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Marking scheme-chemistry-perfect-score-module-form-4-set-2

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  • 1. Set 2 Marking Scheme :Periodic Table of Elements & Chemical Bonds 2010 PERIODIC TABLE OF ELEMENTS PAPER 2 – STRUCTURE No. Rubric Marks 1 (a) (i) Group 1 1 Period 3 1 (ii) F 1 (b) (i) E2L 1 (ii) Soluble in water// high melting point/ boiling point// conducts electricity in molten or aqueous solution 1 (c) (i) E 1 (ii) The nuclei attraction towards the valence electron is weaker in E. 1 Thus it is easier for E to lose/ release an electron to form a positively charged ion. 1 (d) (i) A//C 1 (ii) Covalent bond 1 Total marks 10 No. Explanation Marks 2 (a) (i) T 1 (ii) Q 1 (iii) S 1 (b) Q, P, T, S and R 1 (c) 2.8.3 1 (d) T- 1 (e) Both have the same number of shells of electrons 1 (f) Red litmus paper turns blue 1 (g) Transition elements 1 Total marks 9 Chemistry Perfect Score Module Form 4 2010 Marking Scheme Set 2 10
  • 2. Set 2 Marking Scheme :Periodic Table of Elements & Chemical Bonds 2010 No. Explanation Marks 3 (a) (i) D+ 1 (ii) B2- 1 (b) (i) 18 1 (ii) 2.8.8 1 (c) G 1 (d) (i) DE r: ED, chemical equation 1 (ii) + - - - Ion D+ Ion E- 1. [All electrons and number of shells filled with electron 1 correct] 2. [Nucleus of atom labeled and charges of ion shown 1 correctly] (iii) In aqueous solution//molten state 1 Ions can move freely//free to move 1 Total marks 10 PAPER 2 - ESEI No. Explanation Marks 4 (a) (i) Electron arrangement: 2.8.7 1 Element: Chlorine 1 (ii) 2NaOH + Cl2 NaCl + NaOCl + H2O Correct reactant 1 Correct product 1 Balanced equation 1 (b) 1 The valence shell of electrons in diagram 4.1 is nearer to the nucleus compared to diagram 4.2 Chemistry Perfect Score Module Form 4 2010 Marking Scheme Set 2 11
  • 3. Set 2 Marking Scheme :Periodic Table of Elements & Chemical Bonds 2010 Diagram 4.2 has 3 shells and diagram 4. 1has 2 shells. 1 The nuclei attraction in diagram 4.1 is stronger than diagram 4.2. Diagram 4.1 is more electronegative than diagram 4.2 because it is 1 easier to receive electron. Diagram 4.1 is more electronegative and more reactive than 1+1 diagram 4.2. // Atom diagram 4.1 Atom diagram 4.2 1 Atomic size / Smaller / nearer Bigger / farther distance between nucleus and valence electrons. Nuclei attraction Stronger Weaker between nucleus and valence electrons Tendency to Easier Difficult receive electrons to form negative ion Reactivity More Less (c) Less reactive 1 (d) (i) 1. all connection of the apparatus are tight to avoid the leakage og 1 gas. 2. carry out the experiment in fume chamber. 3. pour the hydrochloric acid carefully to avoid it from spilling. 1 (ii) In Part A; Iron wool reacts with chlorine gas to form solid iron (III) chloride. 3Cl2 + 2Fe 2FeCl3 1 1+1 In Part H; Sodium chloride, sodium chlorate (I) and water are formed from the reaction between excess chlorine and sodium hydroxide solution. 2NaOH + Cl2 NaCl + NaOCl + H2O 1 1+1 Total marks 20 Chemistry Perfect Score Module Form 4 2010 Marking Scheme Set 2 12
  • 4. Set 2 Marking Scheme :Periodic Table of Elements & Chemical Bonds 2010 PAPER 3 - STRUCTURE No. Explanation Marks 5(a) To state the variables Explanation Explanation 6 Manipulated variable : metals of Repeat the experiment by using the Group 1 elements // sodium, metals of sodium, lithium and lithium, potassium. potassium Responding variable: the To observe how fast the metals move reactivity of the reaction with on the surface of water. water // the speed of movement on the water surface Constant variable: size/mass of Use the metal granules with the same metals. Volume of water size. No. Explanation Marks [Able to state the relationship between the manipulated variable and the responding variable correctly] 3 The reactivity of Group 1 elements increases going down the group. No. Explanation Marks (c) [Able to arrange correctly the reactivity series of the metals according to 3 descending order] potassium, sodium, lithium No. Explanation Marks (d) The metal that reacts more vigorously with water is a more reactive metal. 3 No. Explanation Marks (e) [Able to classify the ions correctly] 3 Positive ion/ cation : sodium ion/ Na+, hydrogen ion/ H+ Negative ion/anion : hydroxide ion/ OH- Chemistry Perfect Score Module Form 4 2010 Marking Scheme Set 2 13
  • 5. Set 2 Marking Scheme :Periodic Table of Elements & Chemical Bonds 2010 PAPER 3 - ESEI No. Explanation Marks 6(a) [ Able to state the problem statement clearly and accurately] 3 How does the reactivity of Group 1 elements change when they react with water? [Able to state the problem statement slightly inaccurate] 2 To study the reactivity of Group 1 elements. [Able to provide an idea of a problem statement] 1 The reactivity of Group 1 elements. No response given / wrong response 0 No. Explanation Marks (b) Stating variables [Able to state all the corresponding variables accurately] 3 Manipulated variable : Type of Group 1 metals Responding variable : Reactivity of reaction Fixed variables : Water, size of metals [Able to state two corresponding variables accurately] 2 [Able to state any one corresponding variable correctly] 1 No response given / wrong response 0 No. Explanation Marks (c) [Able to list all materials and apparatus correctly] 3 Materials A small piece of lithium, sodium, potassium and water Apparatus [Suitable container], forceps, Knife, filter paper [Able to list the basic materials and apparatus required] 2 A small piece of lithium, sodium and potassium, water Apparatus [Suitable container], forceps [Able to provide an idea of materials and apparatus used] 1 Group 1 metals, water, forceps No response given / wrong response 0 Chemistry Perfect Score Module Form 4 2010 Marking Scheme Set 2 14
  • 6. Set 2 Marking Scheme :Periodic Table of Elements & Chemical Bonds 2010 No. Explanation Marks [Able to state all experimental steps correctly] 3 1. Cut a small piece of lithium using a knife and forceps. 2. Dry the oil on the surface of the lithium with filter paper. 3. Place the lithium slowly onto the water surface in a trough 4. Observe the reactivity of the reaction 5. Repeat steps 1 to 4 using sodium and potassium to replace lithium [Able to provide 3 steps correctly to carry out the experiment] 2 Steps 3,4 and 5 [Able to provide minimum of 2 steps correctly to carry out the 1 experiment] Steps 3 and 4 No response given / wrong response 0 No. Explanation Marks [Able to construct a table correctly containing the following 3 elements] Metals Observations Lithium Sodium Potassium [Able to construct a tabulation of data containing the following 2 elements] Metals Observation [An idea of a tabulation of data ] 1 - Minimum of 2 rows and columns No response given / wrong response 0 Chemistry Perfect Score Module Form 4 2010 Marking Scheme Set 2 15