Copper Caper
Materials:
o
Dull pennies
o
¼ cup white vinegar
o
1 tsp salt
o
A clear bowl
o
2 steel nails
o
A clean steel screw or bolt
Experiment:
1.
Put
the salt and vinegar in the bowl. Stir
until the salt dissolves.
2.
Dip
one penny halfway into the liquid. Hold
it there for about 10 seconds, then pull it out. What do you see? 
3.
Dump
all the pennies into the liquid. You can
watch them change for the first few seconds. After the you won’t see anything
change.
4.
After
five minutes, take half of the pennies out of the liquid. Put them on a paper towel to dry.
5.
Take
the rest of the pennies out of the liquid.
Rinse them really well under running water, and put them on a paper
towel to dry. Write “rinsed” on the
second paper towel. 
6.
Put
a nail and a screw into the liquid. Lean
another nail against the side of the bowl so that only part of it is in the
liquid.
7.
After 10 minutes, take a look at the
nails. Are they a different color than
they were before? Is the leaning nail 2
different colors? If not, leave the
nails in the bowl and check on them again in an hour or so.
8.
What’s
happening to the screw? You may see lots of bubbles coming from the threads. Is the screw changing color? Leave it in the liquid for a while and see
what happens.
9.
After
about an hour, look at the pennies on the paper towels. What's happened to the one's that you
rinsed? What’s happened to the others?
What color is the paper towel under the unrised pennies? 
Explanation:
Why did the pennies look
dirty before I put them in the vinegar?
Everything around you is made up of tiny particles
called atoms. Some things are made up of
just one kind of atom. The copper of a
penny, for example, is made up of copper atoms.
But sometimes atoms of different kinds join to make molecules. Copper atoms can combine with oxygen atoms
from the air to make a molecule called copper oxide. The pennies looked dull
and dirty because they were covered with copper oxide.
Why did the vinegar and salt
clean the pennies?
Copper oxide dissolves in a
mixture of weak acid and table salt- and vinegar is an acid. You could also clean your pennies with salt
and lemon juice or orange juice, because those juices are acids, too.
Why did the unrinsed pennies
turn blue- green?
When the vinegar and salt dissolve the copper-oxide layer, they
make it easier for the copper atoms to join oxygen from the air and chlorine
from the salt to make a blue-green compound called malachite.