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

So

i might not weight the nails as i dont have a scale that is very accurate. I instead i will observe which which nail is more rusted.

materials update

im going to use boiled water with the salt instead of tap water as the tap water could have impurities which may affect the results and this allows me to see whether the salt is affecting the iron and not the impurities.

yeah

Hey, so methods and materials.

Materials
- tray
- 5 glass cups
- 5 iron nails (same size, weight, brand etc)
- 1 tablespoon of salt, 1/2 tablespoon of oil (put on top of the boiled water to keep air out), 100mls of tap water, 50mls of vinegar, 50mls of boiled water
- sand paper

Method
step 1 : obtain materials listed above
step 2: record weight of each nail
step 3: pour 50mls of tap water, salt dissolved in 50mls of tap water, vinegar, boiled water with oil on top into each of4 cups and leave the last one empty.
step 4: place nails into each glass at same time and place on tray. then put somewhere with a consistent temperature ie each nail is subjected to the same 'environment'.
step 5: record observations.
step 6: after a period of one week, remove nails, sand them down and weigh them again
step 7 : record results
step 8: repeat experiment.