Technical Sciences Grade 12 IEB Paper 2 2019 Memo

Downloaded from hlayiso.com NATIONAL SENIOR CERTIFICATE EXAMINATION NOVEMBER 2019 TECHNICAL SCIENCES: PAPER II MARKING GUIDELINES Time: 3 hours 150 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 © 2019 PLEASE TURN OVER

Downloaded from hlayiso.com NATIONAL SENIOR CERTIFICATE: TECHNICAL SCIENCES: PAPER II – MARKING GUIDELINES Page 2 of 8 QUESTION 1 1.1 C 1.2 C 1.3 D 1.4 C 1.5 C 1.6 A 1.7 B 1.8 B 1.9 C 1.10 C [20] QUESTION 2 2.1 A series of organic compounds that can be described by the same general formula where the one member is separated from the following by a CH 2 - group. 2.2 B and F 2.3 2.3.1 5 carbons 2 chlorides 2.3.2 Aldehyde group Methyl group 2.4 2.4.1 Butanoic acid 2.4.2 Propene 2.5 E 2.6 Positional isomers have the same molecular formula, but different positions of the side chain, substitutions or functional groups. 2.7 IEB Copyright © 2019 PLEASE TURN OVER

Downloaded from hlayiso.com NATIONAL SENIOR CERTIFICATE: TECHNICAL SCIENCES: PAPER II – MARKING GUIDELINES Page 3 of 8 QUESTION 3 3.1 Unsaturated 3.2 Hydrochloric acid 3.3 Hidro-halogenation 3.4 Acid catalyst must be used Excess of water (H 2 O) 3.5 Sodium hydroxide (NaOH) 3.6 Substitution/Hydrolysis 3.7 QUESTION 4 4.1 Monomer is the basic structural unit (a small molecule) from which a polymer (macro molecule) is made. /Small organic molecule that can be covalently bonded to each other in a repeating pattern. 4.2 Polymerisation 4.3 Electrical insulation Milk and fruit juice bottles, butter and margarine containers Detergent containers Re-usable bottles Recycling bins Stadium seats Traffic barrier cones Water & drain pipes Toys (Any two) IEB Copyright © 2019 PLEASE TURN OVER

Downloaded from hlayiso.com NATIONAL SENIOR CERTIFICATE: TECHNICAL SCIENCES: PAPER II – MARKING GUIDELINES Page 4 of 8 QUESTION 5 5.1 The temperature at which the vapour pressure of the liquid is equal to the atmospheric pressure of the liquid. 5.2 Butanol has a longer chain length than propanol, therefore it has a larger contact surface area and it has stronger London forces than propanol. More (heat) energy is needed for higher kinetic energy to overcome the intermolecular forces and therefore it has higher boiling point. 5.3 5.3.1 London forces 5.3.2 Dipole-dipole forces 5.3.3 Hydrogen forces 5.4 The temperature at which the solid and liquid phases of a substance are at equilibrium. 5.5 Butanol 5.6 Butanone has dipole-dipole forces between the molecules. Butanol has strong hydrogen forces between the molecules. Butanol needs more energy to break the hydrogen bonds between the molecules and therefore the melting point will be higher. 5.7 Butene It has the weakest intermolecular forces which gives it the lowest viscosity as the layers can move over each other easily. QUESTION 6 6.1 It is an electrochemical cell where electrical energy is converted into chemical energy. 6.2 A silver layer forms. 6.3 Electrical energy → Chemical energy 6.4 6.4.1 B 6.4.2 A 6.5 Ag+(aq) + 1e–→ Ag(s) 6.6 Instead of using a carbon electrode, the object that is to be silver plated can be connected to the negative pole of the cell and placed in a AgNO 3 solution and silver will be deposited on the object. IEB Copyright © 2019 PLEASE TURN OVER

Downloaded from hlayiso.com NATIONAL SENIOR CERTIFICATE: TECHNICAL SCIENCES: PAPER II – MARKING GUIDELINES Page 5 of 8 QUESTION 7 7.1 7.1.1 No, there is no salt bridge to connect the two containers OR The circuit is not completed. 7.1.2 Chemical energy → Electrical energy 7.1.3 Zn to Cu 7.1.4 Cu-electrode 7.1.5 Cu2+ + 2e–→ Cu 7.1.6 Zn + Cu2+ → Zn2+ + Cu + Bal 7.1.7 Zn(s)/Zn2+ (aq)(1mol.dm–3) //Cu2+(aq)(1mol.dm-3)/Cu(s) 7.2 7.2.1 Loss of electrons 7.2.2 Emf A = E°(reduction) – E°(oxidation) = 0,8 – (–0,44) =1,24V Emf B = E°(reduction) – E(oxidation) = –2,36 – (0,85) = –3,21 V 7.2.3 Reaction A will be spontaneous as the EMF has a positive value. 7.3 7.3.1 PV systems do not emit any harmful air or water pollution. Photovoltaic cells are quiet and no visual disturbance. Small solar plants can be put on roofs of existing buildings. PV cells operate for a long time with little maintenance. Solar energy is a local renewable source of energy. A PV system can be made to any energy requirements. A PV system can be enlarged or moved as the energy requirements change. (Correct answer) 7.3.2 It can be used in isolated areas or in the middle of cities and towns to generate electricity which is used for, for example, pumping water, lights, activating switches, charging batteries, supplying the electric grid. IEB Copyright © 2019 PLEASE TURN OVER

Downloaded from hlayiso.com NATIONAL SENIOR CERTIFICATE: TECHNICAL SCIENCES: PAPER II – MARKING GUIDELINES Page 6 of 8 QUESTION 8 8.1 8.1.1 Refraction 8.1.2 The light ray is moving from a dense to a less dense medium. The speed of the wave changes in a different medium and the wave is refracted. 8.1.3 Critical angle 8.2 8.2.1 Total internal reflection 8.2.2 Angle of incidence must be bigger than the critical angle. The light wave must move from a dense to a less dense medium. 8.2.3 Telescope Binoculars 8.3 8.3.1 Normal is a line which is perpendicular to the surface of the reflective object. 8.3.2 Line of incidence Reflected ray 8.3.3 40° 8.3.4 (a) 7 cm (b) 27 cm (c) Yes IEB Copyright © 2019 PLEASE TURN OVER

Downloaded from hlayiso.com NATIONAL SENIOR CERTIFICATE: TECHNICAL SCIENCES: PAPER II – MARKING GUIDELINES Page 7 of 8 QUESTION 9 9.1 9.1.1 Convex 9.1.2 Real Inverted Same size 9.1.3 When an exact copy of an object is needed. 9.2 9.2.1 9.2.2 Upright, virtual, smaller than object. 9.3 9.3.1 Dispersion 9.3.2 The phenomena whereby white light breaks up into its component colours. 9.3.3 Violet 9.3.4 Violet has the shortest wavelength and is therefore refracted most. IEB Copyright © 2019 PLEASE TURN OVER

Downloaded from hlayiso.com NATIONAL SENIOR CERTIFICATE: TECHNICAL SCIENCES: PAPER II – MARKING GUIDELINES Page 8 of 8 QUESTION 10 10.1 Self propagating, changing magnetic and electric fields that are mutually perpendicular to each other and perpendicular to the direction of propagation of the wave. 10.2 Sound waves need a medium for propagation and electromagnetic waves do not. 10.3 Gamma, X-rays, Ultraviolet, Visible light, Infrared, Microwaves, Radio waves. 10.4 10.4.1 X-rays 10.4.2 Ultra violet rays hc 10.5 E= λ 6,63 × 10 −34 × 3 × 108 = 456 × 10 −9 = 4,36 × 10 −19 J Total: 150 marks IEB Copyright © 2019