Experiment 1E (Effects of Other Metals on Rusting) :
Aim: To study the effects of other metals on rusting.
Problem statement: How do different metals in contact with iron affect rusting?
Hypothesis: When a more electropositive metal comes into contact with an iron nail, the iron does not rust; when a less electropositive metal comes into contact with an iron nail, the iron nail rusts.
Variable:
(a) Manipulated variable : Different metals coiled around the iron nail.
(b) Responding variable : Rusting of iron
(c) Fixed variable : Iron nail.
Materials: Agar solution, phenolphthalein, potassium hexacyanoferrate(III), K3Fe(CN)6 solution, iron nails, magnesium ribbon, Mg, tin strip, Sn, zinc strip, Zn and copper strip, Cu.
Apparatus: Test tubes, test tube rack and sandpaper.
Procedure:
1. Label five test tubes P, Q, R, S and T.
2. Using sandpaper, clean five iron nails, magnesium ribbon, tin strip, zinc strip and copper strip.
3. Coil each nail with magnesium ribbon, zinc strip, tin strip and copper strip respectively.
4. Put each nail coiled with metal into test tubes P, Q, R and S respectively as in Figure 1.42. The nail with no metal coil is placed into test tube T.
5. Pour hot agar mixture containing potassium hexacyanoferrate(III), K3Fe(CN)6 solution and phenolphthalein into each test tube until the nails are completely immersed.
6. Place all test tubes on the test tube rack and leave aside for one day.
7. Record your observations.
Results:
Construct a table to record your observations.
Discussion:
1. What is the function of potassium hexacyanoferrate(III), K3Fe(CN)6 and phenolphthalein in this experiment?
2. Explain why hot agar solution is used in this experiment instead of water.
3. State the relationship between the intensity of the blue colour with the rate of rusting that takes place.
4. State the function of test tube T.
5. Based on the result of this experiment, classify the metals into metals that prevent rusting and metals that accelerate rusting.
6. What is the relationship between the electropositivity of a metal that comes into contact with iron and rusting of iron?
7. Can the hypothesis be accepted? Write a conclusion for this experiment.
Answer:
Result:
1. Potassium hexacyoanoferrate(III) solution is used to verify the presence of Fe2+ ions and phenolphthalein detects the presence of OH− ions.
2. The blue spots and pink spots can be seen clearly and the colour does not mix.
3. The higher the intensity of the blue colour, the higher the rate of rusting of iron.
4. As control.
5.
6. Metals that are more electropositive than iron prevent rusting of iron, while metals that are less electropositive than iron accelerate the rate of rusting of iron.
7. Hypothesis accepted. When a more electropositive metal comes into contact with the iron nail, the iron nail does not rust, while when a less electropositive metal comes into contact with the iron nail, the iron nail rusts.
Aim: To study the effects of other metals on rusting.
Problem statement: How do different metals in contact with iron affect rusting?
Hypothesis: When a more electropositive metal comes into contact with an iron nail, the iron does not rust; when a less electropositive metal comes into contact with an iron nail, the iron nail rusts.
Variable:
(a) Manipulated variable : Different metals coiled around the iron nail.
(b) Responding variable : Rusting of iron
(c) Fixed variable : Iron nail.
Materials: Agar solution, phenolphthalein, potassium hexacyanoferrate(III), K3Fe(CN)6 solution, iron nails, magnesium ribbon, Mg, tin strip, Sn, zinc strip, Zn and copper strip, Cu.
Apparatus: Test tubes, test tube rack and sandpaper.
Procedure:
1. Label five test tubes P, Q, R, S and T.
2. Using sandpaper, clean five iron nails, magnesium ribbon, tin strip, zinc strip and copper strip.
3. Coil each nail with magnesium ribbon, zinc strip, tin strip and copper strip respectively.
4. Put each nail coiled with metal into test tubes P, Q, R and S respectively as in Figure 1.42. The nail with no metal coil is placed into test tube T.
5. Pour hot agar mixture containing potassium hexacyanoferrate(III), K3Fe(CN)6 solution and phenolphthalein into each test tube until the nails are completely immersed.
6. Place all test tubes on the test tube rack and leave aside for one day.
7. Record your observations.
Results:
Construct a table to record your observations.
Discussion:
1. What is the function of potassium hexacyanoferrate(III), K3Fe(CN)6 and phenolphthalein in this experiment?
2. Explain why hot agar solution is used in this experiment instead of water.
3. State the relationship between the intensity of the blue colour with the rate of rusting that takes place.
4. State the function of test tube T.
5. Based on the result of this experiment, classify the metals into metals that prevent rusting and metals that accelerate rusting.
6. What is the relationship between the electropositivity of a metal that comes into contact with iron and rusting of iron?
7. Can the hypothesis be accepted? Write a conclusion for this experiment.
Answer:
Result:
1. Potassium hexacyoanoferrate(III) solution is used to verify the presence of Fe2+ ions and phenolphthalein detects the presence of OH− ions.
2. The blue spots and pink spots can be seen clearly and the colour does not mix.
3. The higher the intensity of the blue colour, the higher the rate of rusting of iron.
4. As control.
5.
6. Metals that are more electropositive than iron prevent rusting of iron, while metals that are less electropositive than iron accelerate the rate of rusting of iron.
7. Hypothesis accepted. When a more electropositive metal comes into contact with the iron nail, the iron nail does not rust, while when a less electropositive metal comes into contact with the iron nail, the iron nail rusts.