Chemistry Paper 3 Answer

PEPERIKSAAN PERCUBAAN SPM 2008 NEGERI KEDAH DARUL AMAN MARKING SCHEME CHEMISTRY PAPER 3 Section A

Question 1 (a)

Explanation

Maximum score

[Able to record all the five readings accurately]: Suggested answer: Pairs of electrodes

Voltage/V

Cu and P

1.5

Cu and Q

1.8

Cu and R

0.6

Cu and S

2.3

Cu and T

1.2

[Able to record any 4 readings accurately] [Able to record any 3 readings accurately] [No response given or wrong response] Question 1 (b)

Explanation [Able to arrange the position of all metals in descending order of electropositivity correctly]

3

2 1 0 Maximum score 3

Suggested answer: S, Q, P, Cu, R, T [Able to arrange the position of at least four metals in descending order of electroposivity correctly] [Able to arrange the position of at least two metals in descending order of electroposivity correctly] [No response given or wrong response]

1

2 1 0

Question 1 (c)

Explanation

Maximum score

[Able to state three variables and the way to control them correctly] Suggested answer: Manipulated variable:

Substituting the electrode T with different metals

Pair of metals Responding variable:

Reading of the voltmeter// voltage

Voltmeter reading

6

Controlled variable: Electrolyte//copper(II) sulphate Use the same concentration of solution//concentration and electrolyte/CuSO4 //use the same volume of electrolyte//same voltmeter//use copper electrode in voltmeter//copper electrode all experiments. [Able to state any 5 of the above information correctly] [Able to state any 4 of the above information correctly ] [Able to state any 3 of the above information correctly] [Able to state any 2 of the above information correctly ] [Able to state any 1 of the above information correctly ] [No response given or wrong response] Question 1 (d)

Explanation

5 4 3 2 1 0 Maximum score

[Able to state the relationship between the manipulated variable and the responding variable and the direction correctly] Suggested answer:The further the distance of the pair of metals in the electrochemical series the higher is the voltage / the voltmeter reading

3

[Able to state the relationship between the manipulated variable and the responding variable in general] Suggested answer:

2

The position of the metal in the electrochemical series affects the reading of the voltmeter// the higher the position of the metal in the electrochemical series, the bigger/ higher is the voltage/ the voltmeter reading. [Able to state an idea of hypothesis] Suggested answer: The electrochemical series is determined by the voltage value//Different metals give different voltage values. [No response given or wrong response]

2

1

0

Question 1(e)

Explanation

Maximum score

[Able to state three observations and three inferences correctly] Observation

Inference

1. copper strip/rod/metal dissolves/ becomes thinner

Copper is oxidised/ loses electron to form copper(II) ion

2. Brown solid is deposited at metal T

Copper is formed

3. The intensity of blue coloured solution remains unchanged

The concentration of Cu2+ in the solution remain unchanged

[Able to state any five of the above information correctly] [Able to state any four of the above information correctly] [Able to state any three of the above information correctly] [Able to state any two of the above information correctly] [Able to state any one of the above information correctly] [No response given or wrong response] Question 1(f)

Explanation

6

5 4 3 2 1 0 Maximum score

[Able to predict the voltage of the three cells accurately] Suggested answer:

Pair of metals

Voltage/ V

P and S

0.8

P and T

2.7

Q and R

2.4

[Able to predict the voltage of any two cells accurately] [Able to predict the voltage of any one cell accurately] [No response given or wrong response]

3

3

2 1 0

Question 1(g)

Explanation

Maximum score

[Able to classify all the metals correctly] Suggested answer:

More electropositive

Less electropositive

P, Q, S

R, T 2

[Able to classify three metals correctly] [Able to classify two metals correctly]

1 0

[No response given or wrong response] Question 1(h)

3

Explanation

Maximum score

[Able to explain the difference in the voltage of the cell] Suggested answer:

3

The distance between Cu and metal S is further than the distance between Cu and metal P in Electrochemical Series. The distance between Cu and metal S is further than the distance between Cu and metal P.. S is more electropositive than P [No response given or wrong response]

2

Explanation

Maximum score

Question 1(i)

1 0

[Able to draw the labeled apparatus set-up completely] Suggested answer:

Copper

Metal T

Copper(II) sulphate solution

T nitrate solution

3

Salt bridge [Able to draw the labeled apparatus set-up incompletely] [Able to draw the apparatus completely without label] [No response given or wrong response]

4

2 1 0

Question 2(a)

Explanation

Maximum score

[Able to write the problem statement of the experiment accurately.] Sample answer: How do lithium, sodium and potassium differ in reactivity with water?

3

[Able to write the problem statement of the experiment correctly.] Sample answer: How do lithium, sodium and potassium differ in reactivity?

2

[Able to write a relevant idea about the problem statement of the experiment//Able to write aim of experiment accurately.] Sample answer: How do lithium, sodium and potassium differ?//To compare the reactivity of lithium, sodium and potassium when react with water.

1

[No response given or wrong response]

0

Question 2(b)

Explanation

Maximum score

[Able to state the hypothesis accurately] Suggested answers: The reactivity of lithium, sodium and potassium towards water increases down the group // The reactivity of lithium, sodium and potassium towards water increases down the group

3

// The reactivity of lithium, sodium and potassium towards water in increasing order is : Lithium, sodium and potassium

[Able to the hypothesis of the experiment] The reactivity of lithium, sodium and potassium are different.

2

// The reactivity of lithium, sodium and potassium towards oxygen/ halogen increases down the group [Able to state that there is a reaction between lithium / sodium / potassium and water ]

1

[No response given or wrong response]

0

5

Question 2(c)

Explanation

Maximum score

[Able to state the three variables correctly.] Sample answer: Manipulated variable : Type of metal 3 Responding variables : Reactivity of metal Fixed variables : Size of metal, volume of water [Able to state any two variables correctly.] [Able to state only one variables correctly.] [No response given or wrong response]

Question 2(d)

Explanation

Maximum score

[Able to state complete materials and apparatus.] Sample answer: Materials: Lithium, sodium, potassium, water Apparatus: Basin/beaker, filter paper, pen knife/blade, forcep/tongs [Able to state any six materials and apparatus correctly.] [Able to state any three materials and apparatus correctly.] [No response given or wrong response]

Question 2(e)

2 1 0

Explanation

3

2 1 0 Maximum score

[Able to write the complete procedure of the experiment correctly] Suggested answer: 1. A small piece of lithium is cut using a knife and a pair of forceps 2. The surface of lithium is dried with filter paper 3. The piece of lithium is placed on the surface of water in a trough

3

4. The movement of lithium and any sound/flame given out is observed and recorded 5 Repeat the experiment using a small piece of sodium and potassium. [Able to write the necessary steps of the expeimental procedure] Steps 1, 3, 4 and 5 [Able to write the minimum experimental procedure] Steps 3 and 5 [No response given or wrong response] Question

Explanation

6

2 1 0 Maximum score

2(f)

[Able to construct a labeled tabulation of data ] Sample answer: Metal

Observation

3

Lithium Sodium Potassium [Able to construct a tabulation of data ] Sample answer: Metal

Observation

2

[Able to construct a table consisting of two rows and two columns.] 1

[No response given or wrong response]

END OF MARKING SCHEME

7

0