Investigatory Project
In Requirement of Grade 9 BC Science
Title: Factors That Affect the Voltage of a Voltaic Cell
Presented by
Peter Ke & William Zhou
05/24/16
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Abstract
In May, we did some research on a voltaic cell, a kind of battery, and wanted
to find out what affects the voltage of the cell. We made a hypothesis which is the
more concentrated the electrolyte solution in a voltaic cell the more voltage it can
produce. But to do an experiment we need to make a voltaic cell, so we collected
materials like copper sulfate, zinc sulfate, copper and zinc stick and a voltmeter.
we made the voltaic cell in the right structure but the voltmeter didn’t show
anything. At first we thought it was because of the solutions or the metal sticks,
but after examining the voltmeter we found it broken. As a result, we bought a
new voltmeter that absolutely works and retried our voltaic cell. It turned out
that out cell can produce about 1.064 volts. Therefore, we can start comparing
the voltage of the cell after we change its concentration of electrolyte solution. As
we prepared another two beakers of copper sulfate and zin sulfate solutions with
about half of the concentration of the previous set, we found that the voltage
decreases to about half the 6.7 volts. Conforming other researches and
experiments online, we concluded that with the same gas pressure and
temperature, the higher the concentration of the electrolyte solution in a Voltaic
cell, the higher voltage it can pressurize.
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Introduction
Battery is what powers most of our devices nowadays, such as laptops,
remotes and phones. There are so many kinds of batteries with different
methods of producing energy or electricity.
This investigatory project attempts to observe a very classic type of battery
called Voltaic cell. We are going to create a Voltaic cell ourselves before
experimenting our hypothesis, therefore we prepared three kinds of electrolytes,
copper sulfate (CuSO4), zinc sulfate (ZnSO4) and potassium chloride (KCl) and a
natural jelly-like substance obtained from algae, along with equipment like
beakers, U-shaped tube, wires and a voltmeter which can measure voltage
around an electric circuit.
Our question is how the concentration of the electrolyte solution in a voltaic
cell can affect the voltage it produces. Our hypothesis is that the more
concentrated the solution is the more voltage it can pressurize. With this project,
we will be able two acknowledge the effects on a Voltaic cell’s voltage in different
environments.
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Table of Contents
Abstract………………………………………………………………………………………………………1
Introduction……………………………………………………………………………………………….2
Table of Contents………………………………………………………………………………………..3
Definition……………………………………………………………………………………………………4
Review of Related……………………………………………………………………………………….6
Methodology……………………………………………………………………………………………….7
Data and Results……………………………………………………………………………………….10
Sharp………………………………………………………………………………………………………..11
Recommendation……………………………………………………………………………………..12
Conclusion………………………………………………………………………………………………..13
Bibliography…………………………………………………………………………………………….14
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Definition
1. Concentration: amount of solute divided by amount of solvent.
2. Agar: a natural, jelly-like substance obtained from algae.
3. Circuit: a complete electrical network with a closed loop giving a return path
for current.
4. Voltmeter: an instrument used for measuring electrical potential difference
(voltage) between two points in an electric circuit.
5. Moore per mL: Moore, a unit only used for pure substances’ mass that equals
to the relative molecular mass of the substance, e.g. 1 Moore of O2 = 32 grams
of O2. Moore per mL is a unit that describes how much mass of a solute in a
mL of solvent.
6. To dissolve: to add a solute to a solvent to make a solution.
7. Distilled water: H2O.
8. Electrode: an electrical conductor used to make contact with a nonmetallic
part of a circuit.
9. Electrolyte: liquid or gel that contains ions.
10. Solvent: a substance that dissolves a solute, resulting in a solution.
11. Solute: a substance dissolved in another substance, known as a solvent.
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12. Solubility: property of a solid, liquid or gaseous chemical substance in a solid,
liquid or gaseous solvent.
13. Saturated: the amount of solute in a solvent has reached its maximum
solubility.
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Review of Related
Previous studies of factors that affect the voltage of a voltaic cell are found on
websites. An account on www.socratic.org included an equation after
experiments and stated that temperature of the voltaic cell determines the
voltage the cell can produce. Here is the source,
Ernest Z. "What Factors Affect Electrochemical Cells?." Socratic Org. Socratic
Org, 25 Sept. 2015. Web. 9 June 2016.
The person also suggested that gas pressure and concentration [1] of the
solution may change the voltage of the cell as well, based on other’s experiments.
So we found this in result,
Ajinkya
N.Https://answers.yahoo.com/question/index?qid=20070610231001AAbiQWx."
Yahoo Answers. Yahoo! Inc., 2007. Web. 9 June 2016.
This Yahoo account explained the effects from gas pressure after a physic
experiment of examining the equation of U=IR. She said that the amount of
oxygen in the atmosphere around a resistance can slightly change the
resistance’s ability to resist electrons. Because the amount of oxygen in the
atmosphere also affects the gas pressure, the gas pressure affects the voltage of a
voltaic cell relevantly. Our experiment wants to observe the effects from
concentration of the solution.
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Methodology
I.
Creating the Voltaic Cell
To create our cell, we collected copper sulfate (CuSO4), zinc sulfate (ZnSO4)
and potassium chloride (KCl) and agar
[2]
, zinc and copper sticks along with
equipment like beakers, U-shaped tube, wires and a voltmeter
measure voltage around an electric circuit [3].
[4]
which can
First, we cleaned the two 250mL beakers and added copper sulfate in one
beaker and zinc sulfate in the other, both at the amount of 1 Moore per mL [5]. We
dissolved [6] the two chemicals in 200mL of distilled water [7]. We kept stirring the
solution to make sure the chemicals were fully dissolved.
Second, we prepared another beaker and inside added 100mL of distilled
water and 2 grams of agar. At about 98 degrees Celsius the agar began to melt
and the water in the beaker dissolved 5 grams of potassium chloride. After fully
dissolved, we cooled down the mixture of KCl and molten agar and poured it
carefully inside the cleaned U-shaped tube before it went back to room
temperature.
Third, we polished the zinc and copper sticks with an abrasive paper, tied
wires to each, and dipped the zinc stick into the zinc sulfate solution and the
copper stick into the copper sulfate solution.
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Fourth, we connected the wire that leads to the zinc stick to the negative
electrode [8] of our voltmeter, and the wire that leads to the copper stick to the
positive electrode. Then we turned on the voltmeter and it was showing no
voltage.
Fifth, we put each terminal of the U-shaped tube into each beaker of chemical
solutions, the voltmeter appears a number describing the voltage in the closed
circuit. It showed that the voltage in the circuit equals 1.064 volts.
Brief Timeline of Procedure
a) Dissolve 1 Moore/mL of CuSO4 and ZnSO4 in 200mL of distilled
water respectively.
b) Melt 2 grams of agar and dissolve 5 grams of KCl in 100mL of
distilled water before cooling it down to room temperature and into
the U-shaped tube.
c) Dip zinc and copper into zinc sulfate and copper sulfate solution,
connect the zinc stick to the negative electrode and the copper stick
to the positive electrode.
d) Dip the two terminals of the salt bridge into each solution and turn
on the voltmeter. The voltmeter indicated that the circuit has 1.064
II.
volts.
Reducing Concentration and Comparing
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We redid the procedure above and changed some of the numbers in order to
prepare solutions less concentrated. We dissolved 0.5 Moore/mL of zinc sulfate
and copper sulfate in two beakers of 200mL of distilled water. Else than this
reduce, other equipment and chemicals remained unchanged. The voltmeter
appeared about 0.67 volts this time, which is approximately 0.394 volts less than
the previous set.
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Data and Results
Temperature of the environment: room temperature
Gas pressure: approx. 100.94kPa (0.9962003 atm)
Location: N390527E1170437
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Sharp
One of the drawbacks of our experiment that we realized is that we failed to
ensure that the experiment was performed at a constant room temperature,
because the temperature of the room was probably affected by the air
conditioner because it was sometimes on. According to our researches online, the
changes of temperature would slightly affect the voltage although we don’t know
whether the slight changes are necessary to be observed or are not serious
enough and should better be ignored.
Another problem is that we had a failed experiment before and spent time
finding the reason. During about half a month’s searching for problems, we forgot
to look after the two solutions, so we are not sure if anything happened to them.
We conjectured that the voltage we measured was lower than it should be in our
Voltaic cell if we succeeded the first time, because we dipped the zinc and copper
stick in the solutions so long that a great number of metal atoms had become
ions, leaving the cell less power or resources to pressurize electric current.
However, we didn’t plan to do further observation because we’re about to take a
big exam and start our holiday.
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Recommendation
We have concluded that with the same gas pressure and temperature, the
higher the concentration of the electrolyte [9] solution in a Voltaic cell, the higher
voltage it can pressurize. However, concentration of a solution has nothing to do
with the amount of water or amount of electrolyte, but how congested the
electrolyte is in the solvent [10]. Since a solute [11] has its solubility [12] at a certain
temperature and the solution will be saturated [13] if the amount of solute reaches
its solubility, there must be a highest concentration of the solution at room
temperature (the temperature at which batteries mostly work). As a result, there
must be a highest voltage the Voltaic cell can produce at that temperature. We
suggest you to do further experiments to find out what that highest voltage is at
room temperature.
Also, we didn’t test if gas pressure and temperature affect the voltage of a
Voltaic cell because we didn’t have much time and equipment to perform an
experiment. Therefore, the observation on these two factors is recommended.
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Conclusion
We started the project around the beginning of May, 2016 if planning and
preparation are included, and we had our first experiment on May 26th which
didn’t work and we thought the problem was with the salt bridge. we spent a
weekend making a salt bridge and performed the experiment for the second time
on May 30th. This time our Voltaic cell didn’t seem to work, either. Then we tried
to test the functions of each equipment and noticed that the voltmeter is broken.
So we bought a new voltmeter that works and our cell finally works on the
morning of June 3rd after we arrived at school. The voltmeter showed 1.064 volts
in the circuit and a week later, we made a video about our Voltaic cell. From our
three experiments, we are able to announce out conclusion, (I can’t believe I’m
saying this for the third time in my report!!!) with the same gas pressure and
temperature, the higher the concentration of the electrolyte solution in a Voltaic
cell, the higher voltage it can pressurize.
Apart from our scientific discovery, we also experienced something new.
Imagine that if we failed the first two times of our experiment and decided to give
up, we might never find out the true voltage of our cell, or even acknowledge that
we had created a Voltaic cell, which is officially the first and only battery
homemade at our school until today. We are so excited and honored to achieve
this in our school, and are so grateful that we didn’t give up after two times of
failure.
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Bibliography
1. Ernest Z. "What Factors Affect Electrochemical Cells?." Socratic Org. Socratic
Org, 25 Sept. 2015. Web. 9 June 2016.
2. Ajinkya N. Https://answers.yahoo.com/question/index?qid=20070610231001
AAbiQWx." Yahoo Answers. Yahoo! Inc., 2007. Web. 9 June 2016.
3. 京昆宁 "原电池" 电子元件网. 电子元件网, 29 Nov. 2012. Web. 12 June 12
2016.
4. Peter’s and William’s parents for providing chemicals and metal sticks.
5. Leo L.’s managing the key to the locker in which we keep the chemical sets.
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