Chemistry Rusting

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Aim:
1. Find out which substances are essential for rusting to occur. 2. Find out how the rusting process can be inhibited and how it can be promoted. Hypothesis:
I predict that air (oxygen) and water are necessary for iron to rust. The nail in water with air will rust while the nails in dry air and in boiled water with no air will not. I also predict that galvanizing the nail with zinc and greasing the nail and painting the nail and electroplating the nail will inhibit rusting. I also predict that adding NaCl to the test tube with water and air will promote rusting of the iron nail. Background information:

Rusting is the chemical reaction between a metal and oxygen in the presence of water. In this case, it is the corrosion of iron. Corrosion is defined as the loss of metallic properties of a metal due to oxidation and it results in them losing strength and electrical conductivity. When iron is in contact with water and oxygen, it will rust. Chemical equation of the rusting of iron: 4Fe+3O2+H20--> 2Fe2O3.H2O There are certain things that will promote the rusting of iron. An example of this is adding NaCl (salt) to the water. When salt is dissolved in water, it is separated into Na+ and Cl- ions. These ions attach themselves separately to the charged parts of the water molecule (H20). When Na and Cl ions are present in water, there is an increase in the ability of the water to carry electrons as there are more ions in the water, therefore the iron will rust faster. There are also many factors that will inhibit the rusting of iron. Examples of this are painting the iron, greasing the iron and electroplating the iron with copper and galvanizing the iron with zinc. Paint and grease are impermeable so oxygen and water cannot come into contact with the iron as the paint and grease would be in the way. Plating the iron (galvanizing) with zinc can inhibit the rusting process. Zinc corrodes more easily than iron does because it is higher in the reactivity series so the zinc will corrode before the iron does. Electroplating prevents rusting because it creates a barrier between the metal and the oxygen and water. In this experiment, the iron nail will be the cathode in the electrolysis. The nail (the cathode) and a piece of copper (the anode) will be placed into copper sulphate solution. The copper sulphate will decompose to form positive copper ions and negative sulphate ions. As the copper ions are positive, they are attracted to the cathode, where they will collect electrons, become neutrally charged and will build up as a layer of copper on the cathode. The copper from the anode will dissolve in the electrolyte to replace the copper ions, deposited on the cathode. This will create a layer of copper on the iron nail. Calcium chloride granules will be added to the test tube with no water because calcium chloride takes water from the air because of its hygroscopic nature. This means calcium chloride has the ability to attract and hold water molecules from the surrounding environment. Apparatus:

8 iron nails
8 test tubes
10ml oil
10ml measuring cylinder
Forceps
30 zinc granules
Boiled water
Power supply
Tongs
2 crocodile clips
Copper sulphate solution (250ml)
Tin lid
Kettle
Piece of Styrofoam
Pot of nail polish
Copper strip
NaCl. H20 (sodium chloride solution)
Vaseline
20 calcium chloride granules

Variables:
ControlledIndependentDependent
Size of test tubesZinc covering nailAmount of rust on iron nail Time given for rusting to occurNaCl in water
Temperature of waterGrease covering nail
Amount of water (except in test tube without water)Paint covering nail Amount of air (except in test tube without air)Copper covering nail
Oil in test tube
Boiled water in test tube

Results:
Results able showing the scale for amount of rust on each iron nail from –5 Scale numberAmount of rust on iron nail
0None
1A very small amount
2A...
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