science form 4- chapter ff5

8/12/2019 Science Form 4- Chapter ff5

1/74

SCIENCE FORM 4

CHAPTER 5:ENERGY AND

CHEMICALCHANGES


2/74


3/74

5.1 PHYSICAL AND CHEMICAL CHANGES

- Examples involving physical changes:(a) Melting of ice

(b) Evaporation of water

(c) Dissolving sugar in water(d) Crystallisation of sodium chloride

from its saturated solution

(e) Heating of iodine crystals

(f) Heating of wax


4/74


Melting of ice Evaporation of water
http://www.google.com.my/url?sa=i&rct=j&q=evaporation++sea+water&source=images&cd=&cad=rja&docid=3ge595uLd_yKhM&tbnid=Z8FSNyQtr3G_qM:&ved=0CAUQjRw&url=http://ga.water.usgs.gov/edu/watercycleevaporation.html&ei=VMSYUZrCNM6trAeG3ICIBA&bvm=bv.46751780,d.bmk&psig=AFQjCNGMjpZtL2Y24coz1qmcq5WSh-1xfw&ust=1369052625762793http://www.google.com.my/url?sa=i&rct=j&q=melting+of+ice&source=images&cd=&cad=rja&docid=64GdR4m9ftaArM&tbnid=zRwGJUH8H1OUlM:&ved=0CAUQjRw&url=http://blogs.yis.ac.jp/19miyoshiay/2012/09/25/science-a-little-bit-of-matter/&ei=W76YUci0L4rIrQf5jYGYAg&bvm=bv.46751780,d.bmk&psig=AFQjCNEIMEToM6e_90RKap1UxiQ0zEbvhw&ust=1369051074421864


5/74


Dissolving of sugar in water Heating iodine crystals
http://www.google.com.my/url?sa=i&rct=j&q=heating+iodine+crystals&source=images&cd=&cad=rja&docid=hwossyD3T0PFDM&tbnid=L8sBAyygOLI72M:&ved=0CAUQjRw&url=http://math.ucr.edu/home/baez/networks/networks_18.html&ei=GcSYUfH9AcWzrAeVyICoAQ&bvm=bv.46751780,d.bmk&psig=AFQjCNHficlrvZBxMwnVeO8g1MQexSKvnQ&ust=1369052484165440http://www.google.com.my/url?sa=i&rct=j&q=dissolving+sugar+in+water&source=images&cd=&cad=rja&docid=2W-fhSf_xh-mCM&tbnid=uU6NHpLKFWOy-M:&ved=0CAUQjRw&url=http://www.whycenter.com/why-does-sugar-dissolve-in-water/&ei=PMOYUYWWBIWFrgfLuYDIDQ&bvm=bv.46751780,d.bmk&psig=AFQjCNH6T7sNbUgz6qKyZRJRYLhhfdxxOw&ust=1369052304601326


6/74


(ii) Chemical change

- Produces new substances that have

properties different from those of the

original substance.- Usually irreversible.

- Examples involving chemical changes:

(a) Burning of a paper(b) Colour of a peeled apple changes

when it is exposed to air

(c) Frying an egg


7/74


(d) Combustion of fuel(e) When iron filings are heated with sulphur

powder, the mixture glows brightly. A

black solid, iron sulphide is formed.Iron + Sulphur Iron sulphide

(f) When magnesium ribbon is heated,

it burns with a bright flame. A white solid,

magnesium oxide is formed.

Magnesium + Oxygen Magnesium

oxide


8/74


(g) Zinc reacts with blue copper sulphatesolution to form a colourless zinc

sulphate solution and brown copper.

Zinc + Copper sulphate Zinc sulphate+ Copper

(h) Iron nail rust when water and oxygen are

present. Rust is brown.

Iron + Oxygen + Water Rust


9/74


(i) Heating green copper carbonateproduces black copper oxide and

releases carbon dioxide.

Copper carbonate Copper oxide +Carbon dioxide

(j) Mixing potassium iodide and lead nitrate

solution forms lead iodide, a yellow

precipitate.

Potassium + Lead Potassium + Lead

iodide nitrate nitrate iodide


10/74


Frying an egg Browning of an apple
http://www.google.com.my/url?sa=i&rct=j&q=brown+oxidation+apple+&source=images&cd=&cad=rja&docid=E40GigtdemxlNM&tbnid=Mtnw0O4PokePQM:&ved=0CAUQjRw&url=http://ursulaethomasardysshealthandwellness.blogspot.com/2010_04_01_archive.html&ei=ugeZUaegNcqJrAfuxIDYDQ&bvm=bv.46751780,d.bmk&psig=AFQjCNEJ7OHO7SpAZACWou4gUPk4gI4UPw&ust=1369069673108365http://www.google.com.my/url?sa=i&rct=j&q=frying+an+egg&source=images&cd=&cad=rja&docid=y3yAiUJvartiIM&tbnid=RGu_fTwuvHF6SM:&ved=0CAUQjRw&url=http://whatscookingamerica.net/Eggs/FriedEgg.htm&ei=pv6YUdbjFMTqrAfxyYDwCg&bvm=bv.46751780,d.bmk&psig=AFQjCNElgBK3nisqBoDeu4JJa7WI-CiRVQ&ust=1369067466410515


11/74


Heating a mixture of iron filings andsulphur powder

Reaction of zinc with coppersulphate solution
http://www.google.com.my/url?sa=i&rct=j&q=zinc+reacting+with+copper+sulfate+solution&source=images&cd=&cad=rja&docid=deDwTD5bQUL7tM&tbnid=fUTUI31WX9WK5M:&ved=0CAUQjRw&url=http://www.visualphotos.com/image/1x6037953/zinc_displacing_copper_in_copper_sulphate_solution&ei=UQSZUfXrMZDorQekn4H4Bw&bvm=bv.46751780,d.bmk&psig=AFQjCNGxQAMqtkdKoW1IP5RTQrwRMBW4Hw&ust=1369068771256525http://www.google.com.my/url?sa=i&rct=j&q=iron+heated+sulfur&source=images&cd=&cad=rja&docid=fxzMKf7_72ajrM&tbnid=HR3ZFcC2gYSEOM:&ved=0CAUQjRw&url=http://www.youtube.com/all_comments?threaded=1&v=q-pWpBcWNek&ei=NQOZUezNMc2GrgfH74HYBw&bvm=bv.46751780,d.bmk&psig=AFQjCNGhEHwTUnkNw6KsNuqpqAG4VzJxQg&ust=1369068667897912


12/74


Aspect Physical changes Chemical changes

Formation of new substance No Yes

Reversibility Reversible Difficult to reverse

Energy needed Less energy needed More energy needed


13/74

5.2 HEAT CHANGE IN CHEMICAL REACTIONS

There are two types of chemical reactions:(i) Exothermic reactions

- Reactions which release heat to the

surroundings are called exothermicreactions.

- Temperature of the surroundings

increases.


14/74


(ii) Endothermic reactions

- Reactions which absorb heat from

the surroundings.

- Temperature of the surroundings

decreases.

During chemical reactions, old bonds in

the reactants are broken and new

bonds in the products are formed.

The breaking down of old bonds absorbs

heat energy whereas the formation of

new bonds releases heat energy.


15/74


Breaking an old bond absorbs heat energy Forming a new bond releases heat energy


16/74


In exothermic reactions, the heat energy

absorbed to break the old bonds in the

reactants is less than the heat energy

released when new bonds are formed in

the products. There is a net of heat

energy loss.

The temperature of the surroundings

increases due to the heat energy that isreleased.


17/74


In endothermic reactions, the heat energyabsorbed to break the old bonds in the

reactants is greater than the heat energy

released when the new bonds are formed

in the products. There is a net of heat

energy gain.

The temperature of the surroundings

decreases due to heat energy is absorbed

from the surroundings.


18/74


In exothermic reactions, the heat energy absorbed to break the old bonds in the

reactants is less than the heat energy released when the new bonds are formed in theproducts
http://www.google.com.my/url?sa=i&rct=j&q=exothermic+reaction+animation&source=images&cd=&cad=rja&docid=jNawKRtgXAN6nM&tbnid=oB5MMP9f0pnA6M:&ved=0CAUQjRw&url=http://www.rpdp.net/sciencetips_v2/P12A6.htm&ei=HmCaUZ2aIYHUrQfgi4GgAQ&bvm=bv.46751780,d.bmk&psig=AFQjCNFF5hcPMshOftc4qcvnQ4BlmWnZ8A&ust=1369157534867967


19/74


In endothermic reactions, the heat energy absorbed to break the old bonds in the

reactants is greater than the heat energy released when the new bonds are formed inthe products
http://rpdp.net/sciencetips_v2/P12A6.htmhttp://rpdp.net/sciencetips_v2/P12A6.htm


20/74


Haber process is used to manufacture

ammoniain the industry. Ammonia is an

important material for making nitrogenous

fertilisers.

In the Haber process, nitrogen and

hydrogen gases are mixed together. The

mixture is passed over an iron catalyst.

Iron catalystNitrogen + Hydrogen Ammonia

450 C

200 atm
http://www.google.com.my/url?sa=i&rct=j&q=reversible+arrow+chemistry&source=images&cd=&cad=rja&docid=OalOMglJ5gOZ0M&tbnid=MyASuVTozRu5aM:&ved=0CAUQjRw&url=http://www.citycollegiate.com/chemical_equilibrium5.htm&ei=dGqaUfmrMcrorQeJ7oCwDw&bvm=bv.46751780,d.bmk&psig=AFQjCNEmU5_wAzU7ulJ0Z_ZvUOwdv7K9_A&ust=1369160671391484


21/74


Iron catalyst

Reactor

Coolant out

Coolant in

Condenser

Leftover H2+ N2

Liquid ammonia

H2+ N2

Haber process
http://www.google.com.my/url?sa=i&rct=j&q=haber+process&source=images&cd=&docid=duDK45jXlHSxoM&tbnid=fShQDJ-zveMOdM:&ved=0CAUQjRw&url=http://www.bbc.co.uk/schools/gcsebitesize/science/add_gateway_pre_2011/chemical/batchcontinuousrev1.shtml&ei=_3maUbnAF4ONrQe964HQAQ&bvm=bv.46751780,d.bmk&psig=AFQjCNFXFpREM9bWgDyJ_C15_Y3hkSwoGQ&ust=1369164608654638http://www.google.com.my/url?sa=i&rct=j&q=haber+process&source=images&cd=&docid=duDK45jXlHSxoM&tbnid=fShQDJ-zveMOdM:&ved=0CAUQjRw&url=http://www.bbc.co.uk/schools/gcsebitesize/science/add_gateway_pre_2011/chemical/batchcontinuousrev1.shtml&ei=_3maUbnAF4ONrQe964HQAQ&bvm=bv.46751780,d.bmk&psig=AFQjCNFXFpREM9bWgDyJ_C15_Y3hkSwoGQ&ust=1369164608654638http://www.google.com.my/url?sa=i&rct=j&q=haber+process&source=images&cd=&docid=duDK45jXlHSxoM&tbnid=fShQDJ-zveMOdM:&ved=0CAUQjRw&url=http://www.bbc.co.uk/schools/gcsebitesize/science/add_gateway_pre_2011/chemical/batchcontinuousrev1.shtml&ei=_3maUbnAF4ONrQe964HQAQ&bvm=bv.46751780,d.bmk&psig=AFQjCNFXFpREM9bWgDyJ_C15_Y3hkSwoGQ&ust=1369164608654638http://www.google.com.my/url?sa=i&rct=j&q=haber+process&source=images&cd=&docid=duDK45jXlHSxoM&tbnid=fShQDJ-zveMOdM:&ved=0CAUQjRw&url=http://www.bbc.co.uk/schools/gcsebitesize/science/add_gateway_pre_2011/chemical/batchcontinuousrev1.shtml&ei=_3maUbnAF4ONrQe964HQAQ&bvm=bv.46751780,d.bmk&psig=AFQjCNFXFpREM9bWgDyJ_C15_Y3hkSwoGQ&ust=1369164608654638http://www.google.com.my/url?sa=i&rct=j&q=haber+process&source=images&cd=&docid=duDK45jXlHSxoM&tbnid=fShQDJ-zveMOdM:&ved=0CAUQjRw&url=http://www.bbc.co.uk/schools/gcsebitesize/science/add_gateway_pre_2011/chemical/batchcontinuousrev1.shtml&ei=_3maUbnAF4ONrQe964HQAQ&bvm=bv.46751780,d.bmk&psig=AFQjCNFXFpREM9bWgDyJ_C15_Y3hkSwoGQ&ust=1369164608654638http://www.google.com.my/url?sa=i&rct=j&q=haber+process&source=images&cd=&docid=duDK45jXlHSxoM&tbnid=fShQDJ-zveMOdM:&ved=0CAUQjRw&url=http://www.bbc.co.uk/schools/gcsebitesize/science/add_gateway_pre_2011/chemical/batchcontinuousrev1.shtml&ei=_3maUbnAF4ONrQe964HQAQ&bvm=bv.46751780,d.bmk&psig=AFQjCNFXFpREM9bWgDyJ_C15_Y3hkSwoGQ&ust=1369164608654638http://www.google.com.my/url?sa=i&rct=j&q=haber+process&source=images&cd=&docid=duDK45jXlHSxoM&tbnid=fShQDJ-zveMOdM:&ved=0CAUQjRw&url=http://www.bbc.co.uk/schools/gcsebitesize/science/add_gateway_pre_2011/chemical/batchcontinuousrev1.shtml&ei=_3maUbnAF4ONrQe964HQAQ&bvm=bv.46751780,d.bmk&psig=AFQjCNFXFpREM9bWgDyJ_C15_Y3hkSwoGQ&ust=1369164608654638http://www.google.com.my/url?sa=i&rct=j&q=haber+process&source=images&cd=&docid=duDK45jXlHSxoM&tbnid=fShQDJ-zveMOdM:&ved=0CAUQjRw&url=http://www.bbc.co.uk/schools/gcsebitesize/science/add_gateway_pre_2011/chemical/batchcontinuousrev1.shtml&ei=_3maUbnAF4ONrQe964HQAQ&bvm=bv.46751780,d.bmk&psig=AFQjCNFXFpREM9bWgDyJ_C15_Y3hkSwoGQ&ust=1369164608654638http://www.google.com.my/url?sa=i&rct=j&q=haber+process&source=images&cd=&docid=duDK45jXlHSxoM&tbnid=fShQDJ-zveMOdM:&ved=0CAUQjRw&url=http://www.bbc.co.uk/schools/gcsebitesize/science/add_gateway_pre_2011/chemical/batchcontinuousrev1.shtml&ei=_3maUbnAF4ONrQe964HQAQ&bvm=bv.46751780,d.bmk&psig=AFQjCNFXFpREM9bWgDyJ_C15_Y3hkSwoGQ&ust=1369164608654638http://www.google.com.my/url?sa=i&rct=j&q=haber+process&source=images&cd=&docid=duDK45jXlHSxoM&tbnid=fShQDJ-zveMOdM:&ved=0CAUQjRw&url=http://www.bbc.co.uk/schools/gcsebitesize/science/add_gateway_pre_2011/chemical/batchcontinuousrev1.shtml&ei=_3maUbnAF4ONrQe964HQAQ&bvm=bv.46751780,d.bmk&psig=AFQjCNFXFpREM9bWgDyJ_C15_Y3hkSwoGQ&ust=1369164608654638http://www.google.com.my/url?sa=i&rct=j&q=haber+process&source=images&cd=&docid=duDK45jXlHSxoM&tbnid=fShQDJ-zveMOdM:&ved=0CAUQjRw&url=http://www.bbc.co.uk/schools/gcsebitesize/science/add_gateway_pre_2011/chemical/batchcontinuousrev1.shtml&ei=_3maUbnAF4ONrQe964HQAQ&bvm=bv.46751780,d.bmk&psig=AFQjCNFXFpREM9bWgDyJ_C15_Y3hkSwoGQ&ust=1369164608654638http://www.google.com.my/url?sa=i&rct=j&q=haber+process&source=images&cd=&docid=duDK45jXlHSxoM&tbnid=fShQDJ-zveMOdM:&ved=0CAUQjRw&url=http://www.bbc.co.uk/schools/gcsebitesize/science/add_gateway_pre_2011/chemical/batchcontinuousrev1.shtml&ei=_3maUbnAF4ONrQe964HQAQ&bvm=bv.46751780,d.bmk&psig=AFQjCNFXFpREM9bWgDyJ_C15_Y3hkSwoGQ&ust=1369164608654638http://www.google.com.my/url?sa=i&rct=j&q=haber+process&source=images&cd=&docid=duDK45jXlHSxoM&tbnid=fShQDJ-zveMOdM:&ved=0CAUQjRw&url=http://www.bbc.co.uk/schools/gcsebitesize/science/add_gateway_pre_2011/chemical/batchcontinuousrev1.shtml&ei=_3maUbnAF4ONrQe964HQAQ&bvm=bv.46751780,d.bmk&psig=AFQjCNFXFpREM9bWgDyJ_C15_Y3hkSwoGQ&ust=1369164608654638http://www.google.com.my/url?sa=i&rct=j&q=haber+process&source=images&cd=&docid=duDK45jXlHSxoM&tbnid=fShQDJ-zveMOdM:&ved=0CAUQjRw&url=http://www.bbc.co.uk/schools/gcsebitesize/science/add_gateway_pre_2011/chemical/batchcontinuousrev1.shtml&ei=_3maUbnAF4ONrQe964HQAQ&bvm=bv.46751780,d.bmk&psig=AFQjCNFXFpREM9bWgDyJ_C15_Y3hkSwoGQ&ust=1369164608654638http://www.google.com.my/url?sa=i&rct=j&q=haber+process&source=images&cd=&docid=duDK45jXlHSxoM&tbnid=fShQDJ-zveMOdM:&ved=0CAUQjRw&url=http://www.bbc.co.uk/schools/gcsebitesize/science/add_gateway_pre_2011/chemical/batchcontinuousrev1.shtml&ei=_3maUbnAF4ONrQe964HQAQ&bvm=bv.46751780,d.bmk&psig=AFQjCNFXFpREM9bWgDyJ_C15_Y3hkSwoGQ&ust=1369164608654638


22/74


Contact process is used to manufacture

sulphuric acid in the industry.

Step 1: Sulphur is burnt in air to produce

sulphur dioxide.Sulphur + Oxygen Sulphur

dioxide

Step 2: A mixture of sulphur dioxide andair are passed over vanadium(V)

oxide catalyst at 450 C to produce

sulphur trioxide.


23/74


Step 3: Sulphur trioxide is dissolved inconcentrated sulphuric acid to

produce oleum.

Sulphur + Concentrated Oleum

trioxide sulphuric acid

Vanadium(V)

oxide catalystSulphur dioxide + Oxygen Sulphur trioxide

450 C
http://www.google.com.my/url?sa=i&rct=j&q=reversible+arrow+chemistry&source=images&cd=&cad=rja&docid=OalOMglJ5gOZ0M&tbnid=MyASuVTozRu5aM:&ved=0CAUQjRw&url=http://www.citycollegiate.com/chemical_equilibrium5.htm&ei=dGqaUfmrMcrorQeJ7oCwDw&bvm=bv.46751780,d.bmk&psig=AFQjCNEmU5_wAzU7ulJ0Z_ZvUOwdv7K9_A&ust=1369160671391484


24/74


Step 4: The oleum is diluted with water to

produce concentrated sulphuric

acid.

Oleum + Water Concentratedsulphuric acid


25/74


26/74

5.3 THE REACTIVITY SERIES OF METALS

Why do gold, silver and platinum exist

as elements in the Earths crust and

whereas metals such as sodium and

potassium do not exist as elements in

the Earths crust?

Some metals are more reactive than

others. Different metals show different

reactivity with water, acids and oxygen.


27/74


The reactions involving metals:

(i) Reaction of reactive metal with water to

produce alkali and hydrogen.

Metal + Water Alkali + Hydrogen(ii) Reaction of reactive metal with dilute

acid to produce a salt and hydrogen.

Metal + Dilute acid Salt + Hydrogen(iii) Reaction of metal with oxygen to form

metal oxide

Metal + Oxygen Metal oxide


28/74


Based on their reactivity with oxygen,

metals and carbon (non-metal) can be

arranged in a reactivity series as follows:Potassium

Sodium

CalciumMagnesium

Aluminium

Carbon

Zinc

Iron

Tin

Lead

Copper

Silver

Gold

Potato

Soup

CanMake

All

Cruel

Zoos

In

The

Land

Change

So

Good


29/74


The position of carbon in the reactivity seriesis determined by comparing its attraction for

oxygen with other metals.

When carbon is heated with a metal oxide,carbon can remove oxygen from the metal

oxide if carbon is more reactive than the

metal.

When zinc oxide and iron oxide are heated

with carbon, the oxygen in the metal oxides

are removed by carbon. Therefore, carbon

is more reactive than zinc and iron.


30/74


When carbon is heated with aluminium

oxide, the carbon cannot remove oxygen

from aluminium oxide.

This means that carbon is more reactive

than zinc and iron but less reactive than

aluminium. Therefore, carbon is positioned

between aluminium and zinc in the

reactivity series.


31/74

5.4 APPLICATION OF REACTIVITY SERIES OF METALS

Most metals in the Earths crust are

reactive. They react readily with other

elements to form compoundssuch as

oxides, sulphides and carbonates. These

compounds are called ores.


32/74


Ore Composition

Bauxite Aluminium oxide

Cassiterite Tin(IV) oxide

Haematite Iron(III) oxide

Sphaletite Zinc sulphide

Sedimentary rock Calcium carbonate


33/74


The method of extracting a metal from its

ore depends on its position in the

reactivity series.

Metals below carbon in the reactivity

series can be extracted from their oxides

with using carbon because they are less

reactive than carbon.

Carbon is used for extraction because it is

cheap and readily available.


34/74


Metals above carbon in the reactivityseries cannot be extracted using carbon

because they are more reactive than

carbon. They are extracted using

electrolysis.

Tin ore or cassiterite is tin(IV) oxide. Tin

is extracted by heating cassiterite with

carbon (coke) and limestone at hightemperature in a blast furnace.


35/74


Carbon removes the oxygen from tin(IV)oxide because it ismore reactive than tin.

Tin(IV) oxide + Carbon Tin + Carbon

dioxide Limestone is added to react with the

impurities in the tin ore. Slag is formed.

Two products are collected at the bottom ofthe blast furnace. Molten slag floats on the

molten tin. This allow the two products to

flow separately.


36/74


Extraction of tin in a blast furnace

Molten iron

Blast furnace

Tin(IV) oxide, coke and

limestone

Slag

Blast of hot air
http://images.yourdictionary.com/blast-furnacehttp://images.yourdictionary.com/blast-furnacehttp://images.yourdictionary.com/blast-furnacehttp://images.yourdictionary.com/blast-furnacehttp://images.yourdictionary.com/blast-furnacehttp://images.yourdictionary.com/blast-furnacehttp://images.yourdictionary.com/blast-furnace


37/74

5.5 ELECTROLYSIS

Electrolysis is the decomposition of an

electrolyte by electricity. An electrolyte is a liquid or solution which

contains free-moving ions that can

conduct electricity.

The electrodes are conductors whichcarry

electricity into or out of an electrolyte.

The electrode joined to the positiveterminal of the dry cell is called the anode

whereas the electrode joined to the

negative terminal is called the cathode.


38/74

5.5 ELECTROLYSIS

During electrolysis, the positively-

charged ions (cations) are attracted to

the cathode and receive electrons. The

negatively-charged ions (anions) are

attracted to the anode and releaseelectrons.


39/74

5.5 ELECTROLYSIS

Bromine

gas Lead

metal

Molten lead

bromide

Electrolysis
http://www.google.com.my/url?sa=i&rct=j&q=electrolysis+lead+bromide+&source=images&cd=&cad=rja&docid=iCQaxh9RpQspuM&tbnid=Z80sv51Q-6MsgM:&ved=0CAUQjRw&url=http://flashscience.co.uk/chemistry/flash_bundles/middle_school/pbbr2.html&ei=p16cUb-7I4PirAfVkoCgCA&psig=AFQjCNE-Eh6SLDB0tNKMfWAR1tLD9KeQUQ&ust=1369288675043203http://www.google.com.my/url?sa=i&rct=j&q=electrolysis+lead+bromide+&source=images&cd=&cad=rja&docid=iCQaxh9RpQspuM&tbnid=Z80sv51Q-6MsgM:&ved=0CAUQjRw&url=http://flashscience.co.uk/chemistry/flash_bundles/middle_school/pbbr2.html&ei=p16cUb-7I4PirAfVkoCgCA&psig=AFQjCNE-Eh6SLDB0tNKMfWAR1tLD9KeQUQ&ust=1369288675043203http://www.google.com.my/url?sa=i&rct=j&q=electrolysis+lead+bromide+&source=images&cd=&cad=rja&docid=iCQaxh9RpQspuM&tbnid=Z80sv51Q-6MsgM:&ved=0CAUQjRw&url=http://flashscience.co.uk/chemistry/flash_bundles/middle_school/pbbr2.html&ei=p16cUb-7I4PirAfVkoCgCA&psig=AFQjCNE-Eh6SLDB0tNKMfWAR1tLD9KeQUQ&ust=1369288675043203http://www.google.com.my/url?sa=i&rct=j&q=electrolysis+lead+bromide+&source=images&cd=&cad=rja&docid=iCQaxh9RpQspuM&tbnid=Z80sv51Q-6MsgM:&ved=0CAUQjRw&url=http://flashscience.co.uk/chemistry/flash_bundles/middle_school/pbbr2.html&ei=p16cUb-7I4PirAfVkoCgCA&psig=AFQjCNE-Eh6SLDB0tNKMfWAR1tLD9KeQUQ&ust=1369288675043203http://www.google.com.my/url?sa=i&rct=j&q=electrolysis+lead+bromide+&source=images&cd=&cad=rja&docid=iCQaxh9RpQspuM&tbnid=Z80sv51Q-6MsgM:&ved=0CAUQjRw&url=http://flashscience.co.uk/chemistry/flash_bundles/middle_school/pbbr2.html&ei=p16cUb-7I4PirAfVkoCgCA&psig=AFQjCNE-Eh6SLDB0tNKMfWAR1tLD9KeQUQ&ust=1369288675043203http://www.google.com.my/url?sa=i&rct=j&q=electrolysis+lead+bromide+&source=images&cd=&cad=rja&docid=iCQaxh9RpQspuM&tbnid=Z80sv51Q-6MsgM:&ved=0CAUQjRw&url=http://flashscience.co.uk/chemistry/flash_bundles/middle_school/pbbr2.html&ei=p16cUb-7I4PirAfVkoCgCA&psig=AFQjCNE-Eh6SLDB0tNKMfWAR1tLD9KeQUQ&ust=1369288675043203http://www.google.com.my/url?sa=i&rct=j&q=electrolysis+lead+bromide+&source=images&cd=&cad=rja&docid=iCQaxh9RpQspuM&tbnid=Z80sv51Q-6MsgM:&ved=0CAUQjRw&url=http://flashscience.co.uk/chemistry/flash_bundles/middle_school/pbbr2.html&ei=p16cUb-7I4PirAfVkoCgCA&psig=AFQjCNE-Eh6SLDB0tNKMfWAR1tLD9KeQUQ&ust=1369288675043203


40/74


41/74

5.5 ELECTROLYSIS

Uses of electrolysis in industry:

(i) Electroplating

- To prevent iron objects from corrosion,

they are electroplated with a thin layerof unreactive metals such as

copper, silver and chromium.

- Electroplating make these objectsresistant to corrosion and more

attractive.


42/74

5.5 ELECTROLYSIS

Electroplating an iron spoon with copper

Copper

asanode

Iron

spoonas

cathode

Copper sulphate

solution

Copper ions

Rules for electroplating:

(i) Anode : Plating metal

(ii) Cathode: Object to be

electroplated(i) Electrolyte: Solution of the

plating metal

Rheostat
http://www.google.com.my/url?sa=i&rct=j&q=electroplating+iron+spoon+with+copper&source=images&cd=&cad=rja&docid=2AtEzCPrCr-0kM&tbnid=kg8fiTogP4yJKM:&ved=0CAUQjRw&url=http://moodle.rockyview.ab.ca/mod/book/print.php?id=118120&chapterid=91369&ei=A3GcUYWsHo-3rAef1YDIBQ&bvm=bv.46751780,d.bmk&psig=AFQjCNHSh945z56_G_BPUO7O2HO-wnKNFQ&ust=1369293258620417http://www.google.com.my/url?sa=i&rct=j&q=electroplating+iron+spoon+with+copper&source=images&cd=&cad=rja&docid=2AtEzCPrCr-0kM&tbnid=kg8fiTogP4yJKM:&ved=0CAUQjRw&url=http://moodle.rockyview.ab.ca/mod/book/print.php?id=118120&chapterid=91369&ei=A3GcUYWsHo-3rAef1YDIBQ&bvm=bv.46751780,d.bmk&psig=AFQjCNHSh945z56_G_BPUO7O2HO-wnKNFQ&ust=1369293258620417http://www.google.com.my/url?sa=i&rct=j&q=electroplating+iron+spoon+with+copper&source=images&cd=&cad=rja&docid=2AtEzCPrCr-0kM&tbnid=kg8fiTogP4yJKM:&ved=0CAUQjRw&url=http://moodle.rockyview.ab.ca/mod/book/print.php?id=118120&chapterid=91369&ei=A3GcUYWsHo-3rAef1YDIBQ&bvm=bv.46751780,d.bmk&psig=AFQjCNHSh945z56_G_BPUO7O2HO-wnKNFQ&ust=1369293258620417http://www.google.com.my/url?sa=i&rct=j&q=electroplating+iron+spoon+with+copper&source=images&cd=&cad=rja&docid=2AtEzCPrCr-0kM&tbnid=kg8fiTogP4yJKM:&ved=0CAUQjRw&url=http://moodle.rockyview.ab.ca/mod/book/print.php?id=118120&chapterid=91369&ei=A3GcUYWsHo-3rAef1YDIBQ&bvm=bv.46751780,d.bmk&psig=AFQjCNHSh945z56_G_BPUO7O2HO-wnKNFQ&ust=1369293258620417http://www.google.com.my/url?sa=i&rct=j&q=electroplating+iron+spoon+with+copper&source=images&cd=&cad=rja&docid=2AtEzCPrCr-0kM&tbnid=kg8fiTogP4yJKM:&ved=0CAUQjRw&url=http://moodle.rockyview.ab.ca/mod/book/print.php?id=118120&chapterid=91369&ei=A3GcUYWsHo-3rAef1YDIBQ&bvm=bv.46751780,d.bmk&psig=AFQjCNHSh945z56_G_BPUO7O2HO-wnKNFQ&ust=1369293258620417http://www.google.com.my/url?sa=i&rct=j&q=electroplating+iron+spoon+with+copper&source=images&cd=&cad=rja&docid=2AtEzCPrCr-0kM&tbnid=kg8fiTogP4yJKM:&ved=0CAUQjRw&url=http://moodle.rockyview.ab.ca/mod/book/print.php?id=118120&chapterid=91369&ei=A3GcUYWsHo-3rAef1YDIBQ&bvm=bv.46751780,d.bmk&psig=AFQjCNHSh945z56_G_BPUO7O2HO-wnKNFQ&ust=1369293258620417http://www.google.com.my/url?sa=i&rct=j&q=electroplating+iron+spoon+with+copper&source=images&cd=&cad=rja&docid=2AtEzCPrCr-0kM&tbnid=kg8fiTogP4yJKM:&ved=0CAUQjRw&url=http://moodle.rockyview.ab.ca/mod/book/print.php?id=118120&chapterid=91369&ei=A3GcUYWsHo-3rAef1YDIBQ&bvm=bv.46751780,d.bmk&psig=AFQjCNHSh945z56_G_BPUO7O2HO-wnKNFQ&ust=1369293258620417http://www.google.com.my/url?sa=i&rct=j&q=electroplating+iron+spoon+with+copper&source=images&cd=&cad=rja&docid=2AtEzCPrCr-0kM&tbnid=kg8fiTogP4yJKM:&ved=0CAUQjRw&url=http://moodle.rockyview.ab.ca/mod/book/print.php?id=118120&chapterid=91369&ei=A3GcUYWsHo-3rAef1YDIBQ&bvm=bv.46751780,d.bmk&psig=AFQjCNHSh945z56_G_BPUO7O2HO-wnKNFQ&ust=1369293258620417http://www.google.com.my/url?sa=i&rct=j&q=electroplating+iron+spoon+with+copper&source=images&cd=&cad=rja&docid=2AtEzCPrCr-0kM&tbnid=kg8fiTogP4yJKM:&ved=0CAUQjRw&url=http://moodle.rockyview.ab.ca/mod/book/print.php?id=118120&chapterid=91369&ei=A3GcUYWsHo-3rAef1YDIBQ&bvm=bv.46751780,d.bmk&psig=AFQjCNHSh945z56_G_BPUO7O2HO-wnKNFQ&ust=1369293258620417http://www.google.com.my/url?sa=i&rct=j&q=electroplating+iron+spoon+with+copper&source=images&cd=&cad=rja&docid=2AtEzCPrCr-0kM&tbnid=kg8fiTogP4yJKM:&ved=0CAUQjRw&url=http://moodle.rockyview.ab.ca/mod/book/print.php?id=118120&chapterid=91369&ei=A3GcUYWsHo-3rAef1YDIBQ&bvm=bv.46751780,d.bmk&psig=AFQjCNHSh945z56_G_BPUO7O2HO-wnKNFQ&ust=1369293258620417http://www.google.com.my/url?sa=i&rct=j&q=electroplating+iron+spoon+with+copper&source=images&cd=&cad=rja&docid=2AtEzCPrCr-0kM&tbnid=kg8fiTogP4yJKM:&ved=0CAUQjRw&url=http://moodle.rockyview.ab.ca/mod/book/print.php?id=118120&chapterid=91369&ei=A3GcUYWsHo-3rAef1YDIBQ&bvm=bv.46751780,d.bmk&psig=AFQjCNHSh945z56_G_BPUO7O2HO-wnKNFQ&ust=1369293258620417http://www.google.com.my/url?sa=i&rct=j&q=electroplating+iron+spoon+with+copper&source=images&cd=&cad=rja&docid=2AtEzCPrCr-0kM&tbnid=kg8fiTogP4yJKM:&ved=0CAUQjRw&url=http://moodle.rockyview.ab.ca/mod/book/print.php?id=118120&chapterid=91369&ei=A3GcUYWsHo-3rAef1YDIBQ&bvm=bv.46751780,d.bmk&psig=AFQjCNHSh945z56_G_BPUO7O2HO-wnKNFQ&ust=1369293258620417http://www.google.com.my/url?sa=i&rct=j&q=electroplating+iron+spoon+with+copper&source=images&cd=&cad=rja&docid=2AtEzCPrCr-0kM&tbnid=kg8fiTogP4yJKM:&ved=0CAUQjRw&url=http://moodle.rockyview.ab.ca/mod/book/print.php?id=118120&chapterid=91369&ei=A3GcUYWsHo-3rAef1YDIBQ&bvm=bv.46751780,d.bmk&psig=AFQjCNHSh945z56_G_BPUO7O2HO-wnKNFQ&ust=1369293258620417http://www.google.com.my/url?sa=i&rct=j&q=electroplating+iron+spoon+with+copper&source=images&cd=&cad=rja&docid=2AtEzCPrCr-0kM&tbnid=kg8fiTogP4yJKM:&ved=0CAUQjRw&url=http://moodle.rockyview.ab.ca/mod/book/print.php?id=118120&chapterid=91369&ei=A3GcUYWsHo-3rAef1YDIBQ&bvm=bv.46751780,d.bmk&psig=AFQjCNHSh945z56_G_BPUO7O2HO-wnKNFQ&ust=1369293258620417http://www.google.com.my/url?sa=i&rct=j&q=electroplating+iron+spoon+with+copper&source=images&cd=&cad=rja&docid=2AtEzCPrCr-0kM&tbnid=kg8fiTogP4yJKM:&ved=0CAUQjRw&url=http://moodle.rockyview.ab.ca/mod/book/print.php?id=118120&chapterid=91369&ei=A3GcUYWsHo-3rAef1YDIBQ&bvm=bv.46751780,d.bmk&psig=AFQjCNHSh945z56_G_BPUO7O2HO-wnKNFQ&ust=1369293258620417http://www.google.com.my/url?sa=i&rct=j&q=electroplating+iron+spoon+with+copper&source=images&cd=&cad=rja&docid=2AtEzCPrCr-0kM&tbnid=kg8fiTogP4yJKM:&ved=0CAUQjRw&url=http://moodle.rockyview.ab.ca/mod/book/print.php?id=118120&chapterid=91369&ei=A3GcUYWsHo-3rAef1YDIBQ&bvm=bv.46751780,d.bmk&psig=AFQjCNHSh945z56_G_BPUO7O2HO-wnKNFQ&ust=1369293258620417http://www.google.com.my/url?sa=i&rct=j&q=electroplating+iron+spoon+with+copper&source=images&cd=&cad=rja&docid=2AtEzCPrCr-0kM&tbnid=kg8fiTogP4yJKM:&ved=0CAUQjRw&url=http://moodle.rockyview.ab.ca/mod/book/print.php?id=118120&chapterid=91369&ei=A3GcUYWsHo-3rAef1YDIBQ&bvm=bv.46751780,d.bmk&psig=AFQjCNHSh945z56_G_BPUO7O2HO-wnKNFQ&ust=1369293258620417http://www.google.com.my/url?sa=i&rct=j&q=rheostat+symbol&source=images&cd=&cad=rja&docid=jF0Gb6tR8aHRwM&tbnid=BWIF3bVfk-YnBM:&ved=0CAUQjRw&url=http://symbologic.info/elec_symbols.htm&ei=fIacUf66OoXuiAfB0IDwCg&bvm=bv.46751780,d.aGc&psig=AFQjCNFyl7OALU1zPWfc87SuF77Z0KxYow&ust=1369298184014919http://www.google.com.my/url?sa=i&rct=j&q=electroplating+iron+spoon+with+copper&source=images&cd=&cad=rja&docid=2AtEzCPrCr-0kM&tbnid=kg8fiTogP4yJKM:&ved=0CAUQjRw&url=http://moodle.rockyview.ab.ca/mod/book/print.php?id=118120&chapterid=91369&ei=A3GcUYWsHo-3rAef1YDIBQ&bvm=bv.46751780,d.bmk&psig=AFQjCNHSh945z56_G_BPUO7O2HO-wnKNFQ&ust=1369293258620417


43/74

5.5 ELECTROLYSIS

- At the anode, the copper dissolves toform positively-charged copper ions.

- At the cathode, the copper ions receive

electrons to form a coat of copper onthe iron spoon.


44/74

5.5 ELECTROLYSIS

- A rheostat is used to control the currentflow in the circuit so that a small

current is used and the object to be

electroplated must be cleaned with asandpaper before electrolysis. These

steps are to obtain good results.


45/74

5.5 ELECTROLYSIS

Iron spoon electroplated with copper
http://www.google.com.my/url?sa=i&rct=j&q=iron+spoon+plated+copper&source=images&cd=&cad=rja&docid=2q7DmUpgjmTcMM&tbnid=WYEj9GqjYWdwsM:&ved=0CAUQjRw&url=http://www.flickr.com/photos/violet_peppermint/2920882662/&ei=LnmcUYyrKI-urAf0qoHIAg&psig=AFQjCNHwENxbab4vTsrh-Y98IWZKAxgSDg&ust=1369295379588372


46/74

5.5 ELECTROLYSIS

(ii) Extraction of reactive metals

- Metals which are more reactive than

carbon are extracted from their ores by

electrolysis.

- For example, aluminium can be

extracted from its ore,bauxite

(aluminium oxide).- Bauxite is first purified and then dissolved

in cryolite. This is to lower the melting

point of aluminium oxide.


47/74

5.5 ELECTROLYSIS

- When aluminium oxide melts, aluminium

ions and oxide ions are free to move.

- When electricity is passed through the

electrolyte, the positively-chargedaluminium ions are attracted to the

cathode. They receive electrons and

become aluminium atoms.- The molten aluminium formed is

channelled into moulds.


48/74

5.5 ELECTROLYSIS

- At the anode, the oxide ions lose

electrons to become oxygen atoms.

The oxygen atoms combine together to

form oxygen gas.

Aluminium is extracted from bauxite by electrolysis
http://www.google.com.my/url?sa=i&rct=j&q=bauxite+electrolysis&source=images&cd=&cad=rja&docid=8LeoAnYaoXyO0M&tbnid=cboLFdvntFIUGM:&ved=0CAUQjRw&url=http://www.ibchem.com/IB/ibnotes/full/ope_htm/hall_cell.htm&ei=a4GcUfOjCsSziQfF5oDQAg&bvm=bv.46751780,d.aGc&psig=AFQjCNEQ6k7XjDvCyDOIyWKcd7-L7LUY3A&ust=1369297640821399


49/74


50/74


51/74

5.6 THE PRODUCTION OF ELECTRICAL ENERGY

FROM CHEMICAL REACTIONS

A simple cell consists of two electrodesand an electrolyte.

The more reactive metal is the negative

terminal which releases electronswhereas the less reactive metal acts as a

positive terminal which receives

electrons.


52/74



A simple cell

Copper

sulphate

solution

Magnesium

Copper
http://www.google.com.my/url?sa=i&rct=j&q=voltaic+cell+&source=images&cd=&cad=rja&docid=qKWWsjTgtoC9dM&tbnid=TTQRS3bNsGSb1M:&ved=0CAUQjRw&url=http://chem2u.blogspot.com/2011/08/simple-voltaic-cell.html&ei=d_ScUdyAO4eBrgfRj4DwCg&bvm=bv.46751780,d.bmk&psig=AFQjCNEtbKRrSqEovYNd44CL4XBWYYTsiw&ust=1369326664256544http://www.google.com.my/url?sa=i&rct=j&q=voltaic+cell+&source=images&cd=&cad=rja&docid=qKWWsjTgtoC9dM&tbnid=TTQRS3bNsGSb1M:&ved=0CAUQjRw&url=http://chem2u.blogspot.com/2011/08/simple-voltaic-cell.html&ei=d_ScUdyAO4eBrgfRj4DwCg&bvm=bv.46751780,d.bmk&psig=AFQjCNEtbKRrSqEovYNd44CL4XBWYYTsiw&ust=1369326664256544http://www.google.com.my/url?sa=i&rct=j&q=voltaic+cell+&source=images&cd=&cad=rja&docid=qKWWsjTgtoC9dM&tbnid=TTQRS3bNsGSb1M:&ved=0CAUQjRw&url=http://chem2u.blogspot.com/2011/08/simple-voltaic-cell.html&ei=d_ScUdyAO4eBrgfRj4DwCg&bvm=bv.46751780,d.bmk&psig=AFQjCNEtbKRrSqEovYNd44CL4XBWYYTsiw&ust=1369326664256544http://www.google.com.my/url?sa=i&rct=j&q=voltaic+cell+&source=images&cd=&cad=rja&docid=qKWWsjTgtoC9dM&tbnid=TTQRS3bNsGSb1M:&ved=0CAUQjRw&url=http://chem2u.blogspot.com/2011/08/simple-voltaic-cell.html&ei=d_ScUdyAO4eBrgfRj4DwCg&bvm=bv.46751780,d.bmk&psig=AFQjCNEtbKRrSqEovYNd44CL4XBWYYTsiw&ust=1369326664256544http://www.google.com.my/url?sa=i&rct=j&q=voltaic+cell+&source=images&cd=&cad=rja&docid=qKWWsjTgtoC9dM&tbnid=TTQRS3bNsGSb1M:&ved=0CAUQjRw&url=http://chem2u.blogspot.com/2011/08/simple-voltaic-cell.html&ei=d_ScUdyAO4eBrgfRj4DwCg&bvm=bv.46751780,d.bmk&psig=AFQjCNEtbKRrSqEovYNd44CL4XBWYYTsiw&ust=1369326664256544http://www.google.com.my/url?sa=i&rct=j&q=voltaic+cell+&source=images&cd=&cad=rja&docid=qKWWsjTgtoC9dM&tbnid=TTQRS3bNsGSb1M:&ved=0CAUQjRw&url=http://chem2u.blogspot.com/2011/08/simple-voltaic-cell.html&ei=d_ScUdyAO4eBrgfRj4DwCg&bvm=bv.46751780,d.bmk&psig=AFQjCNEtbKRrSqEovYNd44CL4XBWYYTsiw&ust=1369326664256544


53/74



Refer to the diagram above: Magnesium and copper strips are used as

electrodes with copper sulphate solution

as the electrolyte. Magnesium (negative terminal) is more

reactive than copper (positive terminal).

Therefore, magnesium atoms releaseelectrons to form magnesium ions which

move into the electrolyte. As a result,

the magnesium strip becomes thinner.


54/74



The electrons flow to the copper stripthrough the wire and this produces

electricity.

Positively-charged copper ions from theelectrolyte receive the electronsand

form copper atoms. This causes copper to

be deposited on the copper strip.

Therefore, the copper strip becomes

thicker.At the same time, the blue colour

of the copper sulphate solution fades.


55/74



Type of cell Uses Advantages Disadvantages

Dry cells Used in portable

devices such as

radios, cassette

players, cameras

and toys

Light

Small

Portable

Cheap

Non-rechargeable

Not long-lasting

Leakage may happen

when the zinc case

becomes thinner

Lead-acid

accumulators

Used in vehicles High voltage

Rechargeable

Long-lasting if

well taken

care of

Heavy

Expensive

Acid might spill

Distilled water needs

to be added
http://www.google.com.my/url?sa=i&rct=j&q=lead-acid+battery&source=images&cd=&cad=rja&docid=h7DrohKW7dCSVM&tbnid=Sex1Y7zMnskfiM:&ved=0CAUQjRw&url=http://en.wikipedia.org/wiki/Lead%E2%80%93acid_battery&ei=CAGdUZ3FD4yMrgfH1oGICA&bvm=bv.46751780,d.bmk&psig=AFQjCNGxAV6vcslpXbAOrCeAWZhLZcAPoQ&ust=1369330288683536http://www.google.com.my/url?sa=i&rct=j&q=dry+cells&source=images&cd=&cad=rja&docid=RAxRua9P86hIUM&tbnid=jfOUxYzQWS_NyM:&ved=0CAUQjRw&url=http://yapmoikui02.blogspot.com/&ei=gwCdUYviEIyMrgfH1oGICA&bvm=bv.46751780,d.bmk&psig=AFQjCNGuqvyoa6OJf12R5XO14Xb-MvOdnw&ust=1369330176556783


56/74


57/74



Type of cell Uses Advantages Disadvantages

Nickel-

cadmium

batteries

Used in electronic

devices such as

digital cameras

Rechargeable

Long-lasting

Expensive
http://www.google.com.my/url?sa=i&rct=j&q=&source=images&cd=&cad=rja&docid=lFAnSaVrSQVedM&tbnid=Z4m14D0QdYOb-M:&ved=0CAUQjRw&url=http://www.theodoregray.com/periodictable/Elements/048/index.s7.html&ei=gkjAUY3UMMWJrAfnuoGoDw&bvm=bv.47883778,d.bmk&psig=AFQjCNF4pjVb1TA6gd09xd4YYD0oAsHAig&ust=1371642353214732


58/74

5.7 CHEMICAL REACTIONS THAT OCCUR IN THE

PRESENCE OF LIGHT

During photosynthesis, chlorophyll absorbslight energy to split water molecules into

hydrogen and oxygen.

The oxygen is released into the atmospherewhereas the hydrogen atoms react with

carbon dioxide to form glucose.

Carbon + Water Light Glucose + Oxygendioxide Chlorophyll


59/74

5.7 CHEMICAL REACTIONS THAT OCCUR IN THE

PRESENCE OF LIGHT

Photosynthesis requires light

5 8 INNOVATIVE EFFORTS IN THE DESIGN OF
http://www.google.com.my/url?sa=i&rct=j&q=photosynthesis&source=images&cd=&cad=rja&docid=yRDvQ_uyvd9hPM&tbnid=ybpWTAx8n_kNcM:&ved=0CAUQjRw&url=https://en.wikipedia.org/wiki/Photosynthesis&ei=wQqdUd-wK4aJrAf7sIDoCg&bvm=bv.46751780,d.bmk&psig=AFQjCNFHEZy13IAU_ko2r0sqUDTMhOwsyg&ust=1369332795219545


60/74

5.8 INNOVATIVE EFFORTS IN THE DESIGN OF

EQUIPMENT USING CHEMICAL REACTIONS AS

SOURCES OF ENERGY

We should use electric cells efficientlytoprevent wastage. Turn off all the

electrical devices when they are not in

use. After using, we should dispose them

wiselyto reduce environmental pollution.

Electric cells contain corrosivechemicals and should not be thrown into

dustbins. They should be collected and

buried underground.

5 8 INNOVATIVE EFFORTS IN THE DESIGN OF


61/74

5.8 INNOVATIVE EFFORTS IN THE DESIGN OF

EQUIPMENT USING CHEMICAL REACTIONS AS

SOURCES OF ENERGY

Fuel cells are electric cells which does not

run down or require recharging.

A hydrogen fuel cell uses hydrogen as fuel

to react with oxygen to produce energy.

The product is water which will not

pollute the environment.


62/74

CHAPTER 5: ENERGY AND CHEMICAL CHANGES QUIZ

1. Which of the following involve chemical

changes?

I. Lighting a match

II. Hard-boiling an eggIII. Melting tin to cast tin bars

A. I and II

B. I and III

C. II and III

D. I, II and III


63/74


2. Which of the following statements about a

chemical which undergoes physical

changes is not true?

A. Its size is changedB. Its state is changed

C. Its shape is changed

D. Its chemical properties are changed


64/74


3. Why does the temperature rise in a

chemical reaction?

A. The reaction is fast

B. The reaction is slow

C. The reaction absorbs heat energy

D. The reaction releases heat energy


65/74


4. The table below shows the result of an

experiment to study the reactivity of

metals X, Y and Z with water and steam.

Based on the observation, put these

metals in order of reactivity. Start with the

most reactive metal.

Metal Reaction withWater Steam

X No Yes

Y No No

Z Yes Yes


66/74


A. X, Y, ZB. Y, X, Z

C. Z, X, Y

D. Y, Z, X



67/74


5. Which of the following metals can be

extracted from their ores by heating their

oxides with carbon?

I. Tin

II. Iron

III. Zinc

A. I and II onlyB. I and III only

C. II and III only

D. I, II and III


68/74


6. Lead can be obtained by heating a

mixture of lead oxide and carbon. This

reaction takes place because carbon

A. is a fuelB. acts as a catalyst

C. is more reactive than lead

D. is a non-metal whereas lead is a metal


69/74


7.

Browngas

Grey

solid

Moltenlead

bromide
http://www.google.com.my/url?sa=i&rct=j&q=electrolysis+molten+lead+bromide&source=images&cd=&cad=rja&docid=iCQaxh9RpQspuM&tbnid=Z80sv51Q-6MsgM:&ved=0CAUQjRw&url=http://flashscience.co.uk/chemistry/flash_bundles/middle_school/pbbr2.html&ei=oR6dUdr0KYKErAe31IHoCQ&bvm=bv.46751780,d.bmk&psig=AFQjCNEHFAStxSDmTfq_52kfLQ2_88NLTA&ust=1369337697849357http://www.google.com.my/url?sa=i&rct=j&q=electrolysis+molten+lead+bromide&source=images&cd=&cad=rja&docid=iCQaxh9RpQspuM&tbnid=Z80sv51Q-6MsgM:&ved=0CAUQjRw&url=http://flashscience.co.uk/chemistry/flash_bundles/middle_school/pbbr2.html&ei=oR6dUdr0KYKErAe31IHoCQ&bvm=bv.46751780,d.bmk&psig=AFQjCNEHFAStxSDmTfq_52kfLQ2_88NLTA&ust=1369337697849357http://www.google.com.my/url?sa=i&rct=j&q=electrolysis+molten+lead+bromide&source=images&cd=&cad=rja&docid=iCQaxh9RpQspuM&tbnid=Z80sv51Q-6MsgM:&ved=0CAUQjRw&url=http://flashscience.co.uk/chemistry/flash_bundles/middle_school/pbbr2.html&ei=oR6dUdr0KYKErAe31IHoCQ&bvm=bv.46751780,d.bmk&psig=AFQjCNEHFAStxSDmTfq_52kfLQ2_88NLTA&ust=1369337697849357http://www.google.com.my/url?sa=i&rct=j&q=electrolysis+molten+lead+bromide&source=images&cd=&cad=rja&docid=iCQaxh9RpQspuM&tbnid=Z80sv51Q-6MsgM:&ved=0CAUQjRw&url=http://flashscience.co.uk/chemistry/flash_bundles/middle_school/pbbr2.html&ei=oR6dUdr0KYKErAe31IHoCQ&bvm=bv.46751780,d.bmk&psig=AFQjCNEHFAStxSDmTfq_52kfLQ2_88NLTA&ust=1369337697849357http://www.google.com.my/url?sa=i&rct=j&q=electrolysis+molten+lead+bromide&source=images&cd=&cad=rja&docid=iCQaxh9RpQspuM&tbnid=Z80sv51Q-6MsgM:&ved=0CAUQjRw&url=http://flashscience.co.uk/chemistry/flash_bundles/middle_school/pbbr2.html&ei=oR6dUdr0KYKErAe31IHoCQ&bvm=bv.46751780,d.bmk&psig=AFQjCNEHFAStxSDmTfq_52kfLQ2_88NLTA&ust=1369337697849357http://www.google.com.my/url?sa=i&rct=j&q=electrolysis+molten+lead+bromide&source=images&cd=&cad=rja&docid=iCQaxh9RpQspuM&tbnid=Z80sv51Q-6MsgM:&ved=0CAUQjRw&url=http://flashscience.co.uk/chemistry/flash_bundles/middle_school/pbbr2.html&ei=oR6dUdr0KYKErAe31IHoCQ&bvm=bv.46751780,d.bmk&psig=AFQjCNEHFAStxSDmTfq_52kfLQ2_88NLTA&ust=1369337697849357http://www.google.com.my/url?sa=i&rct=j&q=electrolysis+molten+lead+bromide&source=images&cd=&cad=rja&docid=iCQaxh9RpQspuM&tbnid=Z80sv51Q-6MsgM:&ved=0CAUQjRw&url=http://flashscience.co.uk/chemistry/flash_bundles/middle_school/pbbr2.html&ei=oR6dUdr0KYKErAe31IHoCQ&bvm=bv.46751780,d.bmk&psig=AFQjCNEHFAStxSDmTfq_52kfLQ2_88NLTA&ust=1369337697849357http://www.google.com.my/url?sa=i&rct=j&q=electrolysis+molten+lead+bromide&source=images&cd=&cad=rja&docid=iCQaxh9RpQspuM&tbnid=Z80sv51Q-6MsgM:&ved=0CAUQjRw&url=http://flashscience.co.uk/chemistry/flash_bundles/middle_school/pbbr2.html&ei=oR6dUdr0KYKErAe31IHoCQ&bvm=bv.46751780,d.bmk&psig=AFQjCNEHFAStxSDmTfq_52kfLQ2_88NLTA&ust=1369337697849357


70/74


When the switch is turned on, what can be

observed?

I. The bulb lights up

II. Brown gas is given off at the anodeIII. A grey solid is deposited at the cathode

A. I only

B. I and II only

C. II and III only

D. I, II and III only


71/74


8. Which of the following is true about

electroplating an iron key with silver?

A. The key is used as the anode

B. A small current is usedC. A silver plate is used as the cathode

D. Copper sulphate solution is used as the

electrolyte


72/74


73/74


10. Photosensitive chemicals are stored indark bottles because they are sensitive

to

A. heatB. light

C. water

D. oxygen


74/74

science form 4- chapter ff5

Documents