Ever wondered how teachers get so adept at conducting experiments in schools? Actually teachers are always sent for trainings to improve the quality and effectiveness of their teaching standards.So this post (Berry Event No.3) is exactly about one of the training sessions for teachers, and in this case about how teachers getting their hands dirty on various experiments to ‘upgrade’ their chemistry practical skills. Berry Readers who are interested in the unseen aspect of a teacher’s life are invited to have a peek on the inner workings of the teaching profession.
(Tips for Teachers and Lab Assistants: There are two experiments shown below which should be conducted for students. They include techniques not written in textbooks.)
Berry Event #3 – Effective Chemistry Practical Course Johor 2010 (Kursus Amali Berkesan Kimia Johor 2010) – Johor Bahru : Jabatan Pendidikan Negeri Johor
- Event: Effective Chemistry Practical Course Johor 2010 (Teknik Amali Berkesan Kimia 2010) Secondary School – Form 4 and 5
- Date: 22nd July 2010
- Venue: Sekolah Menengah Teknik Johor Bahru, Johor Bahru
- Target: Chemistry Teachers in Johor Bahru District
- Event Covered by: Miss Isabelle Wong – The Berry Berry Teacher – Chemistry Teacher
- Speaker: Sheikh Kamal (SM Teknik Johor Bahru, Johor), Lee Wai Siew (SMK Tunku Abdul Rahman Putra, Kulaijaya), Faridah Bte Abdir Kadir (SMK Sultan Ismail, Johor Bahru), Md Sihat Bin Md Amin (SM Teknik Johor Bahru)
- Dedicated to: The dedicated Chemistry Teachers (Guru Cemerlang) in Johor and Laboratory Assistants of SM Teknik Johor Bahru.
Experiment 1 - Form 5 Chapter 3: Redox Reaction – Oxidation & Reduction Effect of Other Metals on the Rusting Of Iron
There is a very effective way in preparing this experiment which can make this experiment interesting and can get effective results in a short time, so all teachers and laboratory assistants must try this out! This method is recommended by Md Sihat Bin Md Amin (Sekolah Menengah Teknik Johor Bahru).
Teachers need to briefly give explanations to students as they should be given some background/pre-knowledge of this experiment. It will help the students to understand the concept of rusting or corrosion better.
Problem 1: How to make the iron nail to rust in the fastest rate and at the same time get to observe the result within a day?
Tips: All the nails must be dipped in concentrated acid for few hours (at least 30 minutes) before the experiment start. Example: hydrochloric acid. This method will remove the antirust coated on the surface of the iron nails. (This method is not stated in any of the textbook, so teachers and laboratory assistants need to take notes!)
Problem 2: How to coil these nails to get the best results?
Tips: There must be some ‘gap’ when coiling the metal on the nail. So the changes of colouration can be seen clearly when the iron nail is contacted with the metal.
There must be a gap for the corrosion to take place.
Problem 3: How to view the result clearly?
Tips: Drop few (2 – 4) drops of potassium hexacyanoferrate(III) solution into the hot jelly but not too much! You cannot get good observation if it is too yellowish.
Make sure there is no air bubble trapped in between the iron nail and metal strip. It will effect the results. Therefore, pour the hot jelly slowly into the test tubes.
About 10 -20 small strips of agar-agar soak in 100 cm3 of distilled water. And only few drops of potassium hexacyanoferrate(III) solution and phenolphthalein solution are added into the hot jelly.
Do not add too much potassium hexacyanoferrate(III) solution.
Pink colouration can be seen clearly in Figure 7.
Blue colouration can be seen clearly in Figure 8.
Problem 4: How to make students to understand this concept in a short time and not to confuse them?
Tips: Time management is extremely important for a teacher. This can be done when teachers prepare a set of result three days beforehand for the students to compare their result. Students need to know what is the relationship between the colouration and the ions present in the jelly before the start of the experiment. Teachers also need to carry out a discussion session with students after the experiment and identify students’ misconceptions towards this activity.
Summary of the results and observation:
|Test tube||Pair of metals||Intensity of dark blue colouration||Intensity of pink colouration||Inference regarding rusting|
|I||Fe only||Low||None||Iron(II) ions present. The iron nail rusts a little.|
|II||Fe + Mg||None||Very high||Iron(II) ions not present. The iron nail does not rust.|
|III||Fe + Cu||Very high||None||Iron(II) ions present. The iron nail rusts very quickly.|
|IV||Fe + Zn||None||High||Iron(II) ions not present. The iron nail does not rust.|
|V||Fe + Pb||High||None||Iron(II) ions present. The iron nail rusts quickly.|
In rusting process, iron(II) ions are produced. These ions form blue colouration with potassium hexacyanoferrate(III) solution.
During the corrosion of metal, the reduction of oxygen forms hydroxide ions, thus it gave rise to alkaline condition. The hydroxide ions give pink colouration with phenolphthalein.
Experiment 2 – Form 4 Chapter 8: Constructing Ionic Equation Using Continuous Variation Method
In this experiment,it is very important for the students to calculating the number of moles of ions in each of the reactant solution and mole ratio of the ions and finally the construction of the ionic equation of the reaction. This method is recommended by MD Sihat Bin Md Amin (SM Teknik Johor Bahru).
Problem 1: How to get a constant precipitation formation in test tube 6 and test tube 7.
Tips: Shake thoroughly with a stopper after volume of lead(II) nitrate and volume of potassium chromate(VI) is added. After that, the test tubes are left aside. Use same size of test tube.
|Volume of lead(II) nitrate (cm3)||5.00||5.00||5.00||5.00||5.00||5.00||5.00|
|Volume of potassium chromate(VI) (cm3)||1.00||2.00||3.00||4.00||5.00||6.00||7.00|
Make sure students do not shake the test tube after the formation of the yellow precipitate.
So there you go, the life of a teacher unseen from the perspective of a student/parent. To be honest, it’s an enriching exercise to be learning from experts who taught us the minute details of conducting experiments. This allows us to transfer our acquired knowledge to our students. Do write to back or drop comments at Berry Berry Easy if you have anything similar to share.