Kimia set 1 perfect score

Set 1 Chemistry Perfect Score Module 2007

Set 1 1

PAPER 2 – STRUCTURESECTION A

1 In an experiment to determine the empirical formula of an oxide of copper , the combustion tube with theporcelain dish are weighed. Oxide of copper is added into the porcelain dish and the tube is weighedagain. The oxide of copper is heated strongly. After the set of apparatus cools down to roomtemperature the combustion tube with its content is weighed again.

The following data is obtained.

Mass of combustion tube + porcelain dish = 19.60 gMass of combustion tube + porcelain dish + oxide of copper = 25.68 gMass of combustion tube +porcelain dish + copper = 24.46 g

(a) What is meant by empirical formula?

……………………………………………………………………………………………………………….[ 1 mark ]

(b) 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 untilall 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 beenremoved.

……………………………………………………………………………………………………………….

……………………………………………………………………………………………………………….

……………………………………………………………………………………………………………….[3 marks ]

Set 1 Chemistry Perfect Score Module 2007

Set 1 2

(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) proton number ?

....................................................................……………………………………….................[1 mark]

(ii) nucleon number ?

................................. ...................................………………………………………................[1 mark]

(b) (i) What is meant by isotope?

...........................................................................................................................................[1 mark]

(ii) 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 Chemistry Perfect Score Module 2007

Set 1 3

(f) (i) What is meant by valence electron?

.....................................................................................…………………………..................[1 mark]

(ii) What is the number of valence electron of atom W ?

...........................................................................................................................................[1 mark]

(g) Write the symbol of atom X in the form ofA

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 actualsymbol of the elements.

1 182 13 14 15 16 17

V X ZY

W

DIAGRAM 3

(a) Write the electron arrangement of Y ion.

…………………………………………………………………………………….....................................[ 1 mark ]

(b) (i) Which of the element is not chemically reactive.

. ...........................................................................................................................................[ 1 mark ]

(ii) Explain your answer in (b)(i).

...........................................................................................................................................[ 1 mark ]

(c) V and W are located in the same group in the Periodic Table of Elements.

(i) Which of the element is more reactive?

..............................................................................................................….........................[ 1 mark ]

(ii) Explain your answer in (c)(i).

…………………………………………………………………………......................................

…………………………………………………………………………......................................

…………………………………………………………………………......................................[ 3 marks]

Set 1 Chemistry Perfect Score Module 2007

Set 1 4

(d) V reacts with Y to form a compound.State one physical property of the compound formed.

…………………………………………………………………………………........................................[ 1 mark ]

(e) 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 Electron arrangementof atom

E 1

F 2.4

G 2.8.7

H 2.8.1

J 2.8.8

L 2.6

TABLE 4(a) Which element in Table 4 are metal and non-metal?

Metal : ..........................................................................................................................

Non- metal : ...........................................................................................................................[2 marks]

(b) State an element that exist as monoatomic gas.Explain your answer.

.....…………………………………………………………………………………………........................

..…………………………………………………………………………………………….......................[2 marks]

(c) Write the formula for the ion formed from an atom of element L.

..................................................………………………………………………………………................[1 mark]

(d) Element F reacts with element G to form a compound

(i) State the type of bond present in this compound.

...........................................................................................................................................[1 mark]

(ii) State two physical properties of compound formed.

………………………………………………………………………………………............

………………………………………………………………………………………............

Set 1 Chemistry Perfect Score Module 2007

Set 1 5

[2 marks]

(e) When element H is burnt in G gas , H burns rapidly and brightly with a yellow flame andliberates 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.

AtomElectron

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.

............................................................................................................................................................[1 mark]

(b) Atom Q and atom X react to form a compound.

(i) Write the formula of compound formed.

....................................................................................................................................................[1 mark]

(ii) State one physical property of the compound.

....................................................................................................................................................[1 mark]

(c) (i) Compare the size of atom W with atom X.

....................................................................................................................................................[1 mark]

(ii) Explain your answer in (c)(i).

....................................................................................................................................................

....................................................................................................................................................

....................................................................................................................................................

Set 1 Chemistry Perfect Score Module 2007

Set 1

[2 marks](d) (i) Element T is not chemically reactive.Explain.

....................................................................................................................................................

....................................................................................................................................................[2 marks]

(ii) State the position of element T in the Periodic Table.

....................................................................................................................................................[1 mark]

6 Graph 6 shows the temperature against time of solid substance X when heated. Substance X is anorganic compound and flammable.

(a) Draw a dia

(b) (i) S

...

(ii) What

PQ :

RS :

Temperature /0C

Time/s

80

P

Q R

S

GRAPH 6

gram of the set-up of the a

tate the melting point of sub

..........................................

is the state of matter of sub

..........................................

.........................................

3

0

6

pparatus used to determine the melting point of substance X.

[ 2 marks]stance X

...........................................................................................................[ 1 mark]

stance X at :

...........................................................................................................

...........................................................................................................[ 2 marks]

36

0

Set 1 Chemistry Perfect Score Module 2007

Set 1 7

(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 Sduring heating.

…………………………………………………………………………………………………………………….[ 1 mark]

(c) If substance X is cooled to the room temperature without stirring, draw the graph of temperature againsttime obtained.

[ 2 marks]

(d) Identify subtance X

.....................................................................................................................................................................[ 1 mark]

Set 1 Chemistry Perfect Score Module 2007

Set 1 8

7 Lactic acid is an acid produced in milk by bacteria that causes the milk to taste sour. Table 7 shows thepercentage 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?

Given that Avogadro number ,NA = 6.02 × 1023

mol-1

[ 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 moleculesof lactic acid. What is the relative molecular mass of ethanoic acid?

[ 1 mark](ii) Determine the molecular formula of ethanoic acid.

Set 1 Chemistry Perfect Score Module 2007

Set 1 9

[ 2 marks]

8 Table 8 shows formula of four ions.

Name of ions Silver ion Zinc ion Nitrate ion Chloride ion

Formula of ions Ag+

Zn2+

NO3-

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 andzinc nitrate solution are formed.

(i) Identify the reactants and products of the reaction.

Reactants : ........................................................................................................................

Products : ........................................................................................................................[2 marks]

(ii) 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.Given that the Molar volume : 24 dm

3at room conditions

[ 2 marks]

Set 1 Chemistry Perfect Score Module 2007

Set 1 10

PAPER 2 – ESSAY SECTION B

9 (a)

Explain the above statement.

Given that relative molecular mass of carbon dioxide = 44 g mol–1

,relative molecular mass of oxygen = 2 g mol

–1

[3 marks]

(b) (i) What is meant by empirical formula? [ 1 mark]

(ii) Describe an experiment in the laboratory to determine the empirical formula ofmagnesium 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 themixture of copper oxide and magnesium powder.

[ 3 marks]

PAPER 2 - ESSAY SECTION C10 Table 7 shows the proton number of atoms P, Q and R.

Element Proton number

P

Q

R

8

12

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) Write a chemical equation for the reaction between gas P and element Q.(ii) 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 ]

The volume of 2.2 g of carbon dioxide gas is less thanthe volume of 2.2 g of hydrogen at the same temperature and pressure.

Set 1 Chemistry Perfect Score Module 2007

Set 1 11

PAPER 3

12. The diagram below shows the apparatus set-up for the experiment to determine the freezing point ofsubstance X.

The diagram below shows the thermometer reading for the cooling of substance X at certain timeintervals.

(a) Record the thermometer readings shown in the diagram above by completing the table below.

time/minute 0 1 2 3 4 5 6 7

Temperature/oC

[3 marks]

Retort stand

thermometer

Substance X

Volumetric flask

90

95

85

0 Minute 1st minute 2nd Minute 3rd minute

85

90

80

85

90

80

85

90

80

85

90

85

90

80

75

80

70

70

75

65

4th minute 5th minute 6th minute 7th Minute

Set 1 Chemistry Perfect Score Module 2007

Set 1 12

(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 theanswer.

…………………….............……………………………………………………………[3 marks]

(e) Based on this experiment, what is meant by freezing point?

……...…………………………………………………………………………………

……...…………………………………………………………………………………

……...…………………………………………………………………………………[3 marks]

(f) If substance X is heated from room temperature until 100oC, what is the temperature when

substance X starts to melt? Explain your answer.

………………………………………………………………………………….......................[3 marks]

Set 1 Chemistry Perfect Score Module 2007

Set 1

12

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 thereactivity of the Group 1 elements based on their reactions with water.

Apparatus set-up Observation towards the metal

Lithium moves slowly on the surface of the waterwith a “hiss” sound.

Potassium moves vigorously and randomly on thesurface of the water with a “hiss” sound.

(a) State the variables that are invName of variables(i) Manipulated variable:

……………………………………..

……………………………………..

(ii) Responding variable:

……………………………………

……………………………………(iii) Controlled variable:

……………………………………..

……………………………………..

Elements in Group 1 of the Periodic Table of Elements can be arranged based on thereactivity of the elements with water.

water

))

sodium

)) )

)))

Potassium

)) ) )

water

Lithium

13

Sodium moves quickly and randomly on thesurface of the water with a “ hiss” sound.

olved in the experiment.Action to be taken(i) The way to manipulate variable:

………………………………………..

………………………………………...

(ii) What to observe in the responding variable:………………………………………..

………………………………………..………

(iii) The way to maintain the controlled variable:

………………………………………

………………………………………

[6 marks]

water

Set 1 Chemistry Perfect Score Module 2007

Set 1 14

“When lithium metal is put in water, it moves very slowly on the surface of the water. Whensodium metal is put in water, it moves quite fast and produces “hiss” sound. When potassiummetal is put in water, it moves very fast and produces small explosions”.

Metal

(b) State one hypothesis for the experiment.

………………………………………………………………………………………

………………………………………………………………………………………[3 marks]

(c) Based on the observations in the figure above, arrange lithium, potassium and sodium in thedescending 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 insolution X into positive ions and negative ions.

Positive Ions Negative Ions

[3 marks]3

Plan an experiment in the laboratory to investigate the reactivity of lithium, sodiumand 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

and potassium with water

[17 marks]

Water

Set 1 Chemistry Perfect Score Module 2007

Set 1 15

Sample AnswerSection A

1 (a) Formula that shows the simplest ratio of the number of atomsfor each element in the compound. 1

(b)

Functional diagram an heating is shown 1Dry hydrogen gas and oxide of copper are labelled 1

(c) Cu O

24.46 – 19.60 / 4.86 25.68 – 24.46 / 1.22 1

4.86 / 0.076 1.22 / 0.076 164 16

CuO 1

(d) CuO + H2 Cu + H2O 1

(e) Collect the gas in a test tube 1Put lighted wooden splinter at the mouth of the test tube 1No pop sound 1

(f) No 1Aluminium more reactive than hydrogen //Hydrogen less reactive than aluminium // hydrogen belowaluminium in reactivity series. 1

12

2 (a) (i) The proton number is the number of protons in an atom 1(ii) The nucleon number is the total number of protons and neutrons

in an atom 1(b) (i) Isotopes are atoms of the same element with different numbers

of neutrons 1(ii) X and Y 1

(c) The number of proton = 11 1The number of electron = 11 1The number of neutron = 12 1

(d) 2.8.7 1

(e)

1

Dry hydrogen gas

Oxide of copper

Heat

Set 1 Chemistry Perfect Score Module 2007

Set 1 16

(f) (i) The electrons in the outermost occupied shell 1(ii) 1 1

(g) 35X

17112

3 (a) 2.8.8 1(b) (i) Z 1

(ii) Achieve octet electron arrangement / / achieve 8electron in the outermost shell // 8 valence electron 1

(c) (i) W 1

(ii) The atomic size of W is bigger than the atomic size of V 1The attraction between the nucleus and the valence electronis weaker in an atom W 1It is easier for atom W to donate / release electron 1

(d) High melting / boiling point// dissolve in water// do not dissolve inorganic solvents // conduct electricity in aqueous solution ormolten state . 1

(e)

Correct number of atoms( 4 of atom Y and 1 of atom X) 1Correct number of shells and electrons 1

10

X YY

Y

Y

Set 1 Chemistry Perfect Score Module 2007

Set 1 17

4(a) Metal : HNon- metal : E, F, G, J , L

11

4(b) J8 electron in the outermost shell // achieve octet electron arrangement

11

4(c) L2-

14(d)(i) Covalent bond. 14(d)(ii) 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 ]

11

4(e)(i) Sodium chloride. 14(e)(ii) 2H + G2 2HG 1

Total 10

5 (a) W / Y 1

(b) (i) QX4 1

(ii) Low melting/boiling point// do not dissolve in water// dissolve in organicsolvents // do not conduct electricity in aqueous solution or molten state .

[ Any one ] 1

(c) (i) The atomic size of X is smaller than the atomic size of W 1

(ii) The number of proton of atom X more than atom W 1The attraction by the nucleus on the electronsin the first three occupied shells in atom X become stronger 1

d) (i) Have eight valence electrons//achieve octet electron arrangement 1

No need to lose , gain or share electrons with atom of another element 1

(ii) Group18 and period 2 1

9

Set 1 Chemistry Perfect Score Module 2007

Set 1 18

6 (a)

[Functional diagram ]

[ Labels :

X, water, thermometer, Bunsen burner/heat ]

1

1

(b) (i) 80 oC 1

(ii) PQ : solidRS : liquid [1 + 1] 2

(iii) The energy absorbed is used to overcome the forces of attractionbetween the particles 1

(iv) The particles move faster 1

(c)

[The shape of the graph is correct ] …1

[ Both axis are labeled with unit ]

x-axis : time/s , y-axis : temperature/ 0C

80 0C on graph …1 2

(d) naphthalene 110

Thermometer

Boiling tube

Water

Substance X

Bunsen burner

Temperature / 0C

Time/s

80

Set 1 Chemistry Perfect Score Module 2007

Set 1 19

7 (a)Element C H O

Number of moles(mol) 12

00.40

= 3.331

67.6

= 6.6716

33.53

= 3.33

Ratio of moles 1 2 1

1

1

The empirical formula of the compound is CH2O 1

(b) n [ 12 + 2(1) + 16 ] = 90

n =30

90

= 3

Molecular formula of lactic acid is C3H6O3

1

1

(c) One molecule of lactic acid contains 6 hydrogen atoms 1 mol of lactic acid contains 6 mol of hydrogen atoms 1 mol of lactic acid contains 6 × 6 .02 × 10

23hydrogen atoms 1

(d)The number of mole of lactic acid =

90

5.4

= 0.05 mol1

(e) 3 × Mr of ethanoic acid = 2 × Mr of lactic acid

Mr of ethanoic acid =3

902 x

= 601

(f) n (30) = 60n = 2

Molecular formula of ethanoic acid is C2H4O2 / CH3COOH

1

110

8 (a) (i) AgNO3 1(ii) ZnCl2 1(iii) AgCl 1(iv) Zn(NO3)2 1

(b) (i) Silver nitrate and zinc chloride 1

Silver chloride and zinc nitrate 1

(ii) 2AgNO3 + ZnCl2 2AgCl +Zn(NO3)2 1

(c) (i)Number of moles of AgNO3 =

170

85

= 0.5 mol1

2 moles of AgNO3 produce 2 moles of Ag

Set 1 Chemistry Perfect Score Module 2007

Set 1 20

0.5 mole of AgNO3 produce 0.5 mole of Ag 1

Mass of Ag = 0.5 × 108= 54 g 1…….…3

(ii) 2 moles of AgNO3 produces 1 mole of O2

0.5 mole of AgNO3 produces 0.25 mole of O2 1

Volume of O2 = 0.25 × 24= 6 dm

31…….…2

10

SECTION B

9 (a) Number of mole of carbon dioxide =44

2.2= 0.05 mol 1

Number of mole of hydrogen =2

2.2= 1.1 mol 1

The number of mole of carbon dioxide is smaller; therefore, its volume is smaller thanthe volume of hydrogen 1

(b) (i) The empirical formula of a compound is the simplest whole number ratio of atoms of eachelement present in the compound. 1

(ii) [ Material and apparatus ][Magnesium ribbon, sand paper, crucible with lid, tongs, Bunsen burner, tripod stand, pipe-claytriangle and balamce.] or [diagram] 2

[ Procedure] A crucible and its lid is weighed and its weight is recorded. 1 A 10 cm length of magnesium ribbon is coiled loosely and is placed in the crucible. 1 The crucible with its lid and content are weighed again and the weight is recorded . 1 The crucible is heated strongly without its lid. 1 When the magnesium starts to burn, the crucible is covered with its lid. Using a pair of tongs, the lid is lifted at intervals. 1 When the burning is completed, the lid is removed and

the crucible is heated strongly for 2 minutes. 1 The rucible is allowed to cool to room temperature. 1 The crucible and its lid and content are weighed again and its weight is recorded. 1

max 5[Precautions taken]

The magnesium ribbon is cleaned with sand paper to remove the layer ofmagnesium oxide on the surface.

The crucible must cover with its lid to prevent the white fumes ofmagnesium oxide of escaping.

The processes of heating, cooling and weighing are repeated untila constant mass is obtained. [any two of the above] 2

[ Results ] Crucible + lid = a g

Crucible + lid + magnesium = b gCrucible + lid + magnesium oxide = c g 1

[ Calculation ]

Set 1 Chemistry Perfect Score Module 2007

Set 1 21

Element Magnesium OxygenMass(g) b-a c-bNumber of molesof atoms

b-a/24 c-b/16

Simplest ratio ofmoles

X y

2Empirical formula = MgxOy 1

(c) 1 Unable to make sure that all the magnesium is oxidised . 12 The products (Cu and MgO) cannot be separated. 13 The mass of copper and oxygen cannot be determined. 1

Total 20

SECTION C

10 (a)(i) 1. Two atoms of P combine through covalent bond. 12. Each atom of P needs two more electrons to achieve octet electron arrangement.3. Each atom of P contributes two electrons to each other for sharing. 14. Two atoms of P share two pairs of electrons. 15. A double covalent bond is formed.

P P

2

(ii) 1. Atom Q and atom R combine through ionic bond. 12. To achieve octet electron arrangement, 13. atom Q with 6 valence electrons loses two electrons to form Q

2+ion 1

4. Two atom R, each atom with 7 valence electronsgains one electron to form R

-ion. 1

5. Q2+

ion and R-ion are attracted to each other by strong electrostatic force.1

_ 2+ _

R Q R

2

(b)(i) 2Q + P2 2QP 1

(ii) 1. Have high melting point 12. Usually soluble in water 13. Conduct electricity in the molten state or aqueous solution. 1

(c) 1. Element Q is located in Group 2 12. because it has two valence electrons 13. Element Q is located in Period 3 14. because it has three shells occupied with electrons 1

Set 1 Chemistry Perfect Score Module 2007

Set 1 22

1 (a) To measure using numbers.

Score Explanation3 Able to record all the readings correctly to 1 decimal place.

Time(minute)

0 1 2 3 4 5 6 7

Temperature(oC)

95.0 89.0 84.5 83.0 83.0 83.0 77.0 70.0

(b) Communication

Score Explanation3 Able to draw the graph with the following elements::

X-axis is labeled(minute) and y-axis temperature(oC) 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

Set 1 Chemistry Perfect Score Module 2007

Set 1

Temperature/oC

Graph of temperature against time

Melting point

23

Time/minute

Set 1 Chemistry Perfect Score Module 2007

Set 1 24

(c) (i) the relationship of space and time

Score Explanation3 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 from95

oC to 83

oC.

Constant temperature at 83oC for 3 minutes.

The temperature decreases again after 83oC

(c) (ii) Inference

Score Explanation3 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 isbalanced by the heat released when bonds are formed.

The freezing process is at 83oC // solid and liquid X exist together

1(d) Data analysisScore Explanation

3 Able to state the freezing point accurately based on the graph with thecorrect unit.

Dotted line is shown on the graph.

Labeling the freezing point at temperature axis.

1(e) Operational definitionScore Explanation

3 Able to give the meaning of freezing point accurrately.Suggested answer:Freezing point is the constant temperature at 83

oC even though substance X is

let to cool to room remperature.

1(f) To predictScore Explanation

3 Able to predict the melting point of substance X accurrately with unit and withcorrect reasons.Suggested answer :83.0

oC

Value of melting point substance X is the same as its freezing point.

Set 1 Chemistry Perfect Score Module 2007

Set 1 25

2(a) To control the variablesScore Explanation Explanation

6 Able to predict the manipulatedvariable, the responding variable andthe constant variable completely.

Suggested answer:Manipulated variable : metals ofGroup 1 elements // sodium, lithium,potassium.

Responding variable: the reactivity ofthe reaction with water // the speed ofmovement on the water surface

Constant variable: size/mass ofmetals. Volume of water

Able to state how to control the manipulatedvariables correctly

Suggested answer:Repeat the experiment by using the metalsof sodium, lithium and potassium

Able to state correctly the way to control themanipulated variable

Suggested answer:To observe how fast the metals move onthe surface of water.

Able to use the metal granules with thesame sizeSuggested answer :Use the metal granules with the same size.

2(b) To make hypothesisScore Explanation

3 Able to state the relationship between the manipulated variable and theresponding variable correctly.

Suggested answer: The reactivity of Group 1 elements increases going down thegroup.

2(c) To interprete dataScore Explanation

3 Able to arrange correctly the reactivity series of the metals according todescending order.Answer: potassium, sodium, lithium

2(d) To classify

Score Explanation3 Able to classify the ions correctly.

[to name or write all the formula of the ions correctly at the cations and anionsgroup.]Answer: positive ion/ cation : sodium ion/ Na

+, hydrogen ion/ H

+

Negative ion/anion : hydroxide ion/ OH-

Set 1 Chemistry Perfect Score Module 2007

Set 1 26

No Explanation Score3(a) [Able to state the aim of experiment accurately]

To compare the reactivity of lithium, sodium and potassium based on the reactionwith water and describing the effect of the solution towards the red litmus paper.

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3(b) HypothesisMetals of lithium, sodium and potassium show different rate of reactivity with waterand the solution formed turns red litmus paper to blue.

3(b) Variablesa) Manipulated variable :type of metalsb) Responding variable : reactivity of reactionc) Constant variable : water and temperature

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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, bluelitmus paper and white tile.

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3(d) [Able to give all the procedures correctly, steps 1 - 7]1. Lithium metal is cut into a small piece2. 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.

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3(e) [Able to show the accurate tabulation of data with correct title.]

Metals ObservationsLithiumSodium

Potassium

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