LAB: WEt-Cell Battery - building a battery
Please fill the blanks for full credit.
DISCUSSION
words bank: chemical reaction, electrons,negative, oxydation-reduction, cathode, current, anode, voltage, electrodes, electrolyte.
A wet cell contains 2 plates called __________, made of different metals or metallic compounds, and a solution called an ________. Chemical reaction occur between the electrodes and the electrolytes. These reactions create a potential difference (or __________) across the 2 electrodes. If the 2 electrodes of a wet cell are connected by a conductor, a ________ will flow through the conductor from one electrode, called the ________ (positively charged) , to the other called the _______ (negatively charged). The current is therefore caused by a _________ ______________. The chemical reaction is an ___________ - ___________ reacion. One electrode (anode) gives its ________ to the __________. We say the cathode more less affinity for electrons than the _________.
Wet cells differ in their potential difference. THe potential difference of a wet cell depends on the materials that makes up the electrodes.
bank: affinities, smaller, cathode, voltage, positively, anode, electrons
REmember the electrostatic lab ? ebonite has more affinity for _________ than fur. And silk has more affinity for ________ than plastic. The same way for metals. Different metals have different ___________ for electrons. When two dissimilar metals (or metal compounds) are put in contact or connected through a conducting medium (electrolyte in our case or acid) there is a tendency for electrons to pass from the metal with the smaller affinity for electrons, which becomes __________ charged (the ______ ), to the metal with the greater affinity which becomes _________ charged (the ________). A _________ (or potential difference) between the metals will therefore build up
OBJECTIVES
In this experiment, you will
- construct a wet cell,
- measure the potential difference of a wet cell with a voltmeter, and
- observe how the potential difference of a cell depends on the electrode materials,
PROCEDURE
0) You have to be very careful when using the acid. Use goggle. Attach your hair. Don't rush. If you feel like arguing, fulling around, please LEAVE ! tolerance = 0
1) You should have 5 or 6 different metal strips. Observe them. The metals available are:
(use a periodic table if you don't know the symbols)
________ , ________, ___________, __________, ___________
2) For this 1st experience, get 2 strips made of the same metal. same strips. Place the 2 strips in the beaker. They should not touch. (see figure below)
3) Very carefully add 75ml of hydrochloric acid to the beaker.
4) Do you predict any difference of potential between the 2 metal ? ____________ why ? ________
(that is do you think one strip will become positively charge, ready to produce a current in a circuit )
Use the voltmeter to check your prediction. The BLACK plug is in COM and the RED one is in VmA. Turn the dial to 2000mV or 200mV. Try to detect the voltage across the strips. conclusion? ___________
5) Carefully remove the strips and rinse them. Dry them with a paper towel. Very CAREFULLY.
6) Now pick aluminium and another metal. Do the experiment again. Try to find the voltage across the electrodes. If you get a minus sign, flip the connection. The anode (+) is the one connected to the red wire. THe cathode (-) is the one connected to the black wire. The cathode has more affinity for ______ than the anode. you find voltage = potential difference = ____________mV = __________V (1 mV = 0.001V)
Can you find the current produced ? To find the current turn the dial to mA.
I = _____mA = _____A (1mA= 0.001A). REport your result in the table.
7)Carefully remove the strips. Observe them. Do you see any change ? Observe the solution any change?
8) REpeat steps 6 through 7, always using aluminium / other metal.
9) CArefully poor the electrolyte in the sink. rinse the sink and the beaker. dry the beaker.
10) Use water + salt as an electrolyte. (sodium chloride). Repeat the experiment with only the pair Aluminum/copper. Voltage = ___________mV = ____________V.
CONCLUSIONS
1) How of you know that a chemical reaction occurred in the wet cell after you added the acid ?
2) Which pair of electrodes produced the greater potential difference ? ____________________
Can you classify the paris according to their potential difference ?
Look at the table10 at the end of the lab. According to the table the pair potassium / Gold produce a potential difference (energy per coulomb) = 2.93 V + 1.50V = 4.43 V
This is only for a given temperature and given concentration of the reactants. But it gives you an idea of the potential you should get. Using this table10, fill the following table:
Did you get the classification right ? are you close ?
3) Bonus. Consider the oxidation-reduction reaction between zinc and copper. Now you know which one loses its electrons and which one gains elecrons. Can you write the 2 half-reactions?
hint: 2 electrons are exchanged between the 2 metals.
4) What electrolyte is better? the salt + water or the acid (1mol).
4) Explain the difference between an electric current and electric potential?
words bank: chemical reaction, electrons,negative, oxydation-reduction, cathode, current, anode, voltage, electrodes, electrolyte.
A wet cell contains 2 plates called __________, made of different metals or metallic compounds, and a solution called an ________. Chemical reaction occur between the electrodes and the electrolytes. These reactions create a potential difference (or __________) across the 2 electrodes. If the 2 electrodes of a wet cell are connected by a conductor, a ________ will flow through the conductor from one electrode, called the ________ (positively charged) , to the other called the _______ (negatively charged). The current is therefore caused by a _________ ______________. The chemical reaction is an ___________ - ___________ reacion. One electrode (anode) gives its ________ to the __________. We say the cathode more less affinity for electrons than the _________.
Wet cells differ in their potential difference. THe potential difference of a wet cell depends on the materials that makes up the electrodes.
bank: affinities, smaller, cathode, voltage, positively, anode, electrons
REmember the electrostatic lab ? ebonite has more affinity for _________ than fur. And silk has more affinity for ________ than plastic. The same way for metals. Different metals have different ___________ for electrons. When two dissimilar metals (or metal compounds) are put in contact or connected through a conducting medium (electrolyte in our case or acid) there is a tendency for electrons to pass from the metal with the smaller affinity for electrons, which becomes __________ charged (the ______ ), to the metal with the greater affinity which becomes _________ charged (the ________). A _________ (or potential difference) between the metals will therefore build up
OBJECTIVES
In this experiment, you will
- construct a wet cell,
- measure the potential difference of a wet cell with a voltmeter, and
- observe how the potential difference of a cell depends on the electrode materials,
PROCEDURE
0) You have to be very careful when using the acid. Use goggle. Attach your hair. Don't rush. If you feel like arguing, fulling around, please LEAVE ! tolerance = 0
1) You should have 5 or 6 different metal strips. Observe them. The metals available are:
(use a periodic table if you don't know the symbols)
________ , ________, ___________, __________, ___________
2) For this 1st experience, get 2 strips made of the same metal. same strips. Place the 2 strips in the beaker. They should not touch. (see figure below)
3) Very carefully add 75ml of hydrochloric acid to the beaker.
CAUTION HYDROCHLORIC ACID CAUSES BURNS.
RINSE ANY SPILLS IMMEDIATLY WITH WATER.
RINSE ANY SPILLS IMMEDIATLY WITH WATER.
4) Do you predict any difference of potential between the 2 metal ? ____________ why ? ________
(that is do you think one strip will become positively charge, ready to produce a current in a circuit )
Use the voltmeter to check your prediction. The BLACK plug is in COM and the RED one is in VmA. Turn the dial to 2000mV or 200mV. Try to detect the voltage across the strips. conclusion? ___________
5) Carefully remove the strips and rinse them. Dry them with a paper towel. Very CAREFULLY.
6) Now pick aluminium and another metal. Do the experiment again. Try to find the voltage across the electrodes. If you get a minus sign, flip the connection. The anode (+) is the one connected to the red wire. THe cathode (-) is the one connected to the black wire. The cathode has more affinity for ______ than the anode. you find voltage = potential difference = ____________mV = __________V (1 mV = 0.001V)
Can you find the current produced ? To find the current turn the dial to mA.
I = _____mA = _____A (1mA= 0.001A). REport your result in the table.
| electrode1= cahode = + |
electrode 2 = anode = - |
potential difference (mV) (voltage = energy per coulomb) | current (mA) |
7)Carefully remove the strips. Observe them. Do you see any change ? Observe the solution any change?
report your observations in the following table.
RINSE THEM. Dry them with a paper towel. Very CAREFULLY.| electrode pair | observations |
| _____ (+) and _______ (-) | |
8) REpeat steps 6 through 7, always using aluminium / other metal.
9) CArefully poor the electrolyte in the sink. rinse the sink and the beaker. dry the beaker.
10) Use water + salt as an electrolyte. (sodium chloride). Repeat the experiment with only the pair Aluminum/copper. Voltage = ___________mV = ____________V.
CONCLUSIONS
1) How of you know that a chemical reaction occurred in the wet cell after you added the acid ?
2) Which pair of electrodes produced the greater potential difference ? ____________________
Can you classify the paris according to their potential difference ?
Look at the table10 at the end of the lab. According to the table the pair potassium / Gold produce a potential difference (energy per coulomb) = 2.93 V + 1.50V = 4.43 V
This is only for a given temperature and given concentration of the reactants. But it gives you an idea of the potential you should get. Using this table10, fill the following table:
| electrodes pair | potential difference (V) according to table 10 | potential difference (V) according to your experiment |
| aluminum/zinc | ||
| aluminium/iron | ||
| aluminium/tin | ||
| aluminium/lead | ||
| aluminium/copper |
Did you get the classification right ? are you close ?
3) Bonus. Consider the oxidation-reduction reaction between zinc and copper. Now you know which one loses its electrons and which one gains elecrons. Can you write the 2 half-reactions?
hint: 2 electrons are exchanged between the 2 metals.
4) What electrolyte is better? the salt + water or the acid (1mol).
4) Explain the difference between an electric current and electric potential?