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MRSM PENGKALAN CHEPA CHEMISTRY UNIT 2013 GUIDELINES FOR ANSWERING PAPER 3.

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Presentation on theme: "MRSM PENGKALAN CHEPA CHEMISTRY UNIT 2013 GUIDELINES FOR ANSWERING PAPER 3."— Presentation transcript:

1 MRSM PENGKALAN CHEPA CHEMISTRY UNIT 2013 GUIDELINES FOR ANSWERING PAPER 3

2 Structure Question NO 1 or NO 2 is to test the mastery of 11 Scientific Skills 1. Observing 2. Classifying 3. Inferring 4. Measuring (burette, stopwatch, thermometer, voltmeter) 5. Predicting 6. Communicating( e.g construct table and draw graph) 7. Space-Time Relationship 8. Interpreting Data 9. Defining Operationally 10. Controlling Variables 11. Hypothesizing

3 Operational definition is a statement that contains: 1. what you do/procedure 2. what you see/observation Examples 1. State OD for coagulation of latex When acid is added into latex, white solid is formed- correct (When acid is added into latex, latex coagulated.- wrong)

4 2. State Op Def for rate of reaction in this experiment When the higher concentration sodium thiosulphate solution is added into sulphuric acid, time taken for `X~ mark to disappear from sight is shorter.

5 3. State Op Def for rusting of iron When iron nail is coiled with copper and immersed into jelly mixed with potassium hexacyanoferrate(III) and phenolphthalein solution, blue spot/colouration is formed.

6 More examples on Operational definition What you do - What is observed 1. Rusting of iron - When an iron nail coiled with a less electropositive metal is immersed in hot agar-agar added with potassium hexacyanoferrate (III) solution, blue spots are formed

7 More examples on Operational definition What you do - What is observed 2. Coagulation of latex - When acid is added to latex White solid is formed

8 3. Reactivity of Group 1 elements When a metal which is lower in Group 1 is put in a basin half filled with water brighter flame is formed 4. Precipitation of silver chloride When silver nitrate solution is added to sodium chloride solution White solid is formed

9 3. 5. Voltaic cell When two different metals are dipped into an electrolyte The needle of the voltmeter deflects//Voltmeter shows a reading

10 More examples on Operational definition What you do What is observed 6. An acid When a blue litmus paper is dipped into a substance which is dissolved in water, blue litmus paper turns red

11 More examples on Operational definition What you do What is observed 7. Heat of combustion When 1 mol of fuel is burnt in excess oxygen Temperature rises//Thermometer reading increases

12 More examples on Operational definition What you do What is observed 8. Hardness of alloy When a weight is dropped on a steel ball bearing taped on an alloy block diameter of dent formed is smaller

13 Hypothesis: ( early conclusion to aim of exp) Statement that relates the MV followed by responding variable with direction. Example: 1.The higher temperature of the reactant the higher the rate of reaction – 3 marks 2. Hexene decolourised brown bromine water but hexane does not

14 Hypothesis: ( early conclusion to aim of exp) Statement that relates the MV followed by RV with direction. Example: 3. When acid is added into latex, latex coagulates, when ammonia is added into latex, latex cannot coagulates

15 ExpMVRVHypothesis (MV→RV) Does size of calcium carbonate affect rate of reaction? Size of calcium carbonate Rate of reactio n When size of calcium carbonate is smaller, the rate of reaction increases

16 ExpMVRVHypothesis (MV→RV) To differentia te between hexene and hexane Hexen e and hexan e Decolouri sed brown bromine water When hexene is added to bromine water, brown colour decolorized, but when hexane is added to bromine water, brown bromine not changed

17 ExpMVRVHypothesis (MV→RV) Heat of combusti on of different types of alcohols Types of alcohol s Heat of combusti on When no of carbon atoms per molecule alcohol increases, the heat of combustion increase

18 ExpMVRVHypothesis (MV→RV) Coagul ation of latex Acid and ammonia solution Coagulat ion of latex When acid is added to latex, coagulation of latex occurs, but when ammonia solution is added to latex, NO coagulation occur

19 How is the reading of apparatus taken? to 1 decimal point or 2 decimal point?

20 STRUCTURE PAPER

21 1Diagram 1 shows three sets, Set I, Set II and Set III, of the apparatus set-up for an experiment to investigate the effect of ethanoic acid and ammonia solution on the coagulation of latex.

22 SetApparatus set-up I II III Latex + ethanoic acid Latex coagulate Latex + ammonia Latex + not coagulate Latex only Latex coagulate

23 (a)State one hypothesis based on Set I and Set II. Acid coagulate latex while alkali does not coagulate the latex

24 (b) Record the time taken for the latex to coagulate in Set 1 and Set III. Set I : 5 minutes // 300 s Set III: 6 hours // 60 minutes// s

25 (c) Construct a table to record the time taken for coagulation in Set I and Set III. SetTime taken I5 minutes III6 hours

26 (d) State one observation that can be obtained from each set of this experiment. Set I : Latex coagulates / A solid lump is formed Set II : Latex does not coagulate / No change / Liquid Set III : Latex coagulates / A solid lump is formed

27 (e) State the operational definition for the coagulation of latex. When acid is added to latex, it becomes solid

28 (f) Manipulated variable: Responding variable : Constant variable : Ethanoic acid / Acid/(Ammonia solution) / Alkali Coagulate //Time taken for coagulation Vol of latex / acid / (ammonia solution) / alkali // latex /temp

29 (g) (i) Set II after 2:00 p.m. What observation can be made about the latex? Latex coagulates // Latex becomes solid/(semi-solid) //Latex is solidified

30 (ii) Explain the answer in l(g) (i). bacteria in air reacts with latex to produce lactic acid ( H + ) Hydrogen ions (H + ) neutralise OH - ions in ammonia solution Hydrogen ions (H + ) neutralised the negative charge of protein membrane, collisions of rubber particles occur, rubber molecules clump

31 (h)Explain why latex can coagulate without acid in Set III. Bacteria in air reacts with latex to produce lactic acid / H + These H + neutralise the negatively charged on the protein membrane of latex particles Latex particles no longer repel each other, so the particles collide, rubber molecules clump

32 i) (i) Explain why the latex in Set I coagulates faster than the latex in Set III. The concentration of hydrogen ion, H + in Set I is higher than in set III In set I, H + produced, neutralise the negatively charged on the protein membrane faster than in set III

33 (ii)The following is a list of chemical substances Nitric acid Sodium hydroxide Methanoic acid Potassium hydroxide Classify these substances into substances that can coagulate latex and substance that cannot coagulate latex.

34 Can coagulate latex Cannot coagulate latex Nitric acid Methanoic acid Potassium hydroxide Sodium hydroxide

35 SPM-P3 2009

36 Exp 1: ELECTROLYSIS CuSO 4 USING C AS ELECTRODE Exp 2: ELECTROLYSIS CuSO 4 USING Cu AS ELECTRODE

37 a. 3 obsvn and inference (not include the colour change of the electrolyte) Colourless gas bubbles released at anode A brown solid is deposited at the cathode and the cathode thicker Oxygen is produced Copper is formed at the cathode Observations inference

38 a. 3 obsvn and inference (not include the colour change of the electrolyte) The copper anode in exp II become thinner Copper anode dissolves to form copper (II) ions Observations inference

39 b. State one hypothesis for the experiment In the electrolysis of copper(II) sulphate solution,the types of products formed at the electrodes depend on the types of electrodes used

40 The type of electrodes used The products formed at anode Concentration of Copper(II) sulphate/ copper(II) sulphate Manipulated variable responding variable Constant variable

41 Solution that produced gas at the anode when electrolysed Solution that does not produced gas at the anode when electrolysed Sodium hydroxide Nitric acid Potassium iodide O2 O2 O2 O2 O2 O2 O2 O2 I 2 but iodine is denser than water, so does not bubble I 2 but iodine is denser than water, so does not bubble

42 In cell I, the blue colour change to light blue. In cell II. No change of colour in the solution. Explain In Cell I, Blue colour is due to Cu 2+ ion. Cu +2 are discharged to form Cu atoms at cathode. (Cu e  Cu) So conc of Cu +2 decrease.

43 In cell I, the blue colour change to light blue. In cell II. No change of colour in the solution. Explain In cell II, Rate of ionization of copper atom to Cu +2 (Cu  Cu 2+ +2e) at anode is equal to rate of discharge of Cu +2 to copper atoms ( Cu e  Cu) at cathode. So conc of Cu +2 remain constant

44 Draw the diagram of electroplating of iron key with silver using silver nitrate solution Silver nitrate solution Iron key Silver rod cathode Anode

45 SPM PAPER 3 STRUCTURES 2010

46

47 I- Lithium burns with a white flame II- Potassium burns with a purple flame flame III- Sodium burns with a yellow flame

48 Potassium reacts vigorously Potassium reacts vigorously with water alkaline solution is produced alkaline solution is produced Heat is released Heat is released 3 inferences from exp II Hypothesis in this experiment The lower the position elements in Group I, the higher the reactivity of metals with water The lower the position elements in Group I, the higher the reactivity of metals with water

49 When Group I elements are placed in water, When Group I elements are placed in water, the intensity of the flame produced shows the reactivity of the elements the intensity of the flame produced shows the reactivity of the elements e) State operational definition of of reactivity of Group I elements

50 Li Na K Li Na K Atomic size increase from lithium atom to potassium atom Atomic size increase from lithium atom to potassium atom Nuclei attraction in K atom is the most Nuclei attraction in K atom is the most K atom is the easiest to release electron to form K + ion K atom is the easiest to release electron to form K + ion Arrange in ascending order of reactivity Give reason in term of atomic size

51 Rubidium burns very brightly Rubidium burns very brightly A lot of bubbles are produced A lot of bubbles are produced A colourless solution with pH 3.2 is produced A colourless solution with pH 3.2 is produced Rb is placed below K in Group I element. Predict 3 observations with Rb

52 Manipulated variable Responding variable Constant variable Water and methyl benzene Water and methyl benzene Effervescence / acidic properties of ethanoic acid Effervescence / acidic properties of ethanoic acid Ethanoic acid, magnesium Ethanoic acid, magnesium

53 Sketch a graph of the volume of hydrogen gas againsts time

54 Strong acid Hydrochloric acid Nitric acid Sulphuric acid Weak acid Ethanoic acid Classify the following acids into strong and weak acids


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