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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(2) 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. 1Thus 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



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+

1. [All electrons and number of shells filled with electron

correct]

2. [Nucleus of atom labeled and charges of ion shown

correctly]

(iii) In aqueous solution//molten state

Ions can move freely//free to move

PAPER 2 - ESEI

No.

4 (a) (i) Electron arrangement: 2.8.7

Element: Chlorine

(ii) 2NaOH + Cl2 NaCl + NaOCl + H

Correct reactant

Correct product

Balanced equation

(b)

The valence shell of electrons in diagram 4.1is nearer to the

nucleus compared to diagram4.2

Ch

Scheme Set 2 11


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. //

1Atom diagram 4.1 Atom diagram 4.2Atomic size / Smaller / nearer Bigger / fartherdistance betweennucleus andvalence electrons.Nuclei attraction Stronger Weakerbetween nucleusand valenceelectronsTendency to Easier Difficultreceive electrons toform negative ionReactivity More Less

(c) Less reactive 1

(d) (i) 1. all connection of the apparatus are tight to avoid the leakage og 1gas.2. carry out the experiment in fume chamber. 13. pour the hydrochloric acid carefully to avoid it from spilling.

(2) In Part A; Iron wool reacts with chlorine gas to form solid iron (III) chloride.

3Cl2 + 2Fe 2FeCl3 1

In Part H;1+1

Sodium chloride, sodium chlorate (I) and water are formed fromthe reaction between excess chlorine and sodium hydroxidesolution.2NaOH + Cl2 NaCl + NaOCl + H2O 1

1+1Total marks 20




PAPER 3 - STRUCTURE


5(a) To state the variables

Explanation Explanation 6

Manipulated variable : metals of Repeat the experiment by using theGroup 1 elements // sodium, metals of sodium, lithium andlithium, potassium. potassium

Responding variable: the To observe how fast the metals movereactivity of the reaction with on the surface of water.water // the speed of movementon the water surface

Constant variable: size/mass of Use the metal granules with the samemetals. Volume of water size.


[Able to state the relationship between the manipulated variable and the 3responding variable correctly]The reactivity of Group 1 elements increases going down the group.


(c) [Able to arrange correctly the reactivity series of the metals according to 3descending order]potassium, sodium, lithium


(d) The metal that reacts more vigorously with water is a more reactive metal. 3


(e) [Able to classify the ions correctly] 3

Positive ion/ cation : sodium ion/ Na+, hydrogen ion/ H+

Negative ion/anion : hydroxide ion/ OH-




PAPER 3 - ESEI


6(a) [ Able to state the problem statement clearly and accurately] 3How does the reactivity of Group 1 elements change when they react withwater?

[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


(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



(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






[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 reaction5. 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 1experiment]

Steps 3 and 4



[Able to construct a table correctly containing the following 3elements]

Metals Observations

Lithium

Sodium

Potassium

[Able to construct a tabulation of data containing the following 2elements]

Metals Observation

[An idea of a tabulation of data ] 1

- Minimum of 2 rows and columns




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