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 Defining Operationally 10. Controlling Variables 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:
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. Exp MV RV
Hypothesis (MV→RV)
Does size of calcium carbonate affect rate of reaction?
Size of calcium carbonate
Rate of reaction
When size of calcium carbonate is smaller, the rate of reaction increases

16. To differentiate between hexene and hexane Hexene and hexane
Exp MV RV
Hypothesis (MV→RV)
To differentiate between hexene and hexane
Hexene and hexane
Decolourised 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. Exp MV RV
Hypothesis (MV→RV)
Heat of combustion of different types of alcohols
Types of alcohols
Heat of combustion
When no of carbon atoms per molecule alcohol increases, the heat of combustion increase

18. Exp MV RV
Hypothesis (MV→RV)
Coagulation of latex
Acid and ammonia solution
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
How is the reading of apparatus taken? to 1 decimal point or 2 decimal point?
1.30
1.6
20.40
24.0

20. STRUCTURE PAPER

21. 1 Diagram 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. Latex + ethanoic acid Latex coagulate Latex + ammonia
Set
Apparatus set-up I II
III
Latex + ethanoic acid
Latex coagulate
Latex + ammonia
Latex + not coagulate
Latex only
Latex coagulate

23. alkali does not coagulate the latex
(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. Set Time taken I 5 minutes III 6 hours
(c) Construct a table to record the time taken for coagulation in Set I and Set III.
Set
Time taken I
5 minutes
III
6 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. 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. Cannot coagulate latex
Can coagulate latex
Cannot coagulate latex
Potassium hydroxide
Sodium hydroxide
Nitric acid
Methanoic acid

35. SPM-P

36. Exp 1: ELECTROLYSIS CuSO4 USING C AS ELECTRODE
Exp 2: ELECTROLYSIS CuSO4 USING Cu AS ELECTRODE

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

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

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

41. I2 but iodine is denser than water, so does not bubble
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
I2 but iodine is denser than water, so does not bubble O2

42. In cell I, the blue colour change to light blue. In cell II
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 2++ 2e  Cu)
So conc of Cu+2 decrease.

43. In cell I, the blue colour change to light blue. In cell II
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
Anode
cathode
Silver rod
Iron key
Silver nitrate solution

45. SPM PAPER 3 STRUCTURES 2010

47. I- Lithium burns with a white flame
13.0
13.1
13.0
I- Lithium burns with a white flame
II- Potassium burns with a purple
flame
III- Sodium burns with a yellow flame

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

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

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

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

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

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

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