LEO the Tiger Goes GER
Lesson Description:
In this experiment students protect iron nails using a variety of
methods including painting, greasing and sacrificial protection. The
nails are placed in test-tubes and covered with corrosion
indicator solution. This contains gelatine and so sets to a jelly-like
consistency. The indicator changes colour from to blue and/or pink
to show where rusting is taking place. By comparing the amount
and position of the blue indicator on each nail, the effectiveness of
the different types of protection can be assessed.
Objectives:
What should the students know as a result of this lesson?
Students will….
• know the difference between oxidation and reduction
• detect the reaction that lead to rust
• understand how rust can be prevented
• identify what materials are best for coating steel
• determine what would be the best additive to a coating out of
copper, zinc, or magnesium
What should the students be able to do as a result of this lesson?
Students will….
• Determine if two metals are touching, which will corrode
• Understand that putting dissimilar metals together can cause
accelerated/decelerated corrosion
• Understand that polymers can protect metals from corrosive
entities
• Be able to use the power of observation to develop answers to
which metals provided are in the electrochemical series
• Discuss their results effectively
Materials Needed:
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Iron nails,
Galvanised (zinc coated) nails,
Stainless steel nail, screw or bolt
Copper foil, small piece
Magnesium ribbon, about 2 cm
Zinc foil, small piece
Cleaning solution, dilute sodium carbonate
Dilute hydrochloric acid, 1 M, about 10 cm3
Paint plus a small brush
Oil
Gelatine, 5 g
Potassium hexacyanoferrate(III), 0.2 g
Phenolphthalein
Per demonstration or pair or group of students:
Evaporation dishes
Marker pen or labels for test-tubes
PowerPoint or Keynote file with multimedia images and/or
videos with lesson description outlined step-by-step.
 Safety goggles
 Lab Procedures (developed with students during discussion)
Lesson Plan (5-E model):
Engagement:
In order to engage the students, the lab was conducted before the lecture. We
allowed the students to get their hands on the materials before beginning the
experiment and this caused them to ask a lot of questions. Through this method, we
were able to do an impromptu ‘introduction’ to corrosion and then tell them what
we were doing for the class period. This allowed for me to have their attention
quickly and then I was able to go over the procedure with everybody on the same
page.
Evaluation for Engagement Activity:
I received several questions during our engagement, which allowed me to casually
introduce the topic of corrosion. Therefore, since I wasn’t forcing the subject upon
them, they were very receptive to the lab overall.
Exploration:
Allow students to test metals and coatings that could be used to protect steel from
corrosion.
Procedure:
a Select some nails which do not show any signs of rusting. Clean them thoroughly with the
cleaning solution and dry them.
b Place one nail as a control into a test-tube.
c Treat the other nails as suggested below. Not every test needs to be done. Label each test-tube.
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Coat one nail with either a maker, paint, or oil and let it dry.
Choose either a small piece of magnesium, zinc, or copper foil
around a section of another nail.
Place these nails in separate evaporation dishes.
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Place a stainless steel nail, bolt or screw into an evaporation dish.
Place two galvanised (zinc coated) nails, one which has been
scratched with a file to remove a patch of zinc coating, into a
evaporation dish.
c Carefully pour the corrosion indicator into each evaporation dish, completely covering each
nail. Leave for at least half an hour.
Assessment for Exploration:
Make sure students are following proper laboratory procedures. If they see blue,
that means the iron is corroding and they did not protect the nail. If they see only
pink or nothing, the iron is not corroding.
Explanation for Exploration:
After they wrote their observations we had a lecture to figure out why some of their
choices did or did not work. We asked them to choose a coating and a metal to
protect iron. Oil and a marker were not sufficient coatings compared to dried paint
meanwhile copper are a very poor protector of iron. Therefore students that chose
the paint and either zinc/magnesium were able to sufficiently protect their nail from
corroding. During the entire lab, the name of the experiment was called ‘Leo the
Tiger Goes GER’. The students would ask constantly what that meant but I kept it
from them to pique their curiosity. Then, during the explanation, I told them that
LEO meant ‘loss of electrons is oxidation’ and GER meant ‘gain of electrons is
reduction’. From this device to memorize the reactions of corrosion, the student
were very responsive to the lecture since I had them answer which metal was LEO
the Tiger and which metal was GER. Most of the time the students were correct.
Elaboration:
After the lecture, we had the students describe what materials they chose and why
the failed or worked using the language they had just learned. From this we asked
the entire class the most efficient way to prevent corrosion with the materials given
in the lab, and the answer would be to make a polymer coating that includes
magnesium as a pigment (which is used in the real-world).
Final Lesson Assessment:
Have students write a short report on their findings. This report can be collected
and evaluated or given orally to the class.
Video:
TV channel WDAM recorded the lab and was broadcast on local television. We
received several comments over the next month from several people in the
community.