spm chemif

孔子补习学院 CONFUCIUS TUTION CENTRE 1 对 1 补习，全 A+的保证，成绩只有上上上！

SPM CHEMISTRY SEMINAR 2015 1 PREPARED BY: MS PHUAN

孔子补习学院 CONFUCIUS TUTION CENTRE 1 对 1 补习，全 A+的保证，成绩只有上上上！MASTERING ESSAY QUESTION IN PAPER 3

Experiment 1 (Chapter 2) Experiment 2 (Chapter 4) SPM 2008 Experiment 3 (Chapter 4)

Aim:To investigate the effect of the presence of impurity to the melting point of naphthalene (becomes lower)

Aim:To investigate the reaction of alkali metals in water

Aim:To investigate the reactions of alkali metals with oxygen / chlorine

Problem statement:How does

Problem statement:How does reactivity of Group 1 elements change when they react with water?

Problem statement:How do alkali metal react with oxygen / chlorine?

Variables:Manipulated:Responding:Fixed (controlled):

Variables:Manipulated: types of alkali metalResponding: reactivity of alkali metalFixed (controlled): size of alkali metal

Variables:Manipulated: types of alkali metalsResponding: reactivity of alkali metalsFixed (controlled): oxygen gas

Hypothesis: Hypothesis: When going down Group 1, alkali metal becomes more reactive in water.

Hypothesis: When going down Group 1, alkali metals becomes more recative in their reaction with oxygen

Materials: Materials: red litmus paper, distilled water, paper, filter paper, small lithium,sodium and potassium

Materials: 3 gas jar filled with oxygen, red litmus paper, paper, filter paper, small lithium,sodium and potassium

Apparatus: Apparatus: water through, knife, forceps Apparatus: gas jar spoon, gas jar cover, small knife, Bunsen burner, pair of forceps

Procedure: Procedure:1) A piece of lithium removed from the bottle with apair of forceps.2) A small piece of lithium is cut using a knife.3) The paraffin oil on the surface of lithium is removed by using a

piece of filter paper.4) The piece of lithium is placed into a water through half-filled with

cold distilled water using pair of forceps.5) When the reaction stops, a piece of red litmus paper is put into the

solution formed.6) All changes occured are recorded.7) Steps 1 to 6 is repeated using potassium and sodium respectively

to remove lithium.

Procedure:1) A piece of lithium removed from the bottle with a pair of

forceps.2) A small piece of lithium is cut using a knife.3) The paraffin oil on the surface of lithium is removed by using a

piece of filter paper.4) The piece of lithium is placed in a gas jar spoon.5) The lithium is start to burn when heated.6) The burning lithium quickly lowered into a gas jar filled with

oxygen.7) When recations stops, 20cm3 of distilled water is poured into gas

jar and shaken well.8) A piece of red litmus paper is put into solution formed.9) All changes that occured are recorded.10) Steps 1 to 9 is repeated using potassium and sodium

respectively to remove lithium.

Tabulation of data: Tabulation of data:Metal Observation

LithiumSodiumPotassium

Tabulation of data:Metal Observation

Lithium

Sodium

Potassium

Experiment 4 (Chapter 4) Experiment 5 (Chapter 6) Experiment 6 (Chapter 6)


孔子补习学院 CONFUCIUS TUTION CENTRE 1 对 1 补习，全 A+的保证，成绩只有上上上！Aim:To investigate the reaction of halogens with iron

Aim:To investigate the effect of concentration of ions on the selective discharge of ions at the electrodes of aqueous hydrochloric acid

Aim:To investigate the effect of the type of electrodes on the products of electrolysis of aqueous copper(II) sulphate solution.

Problem statement:How does reactivity of halogens change when they react with iron

Problem statement:How does the concentration of ions in hydrochloric acid affect the discharge of ions at the anode?

Problem statement:How does the type of electrodes affect the type of products formed during the electrolysis

Variables:Manipulated: types of halogensResponding: reactivity of halogensFixed (controlled): iron

Variables:Manipulated: concentration of chloride ionsResponding: ion discharged at the anodeFixed (controlled): type of electrode

Variables:Manipulated: types of electrodesResponding: types of product at anodeFixed (controlled): type of electrolyte

Hypothesis: The reactivity of halogens decreases down the group from chlorine to bromine when they react with iron.

Hypothesis: When the concentration of chloride ion is higher, then the chloride ion will be preferentially discharged.

Hypothesis: When copper electrodes are used instead of carbon electrodes, the types of products formed at the anode are different

Materials: potassium manganate (VII) crystal, concentrated HCL, liquid bromine, iodine crystals, soda lime and iron wool

Materials: 1.0 moldm-3 hydrochloric acid, 0.001 moldm-3 hydrochloric acid Materials: 0.1 moldm-3 Copper (II) sulphate solution

Apparatus: test tubes, test tube holders, rubbber stoppers, conical flask, combustion tube, delivery tube, Bunsen burner, retort stand with clamp, thistle funnle.

Apparatus: batteries, carbon electrodes, connecting wires, ammeter, electrolytic cell, tet tube, blue litmus paper, wooden splinter and matches

Apparatus: batteries, carbon, copper electrodes, connecting wires, ammeter, electrolytic cells, sandpaper, wooden splinter and matches

Procedure:1) A little iron wool is placed in the middle of combustion tube

and heated strongly.2) Concentrated HCL/liquid bromine/iodine crystal is heated

gently in test tube.3) Chlorine gas/bromine gas/iodine vapour liberated is passed

through the heated iron wool in the combustion tube until no further changes occur.

4) The excess chlorine gas/bromine gas/iodine vapour is absorbed by soda lime.

5) All changes are observed and recorded.

Procedure:1) An electrolytic cell filled with 1.0 moldm-3 hydrochloric acid until

it is half full.2) The circuit is completed by connecting the electrodes to the switch,

ammeter, and batteries.3) The switch is turned on.4) Any observation is recorded.5) The gas produced at anode and cathode are collectedand tested with

a moist blue litmus paper and a lighted wooden splinter,6) Step 1 to 4 is repeated using 0.001 moldm-3 hydrochloric acid to

replace 1.0 moldm-3 hydrochloric acid.7) The gas produced at the anode and cathode are collected and tested

with glowing wooden splinter and lighted wooden splinter.

Procedure:1) Two carbon electrodes are cleaned with sandpaper.2) The Copper (II) sulphate solution is poured into an electrolytic

cell with carbon electrodes until it is half full.3) The circuit is completed by connecting the electrodes to the

switch, ammeter, and batteries.4) The switch is turned on foor 15 min.5) All observation at the anode, cathode and electrolyte are

recorded.6) Gas produced at anode is collected and tested with glowing

wooden splinter.7) Step 1 to 5 is repeated using copper electrodes

Tabulation of data:Halogens ObservationChlorineBromineIodine

Tabulation of data:Electrolyte Observation

Anode Cathode1.0 HCL

0.001 HCL

Tabulation of data:Electrode Observation

Anode Cathode ElectrolyteCarbonCopper

Experiment 7 (Chapter 6) SPM 2007 Experiment 8 (Chapter 6) Experiment 9 (Chapter 7)


孔子补习学院 CONFUCIUS TUTION CENTRE 1 对 1 补习，全 A+的保证，成绩只有上上上！Aim:To construct the electrochemical series based on potential differences between metals

Aim:To construct the electrochemical series using the principle of displacement of metals

Aim:To investigate the role of water in showing their properties of acids

Problem statement:Can an electrochemical series of metals be constructed based on the potential difference between two metals?

Problem statement:How can the electrochemical series of metals be constructed based on the displacement metals?

Problem statement:Is water neede for an acid to show its acidic properties?

Variables:Manipulated: pairs of metalsResponding: potential difference producedFixed (controlled): type and concentration of electrolye

Variables:Manipulated: metal strips/salt solution usedResponding: deposition of metalsFixed (controlled): concentration of salt solution

Variables:Manipulated: types of solventResponding: change in colour of blue litmus paperFixed (controlled): type of acid

Hypothesis: The further apart the two metals in the electrochemical series, the greater the potential difference produced/voltage produced.

Hypothesis: The greater the number of metals that can be displaced by a metal from their solutions, the higher is its position in the electrochemical series.

Hypothesis: an acid will show its acidic properties when dissolves in water.

Materials: 0.1 moldm-3 sulphuric acid, copper strip, lead, iron, zinc, aluminium, magnesium strip, sand paper

Materials: 1.0 mol dm-3 of magnesium nitrate, zinc nitrate, lead nitrate, copper nitrate, magnesium, zinc, lead and copper strips, sandpaper

Materials: glacial ethanoic acid, distilled water, dry propanone, blue litmus paper

Apparatus: 250 cm3 beaker, crocodile clips, voltmeter, and connecting wires.

Apparatus: test tubes, test tube rack Apparatus: test tube, droppers, tets tube rack

Procedure:1) The metal strips are celaned with sanpaper.2) A beaker filled with dilute sulphuric acid until two-thirds full.3) Magnesium strip as electrode A and copper strip as electrode B

are dipped into dilute sulphuric acid.4) The circuit is completed by connecting the metals to a

voltmeter.5) The reading of voltmeter produced is recorded.6) The metal strip that acts as the negative terminal is determined

and recorded.7) Step 1 to 6 are repeated using aluminium, zinc, lead, iron, and

copper to replace magnesium as electrode A.

Procedure:1) The strips are clened with sandpaper.2) 5cm3 og magnesium nitrate, zinc nitrate, lead nitrate, copper nitrate

solution are poured into 4 separate tubes.3) A strip of magnesium is placed into each of the solutions.4) Observation on the deposition of metals are recorded.5) Steps 1 to 4 are repeated using zinc, lead and copper to replace

magnesium strip.

Procedure:1) Three test tubes are labelled as A, B, and C. They are placed in

test tube racks.2) 1cm3 of glacial ethanoic acid is placed into each test tubes usind

a dropper.3) 2cm3 of distilled water is added to test tube B.4) 2cm3 of dry propanone added to test tube C.5) A piece of dry blue litmus paper is placed into each test tube.6) Any changes that occur are observed and recorded.

Tabulation of data:Pair of metal + terminal -terminal Voltage

Zn/CuMg/CuAl/CuAg/CuFe/Cu

Tabulation of data:Metal strip Mg(NO3) Zn(NO3)2 Pb(NO3)2 Cu(NO3)2

MagnesiumZincLead

Copper

Tabulation of data:Test tube Observation

ABC

Experiment 10 (Chapter 2) Experiment 11 (Chapter 7) SPM 2009 Experiment 12 (Chapter 8)


孔子补习学院 CONFUCIUS TUTION CENTRE 1 对 1 补习，全 A+的保证，成绩只有上上上！Aim:To investigate the role of water in showing their properties of alkalis

Aim:To investigate the relationship between pH values with molarity of acid

Aim:To construct the ionic equation for the concentration for the formation of lead(II) chromate(VI)

Problem statement:Is water needed for an alkali to show its alkali properties?

Problem statement:What is the relation between pH values with molarity of an acid?

Problem statement:How to construct an ionic equation for the formation of lead(II) chromate(VI)?

Variables:Manipulated: types of solventsResponding: chnage in colour of red litmus paperFixed (controlled): type of alkali and litmus paper

Variables:Manipulated: molarity of acidResponding: pH valuesFixed (controlled): type of acid

Variables:Manipulated: volumes of lead(II) nitrate solutionResponding: height of yellow precipitateFixed (controlled): volumes of potassium chromate(VI) soution

Hypothesis: an alkali will only show its alkaline properties when dissolve in water

Hypothesis: When the molarity of acid increases, its pH values increases Hypothesis: as the volume of potassium chromate(VI) solution increases, the height of the yellow precipitate increases untill all the lead (II) nitrate has reacted.

Materials: dry ammonia gas stoppered in atest tube, ammonia gas dissolved in propanone, aqueous ammonia solution and red litmus paper.

Materials: hydrocloric acids of 1.0 mol dm-3, 0.1 mol dm-3, 0.01 mol dm-3, 0.001 mol dm-3

Materials: 0.5 mol dm-3 lead (II) nitrate solution and o.5 mol dm-3 potassium chromate (VI) solution

Apparatus: test tubes and droppers Apparatus: pH meter, 100cm3 beakers, and 100cm measuring cylinder Apparatus: test tubes of the same size, test tube rack, 50cm3 burette, retort stand with clamp and ruler

Procedure:1) A piece of dry litmus paper is put into a stoppered test tube of

dry ammonia gas and the test tube is then stoppered back immediately.

2) The effect of the dry ammonia gas on the red litmus paper is recorded.

3) Another piece of dry red litmus aper is put in 5cm3 of aqueous ammonia solution in aseparate test tube.

4) Step 3 of the experiment is repeated using ammonia dissolved in propanone to replace aqueous ammonia solution.

Procedure:1) 30cm3 of 1.0 mol dm-3 hydrochloric acid is put in dry beaker.2) The probe of a pH meter that has been washed with distilled water

is immersed in 30 cm3 of the 1.0 mol dm-3 hydrochloric acid.3) The pH values shown on the pH meter is recorded.4) The pH values of hydric acid solutions with different molarities

are measured one by one in dry beakers as in steps 1 to 3.

Procedure:1. 7 test tubes of same size are labelled from 1 to 7. They are

placed on test tube rack.2. A burette is filled with 0.5 moldm-3 potassium chromate (VI)

solution. 5.0 moldm-3 of the potassium chromate (VI) solution is placed into each test tube.

3. Another burette is filled with 0.5 moldm-3 lead (II) nitrate solution.

4. lead (II) nitrate solution from the burette is added into each of the 7 test tubes.

5. The mixture in each test tube is stirred using glass rod. A yellow precipitate is formed in each test tube.

6. The test tubes are left aside for about an hour.7. The height of precipitate in each test tube is measured using

metre rule. The colour above the precipitate in each test tube is observed and recorded.

Tabulation of data:Condition of ammonia Observation Inference

Tabulation of data:Molarities (mol dm-3) pH values

1.00.10.010.001

Tabulation of data:Test tube 1 2 3 4 5 6 7Volume of 0.5 moldm-3 potassium chromate (VI) solutionVolume of 0.5 moldm-3 lead (II) nitrate solution.Height of precipitateColour of solution above precipitate

Experiment 13 (Chapter 9) SPM 2003/05 Experiment 14 (Chapter 9) SPM 2003 Experiment 15 (Chapter 10)


孔子补习学院 CONFUCIUS TUTION CENTRE 1 对 1 补习，全 A+的保证，成绩只有上上上！Aim:To compare the hardness of pure metal and its alloy

Aim:To compare the rate of rusting between iron, steel and stainless steel

Aim:To investigate the effect of total surface area of the reactant on the rate of reaction

Problem statement:Are alloys harder than pure metal?( is bronze harder than copper )

Problem statement:How does the rate of rusting between iron, steel and stainless steel differ?

Problem statement:How does the total exposed surface area of a solid reactant affect the rate of reaction?

Variables:Manipulated: types of materials to make the metal blockResponding: diameter of the dent made by a steel ball bearingFixed (controlled): size of steel ball bearing

Variables:Manipulated: types of nails(iron, steel, stainless steel)Responding: rate of rustingFixed (controlled): size of nails

Variables:Manipulated: size of marble chipsResponding: rate of reactionFixed (controlled): temperature

Hypothesis: Bronze is harder than copper Hypothesis: pure iron rusts faster than steel while stainless steel does not rust easily

Hypothesis: When the total surface area of marble chips increases, the rate of reaction increases

Materials: copper block, bronze block, ball beraing, cellophane tape and thread

Materials: iron nail, steel nail, stainless steel nail, 5% jelly solution and potassium hexacyanoferrate(III) solution and sandpaper

Materials: 80cm3 0.1moldm-3 hydrochloric acid, 2g large marble chip, 2g small marble chip, water

Apparatus: metre rule, retort stand with clamp, 1 kg weight Apparatus:test tubes

Apparatus: 50cm3 measuring cylinder, 150cm3 conical flask, stopper with delivery tube, basin, burette, electronic balance, stopwatch

Procedure:1) A metre rule is clamped to a retort stand, and a piece of copper

block is placed on the based of the retort stand.2) A steel ball bearing is placed on the copper block and a piece of

cellophane tape is used to hold the ball bearing in place.3) A 1 kg weight is hung at a height of 50 cm above the copper

block.4) The weight is dropped onto the ball bearing placed on the

copper block.5) The diameter of the dent made by the ball bearing is measured

to the nearest 0.5mm.6) Step 1 to 5 is repeated using br onze block to replace copper

block.

Procedure:1) Three test tubes are half filled with jelly solution and are labelled

as A, B and C.2) 1 cm3 of potassium hexacyanoferrate (III) solution is added to

every test tube.3) An iron nail, a steel nail and a stainless steel are polished with

sandpaper to remove any rust formed. The nails are then placed in the three test tubes labelled A, B and C respectively.

4) All test tubes are allowed to stand for 2 days before they are examiined.

5) Changes occurred on the nail are observed and recorded.

Procedure:1) Fill a burette with water and invert it over water in a basin.2) Clamp the burette vertically using a retort stand. Records its

initial reading.3) Measure 40cm3 of 0.1 moldm-3 hydrochloric acid, HCL using a

measuring cylinder. Transfer the acid into a conical flask.4) Weigh 2g of large marble chips. Put them into the conical flask.

Close the conical flask immediately with astopper which is joined to the delivery tube and start the stopwatch.

5) Record the burette reading at intervals of 30 seconds until the reaction stops.

6) Repeate the steps 1 to 6 using 2g of small marble chips to replace 2g of large marble chips.

Tabulation of data:MetalBlock

Diameter of dent (mm)I II II average

CopperBronze

Tabulation of data:Test tube Type of nail Observation

A Iron nailB Steel nailC Stainless steel nail

Tabulation of data:Times

Burette reading

Volume gas

Experiment 16 (Chapter 10) Experiment 17 (Chapter 10) Experiment 18 (Chapter 10) SPM 2010

Aim:To investigate the effect of concentration on the rate of reaction

Aim:To investigate the effect of temperature on the rate of reaction

Aim:To investigate the effect of catalyst on the rate of recation


孔子补习学院 CONFUCIUS TUTION CENTRE 1 对 1 补习，全 A+的保证，成绩只有上上上！Problem statement:How does the concentration of reactant affect the rate of reaction?

Problem statement:How does the temperature affect the rate of reaction?

Problem statement:How does catalyst affect the rate of reaction?

Variables:Manipulated: concentration of sodium thiosulphate solutionResponding: time taken for the cross ‘X’ to disappearFixed (controlled): concentration dilute sulphuric acid

Variables:Manipulated: temperature of sodium thiosulphate solutionResponding: time taken for the cross ‘X’ to diasappearFixed (controlled): concentration of sodium thiosulphate solution

Variables:Manipulated: amount of catalyst usedResponding: the volume of oxygen given off at half-minute intervalsFixed (controlled): volume of hydrogen peroxide

Hypothesis: When the concentration of sodium thiosulphate is higher, the higher the rate of reaction

Hypothesis: The higher the temperature of the reactant, the higher the rate of reaction

Hypothesis: The rate of decomposition of hydrogen peroxide increases when the amount of catalyst used is increased

Materials: 0.2 mol dm-3 sodium thiosulphate solution, 1.0 mol dm-3

sulphuric acid and distilled waterMaterials: 0.1 mol dm-3 sodium thiosulphate solution and 1.0 mol dm-3 sulphuric acid

Materials: 0.2 mol dm-3 hydrogen peroxide nad manganese(VI) oxide

Apparatus: 10cm3 and 100cm3 measuring cylinders, 100cm3 conical flask, white paper marked with cross ‘X’ and stopwatch

Apparatus: conical flask, 10cm3 measuring cylinder, thermometer, stopwatch, white paper marked with cross ‘X’, wire gauze, tripod stand, and Bunsen burner.

Apparatus: measuring cylinder, conical flask, delivery tube, rubber stopper, retort stand, clamp and burette.

Procedure:1) Using ameasuring cylinder, measure and pour 45cm3 of 0.2

moldm-3 sodium thiosulphate, Na2S2O3 solution into a conical flask.

2) Place the conical flask on top of a piece of white paper with mark ‘X’.

3) Using another measuring cylinder, measure 5cm3 of 0.1 mol dm-3 sulphuric acid.

4) Pour the sulphuric acid quickly and carefully into the conical flask and start the stop watch immediately.

5) Swirl the mixture in the conical flask and start the stopwatch immediately.

6) Swirl the mixture in the conical flask a few times and place in back on the white paper.

7) Obeserve the mark ‘X’ vertically from the top through the solution.

8) Record the time t required for the mark ‘X’ to disappear from sight.

9) Repeat the experiment four more times using different volumes of 0.2 mol dm-3 sodium thiosulphate of different concentration.

Procedure:1)

Procedure:1) Using a measuring cylinder, 25 cm3 of 0.2 mol dm-3 hydrogen

peroxide is measured into a conical flask and 0.5 g of manganese(VI) oxide is added to the hydrogen peroxide.

2) The conical flask is immediately closed with a stopper fitted with delivery tube and the stopwatch is started simultaneously. The conical flask is swirled gently.

3) The total volume of oxygen gas given off is determined from

the burette reading at intervals of 12

minute for 4 minutes.

4) The experiment is repeated using 0.20 g of manganese(VI) oxide instead of 0.50 g of manganese(VI) oxide.

Tabulation of data: Tabulation of data: Tabulation of data:

Experiment 19 (Chapter 11) SPM 2006 Experiment 20 (Chapter 12) Experiment 21 (Chapter 13)

Aim:To compare the elasticity of vulcanized rubber and unvulcanized rubber

Aim:To investigate the effect of other metals on rusting

Aim:To determine the heat of combustion of various liquid alcohol


孔子补习学院 CONFUCIUS TUTION CENTRE 1 对 1 补习，全 A+的保证，成绩只有上上上！Problem statement:Is vulcanized rubber more elastic than unvulcanized rubber?

Problem statement:How do different types of metals in contact with iron affect rusting?

Problem statement:Does alcohol with more carbon atoms per molecule have a higher heat of combustion?

Variables:Manipulated: type of rubberResponding: lenght of rubber stripFixed (controlled): size of rubber strip, mass of weight

Variables:Manipulated: different metal in contact with ironResponding: presence of blue colouration//rustingFixed (controlled): clean iron nails

Variables:Manipulated: different types of alcoholResponding: heat oof combustionFixed (controlled): volume of water, copper can

Hypothesis: vulcanized rubber is more elastic than unvulcanized rubber Hypothesis: when a more electropositive metals is in contact with iron, the metal inhibits rusting. When a less electropositive is in contact with iron, the metal speeds up rusting

Hypothesis: the higher the number of carbon atoms in the molecules, the higher the heat of combustion

Materials: vulcanized rubber strip and unvulcanized rubber strip Materials: 5 iron nails, 3cm magnesium ribbon, 3 cm copper strip, 3cm zinc strip, 3cm tin strip, 50cm3 hot jelly solution with a little potassium hexacyanoferrate(III) solution and phenolphthalein, sandpaper

Materials: 50cm3 of Methanol, Ethanol, Propanol, Butanol and 800cm3

water

Apparatus: retort stand and clamp, bulldog clip, metre rule, weights Apparatus: 5 test tubes, test tube rack Apparatus: copper can, tripod stand, thermometer, 100cm3 measuring cylinder, spirit lamp, weighing balance, wooden block, wind shield.

Procedure:1) Hang both rubber strips using bulldog clips.2) Measure the initial lenght of both rubber strips.3) Hang 10g weight to the end of each rubber strip.4) Remove the weight and measure the lenght of both rubber strips.5) Repeat steps 2 to 4 using 20g, 30g, 40g and 50g weights to

replace the 10g weights.6) Record the data.

Procedure:1) Clean all the five iron nails, magnesium ribbon, strips of copper,

zinc and tin with sandpaper.2) Coil four nails tightly with magnesium ribbon, strips of cooper,

zinc and tin each.3) Place all the iron nails in separate test tubes.4) Pour the same volume of hot jelly containing potassium

hexacyanoferrate(III) solution and phenolphthalein indicator int the test tubes in a test tube rack and leave them aside for a day.

5) Record the observation.

Procedure:1) Using a measuring cylinder, measure 200cm3 of water and pour

it into a copper can.2) Place the copper can on atripod stand.3) Measure the initial temperature of the water and record the

reading.4) Pour 50cm3 of methanol into a spirit lamp and then weight the

lamp and its content. Record the mass.5) Put the lamp and light up the wick of the lamp immediately.6) Stir the water continuously until the temperature of water

increase about 30°C.7) Put off the flame and record the highest temperature reached by

the water.8) Weight the lamp and its content immediately and record its

reading.9) Repeat steps 1 to 8 using other alcohol like Ethanol, Propanol,

Butanol.

Tabulation of data: Tabulation of data: Tabulation of data:

Tabulation of data for experiment 21

Alcohol Methanol Ethanol Propan-1-ol Butan-1-olInitial temperature (°C)Highest temperature (°C)Rise in temperature of water (°C)Mass of spirit lamp before burning (g)Mass of spirit lamp after burning (g)


孔子补习学院 CONFUCIUS TUTION CENTRE 1 对 1 补习，全 A+的保证，成绩只有上上上！Mass of alcohol burnt (g)


Test tube Pair of metals Intensity of the blue colour in the solution Intensity of pink colour in the solution inferenceA FeB Fe + ZnC Fe + CuD Fe + MgE Fe + Sn


Type of rubber Unvulcanised rubber Vulcanised rubberInitial length (cm)Stretched length (cm)Increase in length (cm)Length after removal of weight (cm)Difference in length (cm)


Time (s)Burette reading (cm3)Volume of hydrogen gas (cm3)


GUIDELINE ON ANSWERING QUESTIONS IN CHEMISTRY PAPER 3 2015


FORMAT (4541/3)TIME TYPE OF INSTRUMENT NUMBER OF

QUESTIONCONSTRUCT MARKS

1 ½ HOURS

STRUCTURE ITEM OPEN RESPONSE ITEM REPORT ITEM

2 OR 3 COMPULSORY QUESTION 1 & 2 33QUESTION 3 17

QUESTION 1 & 2 : SOME COMMAND WORDS 1. To differentiate between products and observationObservation: describe what you observed Products: names in full , not formula.

2.Examples of observation:- solid or precipitated formed. ( colur must be mentioned)-solid is soluble / insoluble in named reagent-gas released ( gas colour must be stated )-change in colour : state the initial and final colour

incorrect correctclear solution

no reaction seen

hydrogen gas released

movement shown by ammeter

purple colour solution disappear

product of electrolysis at cathode:

brown precipitate seen

litmus paper becomes blue

the solution becomes colourless



OPERATIONAL DEFINITION : What you do ….. What you observe .

Example:


Set Temperature (°C) Time, t(s) 1/time (s-1)I.

II.III.


孔子补习学院 CONFUCIUS TUTION CENTRE 1 对 1 补习，全 A+的保证，成绩只有上上上！IV.V.



CHAPTER 2: MATTER

1. To determine melting point

Water bath – to ensure uniform heating Plot graph – y – axis (Start at 50 o C).

2. The kinetic theory of matter (solid, solid –liquid, liquid, liquid-gas, gas) Matter is made up of tiny and discrete particles (atoms, ions or molecules), there is space between these particles.

a) arrangement of particles-pack closely together, orderly arrangement, far apart from each otherb) Movement of particles-vibrates, rotate, slowly, rapidly, vigorously, randomly.c) kinetic energy content-d) change in energy content-e) force of attraction-strong, weak, weaker


Temperature,oC

Time, s to t1 t2 t3

Boiling point

CoolingHeating

GUIDELINE ON ANSWERING QUESTIONS IN CHEMISTRY PAPER 2 2015


Example:Graph shows the heating curve of element X.Describe the graph in terms of states of matter, particle arrangements and changes in energy.

Sample answer:

Stage State of matter Particles arrangement Changes in energyto – t1 Liquid The particles are close to each other.

The particles arrangement is not orderly.The kinetic energy increases

t1 - t2 Liquid – gaseous

Some of particles are close to each other and some far apart.The particles arrangement is not orderly.

The kinetic energy is constant

t2 – t3 Gaseous The particles are far away from each other.The particles arrangement is not orderly.

The kinetic energy increases

3. Diffusion – the movement of particles (atom/ions/molecule) of substance in between the particles of another substance / from highly concentrated area to less concentrated area. Gas > liquid > solid 4. Isotope – are atoms of the same element (same number of proton) with different number of

neutrons/nucleon number.

Example: Compare atom 12X and atom 14Y 6 6

Atom X YProton number 6 6No. of electron 6 6Valence electron 4 4Number of neutron / nucleon number 6/ 12 8 /14Chemical properties similarPhysical properties differentNo. of occupied shell similar

CHAPTER 3: CHEMICAL FORMULA

1. Empirical formula: chemical formula that shows the simplest whole number ratio of atoms of each element in a compound, CH2

2. Molecular formula: a chemical formula that shows the actual number of atoms of each element that is present in a molecule of the compound, C2H4

a) Unreactive metal – reaction oxide metal with hydrogen gas, (CuO, PbO ,SnO )b) Diagram

Reactive metal ( Mg, Zn – burn in excess oxygen / air ) – more reactive than H2

c) Procedure- Weigh and record the mass of combustion tube with porcelain dish- Add a spatula of copper (II) oxide on the

- Weigh and record a crucible with its lid- Clean Mg ribbon with sand paper then coil the Mg ribbon and place into the crucible. Weigh and record.


6p

6p

X

Y

Hydrogen


porcelain dish. Weigh the tube again.- Allow hydrogen gas flow into the tube for 5 – 10 minutes.- Burn the excess hydrogen.- Heat copper (II) oxide strongly.- Turn off the flame when black solid turns brown completely.- Continue the flow of hydrogen until the set of apparatus cool down to room temperature.- Weigh the combustion tube with its content.- -Repeat the process heating, cooling and weighing until a constant mass is obtained and record.

- Heat strongly- When Mg ribbon start to burn, cover the crucible with lid.- Lift / raise the lid at intervals.- When the burning is complete, remove the lid and heat strongly.-Allow the crucible to cool down.-Weigh and record the crucible with content and lid.-Repeat the process heating, cooling and weighing until a constant mass is obtained and record.- Observation : White fume / solid formed

Result :- combustion tube with porcelain dish = a g- combustion tube with porcelain dish + copper (II) oxide = b g-combustion tube with porcelain dish + copper = c g- mass of copper = ( c- a) g , Mass of oxygen = ( b- c ) g

- mass of crucible + lid = a g- mass of crucible + lid + Mg = b g- mass of crucible + lid + magnesium oxide = c g- mass of Mg = ( b – a ) g- mass of oxygen = ( c – b) g

Calculation:Element / atom Cu O

Mass (g) x yNumber of mole x / 64 y / 16Simplest ratio of mole

Element / atom Mg OMass (g) x yNumber of mole x / 24 y / 16Simplest ratio of mole

Precaution :1. The flow of H2 must be continuous during cooling – to prevent hot copper metal from oxidized.2. Allow hydrogen gas flow into the tube for 5 – 10 minutes to unsure air totally removed. The mixture H2 and air may cause an explosion.3. To determine all air totally removed, collect the air and place lighted splinter, the gas burn quietly.[To prepare H2]4. Zn + 2HCl à ZnCl2 + H2

5. Anhydrous calcium chloride – to dry the H2 gas.6. CuO + H2 à Cu + H2O

Precaution :1. Clean Mg ribbon with sand paper to remove the layer of oxide on its surface.2. Lift / raise the lid at intervals to allow air in3. When Mg ribbon start to burn, cover the crucible with lid to avoid the white fume produced from being escape to the air.4. Repeat the process heating, cooling and weighing to make sure all magnesium is completely reacted with oxygen.5. 2Mg + O2 à 2MgO

3. Based on the two formulae Na2O, CuI(a) State the oxidation number for sodium, and copper.(b) Name both the compound based on IUPAC nomenclature system.(c) Explain the difference between the names of the two compounds based on IUPAC nomenclature

system.

Sample answer:

Na2O CuIOxidation number for sodium and copper

+1 +1



IUPAC Nomenclature Sodium oxide Copper (I) iodideReason Does not have roman number

because sodium has only one oxidation number

Has roman number because copper has more than one oxidation number

CHAPTER 4: PERIODIC TABLE

1. Explain the following statements, referring to the electron arrangement of the elements.(a) The elements of Group 18 are unreative and exist as monoatomic particles (3 marks)

The points are: (Duplet /octet) electron arrangement. No tendency to donate, accept, share electrons Remain as individual particles

(b) The reactivity of Group I elements increases down the group, whereas the reactivity of Group 17 elements decreases down the group. (12 marks)

The points are:

Explanation Group I Group 171 Change in proton number Increases Increases2 Change in number of electrons and electron filled shells Increases Increases3 Change in atomic size/radius/diameter Increases Increases4 Strength of electrostatic attraction between nucleus and

valence electronDecreases /weaker Decreases /weaker

5 Tendency to Releases electron increases

Attract t/ accept electron decreases

6 To become Positive ion Negative ion

7 Reactivity Increases Decreases

(2) Explain how the melting point of Group 1 elements change down the group (4 marks) decreases gradually

Reason atomic size increases metallic bonding between the atoms become weaker Less energy is required / needed to overcome this metallic bonding.

(3) Chemical properties of element in group 17

I Reaction with water Cl2 + H2O à HCl + HOClII Reaction with sodium hydroxide Cl2 + 2NaOH à NaCl + NaOCl + H2OIII Reaction with iron 3Cl2 + 2Fe à 2FeCl3 (brown solid)


Chlorine gas

Soda lime

Hot iron wool

HCl (cons) +

To

produce Cl2II


Example: Compare the reactivity of reactions between chlorine and bromine with iron. [Diagram III]

Reaction Reactants ObservationA Iron + chlorine gas The hot iron wool ignites rapidly with a bright flame.

A brown solid is formed.B Iron + bromine gas The hot iron wool glows moderately with fast.

A brown solid is formed.Sample answer:a) Chemical equation: 3Cl2 + 2Fe à 2FeCl3

b) The reactivity of reaction A is higher than reaction B.c) The atomic size of chlorine is smaller than bromine.d) The forces of attraction of the nucleus toward the electrons are stronger.e) It is easier for chlorine atom to attract/receive electron.

(4) Across period 3, atomic radius (atomic size) decreases / electronegativity increases. Explain.

a) Proton number increases by one unit.b) The number of valence electrons in each atom increases. c) Positive charge of the nucleus increases, thusd) Nuclei attraction on valence electron increases.e) Atomic radius (atomic size) decreasesf) Tendency to receive electron increases (to form negative ion) thus electronegativity increases.

(5) Chemical properties of the oxide of element across Period 3 changes from basic oxide to amphoteric oxide to acidic oxide.Basic oxide – sodium oxide (Na2O)Amphoteric oxide – Aluminium oxide (Al2O3)Acidic oxide – sulphur dioxide, SO2

CHEPTER 5: CHEMICAL BOND

(a) Group 1 elements react with Group 17 elements to produce compounds that have high melting points.(4 marks)

The points are: Ionic compound produced Because involve transfer of electrons between metal atom and non metal atom. Metal atom donates valence electron to form positive ion, non metal atom accepts electron to

negative ion. The oppositely charged ions are held together by strong electrostatic force. More heat energy is needed to overcome the strong force of attraction.

Formation of ionic compound (metal [Group 1,2 & 13] and non metal [ Group 14, 15, 16& 17])

Sample answer:1. Electron arrangement of atoms ( Na , 28.1 ; Cl 2.8.7 ) // valence electrons2. To achieve stable / octet electron arrangement3. Atom ( Na) releases one / valence electron to form sodium ion, Na+

4. Half equation ( Na à Na+ + e)5. Atom (Cl) gain / accept electron to form chloride ion, Cl-

6. Half equation ( Cl + e à Cl- )


III


7. Oppositely charged ion, Na+ & Cl- are attracted to one another by strong electrostatic force of attraction to form ionic compound, NaCl

8. Diagram

Formation of covalent compound (nonmetal)1. electron arrangement of the atom /valence electrons2. to achieve duplet /octet electron arrangement3. Atom (Carbon) contributes 4 electrons while (H) atom contributes 1 electron (for sharing).4. one ( Carbon ) atom share 4 pairs of electrons with 4 (H) atoms to form covalent compound ,

CH4 / ratio 5. diagram

Compare the physical properties of covalent and ionic compound

Properties Covalent compound ( naphthalene) Ionic compound ( sodium chloride)Melting and boiling

- low- consist of molecules- weak inter molecular forces between molecules- less energy needed to overcome the weak forces

- high- consist of oppositely charged ions- the ions are held together by strong electrostatic forces .- more heat energy needed to overcome the strong forces

Electrical conductivity

- consist of molecules- does not conduct electricity in any state (molten or aqueous).

- consist of oppositely charged ions- conduct electricity in molten or aqueous solution.- in molten or aqueous solution, ions can move freely.

CHAPTER 6: ELECTROCHEMISTRY

1. Factor that affect the electrolysis of an aqueous solution(a) position of ions in the electrochemical series (cathode)(b) concentration of ions in the electrolyte - halide ( Chloride, bromide and iodide)(c) type of electrodes used in the electrolysis – ( anode – metal )

Application

(i) Electroplating anode – electroplating metal ( less electropositive metal / Cu, Ag, Ni )cathode – metal /object to be electroplatedelectrolyte - solution that contains the metal ions of electroplating metal

(ii) Purification anode – impure metal ( Cu à Cu2+

+ 2e )cathode –pure metal ( Cu2+ + 2e à Cu )

electrolyte - solution that contains the metal ions ( Cu2+)

(iii) Extraction of metal (reactive metal, sodium, aluminium)– Down`s Process – extraction of sodium from molten sodium chloride.– Extraction of aluminium from molten aluminium oxide ( bauxite)



2. To construct the electrochemistry based on tendency to release electron /potential differences - voltaic cell/ Electrochemical cell.

3. To construct the electrochemistry based on ability / tendency of metal to displace another metal from it salts solution.Displacement reaction: a metal which is higher in the electrochemical series is able to displace a metal below it in a series from its salt solution.

Example: Zn + CuSO4 à ZnSO4 + Cu // Zn à Zn2+ + 2e / Cu2+ + 2e à Cu

Cell P Cell Q4. Compare and contrast cell P and Q. Include in your answer the observation and half equation for the reaction of the electrodes in both cells.

Cell P Characteristics Cell QElectrical àchemical Energy change Chemical à electrical+ve / anode: copper (OXIDATION)-ve / cathode: copper

Electrode +ve/cathode: copper-ve/ anode: lead (OXIDATION)

Cu2+ , H+

OH- , SO42-

Ions present in the electrolyte

Cu2+ , H+

OH- , SO42-

Anode :Cu à Cu2+ + 2e(type of electrode)

Cathode: Cu2+ + 2e à Cu ( ECS)Half equation

Anode: Pb à Pb2+ + 2e

Cathode: Cu2+ + 2e à Cu (ECS)

Anode: copper electrode become thinner Anode: becomes thinner


copper

Copper(II)

lead


Cathode: brown solid formed/ becomes thicker.Electrolyte: intensity blue solution / concentration of Cu2+ solution remain.Rate of ionized of copper atom to form copper (II) ion at the anode same as rate of discharged copper (II) ion at the cathode.

ObservationCathode: becomes thicker / brown solid formedElectrolyte: intensity blue solution decrease / blue becomes paler

CHAPTER 7: ACID AND BASE

An acid is chemical substance which ionizes in water to produce hydrogen ion, H+

A base is a chemical substance which ionizes in water to produce hydroxide ions, OH-

Alkali is a soluble base. Basicity is the number of ionisable hydrogen atoms per molecule of an acid.

1. Explain why these two solutions have different pH values identify strong acid , weak acid definition strong acid definition weak acid concentration of H+

relationship between pH value and concentration of hydrogen ions, H+

Sample answer:1. Hydrochloric acid is a strong acid while methanoic acid is a weak acid.2. Hydrochloric acid completely ionizes in water to form higher concentration of hydrogen ions.

HCl + H2O à H3O+ + Cl- // HCl à H+ + Cl- , H3O+ , hydroxonium ion3. Methanoic acid ionizes partially in water to form lower concentration hydrogen ions

CH3COOH à CH3COO- + H+

4. The higher the concentration of hydrogen ions the lower the pH value.

2. Aim: To determine the end point during the neutralization of potassium hydroxide and hydrochloric acid

Apparatus: 25 cm3 pipette, burette , 250 cm3 conical flask, retort stand, white tileMaterial: potassium hydroxide and hydrochloric acid 0.1 mol dm-3 , phenolphathalein.

Procedure:1. Rinse a burette with a small amount hydrochloric acid 0.1 mol dm-3 .2. Clamp the burette on retort stand.3. Fill the burette with hydrochloric acid 0.1 mol dm-3 .Adjust the meniscus level of acid to a reading at 0.4. Record the initial burette reading.5. Pipette 25.0 cm3 of potassium hydroxide 0.1 mol dm-3 into conical flask.6. Add two drop of phenolphathalein.7. Add hydrochloric acid 0.1 mol dm-3 carefully. Swirl the conical flask during the process.8. When the colour of the mixture turn paler, add hydrochloric acid drop by drop.9. Stop adding the hydrochloric acid as soon as the solution turns colourless.10. Record the final burette reading.


The pH value of 1.0 mol dm-3 hydrochloric acid is 1

The pH value of 1.0 mol dm-3 methanoic acid is 4


11. Repeat steps 1-10 twice. Tabulate your reading.

Result :

Titration 1 2 3Final burette reading, cm3

Initial burette reading, cm3

Volume of hydrochloric acid 0.1 mol dm-3 , cm3

3. Preparation Standard solution ( 0.1 mol dm-3 NaOH, 100 cm3)

1. calculate the mass of solute ( mole = 0.1 x 100/1000 , 0.01 = mass/ 40)2. weigh 0.4g of NaOH in weighing bottle using digital balance / electronic balance3. pour into a beaker, rinse the bottle with distilled water.4. dissolve NaOH with a little ( 10 – 20 cm3 )distilled water.5. transfer the mixture into volumetric flask 100 cm3 rinse the beaker with distilled water.6. pour the washings into volumetric flask 100 cm3

7. add distilled water, shake well8. add distilled water drop by drop to finally bring the volume of solution to the 100 cm3 mark /

calibration mark.

Preparation of a standard solution by dilution method

M1V1 = M2V2

M1 – initial molarityV1 - initial volumeM2 – final molarityV2 – final volume

NOTE : CONCENTRATION – 1. MOLARITY - mol dm-3

2. g dm-3

Neutralization in our daily lives

Agriculture Powdered lime (CaO) , limestone (CaCO3), ashes of burnt woodUsed to treat acidic soil.

Industries 1. Powdered lime (CaO)Used to treat acidic effluent from factories, acidic gas SO2 emitted by power station and industries.2. Ammonia prevent the coagulation of latex by neutralizing the acid produced by bacteria in the latex.

Health 1. Anti-acids contain bases such as aluminium hydroxide and magnesium hydroxide to neutralize the excess acid in the stomach.2. Vinegar (citric acid) is used to cure wasp stings that are alkaline in nature.3. Baking powder (NaHCO3) is used to cure bee stings and ant bites that are acidic in


MAVA = a


nature.4. Toothpaste contains bases that neutralize the acid produces by bacteria in our mouth

CHAPTER 8 SALT

A salt is a compound formed when the hydrogen ion, H+ from an acid is replaced by a metal ion or an ammonium ion, NH4

+

Preparation of soluble salt– acid + reactive metal(Zn / Mg) à salt + H2 / 2H+ + Mg à Mg2+ + H2

– acid + base ( metal oxide) à salt + water – acid + alkali à salt + water / H+ + OH- à H2O ( NaOH, KOH, NH4OH)– acid + carbonate metal à salt + CO2 + H2O / 2H+ + CO3

2+ à CO2 + H2OProcedure:

1. pour ( 25 – 100cm3) acid ( 0.5 – 2.0 mol dm-3) into a beaker2. heat slowly3. add solid (metal / base/ carbonate ) a little until excess / no more dissolve4. stir5. filter the mixture into evaporating dish6. heat (slowly) the filtrate until 1/3 from original volume / saturated solution formed7. cool down the saturated solution (until crystallized )8. filter (to separate the crystals)9. dry / transfer onto filter paper / dry between sheets of filter paper

ObservationChemical equation

Preparation of insoluble salt – precipitation reaction / double decomposition reactionPb2+ + SO4

2- à PbSO4

Example : Preparation of lead(II)sulphate.Procedure

1. pour ( 25 – 50cm3) of soluble salt Pb(NO3)2 into a beaker2. add ( 25 – 50cm3) of soluble salt (Na2SO4)

3. stir4. filter the mixture5. rinse residue / solid / precipitate6. dry between sheets of filter paper

ObservationChemical equationIonic equation

Action of heat on salt

Carbonate à oxide metal (base) + CO2 except Na, K and NH4+

Example: CuCO3 à CuO + CO2

Nitrate à oxide metal + nitrogen oxide + oxygen except Na, K, (2NaNO3 à 2NaNO2 + O2 )Example : 2Mg(NO3)2 à 2MgO + 4NO2 + O2

(Brown gas)



Ammonium chloride à ammonia gas + hydrogen chloride gas, (NH4Cl à NH3 + HCl )Confirmatory test for cation and anion

1. State the material / chemical / reagent2. procedure3. observation 4. conclusion

Example: You are given a bottle of ammonium chloride solution. Describe chemical test to verify the cation and anion.

(a) test for cation (NH4+)

1. pour 2 cm3 the solutions into a test tube2. add 1 cm3 copper (II) sulphate solution3. blue precipitate soluble in excess to form dark blue solution.

OR

4. add 2 to 3 drops of Nessler reagent into the test tube5. brown precipitate.6. Ammonium ions (NH4

+) present.

(b) test for anion (Cl-)1. pour 2 cm3 the solution into a test tube2. add 1 cm3 of dilute nitric acid and silver nitrate solution.3. white precipitate formed4. confirm the presence of chloride ions

Example: You are given lead (II) nitrate and aluminium nitrate solution. Describe chemical test to verify the cation and anion.

(c) test for cation1. pour 2 cm3 the solutions into different test tubes2. add 1 cm3 potassium iodide solution into the test tubes3. yellow precipitate formed 4. lead (II) ion present

(d) test for anion1. pour 2 cm3 of lead (II) nitrate solution into a test tube2. add 1 cm3 of dilute sulphuric acid3. add 1 cm3 of iron (II) sulphate solution4. shake the mixure5. tilt the test tube, add concentrated sulphuric acid carefully // drop by drop down the

side of the test tube 6. the brown ring formed 7. nitrate ion, NO3

- present.



Aim : To construct the ionic equation for the formation of lead (II) chromate(VI) [Continuous variation method]

Apparatus : Test tubes of the same size, test tube rack, burette, retort stand with clamp, ruler, glass rod, dropper.

Material : 0.5 mol dm-3 potassium chromate (VI) solution, 0.5 mol dm-3 lead (II) nitrate solution.

Procedure : 1. Seven test tubes of the same size were labelled from number 1 to 7. They were placed in a test

tube rack.2. A burette was filled 0.5 mol dm-3 lead (II) nitrate solution, 5.00 cm3 of the lead (II) nitrate

solution was run into each the seven tubes.3. Another burette was filled with 0.5 mol dm-3 potassium chromate (VI) solution.4. Potassium chromate (VI) solution from the burette was added into each of the seven test tubes

according to the volumes specified in the table.5. The mixture in each test tube was stirred with a clean glass rod.6. The test tubes were left aside for about an hour.7. The height of the precipitate in each test tube was measured. The colour of the solution above the

precipitate in each test tube was observed and recorded.

Results:Test tube 1 2 3 4 5 6 7

Volume of 0.5 mol dm-3

Pb(NO3)2 /cm3

5.00 5.00 5.00 5.00 5.00 5.00 5.00

Volume of 0.5 mol dm-3

K2Cr O4 /cm3

1.00 2.00 3.00 4.00 5.00 6.00 7.00

Height of precipitate (cm)

0.60 1.20 1.80 2.40 3.00 3.00 3.00

Colour of solution above the precipitate

colourless colourless colourless colourless colourless yellow yellow

Paper 2

DiscussionThe volume of 0.5 mol dm-3 potassium chromate (VI), solution required to exactly react with 5.00 cm3 of 0.5 mol dm-3 lead (II) nitrate solution is 5.00 cm3.

Calculation: Number of moles lead (II) ions = MV = 0.5 x 5.00/1000 = 0.0025 mol.

Number of moles chromate (VI) ions = MV = 0.5 x 5.00/1000 = 0.0025 mol.Simplest mole ratio of lead (II) ions : chromate (VI) ions0.0025 : 0.0025 1 : 1



Discussions:1. A yellow precipitate of lead (II) chromate (VI) is formed in each of the seven test tubes.2. The height of the precipitate increases gradually from test tubes 1 to 5 because more and more lead (II) chromate (VI) is formed due to the increasing amount of potassium chromate (VI) added to the test tubes.3. The colour of solution above the precipitate in test tubes 1 to 4 are colourless due to the excess lead (II) nitrate.4. The colour of solution above the precipitate in test tubes 6 to 7 is yellow due to the excess potassium chromate (VI).5. Ionic equation: Pb2+ + Cr2O7

2- à PbCr2O7

Conclusion:As / when the volume of potassium chromate (VI) solution used increases, the height of the precipitate increases until it achieves a maximum height.

CHAPTER 9 : MANUFACTURED SUBSTANCES IN INDUSTRY

1. Contact process: manufactured sulphuric acid

Stage Equation Explanation1 S + O2 à SO2 Sulphur is burned in the excess of oxygen gas to produce sulphur

dioxide gas.2 2SO2 + O2 à 2SO3 SO2 is then heated in excess oxygen gas, catalyst Vanadium (V)

oxide, 1 atm and 450 – 550 o C , to produce sulphur trioxide gas.3 SO3 + H2SO4 à H2S2O7 Gas sulfur trioxide dissolve in sulphuric acid to produce oleum4 H2S2O7 + H2O à2H2SO4 Oleum is added to water to produce sulfuric acid

Gas SO3 is not dissolve in water to produce H2SO4 straight away because the reaction will produce

a lot of heat which is dangerous( cause the forming of acid fumes)

Usage of sulphuric acid:

To manufacture fertilizer, soap and detergentTo make explosive material, paint / pigment, polymerAs metal cleaner and electrolyte in car battery.

2. Haber Process

N2 + 3H2 à 2NH3

Condition: Catalyst: iron, temperature: 450 – 550 oC, Pressure 200 – 500 atm

Usage: to manufacture fertilizer 2NH3 + H2SO4 à (NH4 )2 SO4

3NH3 + H3PO4 à (NH4 )3 PO4

NH3 + HNO3 à NH4NO3

3. High percentage of nitrogen is a good fertilser for plants. How to calculate %N in fertiliser?urea CO(NH2)2 and ammonium nitrate (NH4NO3), which one is a better fertiliser? [ RAM : N,14; C,12 ;O,16; H,1]



Sample answer:

% N in Urea = mass of nitrogen / RMM urea x 100 = 2x14 / 60 x 100 = 46.67%

% N in NH4NO3 = 2x14 / 80 x 100 = 35.00 %

Urea is a good fertilizer than ammonium nitrate, because the percentage of nitrogen in urea higher than ammonium nitrate.

4. Describe how toxic waste product from factory affects the quality of the environment. Your description should include the following aspects. Source, process and effect.

Sample answer: 1. [Source] sulphur dioxide gas produced by factory or burning of fossil fuels 2. [process ] sulphur dioxide gas dissolves in rain water / water to form acid rain,

2SO2 +O2 + 2H2O à 2H2SO4]3. [effect ] toxic waste / acid flows to into lakes and rivers, acid rain lowers the pH value of water,

soil and air.4. Fish and other aquatic organisms die.5. acid rain corrodes concrete buildings and metal structures6. acid destroys trees in forest 7. Acid rain reacts with minerals in soil to produces salt which are leached out the top soil.8. Plants die of malnutrition and diseases.9. Soil becomes acidic, unsuitable for growth of plants and destroys the roots of plants. 10. sulphur dioxide causes respiratory problems in humans.

5. POLIMER: - large molecules made up of identical repeating sub-units of monomers which are joined together by covalent bonds.

Synthetic polymer Monomer UsesPolythene Ethene Plastic bags, plastic containerPolypropene Propene Piping, car batteriesPolyvinyl chloride, PVC Chloroethene Artificial leather, water pipePerspex Methylmethacrylate Safety glass, reflectors

ALLOYAn alloy is a mixture of two or more elements with a certain fixed composition in which the major component is a metal.

1. The composition , properties and uses of some alloy


polymer (polyethene)monomer ( ethene)


Alloy Composition Properties UsesBronze Cu

Tin-Hard and strong-does not corrode easily-has shiny surface

-in building of statue or monuments.-in making of medals-swords and artistic material

Brass CuZinc

-harder than copper -in making of musical instruments and kitchenware

Steel IronCarbon

Hard and strong -in construction of buildings and bridges-in building of the body of cars and railway tracks

Stainless steel

IronCarbonChromium

-shiny-strong-does not rust

-in making of cutlery-in making of surgicalinstrument

Duralumin AluminiumCopperMagnesiummanganese

-light-strong

-in building of the body of aeroplane and bullet trains

Pewter Tin, Copperantimony

-lustre, shiny-strong

In making of souvenirs

Bronze is harder than pure copper. Explain.

Reason:1. The presence of atoms of other metals / tin that are different sizes2. Disrupt the orderly arrangement of copper atoms3. Tin atoms reduce the layers of copper atoms from sliding 4. Alloy is stronger and harder than pure metal

2. You have learnt the steel is an alloy of iron. Steel is harder than pure iron. Both iron and steel can rust when exposed to air and water. Do they rust at the same rate?

Aim : To compare the rate of rusting between iron, steel and stainless steel

Problem StatementHow does the rate of rusting between iron, steel and stainless steel differ?

Hypothesis Iron rust faster than steel and steel rust faster than stainless steel.

VariablesManipulated : Iron, steel and stainless steel.Responding : intensity / amount of dark blue colour / rate of rusting Fixed : size of nail, concentration of solution, duration of rustingProcedure:

1. Clean the nails with sand paper (to removed the rust from all the nails)2. Place the iron nail, steel nail and stainless steel nail into the test tube A, B and C respectively.3. Prepare a 5 % jelly solution by adding 5 g jelly to 100 cm3 of boiling water. Add a few drop of potassium hexacyanoferrate (III) solution.4. Pour the hot jelly into the test tubes until all the nails are fully immersed.


Copper atom

Stanum atom


5. Leave the nails for 3 days.6. Observe and record the intensity of the dark blue colour.

Tabulation of data

Paper 2Conclusion 1. The concentration of Fe2+ ions in the test tube A is higher than in test tube B. No Fe2+ ions are present in test tube C.2. The rate of rusting in test tube A is higher than that in test tube B. No rusting takes place in test tube C. Alloy slow down the rate of rusting.

Properties, composition and uses different type of glass

Type Properties Chemical composition

Uses

Fused glass -Very high softening point-Highly heat resistant-Does not crack when temperature changes-very resistant to chemical reactions-difficult to be shaped

SiO2 Lenses, telescope mirrors, optical fibres, Laboratory glassware.

Soda lime glass

-low softening point-does not withstand heating-break easily-less resistant to chemical reactions-easy to be shaped- cracks easily with sudden change in temperature

SiO2

CaCO3 / Na2CO3

Flat glass, light bulb, mirrors, glass containers.

Borosilicate

-lower thermal coefficient-heat resistant- Does not crack when temperature changes-very resistant to chemical reactions-does not break easily

SiO2

B2O3

Na2O

Laboratory glassware, cooking utensils. Automobile headlights.

Lead glass -low softening point-high density-High refractive index

SiO2

PbOCaO

Decorative items, crystal glass ware, lens, prism, chandelier

Composite Materials is a structural material that is formed by combining two or more different substances such as metal, alloys, glass, ceramics and polymers.

Composite material

Component Properties of component

Properties of composite

Uses of components

Reinforced concrete

Concrete Hard but brittle, low tensile strength

Stronger, high tensile strength does not

Construction of framework for


Test tube The intensity of the dark blue colour // rate of rusting

ABC


corrode easily, can withstand higher applied forces and loads, cheaper.

highway, bridges and high-rise building

Steel Hard with high tensile strength but expensive and can corrode.

Super-conductor

Copper(II)oxide, barium oxide

Insulators of electricity Conducts electricity Generators, transformers, electric cable, amplifiers, computer partsMRI

Fibre optics Glass of low refractive index

Transparent, does reflect light rays.

reflect light rays and allow light rays to travel along the fiber

Transmit data in the form of light in telecommunications

Glass of high refractive index

Fibre glass Glass Heavy, strong but brittle and non-flexible

Light, strong, tough, resilient and flexible wit high tensile strength not inflammable, low density, easily coloured, shaped and moulded.

Water storage tanks, small boat, helmet

Polyester plastic Light, flexible, elastic but weak and inflammable

Photo-chromic glass

Glass Transparent, does reflect light rays.

Sensitive to light : darkens when light intensity is high, becomes clear when light intensity is low.

Photochromic optical lens, camera lens, car windshields, optical switches, light intensity meters.

Silver chloride or silver bromide

Sensitive to light

CHAPTER 10: RATE OF REACTION

Rate of reaction is the change in selected quantity of reactants or products per time taken.

Aplication 1. Explain why potatoes fried in boiling oil cook faster than potatoes boiled in boiling water?Answer:- Boiling point of oil is higher than boiling point of water- At higher temperature potatoes is faster to cook



2. Based on the collision theory, explain why we need to store fresh milk in refrigerator.Answer:

(i) the temperature inside the refrigerator is lower(ii) bacteria are not active at low temperature(iii) decomposition of milk caused by bacteria will slow down(iv) this will keep the milk fresh for along time

Collision theory

Effective collision: Collision which achieve activation energy (minimum amount) and with correct orientation.

Temperature1. As temperature increases, the kinetic energy of the particles ( H+, S2O3

2- ) increases /2. Frequency of collision between particles ( H+, S2O3

2- ) increases3. Frequency of effective collision increases4. Rate of reaction increases

Size of particles (total surface area)1. The smaller the size of particles, 2. The larger the total surface area exposed to the collision3. Frequency of collision between particles increases4. Frequency of effective collision increases5. Rate of reaction increases

Concentration of the solution1. The higher the concentration of the solution,2. The greater the number of particles per volume3. Frequency of collision between particles increases4. Frequency of effective collision increases5. Rate of reaction increases

Catalyst 1. The presence of catalyst provide an alternative pathway / route 2. with lower activation energy 3. Frequency of effective collision between particles increases4. Rate of reaction increases.

Note: 1. Catalyst – a substance which alters the rate of chemical reaction while remains chemically

unchanged at the end of reaction.2. Observable changes for measuring the rate of reaction.

(a) volume of gas liberated(b) precipitate formation(c) change in mass during reaction, colour ,temperature, pressure

1. Catalyst (Manganese (IV) oxide)a) Decomposition of sodium chlorate (V), 2NaClO3 à 2NaCl + 3O2

b) Decomposition hydrogen peroxide , 2H2O2 à 2H2O + O2



2. Catalytic converters in the car exhaust system contain rhodium, platinum or chromium (III) oxide Cr2O3.

Example:

1. Aim: To investigate the effect of temperature of sodium thiosulphate Na2S2O3 solution on the rate of reaction

Problem Statement:How does temperature of sodium thiosulphate Na2S2O3 solution affect the rate of reaction?

Hypothesis:When the temperature of sodium thiosulphate Na2S2O3 solution increases, the rate of reaction increases.// the higher the temperature of sodium thiosulphate solution, the higher the rate of reaction.

Variables:

Manipulated :Temperature of sodium thiosulphate solution.Responding :Rate of reaction/ Time taken for the cross ‘X’ to disappear from the sight.Fixed : Concentration and volume of sulphuric acid, concentration and volume of sodium

thiosulphate solution.

Apparatus : 150 cm3 connical flask, 50 cm3 measuring cylinder,10cm3 measuring cylinder, stopwatch, thermometer, Bunsen burner, tripod stand, wire gauze.

Materials: 0.2 mol dm-3 sodium thioulphate solution, 1.0 mol dm-3 sulphuric acid, white paper marked “X” at the centre.

Procedure: 1. 50 cm3 of 0.2 mol dm-3 sodium thiosulphate solution is measured using measuring cylinder and poured into a conical flask.2. The temperature of the solution is measured with a thermometer.3. The conical flask is placed on a white paper marked`X`.4. 5 cm3 of 1 mol dm-3 sulphuric acid is measured and then poured quickly and carefully into the sodium thiosulphate solution.5. The stopwatch is started immediately and the conical flask is swirled.6. The mark `X` is viewed / observed vertically from above.7.The stopwatch is stopped as soon as the mark disappear from sight.8.Time taken is recorded.9. Steps 1 to 9 are repeated by using the different temperature of sodium thiosulphate solution. Data and Observation

Experiment Temperature , (oC)

Time taken for the “X” mark to disappear from view, t (s)

1/ time taken ,1/t ( s-1)

1 282 353 404 455 50

Discussion Based on plotted graph: [ calculation ]



The higher the temperature of sodium thiosulphate, the shorter the time taken for cross‘X’ to disappear from the sight.The rate of reaction directly proportional to the temperature of sodium thiosulphate solution used. //As the temperature sodium thiosulphate solution increases, the time taken decreases. Therefore the rate of reaction increases.

Conclusion :The rate of reaction increases as the temperature sodium thioulphate solution increases.

Energy profile diagram

2. Aim: to investigate effect of catalyst on the rate of decomposition hydrogen peroxide.

Problem statement: how does a catalyst affect the rate of decomposition hydrogen peroxide?

Hypothesis: manganese (IV) oxide, MnO2 increases the rate of decomposition of hydrogen peroxide

Variables:Manipulated : presence of manganese (IV) oxide (MnO2)Responding : rate of reactionFixed : concentration of H2O2, initial temperature of H2O2 solution.

Apparatus: test tube, 10 cm3 measuring cylinder, test tube rack, spatula.


1. Ea – activation energy without catalyst

2. Ea’ - activation energy with catalyst

3. Exothermic reaction – heat released /given out

4. Energy content in reactants higher than products

5. ^ H is the energy difference in reactants and products

- ^ H


Materials: (5-10) – volume of H2O2 solution, manganese (IV) oxide (MnO2) powder, wooden splinter

Procedures:1. label two test tube as A and B2. Using a measuring cylinder measure 5 cm3 of 20 – volume of H2O2 solution and pour into test

tube A.3. Add ½ spatula of manganese (IV) oxide powder into test tube A.4. Shake the test tube.5. Immediately place a glowing splinter into the test tube.6. Observe and record the changes.

7. Repeat the same procedure for test tube B without MnO2

Observation: [Paper 2]

Test tube ObservationA Effervescence occurred. The glowing wooden splinter relight.B No effervescence. The glowing wooden splinter did not relight.

Discussion:Manganese (IV) oxide (MnO2) increases the rate of decomposition of hydrogen peroxide. Decomposition of hydrogen peroxide produces oxygen gas. 2H2O2 à 2H2O + O2

CHAPTER 11: CARBON COMPOUND

1. Hydrocarbon – chemical compound containing carbon and hydrogen atom only.2. Alkene – chemical compound containing carbon and hydrogen atom and at least one carbon-carbon double bond ( C = C )

3. Isomers are molecules with the same molecular formula, but with different structural formula.Example: C4H10 – butane


n-butane

2-methylpropane


1. C2H4 + [O] + H2O C2H4(OH)2 [ purple turns colourless] //[ orange turns green]

2. CH3COOH + C2H5OH CH3COO C2H5 + H2O

3. C2H4 + H2O C2H5OH

4. C6H12O6 2C2H5OH + 2CO2

Homologous series

General formula Functional group Member , example

Alkane CnH2n + 2 , n = 1,2.. Single covalent bond between carbon atoms. C- C

Ethane

Alkene CnH2n , n = 2.. Double covalent bond between carbon atoms. C=C

Ethene

Alcohols CnH2n + 1 OH, n = 1,2.. Hydroxyl group / - OH Ethanol

Carboxylic acid

CnH2n + 1 COOH, n = 0,1,2..

Carboxyl group , -COOH Ethanoic acid CH3COOH


H 2SO4, cons

H 3 PO4, 60 atm, 300 oC

CH3COO C2H5

Ethyl ethanoate

CH3COOH

Carboxyl

C2H4

Double bond between C atoms,

C6H12O6

C2H6

C2H5Br

C2H4(OH)2

C2H4Br2

C2H5OH

Esterification

H2SO4

- CH2- CH2-

A

d

d

i

t

i

Oxidation

Fermention

Br2

H2

KMnO4/ H+,

K2Cr2O7/ H+

H2O

HX

CnH 2n+ 2 , n = 1,2 alkane

CnH2n , n = 2, 3 alkene

CnH 2n+ 1 OH, n = 1, 2 alcohol

C2H5OH

Hydroxyl

KMnO4/H+ / K2Cr2O7/ H+

Yeast

KMnO4/ H+,

K2Cr2O7/ H+


4. Your are required to prepare one namely ester by using ethanoic acid is one of the reactants. By using a namely alcohol, describe one experiment to prepare the ester. In your description include the chemical equation and observation involved.

Ester: ethylethanoate

Material: ethanol, etahanoic acid, water, concentrated sulphuric acidApparatus: Boiling tube / test tube, Bunsen burner, test tube holder, beakerProcedure:1. Pour 2 cm3 of ethanol into a boiling tube / test tube2. Add 1 cm3 of ethanoic acid3. Add 2 to 4 drops of concentrated sulphuric acid 4. Heat the mixture gently for about two minutes5. Pour the mixture into a beaker containing water.

Observation: Sweet/ pleasant / fruity smell // insoluble in water

Chemical equation: CH3COOH + C2H5OH à CH3COO C2H5 + H2O



4. Dehydration of alcohol Diagram of set up of apparatus1. Complete and functional2. Labels of set up of apparatus correct

Procedure: a) Place some glass wool in a boiling tube b) Use a dropper to add propan-1-ol to wet the glass wool.c) Clamp the boiling tube horizontally and placed unglazed porcelain chips in the mid section of the boiling tube.d) Heat the unglazed porcelain chips strongly. e) Then heat the glass wool gently to vaporize the propanol.

f) [Description of the chemical test to the gas collected in the test tube.]

Add 1 cm3 of bromine water and shake well.

[Observation]:Reddish brown colour of bromine decolourisedOr,Add 1 cm3

of acidified potassium manganate(VII) solution and shake well. [Observation]:Purple colour of potassium manganate(VII) solution decolourised

Chemical equation: C3H7OH à C3H6 + H2O

Industrial extraction of palm oil



5. Table shows results of latex coagulation

Procedure ObservationPropanoic acid (weak acid) is added to latex Latex coagulates immediatelyLatex is left under natural conditions Latex coagulates slowly

Explain why there is a difference in these observationsAnswer:1. Acid ionizes in water to produce high concentration of / a lot of hydrogen ions2. Hydrogen ions, H+ neutralize the negative charges on the protein membranes 3. The rubber particles collide and the protein membranes break4. Rubber molecules are released and combine with one another and entangle.5. The existence of bacteria in natural conditions6. The growth of bacteria produce / lactic acid /weak acid / low concentration of H+ ions.7. Due to the slow bacterial action, the coagulation of latex takes a longer time to occur. [Monomer of natural rubber: 2 – methylbuta-1,3- diene , C5H8 / isoprene ]

Explain how to prevent coagulation of latex

1. Add ammonia solution


Rubber particles--

-

-

-Protein membranes


2. Ammonia solution contains / ionized to produce hydroxide ions , OH-

3. Hydroxide ions, OH- neutralized the hydrogen ions, H+ / acid produced by the bacteria4. The rubber particles remain negatively charged and coagulation is prevented.

6. [Paper 3]Aim: To compare the elasticity / strength of vulcanised and unvulcanised rubber

Problem statement: Does vulcanised rubber more elastic than unvulcanised rubber

Hypothesis: Vulcanised rubber is more elastic than unvulcanised rubberVariable:Manipulated : vulcanised rubber and unvulcanised rubberResponding : length of rubber strip / elasticityFixed : mass of weight, size of rubber

Material and apparatus: Retort stand, bulldog clip, meter ruler, weight, vulcanised and unvulcanised rubber

Procedure:1. Hang both rubber strips to the retort stand with bulldog clip.2. Measure the initial length of both rubber strips and record.3. Hang 50 g weight to the end of each rubber using bulldog clip.4. Remove the weight and measure the length of both rubber strips and record.//5. Record all the data obtained.

Unvulcanised rubber Vulcanised rubber

Result / Data

Type of rubber Initial length , cm Length after removal of weight , cmvulcanisedunvulcanised

Compares and contrasts the properties of vulcanized rubber

Vulcanized rubber Elasticity Unvulcanised rubberHarder Hardness Less harderMore elastic Elasticity Less elasticStronger Tensile strength WeakerCan withstand higher temperature Resistance to heat Cannot withstand higher

temperatureLess easily oxidized Resistance to oxidation More easily oxidized



Does not become soft and sticky easily Effect of organic solvent Become soft and sticky easily

Conclusion:

1. Vulcanised rubber is more elastic than unvulcanised rubber due to the presence of cross-linkage of sulfur atoms between the rubber molecules. Vulcanised rubber could return to its original length after removal of the weight.

To prepare vulcanised rubber

Rubber can be vulcanized by dipping natural rubber sheets into disulphur dichloride solution in methylbenzene or heated with sulphur.

Note:Vulcanised rubber is more heat resistance due to the presence of cross-linkage of sulfur atoms increases the size of rubber molecules. Force of attraction between molecules will increase.

7. Compare and differentiate between namely alkene and alkane

Alkane ( hexane ) Alkene ( hexene )1 Hydrocarbon ( contain C and H atom)2 Low melting and boiling point3 Insoluble in water, soluble in organic solvent4 Cannot conduct electricity5 Density less than water6 Completely combustion produce CO2 + H2O

7 Saturated , single covalent bond, C-C Unsaturated , contain at least one double bond C=C

8 Unreactive – undergo substitution with halogen in the presence of sunlight / UV ray

Reactive – undergo addition reaction( hydrogenation, halogenations, oxidation, polymerization, with halide, steam(hydration)

9 General formula , CnH2n+2 , n = 1,2 … , CnH2n , n= 2 …

10 Identify test1. Combustion, burn less soot flame. (% of carbon per molecule is lower)

1. More soot flame. ( % of carbon per molecule is higher).



Chemical tests2. add bromine water , brown colour remains3. add acidified KMnO4 , purple colour remains

2. decolorized brown bromine water

3. purple colour is decolourized

CHAPTER 12: REDOX

Redox reactions are chemical reactions involving oxidation and reduction occurring simultaneously.

1. Transfer of electron, Mg à Mg2+ + 2e // Cu2+ + 2e à Cu2. Loss or gain oxygen, C + 2CuO à 2Cu + CO2

3. Loss or gain hydrogen, H2S + Cl2 à 2HCl + S4. changes in oxidation number

Rusting of iron

1. When iron exposed to water and oxygen 2. Iron atom releases 2 electrons to form iron (II) ion, Fe2+ / is oxidized to form iron (II) ion, Fe2+ 3. Fe à Fe2+ + 2e // (anode) [ oxidation]4. Iron acts as reducing agent5. Oxygen and water receives /gain electrons to form hydroxide ions.6. O2 + 2H2O + 4e à 4OH- (cathode) [reduction]7. Oxygen acts as oxidizing agent.8. Iron (II) ion, Fe2+ combine with hydroxide ion, OH- to form iron (II) hydroxide, Fe(OH)2.9. Iron (II) hydroxide, Fe(OH)2 oxidized by oxygen to form iron (III) oxide, brown solid/precipitate,



Fe2O3.x H2O. // Fe2+ à Fe3+ + e

Effect of the contact of other metals on the rusting of iron.

Aim : To investigate the effect of in contact of other metals on the rusting of iron.

Problem statement:How does the effect on rusting when iron is in contact with another metal? //How does different type of metal in contact with affect the rusting of iron?

Hypothesis :When a more electropositive metal is in contact with iron, the metal inhibits rusting.When a less electropositive metal is in contact with iron, the metal speeds up the rusting.

Variable:Manipulated : Type of metal that in contact with iron.Responding : Rusting of ironFixed : Iron nails, temperature, medium in which iron nails are kept.

Apparatus : Test tube, test tube rackMaterials : iron nails, magnesium ribbon, copper strip, zinc strip, tin strip, hot jelly solution, potassium

hexacyanoferat (III) , K3Fe(CN)6 solution, phenolphthalein indicator, sand paper.

Procedure:1. Five iron nails, magnesium ribbon, copper strip, zinc strip and tin strip were cleaned with sand

paper.2. Four iron nails were coiled tightly with the magnesium ribbon, copper strip, zinc strip and tin

strip respectively.3. All five iron nails were placed in separate test tube.4. The volume of hot jelly solution that was mixed with a little K 3Fe(CN)6 solution and phenolphthalein

indicator was poured into the each test tube to completely cover all the nails.5. The test tubes were kept in a test tube rack and were aside for a day.6. All observations were recorded.

Observation

Metal ObservationIntensity of dark blue colouration

Intensity of pink colouration

Condition of nail

Fe Low The surface of the nail was partially covered with reddish brown solid

Fe-Mg

High No reddish brown solid was found on the surface of the nail.

Fe-Zn High No reddish brown solid was found on the surface of the nail.

Fe-Sn Moderate Low The whole surface of the nail was covered with



reddish brown solidFe-Cu High Low The whole surface of the nail was heavily covered

with reddish brown solid

The nail in test tube A rusted a little. No rusting occurred to the nails in test tubes B and C .The nail in test tube D rusted but the nail in test tube E rusted even more.

Discussion 1. Based on the observations magnesium and zinc metals inhibit rusting of iron, while copper and tin

metals speed up rusting of iron.2. This is because magnesium and zinc are more electropositive than iron. Magnesium atom or zinc

atom releases its electron more easily than iron.Mg à Mg2+ + 2eO2 + 2H2O + 4e à 4OH-

3. Copper and tin are less electropositive than iron. Iron atom releases its electrons more easily than copper atom or tin atom.

4. Fe à Fe2+ + 2e5. The less electropositive metals that in contact with iron, the faster the rusting of iron occurs.6. The more electropositive metals that in contact with iron prevent iron from rusting.

Conclusion:

Rusting can be prevented when iron is in contact with a more electropositive metal. Rusting occurs faster when iron is in contact with a less electropositive metal.

1. Displacement reaction Metal:

Example: Zn + CuSO4 à ZnSO4 + Cu // Zn + Cu2+ à Cu + Zn2+

a) Zn atom oxidized to Zn2+ , Zn à Zn2+ + 2eb) Oxidation number of Zn changes / increase from 0 to +2, c) Zn acts as reducing agent.d) Copper (II) ion reduced to Cu, Cu2+ + 2e à Cue) Oxidation number of copper changes / decrease from +2 to 0f) Cu2+ ion acts as oxidizing agent

Example:

An experiment is carried out to determine the relative position of three metals, silver, L and M, in the electrochemical series.

Experiment

Observation grey deposit colourless solution

grey deposit light blue solution

no change

Based on results, arrange the three metals in order of increasing electropositivity. Explain you answer.


silver nitrate

silver nitrate

L nitrate

solutionL MM


Sample answer:

1. Silver, M and L2. L can displace silver from silver nitrate solution.3. L is more electropositive than silver // L is higher than silver in electrochemical series.4. M metal can displace silver from silver nitrate solution.5. M is more electropositive than silver // M is higher than silver in the electrochemical series.6. M cannot displace L from L nitrate solution.7. M is less electropositive than L // L is higher than M in the electrochemical series.

2. Displacement of Halogen:

Aim: To investigate oxidation and reduction in the displacement of halogen from its halide solution.

Procedure:1. Pour 2m cm3 of potassium bromide solution into a test tube.2. Add 2 cm3 of chlorine water to the test tube and shake the mixture.3. Add 2 cm3 of 1,1,1-trichloroethane / tetrachlorometane to the test tube and shake the mixture and leave it on the test tube rack4. Record theobservation. 5. Repeat steps 1 to 4 using another halogens and halide solutions.

Tabulation of data:

HalogenHalide solution

Chlorine Bromine Iodine

Potassium chloride X XPotassium bromine / XPotassium iodide / /

Example: Cl2 + 2KI à 2KCl + I2 // Cl2 + 2I- à I2 + 2Cl-



Cl2 + 2e à 2Cl- ( reduction) 2I- à I2 + 2e (oxidation

3. Transfer of electron at a distance – U-tube

Procedure:1. clamp a U-tube to a retort stand2. pour dilute sulphuric acid3. add solution (oxidizing agent) into one end of the arm of the U-tube4. Add solution (reducing agent) into the other end.5. place / dip carbon electrodes into each arm of the U-tube6. connect the electrodes to a voltmeter/ galvanometer using connecting wire7. leave the apparatus for 30minutes8. record the observation

4. Based on electron transfer, EXPLAIN the oxidation and reduction reaction in

(i) Changing of Fe2+ ions to Fe3+ ions (ii) Changing of Fe3+ ions to Fe2+ ions Use a suitable example for each of the reaction. Include half equations in your answer.

Sample answer:(i)

a. Fe+2 Fe+3 + eb. Br2 + 2e 2Br –

2. Iron (II) ions releases / donates electron to become iron(III) ions. Iron(II) ions are oxidized.3. Bromine molecules receive/ gain electrons to form bromide ions. Bromine molecules are reduced.

(any suitable oxidizing agent, Cl2, KMnO4/H+ )(ii) 1. Fe+3 + e Fe+2 2. Zn Zn+2 + 2e3. Iron(III) ions gain electron to become iron(II) ions. Iron(III) ions are reduced.4. Zinc atoms releases/ donates electrons to form zinc ions. Zinc atoms are oxidized.(a: any suitable reducing agent)

5. Describe an experiment to investigate oxidation and reduction in the change of iron(II) ions to iron(III) ions and vice versa.

(i) Changing of Fe2+ ions to Fe3+ ions


bromine water potassium iodide solution


Procedure: 1. Pour 2 cm3 of freshly prepared iron(II)sulphate solution into a test tube.2. Using dropper, add bromine water drop by drop until no further changes are observed.3. Heat slowly / gently4. Add 3 drops of potassium hexacyanoferrate (II) solution / sodium hydroxide solution.5. Dark blue precipitate // brown precipitate formed.

(ii) Changing of Fe3+ ions to Fe2+ ions

Procedure:1. Pour 2 cm3 of iron(III)sulphate solution into a test tube.2. Add half spatula of zinc / Mg powder to the solution.3. Shake the mixture until no further changes are observed.4. Filter the mixture.5. Add 3 drops of potassium hexacyanoferrate (III) solution / sodium hydroxide solution into the filtrate.6. Dark blue precipitate // green precipitate formed.

Reactivity series1. reactive metal with oxygen

Aim: 1. to investigate the reactivity of metal with oxygen 2. To arrange metals in term of their reactivity with oxygen

Procedure:1. Put one spatula of potassium manganate(VII), KMnO4 , into a boiling tube.2. Push some glass wool into the boiling tube and clamp horizontally.3. Place one spatula magnesium powder on a piece of asbestos paper and put into the boiling tube.4. Heat magnesium powder strongly and then heat the solid KMnO4.5. Observe and record how vigorous the reaction and colour of the residue when it is hot and when it is cold.

2Mg + O2 à 2MgO


K

Na

Ca

Mg

Al

C

Zn

H

Fe

Positions of carbon and hydrogen in the reacting series of metal

Produce oxygen


2. hydrogen gas with oxide of less reactive metalH2 + PbO à Pb + H2O

3. carbon with oxide metalC + 2CuO à 2Cu + CO2

Aim: To determine the position of carbon in the reactivity series of metals

Procedure:1. Mix thoroughly a spatula of carbon powder and a spatula of copper(II)oxide in a crucible.2. Heat the mixture strongly.3. Record the observation.4. Repeat steps 1 to 3, using magnesium oxide, aluminium oxide and zinc oxide to replace copper(II)oxide.

4. Carbon dioxide with metalCO2 + 2Mg à 2MgO + C

Application of reactivity series in the extraction of metals

Extraction of iron from its ores, hematite, Fe2O3

Extraction of tin from its ores, cassiterite, SnO2

- in blast furnace , carbon / coke as a reducing agent.

Example:C + O2 à CO2

C + CO2 à 2COC, CO2 , 2CO reduced the iron oxides to iron

2 Fe2O3 + 3C à 4Fe + 3CO2

Fe2O3 + 3CO à 2Fe + 2CO2

CaCO3 à CaO + CO2 ( lime stone decomposed) CaO + SiO2 à CaSiO3 ( impurities )


Oxidizing reducing

agent agent


Redox reaction in various chemical cells



CHAPTER 13: THERMOCHEMISTRY

1. Exothermic – A chemical reaction that gives out heat to the surroundings- The reactants lose heat energy to form the products- The energy content of reactants is higher than products- ΔH negative2. Energy level diagram (label energy, reactants and product with correct chemical / ionic formula, heat of reaction with unit.3. Heat of reaction – heat change/releases when 1 mole of product formed. [ kJmol- ]

= mCǾ / mole

Heat of neutralization – heat releases when 1 mole of H+ combines with 1 mol of OH- to form 1 mole of water. H+ + OH- à H2O

4. Heat of combustion – heat releases when 1 mole of alcohol burnt completely in excess oxygen.C2H5OH + 3O2 à 2CO2 + 3H2O

5. As the number of carbon atom per molecule increases, the heat of combustion increases, due to more products formed (CO2 & H2O) . Therefore more heat released when more bonds are formed.



6. To determine heat of combustion (material and apparatus, procedure, tabulation of data, calculation, observations, precautions).

Procedure:1. (100 – 200) cm3 of water is measured using a measuring cylinder 2. and poured into a copper tin.3. The initial temperature of water is measured and recorded, θ 1

4. A spirit lamp is filled with butanol/ other alcohol and weighed, x gram5.The spirit lamp is light and put under the copper can.6.The water is stirred continuously with a thermometer.7.When the temperature of water increased by 30oC, the flame is put off.8.The spirit lamp is weighed again, y gram9.The highest temperature is recorded, θ2

Results:Mass of weight of spirit lamp + butanol /g xFinal mass of spirit lamp + butanol /g yMass of butanol used/g (x-y) // zHighest temperature of water /oC θ1

Initial temperature of water /oC θ2

Increased in temperature /oC (θ1 - θ2 ) // θ3

Calculation:Heat change = mcθ = 100 x 4.2 x (θ2 – θ1) = a J

Precautions: 1. Make sure the flame from the combustion of ethanol touches the bottom of the copper can // The

spirit lamp is placed very close or just beneath the bottom of the copper can.2. Stir the water in the copper can continuously.3. The spirit lamp must be weighed immediately (because the ethanol is very volatile).4. A wind shield must be used during experiment.

Heat of displacementAim: To determine the heat of displacement of copper by zinc and iron

Procedure:1. Measure 25 cm3 of 0.2 mol dm-3 of copper(II)sulphate solution and pour into a plastic cup / polystrene cup.2. Record the initial temperature of the solution.3. Pour 0.5g of zinc powder into the solution.4. Stir the mixture with thermometer 5. Measure and record the highest temperature of the reacting mixutre.

Tabulation of data:

Metal Initial temperature, oC Highest temperature, oCZinc


Heat of combustion of butanol = a J

(z/74) mol


Iron

Heat of precipitation Aim: To determine the heat of precipitaion of silver chloride, AgCl

Apparatus: plastic cup, thermometer, measuring cylinder Material : silver nitrate solution , 0.5 mol dm-3 , sodium chloride solution, 0.5 mol dm-3

Procedure:1. Measure 20 cm3 0.5 mol dm-3 of silver nitrate solution and pour into plastic cup.2. Measure and record the initial temperature of silver nitrate solution.3. Measure 20 cm3 0.5 mol dm-3 of sodium chloride solution and pour into plastic cup.4. Measure and record the initial temperature of sodium chloride solution.5. Add the sodium chloride soltuions into the silver nitrate solution quickly and stir the mixture.6. Measure and record the highest temperature of the reacting mixture.

Tabulation of data:

initial temperature of silver nitrate solution, oCinitial temperature of sodium chloride solution, oCAverage temperature of both solutions, oChighest temperature of the reacting mixture, oC

Heat of precipitation is the heat released / heat change when one mole of precipitate is formed from their ions in aqueous solution.

Aplication of exothermic and endothermic reaction


ammonium nitrate (NH4NO3) Calcium chloride or

magnesium sulphatesodium acetate crystals


CHAPTER 14: CHEMICALS FOR CONSUMERS

Example:1. (a) A student washed his socks which had oily stains. Explain the cleansing action of soap on the oily stains.

In water soap ionizes to form ions/anion CH3(CH2)x COO- and cation, sodium ions, Na+

The anions consists of hydrophilic part ( -COO -) and hydrophobic part (hydrocarbon) Hydrophilic part dissolve in water only but hydrophobic part dissolve in grease only. The anions reduce surface tension of water, causing wetting of greasy surface. During washing and scrubbing, the anions pull the grease and lifted it off the surface and break it

into a small droplets (Emulsifying agent) Rinsing away the dirty water removes the grease (the dirt) and excess soap and the surface is

clean.

(b) Another student carried out four experiments to investigate the cleansing effect of soap and detergent on oily stains in soft water and hard water respectively.



Compare the cleansing effect between(i) Experiments I and II (ii) Experiment II and IV

Explain the differences in the observation

Exp. I and II The oily stain disappears in Experiment I but remains oily in Experiment II. Hard water contains Ca2+ and Mg2+ ions which reacts with soap ions to form

scum (insoluble salt) The formation of scum makes anions less efficient for cleaning the oily stain on the sock In soft water, all anions are used to clean the oily stain Thus, soap is only effective as a cleansing agent in soft water and ineffective in hard water.

Exp. II and IV The sock in Experiment II remains oily but is clean in experiment IV. The soap anions form scum when reacts with Ca2+ and Mg2+ ions in hard water. The formation of scum makes anions less efficient for cleaning

The detergent anions CH3(CH2)x OSO3- / CH3(CH2)x SO3

- do not form a precipitate with Ca2+ and Mg2+ in hard water.

Hence, detergent cleans effectively in hard water but soap does not clean effectively in hard water.

2. Preparation of soap

Procedure 1. pour 10 cm 3 palm oil ( vegetable oil ) into a beaker2. add 50 cm 3 of 5.0 mol dm-3 NaOH / KOH solution3. heat the mixture for (10 minutes)4. stir 5. stop heating, add 50 cm 3 distilled water and solid NaCl6. boil the mixture for 5 minutes7. cool8. filter, wash / rinse9. dry ( press the residue between filter papers

Test 10. Place a small amount of the residue into a test tube add distilled water, shake it well.

produce a lot of lather ( very foamy)

Observation : white solid, slippery and produce a lot of lather ( very foamy).

Chemical equation:


O


3. You are given liquid soap, sample of hard water, sample of soft water and other materials. Describe an experiment to investigate the effect of cleaning action of the soap in different types of water. You description must include example of hard water and soft water, observation and conclusion.

[10 marks]Sample answer:

1. hard water : sea water2. soft water : distilled water

Materials: liquid soap, sea water, distilled water, pieces of cloth with oil stain.Apparatus: beaker (suitable container), glass rod, measuring cylinder

Procedure:1. pour (100 – 200) cm 3 sea water into a beaker/ suitable container2. Add (10 – 20 ) cm 3 liquid soap into the beaker.3. stir the mixture4. Place a piece of cloth with oil stain into the beaker.5. Record the observation.6. Repeat step 1 – 4 using distilled water.

Observation:1. The oil stain in hard water remained but removed in soft water.

Conclusion:

1. Hard water contains Mg2+ or Ca2+. Soap anion formed scum (insoluble salt) when react with Mg2+ or Ca2+.2. Soap is not an effective cleansing agent in hard water but only effective in soft water.



Compare and contrast soap and detergent

Soap Detergent

Sodium carboxylate Sodium alkyl sulphate Sodium alkylbenzene sulphonate

Material : fat, vegetable oil, NaOH / KOH, mol dm-3

Petroleum fractions : long chain alcohol, NaOH / KOH,5 mol dm-3 , H2SO4

Petroleum fractions : long chain alkene, NaOH / KOH,5 mol dm-3, H2SO4

PreparationSaponification

1. sulphonation2. neutralization

1. alkylation2. sulphonation3. neutralization

The additives in detergent

Type Function ExampleFragrances To add fragrance to both the detergent and

fabricsBiological enzymes

To remove protein stains such as blood Amylases, proteases, celluloses, lipases

Whitening agents To convert stains into colourless substances

Sodium perborate

Suspension agents To prevent the dirt particles removed from redepositing onto cleaned fabrics

Carboxymethylcellulose (CMC)

Fillers To add to the bulk of the detergent and enable it to be pour easily

Sodium sulphate, sodium silicate

Optical whitening To add brightness and whiteness to white fabrics.

Fluorescent dyes

Builder To enhance the cleaning efficiency of detergent by softening the water

Sodium tripolyphosphate


CH3 (CH2)15 COO- Na+


Food additive

Type Function ExamplesPreservatives To slow down/ prevent the

growth of microorganism, therefore food can kept for longer periods of time

Salts/sugar: draws the water out of the cells of microorganism and retards the growth of microorganism.Vinegar: provides an acidic condition that inhibits the growth of microorganism.NaNO3 (Burger)Benzoic acid / sodium benzoate: to slow down the growth of microorganism.

Antioxidants To prevent oxidation that can causes rancid fats and brown fruits

Ascorbic acid and vitamin E (Tocopherol)

Flavorings To improve the taste of food and restore taste loss because of processing.

Sugar , salt, MSG, vinegar, aspartame and synthetic essences (ester)

Stabilizers To prevent emulsion from separating out.

Lecithin, fatty acid

Thickeners Its use to thicken foods Pectin, acacia gum, gelatin

Dyes To add or restore the colour in food in order to enhance its visual appeal and match consumers expectations.

Natural dyes and artificial dyes: Azo compounds or triphenyl compound.

MedicineType Function Example Effect on health

Analgesic To relieve pain without affected consciousness

Aspirin -Internal bleeding and ulceration-can cause brain and liver damage to children

Paracetamol Over dose can cause brain and liver damage

Codeine Addiction, depression and nausea

Antibiotics To treat infections cause by bacteria (tuberculosis, TB) and pneumonia. Can kill or slow down the growth of bacteria.

Penicillin(Penicillium notatum)

Can cause allergic reaction.

Streptomycin Can cause nausea, vomiting, dizziness, rashes, fever

Psychotherapeutic To alter the abnormal thinking, feelings and behaviors. Divide into 3 categories :a) stimulant: to reduce fatigue Amphetamines

-High dose can lead to anxiety, hallucinations, severe depression, and psychological dependence.



b) antidepressant:to reduce tension and anxiety

c) antipsychotic: to treat psychiatric illness

Barbiturate / tranquilizer

chlorpromazinehaloperidol, clozapine

Overdose can lead to respiratory difficulties, sleeplessness, come, death.

Dizziness, drowsiness, rapid heartbeat.

The existence of Chemicals1. Detergent:

* wear gloves when working with strong detergents to protect your hands* use biodegradable detergent* use appropriate amounts of detergents

2. Food additives* Be wise consumer. Read the label to know what you are eating.* Avoid consuming too much salts and sugar* avoid foodstuff with additives which are you sensitive to.* avoid rewarding children with junk food.

3. Medicine:* do not store up medicines.* no self medication* do not take medicine prescribe for someone else* check for expiry date * follow your doctor`s instructions for taking medicine.* keep away from children* do not overdose



Some common medical plant and their


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