2013-no change

1:30-5:30 sleeping

7:30 am

1973-lighter

1977-penny is lighter

1978-penny is rusty

2000-lighter

2013-no changes

9:30 am

Remove pennies from cola

1973-looks cleaner not shiny

1977-looks cleaner not shiny

1978-dark rusty looking

2000-looks clean not shiny

2013-no changes

## Results/Conclusions

The 1973 penny is still copper color its cleaner but not shiny.

The 1977 penny is still copper color its cleaner but not shiny.

The 1978 penny is rusty looking I can still see that it is copper color.

The 2000 penny is brighter but not shiny.

The 2013 penny has not changed.

The coca-cola did not melt the copper off the pennies. The cola made the dark colored pennies cleaner looking. The pennies are still copper color and I can still see the pictures.