Chemistry (S3) Unit 12: Corrosion of metals and their protection
Topic: Rusting and their conditions
Lesson plan of the 1st lesson (one double period)
Time / Objective / Teacher’s activity / Students’ activity / Materials1. / 00-10 / à Asking why there is a discount on the food can. / à Going to laboratory and settling down
à Observing the can
à Noticing that rust / a brown substance is formed on the can.
à Noticing that rust is in powdered form / Rusted food can x6
PP “12Rusting.ppt”
2. / 10-20 / Rust is brown in colour. / à Asking for examples that we can find in the laboratory
à Showing photographs of some examples by PP / à Finding examples on which rust can be found
à Noticing that the new substance is of brown colour. / à Ws p.1
3. / Rust is formed on iron articles only. / à Showing a coin with blue substance and asking if the blue substance is rust.
à Pointing out the examples of a stand (brown, \ made of iron); the gas tap (screw is brown,\ made of iron; the tap itself is green, \ not made of iron) / à Noticing that the blue substance on the coin is not rust.
à Noticing that rust only forms on iron
à Implying that an article is made of iron if brown substance is found / an article is not made of iron if brown substance is not found.
3. / 20-25 / Rust is a compound of iron but not iron in another form. / ¨ Asking whether rust is a type of iron or is a compound containing iron.
¨ Adding dilute HCl to test tubes containing iron powder and rust respectively. / ¨ Students may point out that iron and rust have different colour.
¨ Noticing that difference in colour is not a prove to distinguish different substances.
¨ Noticing that different substances would have different chemical properties.
¨ A student is helping to scratch rust off a plough
¨ Noticing that colourless bubbles evolve from the tube containing iron powder only.
¨ Deducing that rust is different from iron. / ¨ A heavily rusted plough, dilute HCl, 2 test tubes
4. / 25-35 / Rust is hydrated iron(III) oxide. / à Asking what rust is
à Stating that hydrated iron(III) oxide is a compound containing iron, hydrogen and oxygen / à Comparing the colour of rust with different iron-containing compounds
à Noticing that rust is hydrated iron(III) oxide
à Noticing that rust is made up of iron, oxygen and water. / à Samples of FeCO3, hydrated FeSO4, hydrated Fe2O3, hydrated Fe2(SO4)3
5. / 35-40 / Proposed that oxygen and water are the 2 necessary conditions of rusting / à Asking the ways to test for the presence of iron, oxygen and water in rust.
à Suggesting that we can make rust instead of testing for the presence of those parts
à Asking where the water and oxygen of rust come from
à Noting that it is the oxygen gas but not other substances in air that causes rusting / à Proposing tests like Flame test, glowing splint, anhydrous copper(II) sulphate… and noticing that the difficulty in doing these tests in the school laboratory
à Deducing that the water of rust comes from water / water vapour in the air
à Deducing that the oxygen of rust comes from air
6. / 40-45 / Brainstorming the conditions of rusting / à Discussing with students the conditions of rusting
à Summing up possible conditions of rusting / à Deducing different conditions of rusting (e.g. 1iron, 2water, 3oxygen, 4the presence of salt)
7. / 45-80 / Discussion on the design of a set of experiments to investigate the conditions of rusting
Performing experiment / à Brief revision on designing a fair test
à Discussing and amending the set-ups
à Briefing about the experiments and the necessary precautions to be taken / à Students’ presentation (one set-up per bench)
à Performing experiments in groups / à Experimental worksheet investigating conditions of rusting
à Chemicals and apparatus
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Topic: Rusting and their conditions
Lesson plan of the 2nd lesson (one single period)
Time / Objective / Teacher’s activity / Students’ activity / Materials1. / 0-5 / à Going to laboratory and settling down
2. / 05-10 / ¨ Discussing within group about their deduction / Expt Ws (p.3)
3. / 10-25 / ¨ In addition to iron, oxygen and water are the 2 necessary conditions for rusting. / ¨ Bringing out that A is the control
¨ Bringing out that we should compare each test tube with A
¨ D: Some can find rust. Ask students to discuss why is / is not formed. Ask if any error in doing the experiment. / ¨ Deducing from the experimental results that:
A: control
B vs A: Iron is necessary.
C vs A: Water is necessary.
D vs A: Oxygen is necessary.
E vs A: Bacteria is not necessary.
F vs A: Salt is not necessary.
G vs A: High temp is not necessary.
H vs A: Low temp is not a necessary.
4. / 25-35 / ¨ One daily example / ¨ Distributing Ws (p.3)
¨ Asking students to do Q1 (about the rusted food can)
¨ Class discussion / ¨ Doing Q1 for about 3 minutes
¨ Discussion within group for about 2 minutes
¨ Class discussion for about 5 minutes / Ws (p.3)
5. / 35-40 / ¨ Opening the can / ¨ Observing that no rust can be found inside the can
¨ Concluding that rust is not formed because there is no oxygen inside the can. / The food can