Physical Sciences Grade 10 P2 Gauteng November 2020 Memo

Downloaded from hlayiso.com GAUTENG DEPARTMENT OF EDUCATION PROVINCIAL EXAMINATION NOVEMBER 2020 GRADE 10 PHYSICAL SCIENCES (CHEMISTRY) PAPER 2 MARKING GUIDELINES 5 pages

Downloaded from hlayiso.com PHYSICAL SCIENCES (CHEMISTRY) MARKING GUIDELINES PAPER 2 GR 10 QUESTION 1: MULTIPLE CHOICE QUESTIONS 1.1 A (2) 1.2 A (2) 1.3 B (2) 1.4 C (2) 1.5 D (2) [10] QUESTION 2 2.1 2.1.1 liquid  (1) 2.1.2 Is the temperature of a liquid at which its vapour pressure equals the external (atmospheric) pressure. (2) 2.1.3 32  ° C (marks may be given for 30 to 35° C) (2) 2.1.4 (a) increase  (1) (b) remains the same  (1) 2.1.5 During this interval the particles have the same temperature. Temperature is a measure of the average kinetic energy of the particles. The energy from the heat is used for potential energy to have a phase change.  (3) [10] QUESTION 3 3.1 3.1.1 19  3.1.2 20  3.1.3 19  3.1.4 24  3.1.5 10  (5) 3.2 Atoms of the same element having the same number of protons, but different number of neutrons. (2) 3.3 (7)(6)  (93)(7) Ar(Li) = = 6,93 100  (3) [10] 2

Downloaded from hlayiso.com PHYSICAL SCIENCES (CHEMISTRY) MARKING GUIDELINES PAPER 2 GR 10 QUESTION 4 4.1 The transfer of electrons to form cations and ions that attract each other to form a formula-unit. (2) 4.2 MgCℓ2 (2) 4.3 4.3.1 3 energy levels Level 1 and 2 complete  7 valence electrons in level 4 (3) 4.3.2 3s² 3p5 (1) 4.4 1s² 2s² 2p6 3s²  (2) 4.5   2 x Cℓ– Mg2+ + 2Cℓ– → MgCℓ2 (4) [14] 3

Downloaded from hlayiso.com PHYSICAL SCIENCES (CHEMISTRY) MARKING GUIDELINES PAPER 2 GR 10 QUESTION 5 5.1 The simplest whole number ratio of atoms in a compound.  (2) 5.2   Pb : N :O n = 0,302 mol Pb  1 :2 :6  or Pb(NO3)2  n = 0,604 mol N  n = 1,816 mol O (6) [8] QUESTION 6 6.1 A: 2SO2(g) + 3O2 → 2SO3(g)  B: 2KCℓO3(s) → 2KCℓ(s) + 3O2(g)  C: 2Aℓ + Fe2O3 → Al2O3(s) + 2Fe(s)  D: 2C2H6(g) + 7O2(g) → 4CO2 + 6H2O(g)  (4) 6.2 The Law of constant composition states that different samples of a pure compound always contain the same elements in the same mass proportion. (2) 4

Downloaded from hlayiso.com PHYSICAL SCIENCES (CHEMISTRY) MARKING GUIDELINES PAPER 2 GR 10 6.3 2NaBr(aq) + Cℓ2(g) → 2NaCℓ(aq) + Br2(ℓ)  m = 206 g NaBr  m = 71 g Cℓ2 206 + 71 = 277 g reactants  m = 117 g NaCℓ  m = 160 g Br2 117 + 160 = 277 g products Mass of reactants equal mass of products; mass is conserved. (5) [11] QUESTION 7 7.1 aqueous solution or solution in which water is the solvent  (1) 7.2   n = 0,316 mol Na2CO3 (3) 7.3 1 mol Na2CO3 reacts with 2 mol HCℓ 0,316 mol Na2CO3 reacts with 0,632 mol HCℓ (2) 7.4 To test for CO2  (1) [7] TOTAL: 70 5