Rusting Lab. Hypothesis: I think that the presence of salt will speed up the rusting. The greater the amount of salt present in the test tube, the faster/more the iron nails will rust.

Hypothesis:

I think that the presence of salt will speed up the rusting. The greater the amount of salt present in the test tube, the faster/more the iron nails will rust.

Variables:

Independent variable:

Amount of salt (NaCl)

Dependant variable:

The amount the iron nails rust (increase in mass of iron nail)

Controlled:

All apparatus

All ambient conditions

Time for experiment

Apparatus:

1. 6 test tubes
2. 60 ml of water
3. A Measuring cylinder
4. 6 bungs
5. 12 iron nails
6. Electronic weighing scale
7. 6g of NaCl

Method:

1. Use the measuring cylinder to measure out 10ml of distilled water each in 6 test tubes.
2. Take a marker and label each test tube with numbers from 1 to 6.
3. Take the 10 nails and divide them in 6 sets of 2 nails each. Weigh out each set of nails before noting the test tube number in which they are dropped.
4. Use an electronic weighing scale and weigh out 0.2g of NaCl to be added to test tube 2, 0.4g of NaCl to be added to test tube 3, 0.6g of NaCl to add to test tube 4, 0.8g of NaCl to test tube 5 and 1.0g of NaCl to test tube 6 leaving test tube 1 without salt.
5. Secure each test tube with a rubber bung.
6. Wait for a week.
7. Re-weigh each set of nails from their test tubes and note these down.

Results:

Raw Data Table:

Processed Data Tables:

To find the mass of the rust(hence, the amount of rust):

Mass of rust = Final Mass of Iron Nails – Initial Mass of Iron Nails   

Graphical Analysis:

The graph above shows that the amount of rust produced increases with the presence of salt, a higher quantity of salt resulting in a higher amount of rust produced. The graph shows a strong positive co-relation. The graph shows that the amount of rust almost increases in proportion to the amount of salt added to the test tube. This can be seen on all points on the graph except the one for the test tube with 0.4g of NaCl. The reading for this test tube is an anomalous reading and may be due to some of the rust falling of the iron nail and into the water that submerges the nails. On a wider basis, we see that the presence of 1g of salt compared to 0g causes the presence of 0.06g of rust on iron nails weighing approximately0. 50g. This is a 12% increase showing that, adding 1g of salt to iron nails in 10ml of water causes a production of rust that is 125 the weight of the submerged iron nails.

Conclusion:

The amount of rust increases almost in proportion to the amount of salt added. This is because salt water is a good conductor of electricity and ,given that rusting is a redox reaction, the greater the presence of salt the electron transfer occurs more rapidly.

Evaluation:

The experiment was carried out well but there were points that could be improved on.

• Some of the rust floated into the water and was thus not taken into account during the calculations.

Fair test:

• The test tubes were secured with a rubber bung so that the ambient changes in the chemistry lab would not affect the experiment.
• The water was free from impurities that could alter the readings.
• All apparatus, conditions and time were kept constant.