edit

so when doing my experiment ive change the amount of solutions from 50mls to 60mls which is just enough to cover the nail. Also ive added bolied water without pouring oil on top to see if are presence of air really affects the rate of rusting. Also i am using half a tablespoon (10mls) of salt instead of 1 because not alll the salt dissolves.The nails i have chosen are 60mm and weigh about 3 g each.

Method updated

Materials
6 glass/plastic cups
6 iron nails
1/2 tablespoon of salt
1/2 table spoon of oil
120mls boiled and rested water
60mls tap water
60mls white vinegar

Method
1. Obtain materials listed above
2. Label each of the cups as tap water, salt water, boiled water, boiled water (oil), empty and vinegar
3. Pour 60mls of tap water into cup.
4. Repeat step 2 with vinegar, 2 x boiled water and salt boiled water into 4 different cups. Leave two cups empty.
5. Place nails into each of the 6 cups
6. Pour 1/2 tablespoon of oil into the boiled water.
7. Place in area with a consistant atmosphere.
8. In a period of one week, record observations each day.
9. Repeat experiment