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Chemistry SBA

Chemistry SBA. BAC (Qualitative analysis) [Version 1]. Link with NSS curriculum: Topic IV (Acids and Bases) Number of period required 1  40 minutes Experimental work: 20 minutes Prior knowledge sub-sections (a) and (d) of topic IV Objective

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Chemistry SBA

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  1. Chemistry SBA

  2. BAC (Qualitative analysis) [Version 1] • Link with NSS curriculum: • Topic IV (Acids and Bases) • Number of period required • 1  40 minutes • Experimental work: 20 minutes • Prior knowledge • sub-sections (a) and (d) of topic IV • Objective • To test the students’ knowledge on precipitation reactions and acid-carbonate reactions • Assessment: • Mainly based on the written worksheet

  3. BAC (Qualitative analysis) [Version 1] • Instructions • Given: MgSO4(aq); Na2CO3(aq); Pb(NO3)2; and HCl(aq) • Perform the tests as in table below. • Observations? • Identification?

  4. BAC (Qualitative analysis) [Version 1]

  5. Assessment considerations • Mainly based on written worksheets • Any unsafe practice? • Marks to be deducted • With prior notice

  6. Marking criteria

  7. BAC (Qualitative analysis) [Version 1: EXEMPLAR]

  8. In this exemplar, the student correctly identified the four substances. However, in recording his observations, he wrongly stated no observable change as no observations. Moreover, the description on his deduction is not systematic and could not convey his ideas clearly. BAC (Qualitative analysis) [Version 1: EXEMPLAR]

  9. BAC (Qualitative analysis) [Version 2] • Link with NSS curriculum • Topic IV (Acids and Bases); Topic VII (Redox reactions) • Number of periods required • 1  40 minutes • The students are able to complete the experiment and hand in the worksheet within 30 minutes.

  10. BAC (Qualitative analysis) [Version 2]

  11. BAC (Qualitative analysis) [Version 2] • Note: 2/3 of the marks are allocated to the observations. 1/3 of the marks are allocated to the interpretation of the observations and the deduction of the chemical nature of the sample. • Summarise, in the space below, your conclusions as to the chemical nature of the sample. Deduce, where possible, what ionic and / or molecular species are present in the sample.

  12. BAC (Qualitative analysis) [Version 2: EXEMPLAR]

  13. BAC (Qualitative analysis) [Version 2: EXEMPLAR]

  14. Points to take note • Safety practice • Safety goggles • Safety first before assessment • Adequate number of apparatus / chemical reagents • Use reagent bottles with dropper • Flame test • 2 fume cupboards [F&E] • Test tube vs. microscale

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