The end result of the experiment is the amount of rust present on the iron when the experiment is over and what colour the rust is. The amount of experiments taking place allows for a good look at what things prevent rusting and what things help speed up rusting.
Fair test
To make it a fair test the nail must remain the same size and for there to be the same amount of nails in each test tube. The amount of solution/powder in each test tube must be equal also to enable the test to be fair. They must all have the solutions added at the same time and be left for the same amount of time to enable the results to be fair and for there to be no specific variables (like room temperature etc.) for each test tube.
What will be changed is what the solution/powder is that is added in with the nail and what the nail may be surrounded in. These will be changed so that it can be established what speeds up or slows down rusting.
Accuracy
The results, to ensure accuracy, to help with averages and to dispel any incorrect results, will be repeated. It will be carried out a total of 3 times especially those that are odd and do not fit in with the others.
To make it accurate the liquid is being measured in mm because it is a more accurate measurement.
Prediction
I predict that the ones that will rust will be the control and the one with salt water, air and water. The one that has the nail surrounded with magnesium will react in a different way. Magnesium is higher in the reactivity series than iron, and thus is more reactive. Due to this the magnesium will take on the reactions of the iron, and rust, (in sacrificial protection) leaving the iron free from rust.
The control will rust because rust is a compound created from the reaction of iron with oxygen and water. The iron needs both oxygen and water to rust, which is why the one with the drying agent (and no water) and the one with the boiled water (and no oxygen) will not rust.
The one with the salt should react the most. This is due to the fact that salt is a catalyst to the effects of rusting and will produce more rust at a faster speed. The reason for this quicker reaction is that salt dissolved in water is a good conductor of electricity. In order for the iron to rust, electrons must flow from the iron atoms to the oxygen from the air. Iron plus oxygen makes iron oxide. Iron oxide is rust. When the iron producing iron oxide comes into contact with the conductive salt solution, rusting becomes a quicker process.
Results
Evaluation
The practical experiment went according to plan to produce sensible, clear results that went well with the prediction. There were no results that did not fit.
If I re-did the experiment I would ensure that the water would boil more in the ‘no air’ experiment to ensure that absolutely no air got in and it would produce no rust at all as there was a small amount.
The one that worked the best was the one containing drying agent. This presented no rust and had the reaction (ie. None) that was expected and was the easiest to tell that it had worked.
Conclusion
I conclude that without water or oxygen iron will not rust. Also if you place a more reactive metal around the iron nail it will become sacrificial protection and the more reactive metal will take on the rust leaving the iron without rust. Salt, as predicted, worked as a catalyst to speed up the reaction of rusting onto the iron.
Therefore to prevent rusting you can coat it in a more reactive metal so that the more reactive metal will take on the rust or you can take away all moisture or oxygen. The things cause rusting are water and oxygen but when salt is added to the mixture it speeds up.
