Life Sciences Grade 12 IEB Paper 3 2017 Memo

Downloaded from hlayiso.com NATIONAL SENIOR CERTIFICATE EXAMINATION NOVEMBER 2017 LIFE SCIENCES: PAPER III MARKING GUIDELINES Time: 1½ hours 50 marks These marking guidelines are prepared for use by examiners and sub-examiners, all of whom are required to attend a standardisation meeting to ensure that the guidelines are consistently interpreted and applied in the marking of candidates' scripts. The IEB will not enter into any discussions or correspondence about any marking guidelines. It is acknowledged that there may be different views about some matters of emphasis or detail in the guidelines. It is also recognised that, without the benefit of attendance at a standardisation meeting, there may be different interpretations of the application of the marking guidelines. IEB Copyright © 2017 PLEASE TURN OVER

Downloaded from hlayiso.com NATIONAL SENIOR CERTIFICATE: LIFE SCIENCES: PAPER III – MARKING GUIDELINES Page 2 of 4 PART 1 INVESTIGATION 1.14 Suitable heading. Columns correct with a column for Before and a column for After heating. Three samples plus water shown. Results given correctly for D – blue colour for before and after. 1.15 Samples of urine provided. 1.16 Colour change when indicator added or amount of glucose present. 1.17 Control, to compare results of investigation samples against. 1.18 Same volume of sample in each test tube – 20 ml in each measured. Amount of indicator added the same – 3 ml added to each test tube. All heated at the same temperature in water/boiling water bath. Time in the water bath the same – 1 to 2 minutes for all to be in the water bath. 1.19 Tube A – (colour change to green/light orange) – glucose is present – possibly diabetic. Tube B – (colour change to bright orange) – lots of glucose is present – diabetic. Tube C – (very slight colour change to green/yellow) – small amount of glucose is present – may have had a high carb meal. Tube D – (no colour change) – is pure water/control so no glucose as indicator stays blue /is not urine. 1.20 Excess glucose build-up/cannot be absorbed by the body cells/kidney and so is excreted into the bladder with urine. 1.21 1.21.1 Tom 1.21.2 330–340 mg/dl 1.21.3 Suzy additional peak shown after lunch. 1.21.4 Quantitative – as numerical values being given. 1.22 magnified length/magnification = 44 mm /300 = 0,15 mm IEB Copyright © 2017 PLEASE TURN OVER

Downloaded from hlayiso.com NATIONAL SENIOR CERTIFICATE: LIFE SCIENCES: PAPER III – MARKING GUIDELINES Page 3 of 4 PART 2 EXPERIMENTAL DESIGN 2.1 Benedict's solution in the presence of glucose at a concentration of 30 mg/litre will change from blue to a brick red colour. Statement 2.2 To investigate that the only simple sugar that is detected by Benedict's solution is glucose. 2.3 Types of sugar being tested with Benedict's. 2.4 (1) Label four identical test tubes A to D. (2) Into test tube A, using a syringe, add 20 ml of water. (3) Into test tube B, using a syringe, add 20 ml of 30 mg/l of glucose. (4) Into test tube C, using a syringe, add 20 ml of 30 mg/l of sucrose. (5) Into test tube D, using a syringe, add 20 ml of 30 mg/l of lactose. (6) Using a syringe add 3 ml of Benedict's solution to each of the four test tubes. (7) Place all four test tubes into a water bath of boiling water and wait two minutes. (8) Observe any colour changes in the test tubes. (9) Record observations in a table. (10) Repeat the investigation to check for validity/reliability of your result. IEB Copyright © 2017 PLEASE TURN OVER

Downloaded from hlayiso.com NATIONAL SENIOR CERTIFICATE: LIFE SCIENCES: PAPER III – MARKING GUIDELINES Page 4 of 4 Use the attached rubric for assessment for Question 2.4. Method Rubric 5 4 3 2 1 0 Criteria L Layout – Layout meets criteria Layout is untidy and appearance of below: hard to read. method neat and tidy and OR bulleted/numbered. Method is not formatted correctly with bullet points or numbers. A Aim – method Method clearly tests Method relates to the Method does not relates to an aim that relates to prescribed aim given, relate to the prescribed the prescribed but is a little prescribed aim or experiment experiment and confusing and does achieve the desired achieves the required not achieve the result. Method given result. required result. is the same as the given experiment. M Method – This All 5 criteria given An original An original An original An original None of the 5 criteria needs to be below are met: experiment provided. experiment provided. experiment provided. experiment provided. are met. appropriate and 1. An original OR relevant to the experiment Plus 3 of 5 criteria are Plus 2 of 5 criteria are Plus 1 of 5 criteria is Method a copy of the aim, clearly logical provided. met. met. met. original, given and sequential. If 2. Equipment is experiment. apparatus is given appropriate and in the examination used correctly. paper, the method 3. Measuring of should resemble solutions, reagents the one given in and marking of the marking equipment are guidelines. explained and this assists in the control of variables. 4. Instructions are scientifically valid and ordered. 5. Instructions are complete to produce measurable results that are recorded. Total: 50 marks IEB Copyright © 2017