1. Set 1
Chemistry Perfect Score Module 2007
PAPER 2 – STRUCTURE
SECTION A
1
In an experiment to determine the empirical formula of an oxide of copper , the combustion tube with the
porcelain dish are weighed. Oxide of copper is added into the porcelain dish and the tube is weighed
again. The oxide of copper is heated strongly. After the set of apparatus cools down to room
temperature the combustion tube with its content is weighed again.
The following data is obtained.
Mass of combustion tube + porcelain dish
Mass of combustion tube + porcelain dish + oxide of copper
Mass of combustion tube +porcelain dish + copper
=
=
=
19.60 g
25.68 g
24.46 g
(a)
What is meant by empirical formula?
(b)
……………………………………………………………………………………………………………….
[ 1 mark ]
Draw a labelled diagram of the set-up of the apparatus for the experiment.
[ 2 marks ]
(c)
Calculate the empirical formula of the oxide of copper.
Given that the relative atomic mass of O=16 , Cu=64
[ 3 marks ]
(d)
Write the chemical equation for the reaction in the experiment.
…………………………………………………………………………………….....................................
[ 1 mark ]
(e)
Before oxide of copper is heated, hydrogen gas is allowed to pass through the apparatus until
all the air in the combustion tube is completely removed.
Describe the steps that should be taken to ensure that all air in the combustion tube has been
removed.
……………………………………………………………………………………………………………….
……………………………………………………………………………………………………………….
……………………………………………………………………………………………………………….
[3 marks ]
Set 1
1

2. Set 1
Chemistry Perfect Score Module 2007
(f)
Can the empirical formula of aluminium oxide be determined using the same method as above?
Explain your answer.
…………………………………………………………………………………….....................................
…………………………………………………………………………………….....................................
[ 2 marks ]
2
Table 2 shows proton number and nucleon number for atom W, X and Y.
Atom
Proton number
Nucleon number
W
11
23
X
17
35
Y
17
37
TABLE 2
(a)
What is meant by :
(i)
(ii)
....................................................................……………………………………….................
[1 mark]
nucleon number ?
(i)
................................. ...................................………………………………………................
[1 mark]
What is meant by isotope?
(ii)
(b)
proton number ?
...........................................................................................................................................
[1 mark]
State the atoms which are isotope.
...........................................................................................................................................
[1 mark]
(c)
State the number of protons, electrons and neutrons in atom W
The number of protons: .................................................................................................................
The number of electrons: ..............................................................................................................
The number of neutrons: ...............................................................................................................
[3 marks]
(d)
Write the electron arrangement of atom X
................................................................………………………………………………......
[1 mark]
(e)
Draw the electron arrangement for atom Y
[1 mark]
Set 1
2

3. Set 1
Chemistry Perfect Score Module 2007
(f)
(i)
What is meant by valence electron?
(ii)
.....................................................................................…………………………..................
[1 mark]
What is the number of valence electron of atom W ?
...........................................................................................................................................
[1 mark]
(g)
Write the symbol of atom X in the form of
A
z
X.
........................................................................................................................................................
[1 mark]
3
Diagram 3 shows part of the Periodic Table of Elements.V,W,X,Y and Z do not represent the actual
symbol of the elements.
1
18
2
13
V
14
X
15
16
17
Z
Y
W
DIAGRAM 3
(a)
Write the electron arrangement of Y ion.
(b)
…………………………………………………………………………………….....................................
[ 1 mark ]
(i)
Which of the element is not chemically reactive.
.
(ii)
(c)
...........................................................................................................................................
[ 1 mark ]
Explain your answer in (b)(i).
...........................................................................................................................................
[ 1 mark ]
V and W are located in the same group in the Periodic Table of Elements.
(i)
Which of the element is more reactive?
(ii)
..............................................................................................................….........................
[ 1 mark ]
Explain your answer in (c)(i).
…………………………………………………………………………......................................
…………………………………………………………………………......................................
…………………………………………………………………………......................................
[ 3 marks]
Set 1
3

4. Set 1
Chemistry Perfect Score Module 2007
(d)
(e)
V reacts with Y to form a compound.
State one physical property of the compound formed.
…………………………………………………………………………………........................................
[ 1 mark ]
X reacts with Y to form a compound.
Draw the electron arrangement for the compound formed.
[ 2 marks]
4
Table 4 shows the electron arrangement of atoms of elements E, F, G, H, J, and L.
Element
E
F
G
2.8.7
H
2.8.1
J
2.8.8
L
(a)
Electron arrangement
of atom
1
2.4
2.6
TABLE 4
Which element in Table 4 are metal and non-metal?
Metal
Non- metal
(b)
: ..........................................................................................................................
: ...........................................................................................................................
[2 marks]
State an element that exist as monoatomic gas.Explain your answer.
.....…………………………………………………………………………………………........................
(c)
..…………………………………………………………………………………………….......................
[2 marks]
Write the formula for the ion formed from an atom of element L.
(d)
..................................................………………………………………………………………................
[1 mark]
Element F reacts with element G to form a compound
(i)
State the type of bond present in this compound.
(ii)
...........................................................................................................................................
[1 mark]
State two physical properties of compound formed.
………………………………………………………………………………………............
………………………………………………………………………………………............
Set 1
4

5. Set 1
Chemistry Perfect Score Module 2007
[2 marks]
(e)
When element H is burnt in G gas , H burns rapidly and brightly with a yellow flame and
liberates white fumes.
(i)
Suggest the name of the white fumes.
...........................................................................................................................................
[1 mark]
(ii)
Write the equation for the reaction between element H and G gas.
...........................................................................................................................................
[2 marks]
5 Table 5 shows the electron arrangement for six atom , Q ,R ,T,W,X and Y.
Electron
Atom
arrangement
Q
2.4
R
2.6
T
2.8
W
2.8.1
X
2.8.7
Y
2.8.8.1
TABLE 5
(a)
By using symbols and information in the table 5 , choose one atom that formed cation.
(b)
............................................................................................................................................................
[1 mark]
Atom Q and atom X react to form a compound.
(i)
(ii)
(c)
Write the formula of compound formed.
....................................................................................................................................................
[1 mark]
State one physical property of the compound.
(i)
....................................................................................................................................................
[1 mark]
Compare the size of atom W with atom X.
....................................................................................................................................................
[1 mark]
(ii)
Explain your answer in (c)(i).
....................................................................................................................................................
....................................................................................................................................................
....................................................................................................................................................
Set 1
5

6. Set 1
Chemistry Perfect Score Module 2007
[2 marks]
(d)
(i)
Element T is not chemically reactive.Explain.
....................................................................................................................................................
....................................................................................................................................................
[2 marks]
State the position of element T in the Periodic Table.
(ii)
....................................................................................................................................................
[1 mark]
6
Graph 6 shows the temperature against time of solid substance X when heated. Substance X is an
organic compound and flammable.
0
Temperature / C
S
Q
R
80
P
Time/s
3
0
GRAPH 6
36
0
(a) Draw a diagram of the set-up of the apparatus used to determine the melting point of substance X.
[ 2 marks]
(b) (i)
(ii)
State the melting point of substance X
........................................................................................................................................................
[ 1 mark]
What is the state of matter of substance X at :
PQ : .....................................................................................................................................................
RS : ....................................................................................................................................................
[ 2 marks]
Set 1
6

7. Set 1
Chemistry Perfect Score Module 2007
(iii) Explain why the temperature remains constant from Q to R.
...............................................................................................................................................................
...............................................................................................................................................................
[ 2 marks]
(iv) State how the movement of substance X particles changes between R and S
during heating.
…………………………………………………………………………………………………………………….
[ 1 mark]
(c) If substance X is cooled to the room temperature without stirring, draw the graph of temperature against
time obtained.
[ 2 marks]
(d) Identify subtance X
.....................................................................................................................................................................
[ 1 mark]
Set 1
7

8. Set 1
Chemistry Perfect Score Module 2007
7
Lactic acid is an acid produced in milk by bacteria that causes the milk to taste sour. Table 7 shows the
percentage of composition by mass of each element in lactic acid.
Element
Percentage
Carbon
40.00
Hydrogen
6.67
Oxygen
53.33
TABLE 7
(a) Based on the information above, calculate the empirical formula of lactic acid.
Given that the relative atomic mass of H = 1 ; C = 12 ; O = 16
[ 3 marks]
(b) Relative molecular mass of lactic acid is 90. Determine the molecular formula of lactic acid.
[ 2 marks]
(c) Calculate the number of hydrogen atom in 1 mol of lactic acid?
23
-1
Given that Avogadro number ,NA = 6.02 × 10 mol
[ 1 mark]
(d) Calculate the number of moles of 4.5 g lactic acid.
Given that the relative atomic mass of H = 1 ; C = 12 ; O = 16
[ 1 mark]
(e) Vinegar or ethanoic acid has a similar empirical formula with lactic acid.
(i) Given that three molecules of ethanoic acid have the same mass as two molecules
of lactic acid. What is the relative molecular mass of ethanoic acid?
[ 1 mark]
(ii) Determine the molecular formula of ethanoic acid.
Set 1
8

9. Set 1
Chemistry Perfect Score Module 2007
[ 2 marks]
8
Table 8 shows formula of four ions.
Name of ions
Silver ion
Formula of ions
Zinc ion
+
Ag
Zn
Nitrate ion
Chloride ion
NO3
2+
Cl
-
TABLE 8
(a) Write the formula for each compound below :
(i)
Silver nitrate
………..…..........................................................................................
(ii) Zinc chloride
: .......................................................................................................
(iii) Silver chloride
: .......................................................................................................
(iv) Zinc nitrate
: .......................................................................................................
[4 marks]
(b) When silver nitrate solution is added to zinc chloride solution, white precipitate, silver chloride and
zinc nitrate solution are formed.
(i)
Identify the reactants and products of the reaction.
Reactants : ........................................................................................................................
(ii)
Products : ........................................................................................................................
[2 marks]
Write the chemical equation for the reaction occurs in (b).
...........................................................................................................................................
[1 mark]
(c) The following equation shows the decomposition of silver nitrate by heat.
2AgNO3
2Ag
+ 2NO2
+
O2
If 85.0 g of silver nitrate is heated completely, calculate :
(i)
the mass of silver formed.
Given that the relative atomic mass of N =14; O = 16; Ag =108
3 marks]
(ii)
the volume of oxygen gas formed at room conditions.
3
Given that the Molar volume : 24 dm at room conditions
[ 2 marks]
Set 1
9

10. Set 1
Chemistry Perfect Score Module 2007
PAPER 2 – ESSAY SECTION B
9
(a)
The volume of 2.2 g of carbon dioxide gas is less than
the volume of 2.2 g of hydrogen at the same temperature and pressure.
Explain the above statement.
–1
Given that relative molecular mass of carbon dioxide = 44 g mol ,
–1
relative molecular mass of oxygen = 2 g mol
[3 marks]
(b)
(i)
What is meant by empirical formula?
[ 1 mark]
(ii)
Describe an experiment in the laboratory to determine the empirical formula of
magnesium oxide. Your answer should consist of the following.
 Procedures of the experiment
 Calculation involved
 Precautions need to be taken
Given that relative atomic mass of Mg = 24, O = 16
[13 marks]
(c)
Magnesium can reduced copper oxide to copper.
Explain why the empirical formula of the copper oxide cannot be determined by heating the
mixture of copper oxide and magnesium powder.
[ 3 marks]
PAPER 2 - ESSAY SECTION C
10
Table 7 shows the proton number of atoms P, Q and R.
Element
Proton number
P
8
Q
12
R
17
TABLE 7
(a) Based on electron arrangement, explain the formation of chemical bond between
(i)
element P and element P
[5 marks ]
(ii)
element Q and element R
[7 marks ]
(b) Gas P reacts with element Q to produce a white solid.
(iii)
(ii)
Write a chemical equation for the reaction between gas P and element Q.
State three physical properties of the white solid.
[ 4 marks ]
(c) What is the position of elelment Q in the Periodic Table of the elements?
Explain how do you obtain your answer.
[ 4 marks ]
Set 1
10

11. Set 1
PAPER 3
Chemistry Perfect Score Module 2007
12. The diagram below shows the apparatus set-up for the experiment to determine the freezing point of
substance X.
thermometer
Retort stand
Substance X
Volumetric flask
The diagram below shows the thermometer reading for the cooling of substance X at certain time
intervals.
95
90
90
90
90
85
85
85
85
80
80
80
2nd Minute
3rd minute
1st minute
0 Minute
90
90
80
75
85
85
75
70
80
70
65
4th minute
(a)
6th minute
5th minute
7th Minute
Record the thermometer readings shown in the diagram above by completing the table below.
time/minute
0
1
2
3
4
5
6
7
o
Temperature/ C
[3 marks]
Set 1
11

12. Set 1
Chemistry Perfect Score Module 2007
(b)
Draw the graph of temperature against time on the graph paper provided.
(c)
Based on the graph in (b),
(i)
State the change in temperature of substance X for the whole experiment.
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
[3 marks]
(ii)
State the inference for your answer in (c) (i) .
...........................................................................................................................
...........................................................................................................................
...........................................................................................................................
[3 marks]
(d)
What is the freezing point of substance X? Show and label it on the graph how you obtained the
answer.
…………………….............……………………………………………………………
[3 marks]
(e)
Based on this experiment, what is meant by freezing point?
……...…………………………………………………………………………………
……...…………………………………………………………………………………
……...…………………………………………………………………………………
[3 marks]
(f)
o
If substance X is heated from room temperature until 100 C, what is the temperature when
substance X starts to melt? Explain your answer.
………………………………………………………………………………….......................
[3 marks]
Set 1
12

13. Set 1
12
Chemistry Perfect Score Module 2007
Elements in Group 1 of the Periodic Table of Elements can be arranged based on the
reactivity of the elements with water.
An experiment is carried out to investigate the statement above.
The table below shows the apparatus set up and the observations for the experiment to determine the
reactivity of the Group 1 elements based on their reactions with water.
Apparatus set-up
Observation towards the metal
Lithium
))
water
Lithium moves slowly on the surface of the water
with a “hiss” sound.
Potassium
)) ) )
)))
water
Potassium moves vigorously and randomly on the
surface of the water with a “hiss” sound.
sodium
)) )
water
Sodium moves quickly and randomly on the
surface of the water with a “ hiss” sound.
(a)
State the variables that are involved in the experiment.
Name of variables
Action to be taken
(i) Manipulated variable:
(i) The way to manipulate variable:
……………………………………..
………………………………………..
……………………………………..
………………………………………...
(ii) Responding variable:
(ii) What to observe in the responding variable:
………………………………………..
……………………………………
………………………………………..………
……………………………………
(iii) Controlled variable:
(iii) The way to maintain the controlled variable:
……………………………………..
………………………………………
……………………………………..
………………………………………
[6 marks]
Set 1
13

14. Set 1
Chemistry Perfect Score Module 2007
(b)
State one hypothesis for the experiment.
………………………………………………………………………………………
………………………………………………………………………………………
[3 marks]
(c)
Based on the observations in the figure above, arrange lithium, potassium and sodium in the
descending order of reactivity of metals towards water.
Descending order of reactivity of metals towards water.
[3 markah]
(d)
Solution X was produced from the reaction of sodium with water. Classify the ions that exist in
solution X into positive ions and negative ions.
Positive Ions
Negative Ions
[3 marks]
3
“When lithium metal is put in water, it moves very slowly on the surface of the water. When
sodium metal is put in water, it moves quite fast and produces “hiss” sound. When potassium
metal is put in water, it moves very fast and produces small explosions”.
Metal
Water
Plan an experiment in the laboratory to investigate the reactivity of lithium, sodium and potassium with water
and describe the effect of the solution produced towards a red litmus paper.
The planning of your experiment must consist of the following:
(a) Aim of experiment
(b) Statement of the hypothesis
(c) All the variables
(d) List of substances and apparatus
(e) Procedure of the experiment
(f) Tabulation of data
[17 marks]
Set 1
14

15. Set 1
Chemistry Perfect Score Module 2007
Sample Answer
Section A
1
(a)
Formula that shows the simplest ratio of the number of atoms
for each element in the compound.
1
Oxide of copper
(b)
Dry hydrogen gas
Heat
Functional diagram an heating is shown
Dry hydrogen gas and oxide of copper are labelled
(c)
Cu
O
24.46 – 19.60 / 4.86
4.86
64
1
1
/ 0.076
25.68 – 24.46 / 1.22
1
1.22 / 0.076
16
1
CuO
1
(d)
1
(e)
Collect the gas in a test tube
Put lighted wooden splinter at the mouth of the test tube
No pop sound
1
1
1
(f)
2
CuO + H2  Cu + H2O
No
Aluminium more reactive than hydrogen //
Hydrogen less reactive than aluminium // hydrogen below
aluminium in reactivity series.
1
(a)
(i)
(ii)
(b)
(i)
(ii)
1
12
The proton number is the number of protons in an atom
1
The nucleon number is the total number of protons and neutrons
in an atom
1
Isotopes are atoms of the same element with different numbers
of neutrons
1
X and Y
1
(c)
The number of proton = 11
The number of electron = 11
The number of neutron = 12
1
1
1
(d)
2.8.7
1
(e)
1
Set 1
15

16. Set 1
Chemistry Perfect Score Module 2007
(f)
(i)
(ii)
(g)
The electrons in the outermost occupied shell
1
35
X
17
3
(a)
(b)
(c)
2.8.8
(i)
(ii)
1
1
1
12
Z
Achieve octet electron arrangement / / achieve 8
electron in the outermost shell // 8 valence electron
1
1
1
W
1
(ii)
(d)
(i)
The atomic size of W is bigger than the atomic size of V
The attraction between the nucleus and the valence electron
is weaker in an atom W
It is easier for atom W to donate / release electron
1
High melting / boiling point// dissolve in water// do not dissolve in
organic solvents // conduct electricity in aqueous solution or
molten state
.
1
1
1
(e)
Y
Y
X
Y
Y
Correct number of atoms( 4 of atom Y and 1 of atom X)
Correct number of shells and electrons
Set 1
16
1
1
10

17. Set 1
Chemistry Perfect Score Module 2007
4(a)
Metal : H
Non- metal : E, F, G, J , L
J
8 electron in the outermost shell // achieve octet electron arrangement
2L
Covalent bond.
Low melting/boiling point// do not dissolve in water// dissolve in organic
solvents // do not conduct electricity in aqueous solution or molten state
.
[ Any two ]
Sodium chloride.
2H + G2
2HG
Total
4(b)
4(c)
4(d)(i)
4(d)(ii)
4(e)(i)
4(e)(ii)
5
(a) W / Y
(b) (i)
(ii)
1
1
1
1
1
1
1
1
1
1
10
1
QX4
1
Low melting/boiling point// do not dissolve in water// dissolve in organic
solvents // do not conduct electricity in aqueous solution or molten state .
[ Any one ]
(ii)
d) (i)
(ii)
The atomic size of X is smaller than the atomic size of W
1
The number of proton of atom X more than atom W
The attraction by the nucleus on the electrons
in the first three occupied shells in atom X become stronger
1
Have eight valence electrons//achieve octet electron arrangement
1
No need to lose , gain or share electrons with atom of another element
(c) (i)
1
1
Group18 and period 2
1
1
9
Set 1
17

18. Set 1
6
Chemistry Perfect Score Module 2007
(a)
Thermometer
Boiling tube
Water
Substance X
Bunsen burner
[Functional diagram ]
[ Labels :
 X, water, thermometer, Bunsen burner/heat ]
(b) (i)
(ii)
(iii)
(iv)
(c)
1
80 oC
1
PQ : solid
RS : liquid
1
[1 + 1]
2
The energy absorbed is used to overcome the forces of attraction
between the particles
1
The particles move faster
1
Temperature / 0C
80
Time/s
[The shape of the graph is correct ]
[ Both axis are labeled with unit ]
 x-axis : time/s , y-axis : temperature/ 0C
 80 0C on graph
(d)
Set 1
naphthalene
…1
…1
2
1
10
18

19. Set 1
7
Chemistry Perfect Score Module 2007
(a)
Element
C
H
O
40.00
12
6.67
1
53.33
16
= 3.33
= 6.67
= 3.33
1
Number of moles
(mol)
2
1
Ratio of moles
1
1
The empirical formula of the compound is CH2O
(b)
n [ 12 + 2(1) + 16 ]
n
1
= 90
=
90
30
1
= 3
Molecular formula of lactic acid is C3H6O3
(c)
(d)
1
One molecule of lactic acid contains 6 hydrogen atoms
 1 mol of lactic acid contains 6 mol of hydrogen atoms
23
 1 mol of lactic acid contains 6 × 6 .02 × 10 hydrogen atoms
1
The number of mole of lactic acid
=
4.5
90
1
= 0.05 mol
(e)
3 × Mr of ethanoic acid = 2 × Mr of lactic acid
Mr of ethanoic acid =
2 x 90
3
= 60
(f)
n (30)
n
1
= 60
= 2
1
Molecular formula of ethanoic acid is C2H4O2 / CH3COOH
8
1
10
(a) (i)
(ii)
(iii)
(iv)
AgNO3
ZnCl2
AgCl
Zn(NO3)2
1
1
1
1
(b) (i)
Silver nitrate and zinc chloride
1
Silver chloride and zinc nitrate
1
(ii)
(c) (i)
2AgNO3
+ ZnCl2
Number of moles of AgNO3
2AgCl
=
+Zn(NO3)2
85
170
= 0.5 mol
2 moles of AgNO3 produce 2 moles of Ag
Set 1
1
19
1

20. Set 1
Chemistry Perfect Score Module 2007
0.5 mole of AgNO3 produce 0.5 mole of Ag
Mass of Ag
(ii)
1
= 0.5 × 108
= 54 g
1…….…3
2 moles of AgNO3 produces 1 mole of O2
0.5 mole of AgNO3 produces 0.25 mole of O2
Volume of O2
1
= 0.25 × 24
3
= 6 dm
1…….…2
10
SECTION B
9
(a) Number of mole of carbon dioxide =
Number of mole of hydrogen
=
2 .2
=
44
2 .2
2
0.05 mol
= 1.1 mol
1
The number of mole of carbon dioxide is smaller; therefore, its volume is smaller than
the volume of hydrogen
(b) (i)
(ii)









1
1
The empirical formula of a compound is the simplest whole number ratio of atoms of each
element present in the compound.
1
[ Material and apparatus ]
[Magnesium ribbon, sand paper, crucible with lid, tongs, Bunsen burner, tripod stand, pipe-clay
triangle and balamce.] or [diagram]
2
[ Procedure]
A crucible and its lid is weighed and its weight is recorded.
A 10 cm length of magnesium ribbon is coiled loosely and is placed in the crucible.
The crucible with its lid and content are weighed again and the weight is recorded .
The crucible is heated strongly without its lid.
When the magnesium starts to burn, the crucible is covered with its lid.
Using a pair of tongs, the lid is lifted at intervals.
When the burning is completed, the lid is removed and
the crucible is heated strongly for 2 minutes.
The rucible is allowed to cool to room temperature.
The crucible and its lid and content are weighed again and its weight is recorded.
1
1
1
1
1
1
1
1
max 5



[Precautions taken]
The magnesium ribbon is cleaned with sand paper to remove the layer of
magnesium oxide on the surface.
The crucible must cover with its lid to prevent the white fumes of
magnesium oxide of escaping.
The processes of heating, cooling and weighing are repeated until
a constant mass is obtained.
[any two of the above]
[ Results ]

Crucible + lid
Crucible + lid + magnesium
Crucible + lid + magnesium oxide
[ Calculation ]
Set 1
20
= a g
= b g
= c g
2
1

21. Set 1
Chemistry Perfect Score Module 2007
Element
Mass(g)
Number of moles
of atoms
Simplest ratio of
moles
Magnesium
b-a
b-a/24
Oxygen
c-b
c-b/16
X
y
2
1
Empirical formula = MgxOy
(c)
1
2
3
Unable to make sure that all the magnesium is oxidised .
The products (Cu and MgO) cannot be separated.
The mass of copper and oxygen cannot be determined.
1
1
1
Total 20
1.
2.
3.
4.
5.
Two atoms of P combine through covalent bond.
1
Each atom of P needs two more electrons to achieve octet electron arrangement.
Each atom of P contributes two electrons to each other for sharing.
1
Two atoms of P share two pairs of electrons.
1
A double covalent bond is formed.
SECTION C
10
(a)(i)
P
P
2
(ii)
1.
2.
3.
4.
5.
Atom Q and atom R combine through ionic bond.
1
To achieve octet electron arrangement,
1
2+
atom Q with 6 valence electrons loses two electrons to form Q ion
1
Two atom R, each atom with 7 valence electrons
gains one electron to form R ion.
1
2+
Q ion and R ion are attracted to each other by strong electrostatic force.1
_
R
2+
Q
_
R
2
(b)(i) 2Q + P2
(ii)
(c)
Set 1
2QP
1
1.
2.
3.
Have high melting point
Usually soluble in water
Conduct electricity in the molten state or aqueous solution.
1
1
1
1.
2.
3.
4.
Element Q is located in Group 2
because it has two valence electrons
Element Q is located in Period 3
because it has three shells occupied with electrons
1
1
1
1
21

22. Set 1
1
Chemistry Perfect Score Module 2007
(a) To measure using numbers.
Score
3
Explanation
Able to record all the readings correctly to 1 decimal place.
Time
(minute)
Temperature
o
( C)
0
1
2
3
4
5
6
7
95.0
89.0
84.5
83.0
83.0
83.0
77.0
70.0
(b) Communication
Score
3
Explanation
Able to draw the graph with the following elements::




Set 1
o
X-axis is labeled(minute) and y-axis temperature( C) with consistent
scales
Size of the graph is at least half the page of the graph paper.
All the points are plotted correctly
Curve of the graph is correct and smooth
22

23. Set 1
Chemistry Perfect Score Module 2007
Graph of temperature against time
Temperature/oC
Melting point
Time/minute
Set 1
23

24. Set 1
Chemistry Perfect Score Module 2007
(c) (i) the relationship of space and time
Score
3
Explanation
Able to explain the change of temperature with time from the graph.
Suggested answer:



In the first 3 minutes, the temperature of substance X will decrease from
o
o
95 C to 83 C.
o
Constant temperature at 83 C for 3 minutes.
o
The temperature decreases again after 83 C
(c) (ii) Inference
Score
3
Explanation
Able to make the correct inference.
Suggested answer:



Temperature decreases because heat is released to the surrounding.
Temperature is contant because heat released to the surrounding is
balanced by the heat released when bonds are formed.
o
The freezing process is at 83 C // solid and liquid X exist together
1(d) Data analysis
Score
3
Explanation



Able to state the freezing point accurately based on the graph with the
correct unit.
Dotted line is shown on the graph.
Labeling the freezing point at temperature axis.
1(e) Operational definition
Score
Explanation
3
Able to give the meaning of freezing point accurrately.
Suggested answer:
o
Freezing point is the constant temperature at 83 C even though substance X is
let to cool to room remperature.
1(f) To predict
Score
Explanation
3
Able to predict the melting point of substance X accurrately with unit and with
correct reasons.
Suggested answer :
o
83.0 C
Value of melting point substance X is the same as its freezing point.
Set 1
24

25. Set 1
Chemistry Perfect Score Module 2007
2(a) To control the variables
Score
Explanation
6
Able to predict the manipulated
variable, the responding variable and
the constant variable completely.
Suggested answer:
Manipulated variable : metals of
Group 1 elements // sodium, lithium,
potassium.
Responding variable: the reactivity of
the reaction with water // the speed of
movement on the water surface
Constant variable: size/mass of
metals. Volume of water
2(b) To make hypothesis
Score
3
Explanation
Able to state how to control the manipulated
variables correctly
Suggested answer:
Repeat the experiment by using the metals
of sodium, lithium and potassium
Able to state correctly the way to control the
manipulated variable
Suggested answer:
To observe how fast the metals move on
the surface of water.
Able to use the metal granules with the
same size
Suggested answer :
Use the metal granules with the same size.
Explanation
Able to state the relationship between the manipulated variable and the
responding variable correctly.
Suggested answer: The reactivity of Group 1 elements increases going down the
group.
2(c) To interprete data
Score
Explanation
3
Able to arrange correctly the reactivity series of the metals according to
descending order.
Answer: potassium, sodium, lithium
2(d) To classify
Score
3
Set 1
Explanation
Able to classify the ions correctly.
[to name or write all the formula of the ions correctly at the cations and anions
group.]
+
+
Answer: positive ion/ cation : sodium ion/ Na , hydrogen ion/ H
Negative ion/anion : hydroxide ion/ OH
25

26. Set 1
Chemistry Perfect Score Module 2007
No
3(a)
Explanation
[Able to state the aim of experiment accurately]
To compare the reactivity of lithium, sodium and potassium based on the reaction
with water and describing the effect of the solution towards the red litmus paper.
3(b)
Hypothesis
Metals of lithium, sodium and potassium show different rate of reactivity with water
and the solution formed turns red litmus paper to blue.
3(b)
Variables
a) Manipulated variable :type of metals
b) Responding variable : reactivity of reaction
c) Constant variable :
water and temperature
Score
3
3 x1
2x1
1x1
3(c )
[Able to list the correct and complete substances and apparatus.]
Substances and Apparatus
Lithium, sodium and potassium metals with water, basin, knife, forceps, blue
litmus paper and white tile.
3
3(d)
[Able to give all the procedures correctly, steps 1 - 7]
1. Lithium metal is cut into a small piece
2. The paraffin oil on the surface of the metal is wiped with the filter.
3. A basin is filled with water.
4. Lithium metal is put on the surface of the water with a pair of forceps.
5. Reactivity of the reaction is observed and recorded.
6. The experiment is repeated with sodium and potassium metals.
3
3(e)
[Able to show the accurate tabulation of data with correct title.]
Metals
Lithium
Sodium
Potassium
Set 1
Observations
26
3