Hypothesis: I predict that the metals that are good conductors will show a high voltage on the voltmeter and that the metals with low conduction ability will show a low voltage.Equipment: A small beaker
Diluted sulfuric acid/salt solution
Metal and graphite electrodes
2 crocodile clips
Step 1: Half fill the beaker with diluted sulfuric acid.
Step 2: Attach a crocodile clip to the wires.
Step 3: Choose two different electrodes (different metals). And connect the wires to them using the crocodile clips.
Step 4: Attach the end of each wire to a voltmeter.
Step 5: Dip the two electrodes in sulfuric acid without letting them touch each other.
Step 6: Document your choice of metals and the reading on the voltmeter.
Step 7: Then repeat the experiment with different metals.
Step 8: Work together with another group.
Step 9: Connect both groups’ beakers with electrodes in series. Document the readings.
Step 10: Make sure you have used the same combination of electrodes in both parts of the experiment.
The results of this experiment were:
Zinc + Silver: 0,35 V
Zinc + Zinc: 0 V
Zinc + Graphite: 0,7 V
Zinc + Copper: 0,8 V
Copper + Silver: 0,03 V
Copper + Graphite: 0,10 V
Silver + Graphite: 0 V
Lead + Zinc: 0,19 V
Lead + Copper: 0 V
Lead + Graphite: 0,40 V
Lead + Silver: 0,42 V
Silver + Silver: 0V
Electricity is generated when two electrodes of different metals are dipped into sulfuric acid without touching each other. This is a form of electrochemistry.
Electrochemistry is the part of chemistry that deals with the interrelationship of electrical currents and chemical reactions. In the broadest sense, electrochemistry is the study of chemical reactions that produce electrical effects.
Most organic chemical compounds, when in a molten state or when dissolved in water or other liquids, exist in the form of ions that can move: that is, their molecules become dissociated into positively and negatively charged ions, which have the property of conducting an electric current. The solution or molten compound is called an electrolyte. If a pair of electrodes is placed in a solution of an electrolyte and a source of direct current is connected between them, the positive ions in the solution move toward the negative electrode and the negative ions toward the positive electrode. On reaching the electrodes, the ions may gain or lose electrons and be transformed into neutral atoms or molecules.
All chemical changes involve a regrouping or readjustment of the electrons in the reacting substances; hence all such changes may be said to be electrical in character. To produce an electrical current from a chemical reaction, it is necessary to have a reducible substance, that is, a substance that can gain electrons easily; and an oxidizable substance, one that can give up electrons easily. A reaction of this kind can be understood from the operation of a simple type of electrochemical cell. If a zinc rod is placed in a dilute solution of sulphuric acid, the zinc, which oxidises readily, will lose electrons, and positive zinc ions will be liberated into the solution. The free electrons stay in the zinc rod. If the rod is connected through a conductor to an inert-metal electrode placed in the sulphuric acid solution, the electrons will flow around this circuit into the solution, where they will be taken up by the positive hydrogen ions of the diluted acid. The combination of the electrons and the ions produces hydrogen gas, which appears as bubbles on the surface of the electrode. The reaction of the zinc rod and sulphuric acid thus produces a current in the external circuit. An electrochemical cell of this kind is known as a primary cell, or voltaic cell.
In the storage battery or accumulator, commonly known as a secondary cell, electrical energy is fed to the cell from an outside source and stored within in the form of chemical energy. The chemical reaction of a secondary cell is reversible, proceeding in one direction when the cell is being charged, and in the opposite direction when it is discharging. Because the reaction is of this type, a secondary cell can be discharged again and again.
Luigi Galvani (1737-1798) was an Italian physician and science teacher. One day he was working on an experiment involving electricity. His wife often helped him. She had prepared some frog legs for Luigi’s next experiment. Somehow the power source got connected to the wet frog legs and they started moving. Galvani thought that the muscles in the animals produce animal electricity. He did not continue to study this but his friend and colleague Alessandro Volta (1745-1827) did. He found out that you did not even need a power source to make the frog legs move. He built a pile of two different metals with damp cloth between them and a wire connecting both of the two ends of the pile. The cloth had to be damp because Volta found out that he got more electricity flow when the matter was drenched in a liquid that conducts electricity. This so-called a Voltaic Pile was the first electric battery.
The battery is basically two poles with an acid between them. The shell of a battery is one pole, usually made out of Zinc. In the battery there is a graphite pole. The graphite is the positive pole and the Zinc the negative pole. The acid in the battery might easily leak out but it does not because it is mixed with gelatin.