Assessment for Learning in AL & ASL Chemistry Through TAS Chan Kam Yuen TWGHs Mrs Wu York Yu Memorial College/ EDB Seconded Teacher 05-06
New AL syllabus • Starts from year 05-06 • No phase equilibrium • Mechanistic base learning in Organic Chemistry • No Chemistry and Society • Add Chemistry in Action • Drug Chemistry & Green Chemistry
TAS Handbook • 5 main areas of assessment (Form 902) • (a) Methodical Working • (b) Experimental Technique • (c) Manual Dexterity • (d) Orderliness • (e) Skill in Observations
Assessment in Synthesis Expt. • Expt 4: Synthesis of Ferrate(VI) ions • Ferrate(VI) FeO42- consists of iron in the +6 oxidation state. It is an environmental friendly but powerful oxidising and disinfecting agent. It can oxidise harmful organic and inorganic species.
Synthesis of Ferrate(VI) ions • Part A: Preparation of FeO42- • Part B: Oxidation of organic and inorganic pollutants
(a) Methodical Working • A pre-written experiment with experimental procedure (any planning??) • Procedure is carried out in a correct sequence • Equipment is utilized effectively and purposefully • mortar & pestle and filtration apparatus • Time available is managed efficiently (at most 1 hour)
(b) Experimental Technique • Experimental apparatus are handled correctly. • Operations (filtration) is carried out correctly and efficiently. • Chemicals are handed in a safe manner (NaOH pellets, bleaching water).
(c) Manual Dexterity • Practical task is executed in a swift, confident and assured manner (observe and communicate) • Operation is successfully completed. (It can be succeed)
(d) Orderliness • Working area is kept clean and tidy. • Bench space is fully utilized. • Equipment is placed in an organized way. (General Impression)
(e) Skill in Observation • Student’s oral report on their findings, made simultaneously with the observation or immediately following the event, attains a reasonable standard.
Part A: Preparation of FeO42- • Add 10 cm3 of bleaching water in a 100-cm3 beaker. • (b) Handle bleach water in a safe manner • Grind NaOH pellets into powder and add 3 g of it to the beaker with stirring. • (b) Handle NaOH in a safe manner • (b) Mortar & Pestle is handled correctly
When most of the NaOH powder dissolves and the mixture remains hot, add 5 drops of 0.3 M FeCl3 solution with stirring for a few seconds. • (e) Skill in observation (record immediately?)
Add 2 g of NaOH powder into the reaction mixture. • (a) Procedure is carried out in a correct sequence (miss or mix up with other steps) • Allow the reaction mixture to cool down • (a) Procedure is carried out in a correct sequence (without waiting)
Place a small amount of cotton wool into a dropper. Filter the reaction mixture through the dropper with cotton wool. • (a) equipment is utilized effectively and purposefully (dropper enough?) • (b) operations is carried out correctly and efficiently • (c) operation is successfully completed • (e) skill in observation
Part B: Oxidation of organic and inorganic pollutants • Test 1: Add ~2 cm3 of absolute or normal ethanol to a test tube containing 2 cm3 of the filtrate collected in Part A. Record your observations. • Test 2: Add a few drops of the filtrate collected in Part A to a test tube containing 2 cm3 of 2 M H2SO4 solution. Record your observations. • (e) Skill in observation
Oxidation of ethanol ethanol
Kl l2 Oxidation of KI
Some remarks • Fully understand the principles and sequences of experiment • Think in detail about each step (requirement and technique) • Understand common mistakes of students