UTF-8voltaic cellSimple Model for a Voltaic Cell
Your name:________________. Save this as a file called "Your Name Voltaic Cell 1"
This is a simple but incomplete model for a Voltaic Cell. Your challenge is to understand how it works and
come up with ways to make it work better. The purpose of a Voltaic Cell is to store energy and to provide it
in the form of electric current. A Voltaic Cell consists of two materials which can accept or lose electrons. They
are attached to or interact with two solid objects called the "electrodes." In our model, the electrodes are on
the right and left, connected by an external wire that can be connected to a device that uses electric current
to operate.
Before running the simulation write down some information:
How many atoms comprise the "electrode" on the left? The "wire"? The "electrode" on the right?
{ In electrode on left: __________ In wire:____________ In electrode on right?
}
Which electrode is reduced and which is oxidized? Count the number of "electrons" before the simulation
starts. Also check the charges on all the atoms:
{ Number of "electrons" in:
Electrode on left: __________ In wire:____________ In electrode on right:__________
Electrical charges of atoms:
On left electrode:___________ On wire: ____________ in right electrode: ____________
}
As you run the simulation, watch the Potential Energy (most of which is Electrical Potential Energy).
Write down the PE at the Start and at the end of the simulation:
{ Average PE at start: _____________ Average PE at end:______________
Did it increase or decrease?___________
}
Now run the simulation for at least 200 ps (200,000 fs).
Where are the "electrons" now? Count them:
{Number of electrons on:
Electrode on left: __________ In wire:____________ In electrode on right:__________
}
Did the "voltaic cell" produce a net transfer of electrons, in other words was there an "electric current"?
Explain why the electrons tend to move to the right side and more of them remain on the right side than on the
left side. Hint: What concept should you refer to in making your explanation?
{The concept I will use in making my explanation:
My explanation for why the electrons tend to accumulate in greater numbers on the right side:
}
Stop the simulation and move all the extra electrons to the right side, leaving one for each atom in the "wire."
Run the simulation again. Do some electrons move back to the electrode on the left? Explain why:
{The concept I will use in making my explanation:
My explanation for why some electrons return to the left side when the simulation starts with all
the electrons on the right, but still most remain on the right:
}
How can you "recharge" your cell, to return the electrons to the left side? Explain what you did and do it!
{The concept I will use in making my explanation:
My explanation for why some electrons return to the left side when the simulation starts with all
the electrons on the right, but still most remain on the right:
}
The problem with our Voltaic cell is that it becomes "polarized." When all the easily oxidized atoms lose
an electron they attract the electrons back. One problem is that we do not have a complete circuit.
Redesign the Voltaic cell and introduce anything else you think is needed to make a complete circuit so as
to allow the cell to operate until ALL the electrons get transfered from the easily oxidized to the easily
reduced material. Explain what you did and why you did it. You can change the size, add new barriers, add
additional ions of various sizes. Just keep the same size, charge and number of the atoms in the right and left electrodes.
You will know you have succeeded if all the "electrons" are transferred from the left to the right electrodes.
Something you might find useful is using barriers that only allow certain things to go through them.
{How I designed an improved Voltaic cell with a complete circuit :
}
If you need a review of how Voltaic cells work (also called "Galvanic cells") -- check out the the explanation of a simple zinc/copper cell
first and then a more sophisticated, modern Cadmium/Nickel cell on this site:
http://www.wwnorton.com/college/Chemistry/gilbert/tutorials/ch17.htm
Here is a tutorial on zinc/copper cells:
http://www.mhhe.com/physsci/chemistry/essentialchemistry/flash/galvan5.swf
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