chemistry syllabus summaries.docx

8/9/2019 Chemistry Syllabus Summaries.docx

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8.2 The Chemical Earth

1. The living and non-living components of the Earth contains mixtures

Students learn to:

Construct word and balanced formulae equations of chemical reactions as they are

encountered.

• To balance a chemical equation, begin by writing down all the elements/compounds

which are involved in the chemical reaction. When constructing a chemical equation, place all the reactants on the left and all the products on the right, with an arrow in

between. Proceed to add phase descriptors/subscripts, (s) solid, (l) liquid, (g) gaseous,

and (aq) aqueous (dissolved in water). To balance the equation, we must count the

number of each element in the equation, and add coefficients to either side, and on

whichever relevant element, to ensure that the amount of elements on either side is the

same. That is, we ma!e sure we are not creating or destroying matter.

Identify the difference between elements, compounds and mixtures in terms of

particle theory

• "lements are pure substances, both chemically and physically. #n an element, there is

only one type of atom. $ good e%ample of an element is pure iron.

• &ompounds are pure substances only physically. #n a compound, there are multiple

different types of atoms chemically bonded together. They are usually chemical

compounds, such as dihydrogen mono%ide.

'i%tures are pure neither chemically or physically pure. They are usually an

amalgamation of compounds or elements, oined together only physically or with

intermolecular bonding. $n e%ample is salt dissolved in water.

Contrast between elements and compounds &ompounds can be further

decomposed by chemical means into separate pure substances (elements), while

elements cannot.

Contrast between pure substances and mixtures 'i%ture can be further

separated by physical means into separate pure substances (compounds and elements),

while compounds cannot. 'i%tures possess a variable composition while pure

substances do not, and because of this, mi%tures possess variable properties that

change when purified while pure substances do not.

• Contrast between compounds and mixture 'i%ture retain the properties of its

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composite substances, such as salt water tasting salty, while compounds possess new

properties different from its composite elements. 'i%ture can have a variable

composition while compounds have the same ratio of elements in any sie (in essence,

mi%tures can be both homogeneous and heterogeneous, but compounds are only ever

the former.)

Identify that the biosphere, lithosphere, hydrosphere and atmosphere contain

examples of mixtures of elements and compounds.

• The biosphere is the sphere wherein life e%ists. #t is the collection of all life on earth.

+ife e%ists in the form of multiple mi%tures, including basically every liquid in every

organism li!e blood. &ompounds in living organisms are all based on the element

carbon. &ompounds also e%ist in life, being in the form of carbon dio%ide, or water,

which e%ists within us.

• The lithosphere is the sphere of the crust, roc!s and soil. #t is made up of

mi%tures (ore) of compounds (minerals). 'inerals are effectively naturally

occurring solid elements or compounds with a range of compositions.

"%amples of mi%tures in the lithosphere include feldspars, as well as any roc!.

&ompounds in the lithosphere include silicon dio%ide (the most common in the

earths crust), and metal ores, such as bau%ite.

• The hydrosphere is the sphere of water bodies. $nywhere where water e%ists

can be considered part of the hydrosphere. #ts maor constituent is water, with

small quantities of random compounds, such as salt. The main compound in

the hydrosphere is water, and elements, such as chlorine, sulfur and bromine

e%ist in small quantities.

• The atmosphere is the mi%ture of light gases which e%ist around us. #t is

largely made up of uncombined light elements such as nitrogen and o%ygen.

&ompounds such as carbon dio%ide and methane also e%ist, but in small

quantities.

Identify and describe procedures that can be used to separate naturally occurring

mixtures of:

Solids of different sizes

Solids and liquids

Dissoled solid and liquids

!iquids

"ases

#ssess separation techniques for their suitability in separating examples of earth

materials, identifying the differences in properties which enable these separations.

Sieving 0olids of different sies can be separated using a sieve. The sieve is simply

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a grater with specially sied holes so only one of the solids can fall through. The

physical property used in this process is the sie of particles. This method is especially

effective with powders with different sied particles, or a mi%ture of soil, pebbles and

roc!s.

Filtration $n insoluble solid suspended in a liquid can be separated by filtration.1ilter paper is used so that the liquid is able to pass through a funnel while the solids

remain. The physical property used in this process is the different states of the

compounds in mi%ture. This is useful in situations such as filtering water of

impurities.

Evaporation 0olids and liquids can be separated through evaporation, or

vaporisation, where liquids in the mi%ture are heated so they evaporate into the

atmosphere, leaving the solid behind. This is preferred when the liquid(s) have a low

boiling point, so the energy required to evaporate is low. This is effective on both

soluble and insoluble solids. The physical property used in this process is different boiling points.

Crystallisation The mi%ture of compounds is dissolved in a hot solvent such as hot

water. -igher temperatures allow the solution to become saturated. The solution is

then cooled down, and the less soluble of the compounds in the mi%ture crystallises

out of the solution, thus allowing it to be separated from the mi%ture. The physical

property used in this process is in the difference solubility of the compounds in a

solvent.

ecanting #nsoluble solids and liquids can also be separated by decanting. #f the

solid is denser than the liquid, the solids settle out, allowing the liquid to be decanted

or poured out while leaving the solids behind. 2ecanting is generally not preferred,

due to the amount of human error, as well as its inherent inaccuracy. $nother version

of sedimentation is centrifugation, which is when the mi%ture is spun around rapidly,

as to force the more dense solids (or indeed, even liquids) to the bottom through

centripetal force and inertia. The physical property used in this process is density.

istillation +iquids and gases can be separated by distillation. The temperature of

the mi%ture is raised until the more volatile (lower boiling point) liquid evaporates off

as a distillate. This distillate rises up and is directed into a condenser and condenses

bac! into a liquid. 2istillation is only suitable to separate liquids/gases with distinct

boiling points. To distill liquids/gases with similar boiling points, fractional

distillation is used. This is distillation with the addition of a fractionating column,

which causes the vapour to condense and vapourise repeatedly in order to further

separate the two substances. The physical property used in this process is different

boiling points.

Separating immiscible li!uids 'iscible liquids form homogenous solutions in all

proportions, while immiscible liquids do not. 1or instance, oil and water are

immiscible, and so separate. 'i%tures of immiscible liquids can be separated by a

separating funnel, in which the more dense liquid is slowly removed. The physical

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property used in this process is the immiscibility between two liquids.

Chromatography The mi%ture is dissolved in a solvent such as water and made to

pass through a structure such as paper. The components of the mi%ture move at

different speeds, thus separating them. Paper chromatography occurs where the

structure is paper3 the solvent, usually water, runs up the paper and draws the mi%turewith it. &olumn chromatography involves a column pac!ed with some material such

as alumina or silica. The mi%ture is placed into this column through the top, and then a

dripping funnel filled with pure solvent is made to drip into the column. The mi%ture

is dissolved and runs down through the alumina. 2ifferent components of the mi%ture

adhere to the alumina with different strengths, and so separate and drip out the bottom

of the column at different times. The physical property used in this process varies, but

can be summarised as the strength at which the compound adheres to and the rate at

which it rises up a material.

"agnetic separation 'agnetic material such as iron and cobalt can be removedfrom a mi%ture using a magnet. The physical property used in this process is the

magnetic attraction of different metals and materials.

• #i!uid-li!uid extraction $ solute can be removed from a solvent by mi%ing the

solvent with a second solvent that is immiscible with the solvent but with which the

solute has a greater solubility. 1or instance, inc and lead are immiscible, and silver

dissolves well in inc and poorly in lead. The solute preferentially dissolves in the

second solvent, which can then be separated from the first solvent using normal

separation techniques for immiscible liquids. Thus, inc can be added to lead

contaminated with silver in order to remove the silver. 1urther separation would then

be required to remove the solute from the second solvent. (4ote5 the removal of silver

from lead using inc is !nown as the Par!es process). The physical property used in

this process is the different solubility of the solute in different solutions, and

immiscibility between the two solvents.

Describe situations in which graimetric analysis supplies useful data for chemists

and other scientists.

• 'ining 0oil and mineral samples from an area are collected and gravimetrically

analysed to determine the percentage of ore in the area. This allows an areas

economic feasibility to be determined.

• 2etermining the atomic mass of elements.

• $griculture 0oil composition is measured in order to determine whether crops can

be grown in it.

• 2etermining the composition of chemical products such as those used in food.

• 2etermining the amount of pollution and impurities in water.

#pply systematic naming of inorganic compounds as they are introduced in the

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laboratory.

Covalent substances The element closer to the bottomleft of the Periodic Table is

written first. The second elements suffi% is changed to ide. When an element e%ists

in multiples in a compound, an appropriate prefi% for the number is added to thatelement. 1or instance, dinitrogen tetro%ide ( N2O4) and silicon dio%ide (Si2O).

$onic substances The cation (left side of the Periodic Table) is named first, and

then the anion. 1or instance, sodium chloride ( NaCl ). #n the case of transition metals,

always include their valence ( Iron (III) oxide).

• %ydrates #n lattices containing water of crystallisation, 67hydrate6 is added to the

end of the compound name, where 7 is the appropriate prefi% for the number of water

molecules. 1or e%ample, CuSO4.5H2O is called copper sulate pentah!drate.

Identify I$%#C names for carbon compounds as they are encountered.

• 1or basic carbon compounds, simple names we learned in year 8, such as butane or

ethene,are fine.

• These compounds are named based on a prefi%suffi% system. The prefi% is based on

the longest chain of carbons that can be obtained. The suffi% is based on the bonds

between the carbons.

• 'eth

•

"th 9• Prop :

• ;ut <

• Pent =

• ane $ll single bonds

• ene >ne double bond

• yne >ne triple bond

• When naming carbon compounds with double and triple bonds, we use a number in

the name to signify where the bond is in the chain. 1or e%ample, a butene moleculewith a double bond in its second lin! is called but9ene. 0imilarly, a butene molecule

with the double bond in its third slot is called but:ene.

Students:

"ather and present information from first&hand or secondary sources to write

equations to represent all chemical reactions encountered in the %reliminary

course.

• ?efer to prac boo!

Identify data sources, plan, choose equipment and perform a first&hand

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inestigation to separate the components of a naturally occurring or appropriate

mixture such as sand, salt and water.

"ather first&hand information by carrying out a graimetric analysis of a mixture

to estimate its percentage composition.


Identi! data sources" gather" process and anal!se inor#ation ro# secondar!

sources to identify the industrial separation processes used on a mixture obtained

from the biosphere, lithosphere, hydrosphere or atmosphere and use the eidence

aailable to:

Identify the properties of the mixture used in its separation

Identify the products of the separation and their uses

Discuss issues associated with wastes from the processes used.

Separation of &ir'

• The atmosphere is a mi%ture containing @A.8AB nitrogen, 98.C=B o%ygen,

8.C:B argon and 8.8%ygen (;P A:D&) remains as a liquid and is stored as a gas.

• ;oiling point is used to separate the mi%ture.

+iquid nitrogen used for cooling products in industrial processes, to reduce the

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ris! of fires, and to prevent reagents from chemical reactions with the

atmosphere. >%ygen is used in gas welding, the smelting of metals such as

copper, medical and life support machinery, bleaching paper in pulp and paper

industry, ensure full combustion during the incineration of waste materials, and

chemical manufacturing. $rgon is used as a shielding gas in welding processes, protecting the products from gases that may react such as o%ygen

and nitrogen, and in incandescent light bulbs to prevent the filament from

o%idising.

(aste material +ess than 8.B of air collected is waste, but buildup of

these gases over a long period of time require consideration. -ydrocarbons are

e%plosive and need to be disposed responsibly. 'uch of the equipment used

becomes waste, such as absorbent molecular sieves that become clogged with

waste gases. &ooling of air would lead to thermal pollution that could raise the

temperatures of streams and rivers near air plants and thus disrupt aquaticecosystems.

). &lthough most elements are found in combinations on Earth* some elements are

found uncombined.

Students learn to:

'xplain the relationship between the reactiity of an element and the li(elihood of

its existing as an uncombined element.

• The more reactive an element is, the more li!ely it is to have reacted with its

surrounding elements, meaning that they are rarer in their uncombined forms. 1or

e%ample, sodium, a highly reactive metal, is never found in its uncombined state.

&ompare this to gold, which has a very low reactivity, can be found in almost a pure

form.

• $ny metal discovered in its uncombined state is called a native metal.

Classify elements as metals, non&metals and semi&metals according to their physical

properties.

'etals, nonmetals and semimetals are grouped based on a number of !ey physical

properties. 4ote that semimetals have mi%ed properties, and are named semimetals

due to their inability to be classified.

+oiling and "elting ,oint ;oiling and melting points are a measure of

when the element changes state. The elements with the lowest 'P and ;Ps are

the nonmetals which form small, individual molecules. "%amples include

hydrogen and o%ygen. $bove them in 'P and ;P are the metals. 'ost metals

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are solid at room temperature, with the e%ception of mercury. $bove them still

are the nonmetals and semimetals which form themselves into lattice li!e

structures. "%amples include carbon (most of its allotropes) and silicon

(although silicon is a semimetal).

%ardness -ardness is a measure of how much force a material can ta!ewithout deformation. -ardness is measured on the ;rinell scale. $s can be

e%pected, the nonmetals which are gaseous at room temperature are not on

this list. 'etals are usually quite hard, although a range does e%ist. 1or

e%ample, a metal li!e tungsten is e%tremely hard, whereas gold is not.

-owever, there are several nonmetals which are harder than most metals5

those which form themselves into a covalent lattice structure, most

prominently carbon, whose allotropes include diamond, the hardest naturally

occurring substance.

ElectricalThermal Conductivity Thermal and electrical conductivity are both based on one thing5 electrons, and electron flow. -eat is conducted as

electrons in the element gain energy, and transfers that energy between the

electrons, causing them to transfer the energy through the material. 0imilarly,

electricity is conducted through the use of mobile charge carriers, which can

charge between locations. Typically, nonmetals have poor thermal and

electrical conductivity, by virtue of their few free electrons. Thus, they

typically serve as insulators. 'etals, on the other hand, with their sea of

delocalised electrons, are highly efficient thermal and electrical conductors.

ensity 2ensity is a measure how much mass an obect has per unit of

volume. Fenerally spea!ing, metals are high to moderate density while non

metals are moderate to low.

#ustre +ustre is how shiny an obect is, or how much light it reflects.

'etals are lustrous, and nonmetals are not. This is because lustre is based on

electrons, and materials reflect light by having their electrons being e%cited,

and then rereleasing the energy as light.

• uctility"alleability 2uctility is a measure of how well a substance can

be drawn into a wire, and malleability is a measure of how well a substance

can be beaten into a sheet. 'etals are ductile and malleable, while nonmetals

are not (they are brittle, meaning they shatter into powder.)

#ccount for the uses of metals and non&metals in terms of their physical properties.

• "etals

• The malleability and ductility of metals have allowed it to be wor!ed

into many different forms suitable for a huge variety of uses. 1or

instance, aluminium is used in roofing, aircraft structures, aluminiumfoil, utensils such as for!s and the common soda can, all due to the

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ability of aluminium to ta!e on different shapes.

• The attractive lustre of metals leads to them being used as ornamental

fi%tures and in ewellery. This is clear in current gold and silver

ewellery, as well as the popularity of copper during the &opper $ge to

be used as ornaments.• The high electrical conductivity of metals such as silver, gold and

copper has been vital in affecting the role of electricity in history and

society, both in the transport and manipulation of electricity. 1or

e%ample, copper wires transporting electricity over large distances

allowed the telegraph to be possible, and the ability of wires to direct a

current has led to the creation of the electromagnet.

• The high thermal conductivity of metals such as copper and iron

means they are suitable for coo!ing.

The hardness of metals is the main reason it is so widely used in

supporting structures such as buildings. The hardness of metals also

contributed heavily during the &opper, ;rone and #ron $ges in the

quality of weapons, armor and shields3 this was the main reason for

progressing through the different ages, and was a driving factor in one

metal displacing another in popularity.

Example' Tungsten is used in light bulbs due to its high melting point.

on-"etals 4onmetals possess a wide variety of properties that ma!es

them suitable for different applications. "%amples of nonmetals and their

usages based on physical properties include5

/raphite 0carbon allotrope $ wide variety of uses, including dry

lubricant (layer structure allows layers to slid over one another) and

electrodes because it is the only nonmetal to be electrically

conductive.

iamond 0carbon allotrope "%treme hardness and high melting

point means it is used in drill tips. -igh refractive inde% and

transparency means it is used in ewellery.

• %elium +ow density and lac! of reactivity (as compared tohydrogen) ma!es it suitable for flotation devices such as blimps and

airships.

Students:

%lan and perform an inestigation to examine some physical properties, including

malleability, hardness and electrical conductiity, and some uses of a range of

common elements to present information about the classification of elements as

metals, non&metals or semi&metals.

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?efer to prac boo!

#nalyse information from secondary sources to distinguish the physical properties

of metals and non&metals.

• 'etals are thermally and electrically conductive while nonmetals are not (the

e%ception is graphite). This is because the delocalised sea of electrons in metallic

bonding allows a current to be passed through the material and also improves the

transfer of heat, while no such mobile charge carriers e%ist in usuallycovalently

bonded nonmetals.

• 'etals are malleable and ductile while nonmetals are brittle. This is because the

delocalised sea of electrons in metallic bonding allows the individual positive metal

ions to roll over one another without repelling each other. 4onmetals either e%ist as

covalent networ!s, which are not malleable or ductile due to the rigid lattice structure

made by strong covalent bonds, or covalent molecules, which e%ist as discrete

particles with wea! intermolecular forces that are easily bro!en and so are also brittle.

• 'etals have a lustrous appearance while nonmetals in general do not. This is

because the delocalised sea of electrons gathers on the surface of the metal, and

electrons become e%cited when hit by photons. This prevents photons from

penetrating deeply into the metal and e%cited electrons reemit the light bac! out3

essentially, the electron reflects light effectively. This does not occur in nonmetals.

%rocess information from secondary sources and use a %eriodic )able to present

information about the classification of elements as:

*etals, non&metals and semi&metals.

Solids, liquids and gases at +-C and normal atmospheric pressure.

• Foing down the Periodic Table and to the left, elements move from nonmetals to

semimetals to metals. #n general, nonmetals form anions and metals form cations.

• -ydrogen is the e%ception if you classify it as a nonmetal, both being on the

left of the Periodic Table and able to form cations. ;ecause of this, hydrogen is

sometimes unclassified as an e%ception.• The semimetals form a diagonal strip across the right part of the Periodic Table,

separating the nonmetals on the right from the metals on the left.

• "leven elements e%ist as gases at room temperature hydrogen, helium, o%ygen,

nitrogen, fluorine, neon, chlorine, radon, %enon, !rypton, argon.

• Two elements e%ist as liquids at room temperature bromine and mercury.

$ll other elements e%ist as solids.

2. Elements in Earth materials are present mostly as compounds because of interactions

at the atomic level.

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Students learn to:

Identify that matter is made of particles that are continuously moing and

interacting.

• 'atter is made up of tiny particles !nown as atoms, which constantly vibrate and

move due to energy. This movement wor!s against the bonds between particles, be it

molecules, ions or atoms.

• The three states of matter solid, liquid and gas depend on the amount of energy,

and thus particle vibration, within a substance.

• 0olids are tightly pac!ed with many strong bonds between its particles,

allowing the particles to only vibrate in place and not move freely. -ence

solids have a definite shape and are in general denser than liquids and gases.

• +iquids possess with less and wea!er bonds between particles, allow the

particles to move relatively freely. -ence liquids deform to ta!e the shape of

its container.

• Fases are the least dense of the states of matter. #n gases, the particles are not

bonded together, and move rapidly around independent of one another. 2ue to

this movement, gases fill up their containers.

• 0tronger bonds, such as covalent or metallic bonding, require more energy for the

particles to brea! free of these bonds and move from solid to liquid to gas than wea!er

bonds, such as the intermolecular bonding between water molecules.

Describe qualitatiely the energy leels of electrons in atoms.

• "lectrons e%ist in a set of electron shells, around the nucleus, held there by

electrostatic charge between the protons in the nucleus and the electrons.

• They do not orbit regularly li!e planets, both in terms of distance from nucleus and

direction of movement.

• $ certain shell can fit only a certain ma%imum number of electrons. "ach additionalelectron into a shell leads the shell to contract, due to a more positive nucleus leading

to a stronger electrostatic attraction. The first shell fits 9, the second shell fits A, the

third shell fits A, the fourth shell fits :9 (in general, the nth shell has a ma%imum

electron capacity of 9nG9.) $ny electrons beyond the ma%imum allowed in a shell will

ta!e up a new shell.

• The outermost shell, usually incompletely filled, is called the valence shell, and

heavily affects the property of the element, including the type of ions they will form.

• "lectrons preferentially fill electron shells for the most stability3 following rules such

as the >ctet rule (hence potassium is 9, A, A, and not 9, A, C despite the space

available).

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• 2ifferent shells e%ist at discrete energy levels, decreasing with each new shell.

"lectrons in an atom cannot e%ist at intermediate energy levels and require specific

energy gain or loss to move between shells.

• The smaller, inner shells e%ist at a lower energy level than the larger shells. -ence,

electrons emit energy when they drop from a higher energy level to a lower one(called emission), and absorb energy, such as that from a photon, when reaching a

higher energy level (called excitation.)

Describe atoms in terms of mass number and atomic number.

• The atomic number of an atom describes the number of protons in the nucleus. The

atomic number determines the specific element the atom is and its properties.

• The mass number of an atom is the total number of protons and neutrons in the

nucleus. The mass number is not to be confused with the relative atomic mass, which

is the average of the different isotopes of the element in a sample. The mass number

of a !nown element can be used to determine how many neutrons, and thus what

isotope, a specific atom is.

Describe the formation of ions in terms of atoms gaining or losing electrons.

$n ion is a particle that has a number of electrons different to its number of protons,

thus giving it a charge. $n ion is not an atom, which is a particle with the samenumber of electrons to the number of protons.

• 3ctet rule $toms naturally see! to possess a full valence shell of electrons, either

by removing electrons from the outermost valence shell to erase it and cause the ne%t

shell down to become the valence shell, or by adding electrons to its valence shell in

order to fill it up. Halence shells are filled when there are eight electrons (the

e%ception is the first shell, which applies for hydrogen, helium, lithium, beryllium and

boron.) $s a side effect of this, atoms often become ions due to a changed number of

electrons. $ filled valence shell possesses a stability that is clear in the noble gases,

which naturally have full valence shells without needing to become ions and thus havehigh ionisation energy and e%ist as monatomic molecules.

• $ positive ion (or an atom that has lost electrons) is called a cation. >nly metals form

cations (the e%ception is hydrogen.) When an atom becomes a cation, it is called an

o%idation reaction.

• $ negative ion (or an atom that has gained electrons) is called an anion. >nly non

metals form anions (the e%ception is hydrogen.) When an atom becomes an anion, it is

called a reduction reaction.

• 1or one atom to become a cation, another atom must accept the electrons that it loses

and become an anion. -ence o%idation and reduction reactions always occur

simultaneously, and are collectively !nown as redo% reaction.

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#pply the %eriodic )able to predict the ions formed by atoms of metals and non&

metals.

• The left side of the Periodic Table (metals) forms cations, while the right side(nonmetals) forms anions.

• The specific Froup of the Periodic Table details what charge the ion will have.

1or instance, Froup # elements form ions with a charge I.

The elements in the middle of the Periodic Table the transition metals

cannot have their ions predicted simply with the Periodic Table. #n general, they form

9I ions.

#pply !ewis electron dot structures to:

)he formation of ions.

)he electron sharing in some simple molecules.

• #ewis electron dot structures are a means of displaying information about atoms.

+ewis dot structures, or electron dot structures, depict elements and their valence

electrons, which are the crucial factor that determines that elements ionic and

covalent bonding.

• +ewis electron dot structures depict how elements form ions due to the lost or gaining

of electrons with regards to its valence shell.

• +ewis electron dot structures depict how atoms form covalent bonds and the nature ofthese bonds between atoms (single, double, and triple).

• +ewis electron dot structures are also used to depict polyatomic ions, showing both

the covalent structure of the atoms within the ion as well as the addition/loss of

electrons that turns them into ions.

Describe the formation of ionic compounds in terms of the attraction of ions of

opposite charge.

• When ions are formed, the newly formed cations and anions possess immediate

charge and become attracted to one another due to their pro%imity. They quic!ly form

ionic compounds unless they are in solution and are soluble (wherein the hydrogen

bonds formed with water molecules replace ionic bonds between cations and anions.)

• #onic compounds e%ist in the form of a lattice, or a repeating crystalline structure. 1or

instance, sodium chloride (4a&l) has one sodium ion surrounded by si% chloride ions,

and each of those chloride ions surrounded by si% sodium ions, forming a cubic grid

lattice.

• #onic compounds are given as empirical formula, which means they only describe the

ratio of elements in the compound and not the specific number per molecule. This is

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because ionic compounds do not e%ist as discrete molecules but a repeating lattice.

1or instance, the formula for sodium chloride is 4a&l, implying that in any given

quantity of sodium chloride, there will be one sodium ion for every chloride ion

present.

• The ratio of an ionic compound rests with the charge of each ion, such that there is alarger quantity of a small charge ion so that overall the net charge on an ionic

compound is neutral. 1or instance, sodium ions possess a charge of I, while chloride

ions possess a charge of , so they are of the same magnitude and leads to the 5

ratio within sodium chloride. >n the other hand, in calcium chloride (&a&l9), the

charge on a calcium cation is 9I, hence being large in magnitude than chloride and

occurring in a smaller quantity within the lattice.

Describe molecules as particles which can moe independently of each other.

• $ molecule is the smallest particle of an element or compound capable of independent

movement. 1or e%ample, an o%ygen molecule is >9, because a single o%ygen atom is

not capable of its own movement and e%istence due to chemically instability.

• 'olecules can be monatomic (made up of only one atom) in the case of noble gases,

but is in general diatomic (two atoms) or greater. The atoms within a molecule are

held together by strong covalent intramolecular chemical bonds.

• 'olecules only possess wea! intermolecular bonds with other molecules and

compounds. These bonds can be easily bro!en given enough energy (heat), and so

molecules are capable of moving independently of each other when these bonds are

bro!en.

• "leven elements e%ist as gases at room temperature the si% noble gases (helium,

neon, argon, !rypton, %enon and radon), hydrogen, nitrogen, o%ygen, fluorine and

chlorine. 4otice that these last five all form diatomic molecules.

Distinguish between molecules containing one atom the noble gases/ and

molecules with more than one atom.

• The atoms of noble gases already possess chemical stability (see5 the >ctet rule), so

they are able to e%ist freely in molecules consisting of only one atom, or monatomic

molecules.

• The atoms of other nonmetal elements, such as o%ygen, reach chemical stability

when they react with other atoms, including other atoms of the same element. -ence

as pure elements, they e%ist bonded together in molecules consisting of multiple

atoms. -ydrogen, o%ygen, nitrogen, fluorine, chlorine, bromine and iodine all e%ist as

molecules consisting of two atoms, and are called diatomic molecules.

Describe the formation of coalent molecules in terms of sharing of electrons.

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• $toms bonded covalently share electrons in order to achieve a stable valence shell and

a noble gas configuration. $n electron that is shared between two atoms possesses

electrostatic attraction to the positive nucleus of both atoms and so contributes to the

valence shell of both atoms.• 'any pure substances, such as hydrogen and o%ygen, e%ist as covalently bonded

molecules consisting of a number of atoms because it is the most stable configuration.

1or instance, o%ygen molecules (O2) are more stable than o%ygen atoms due to the

desire to reach a noble gas configuration.

• $ single bond involves the sharing of one pair of electrons. $ double bond involves

the sharing of two pairs of electrons, two from each atom. $ triple bond involves the

sharing of three pairs of electrons.

• $n atoms valence describes the number of covalent bonds that it can form (imagining

that doublebonds are two and triplebonds are three.) 1or instance, the valence of

o%ygen (9) means that it can form two bonds, either two single bonds or one double

bond. "ach bond adds one electron to its valence shell, and the valence describes the

number of electrons required for a noble gas configuration.

&ovalent bonds are called directional, meaning that covalent compounds and bonds

prefer specific orientations, giving molecules such as water definitive shapes.

• Coordinate covalent bonds $lso !nown as dative covalent bonds, a coordinate

covalent bond is a single bond between two particles in which one supplies both

electrons for the pair. 1or instance, when a hydrogen cation (or a proton) forms a

covalent bond with any other particle, the other particle must supply all electrons.

$fter the bond is formed, there are no differences in properties between a coordinate

covalent bond and a normal one. #n diagrams of compounds with coordinate covalent

bonds, the coordinate bond is often depicted as an arrow from the atom donating the

two electrons to the one ta!ing. 1or instance, in ammonium (4-< I) or oone (>:)

Construct formulae for compounds formed from:

Ions.

#toms sharing electrons.• 4aI I &l 4a&l

• & I >9 &>9

Students:

#nalyse information by constructing or using models showing the structure of

metals, ionic compounds and coalent compounds.

• 2one in class involving hydrocarbons

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Construct ionic equations showing metals and non&metal atoms forming ions.

•#onic equations describes electrolytes, or any substance containing free ions, in termsof the disassociated ions. $ll other substances, including wea! electrolytes that do not

contain a sufficient concentration of free ions, are written in their neutral, molecular

forms.

• #onic equations are used mostly to describe precipitation reactions, when free ions in

solution form an insoluble product. #n such reactions, the ionic equation writes the

reagent compounds (such as silver nitrate and sodium hydro%ide) in the form of free

ions (silver ions, nitrate ions, etc.) and the insoluble product as a neutral compounds

(silver hydro%ide) because it is not an electrolyte.

#onic equations are also used in reactions involving acids and bases, such as

neutralisation (acid/base) reactions and acid reacting with a carbonate to form carbon

dio%ide.

'etal I 4onmetal 0alt

"g. 4aI 4 &l 4a&l

5. Energy is re!uired to extract elements from their naturally occuring sources.

Students learn to:

Identify the differences between physical and chemical change in terms of

rearrangement of particles.

• #n physical changes, no new substances are formed and the particles e%isting

substances are only rearranged. #ntermolecular bonds are often bro!en or new bonds

formed in physical changes. Physical changes are reversible through physical means,

such as dissolving salt and then evaporating it out. $ll forms of mi%ture separation are

physical changes.

Summarise the differences between the boiling and electrolysis of water as an

example of the differences between physical and chemical change.

• The boiling of water is a physical change for two main reasons5

• The change is easily reversible and with little energy changes3 you simply

lower the temperature and the steam returns to being water.

• 4o new substances were formed. The steam you produce is simply gaseouswater.

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• "lectrolysis, however, is different. "lectrolysis is a chemical change, for these

reasons.

• The change is much more difficult to reverse. Jou must combust the hydrogen

in an o%ygenated environment for them to combine.

• 4ew substances are formed in the electrolysis of water. 4amely, the o%ygen

and hydrogen gas which can be seen in the -offman Holtameter.

Identify light, heat and electricity as the common forms of energy that may be

released or absorbed during the decomposition or synthesis of substances and

identify examples of these changes occurring in eeryday life.

+ight, heat and electricity are simply different forms of the same thing, and they can

be switched from one to another with relative ease. $s far as their role in the

decomposition or synthesis of substances. 4ote that many chemical reactions (which

decompose and synthesise substances) require energy to begin, and (depending on

whether they are endothermic or e%othermic), require energy to continue.

• #ight The two most obvious e%amples of light being used in chemical

reactions are photosynthesis and photography.

• Photosynthesis is the process which plants use to produce food, by

turning water and carbon dio%ide into glucose. The reaction in

endothermic and the energy for the reaction is provided by the sun, in

the form of light.

Photography is when light is used to record images, regardless of what

that image may be. #n times gone by, silver halides (which decompose

under light) were used to capture images, as different parts of the halide

would decompose at different rates, depending on their e%posure to

light.

• %eat Thermal decomposition is an e%tremely common way that compounds

decompose. #ndustry thermal decomposition, such as the decomposition of

aluminium hydro%ide into water and alumina, is called calcinations. Thermal

decomposition is endothermic. >ne important thermal decomposition reactionto remember is the strong heating of a carbonate, the general ionic equation

listed below.

• CO$ 2% & O (2') ' CO2 (g)

'xplain that the amount of energy needed to separate atoms in a compound is an

indication of the strength of the attraction, of bond, between them.

• #n order to chemically decompose a chemical compound into its composite

elements/atoms, energy is required, such as by strong heating or electrolysis. This is

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because the bonds between atoms or ions, such as ionic bonds or covalent bonds, are

strong and require energy input in order to brea! them.

• The measure of a covalent bonds strength is its bond energy, or the amount of energy

(usually in !ilooules) required to brea! that bond in one mole of the molecule and

form its constituent particles. 1or instance, the bond energy the >- bond in water isthe amount of energy required to brea! one mole of water into hydrogen and

hydro%ide.

• &onversely, the bond energy is the amount of energy released when the bond is

formed in one mole of the substance. 1or instance, the bond energy of water

describes the amount of energy produced when one mole of hydrogen ions

reacts with one mole of hydro%ide ions to form water (in this case, the bond

energy is written as negative to describe the reaction as e%othermic.)

• The measure of an ionic bonds strength is its lattice energy, or the amount of energy

(usually in !ilooules) required to brea! the ionic bonds between ions and decompose

one mole of the ionic compound into its gaseous free ions.

• &onversely, the lattice energy is the amount of energy released when one mole

of a salt is formed from the gaseous ions.

Students:

%lan and safely perform a first&hand inestigation to show the decomposition of a

carbonate by heat, using appropriate tests to identify carbon dioxide and the oxide

as the products of the reaction.

?efer to prac boo!

"ather information using first&hand or secondary sources to:

0bsere the effect of light on siler salts and identify an application of the use of

this reaction.

?efer to prac boo!

0bsere the electrolysis of water, analyse the information proided as eidence that

water is a compound and identify any application of the use of this reaction.


#nalyse and present information to model the boiling of water and the electrolysis

of water tracing the moements of and changes in arrangements of molecules.

• +iquid water e%ists as water molecules bonded together with intermolecular bonds

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!nown as hydrogen bonding. The water molecules themselves consist of two

hydrogen atoms covalently bonded to an o%ygen atom.

• #n the boiling of water, intermolecular bonds are bro!en. Water molecules on the

surface of the water brea! off to form gaseous water molecules that are not bonded

with one another. The intramolecular bonding in water is unaffected because boiling issimply a physical change. 4o new substances are formed.

• #n the electrolysis of water, the intramolecular bonding within water molecules,

between o%ygen and hydrogen atoms, are bro!en due to the electric circuit.

• 2 H2O (l) & 2 H2 (g) ' O2 (g)

The intermolecular bonding between particles is bro!en due to a lac! of appropriate

dipoles in the newly formed o%ygen or hydrogen gas. -ence the products are gases.

6. The properties of elements and compounds are determined by their bonding and

structure.

Students learn to:

Identify differences between physical and chemical properties of elements,

compounds and mixtures.

• ,hysical properties are aspects of a substance or mi%ture that can be observed

without changing the composition of the matter3 for instance, the boiling point of a

compound can be determined without changing the compound chemically.

"%amples of physical properties include ductility, electrical conductivity,

malleability, boiling point, melting point, thermal conductivity and mass.

• Chemical properties are properties which affect its behavior in chemical reactions.

• "%amples of chemical properties include its valency, electronegativity, and

how it reacts with o%ygen and acids.

• The physical and chemical properties of compounds and its composite elements can

vary widely.

•The physical properties of mi%tures can widely vary depending on the composition ofthe mi%ture.

• The physical and chemical properties of a mi%ture can differ in different areas of the

mi%ture if it is heterogeneous. The physical and chemical properties of pure

substances are constant and uniform throughout the sample.

Describe the physical properties used to classify compounds as ionic or coalent

molecular or coalent networ(.

• &ovalent molecular substances have the lowest melting and boiling point of all types

of bonding, due to the wea! intermolecular bonds that holds its constituent molecules

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21/61

charges due to the delocalised electrons. 'etals are highly dense because the metal

ions are able to pac! tightly together without repulsion, again than!s to the sea of

electrons. This delocalised sea is also responsible for a metals high electrical

conductivity (due to the presence of mobile charge carriers) and thermal

conductivity (electrons absorb energy and begin moving more rapidly, quic!lyspreading the heat from the heat source throughout the metal.) 1inally, the strong

attractions between metal ions and electrons lead to high boiling and melting points.

Describe ionic compounds in terms of repeating three&dimensional lattices of ions.

• $onic compounds are formed by the electrostatic attraction between positive and

negative ions, or in other words ionic bonds between cations and anions. #n many

ionic compounds, each cation is surrounded on si% sides by si% anions to which it is

ionic ally bonded. "ach anion is similarly bonded to si% cations. This forms a threedimensional lattice a!in to a cube.

• The reason for this particular lattice structure is because the ions attempt to

form as many ionic bonds with ions of the opposite charge as possible, as each

one releases energy and so allows the system to e%ist at a lower energy level,

and si% is the ma%imum possible before ions of similar charges begin to repel

one another.

• >ther types of lattices do e%ist, such as caesium chloride.

'xplain why the formula for an ionic compound is an empirical formula.

• #onic compounds do not e%ist as discrete entities but instead as a repeating lattice of

anions and cations that hypothetically could go on forever. -ence the ionic compound

is not defined by the number of atoms in a molecule, as it does not e%ist as molecules,

but as the ratio of anions to cations in any given sample of the substance.

Identify common elements that exist as molecules or as coalent lattices.

• "leven elements e%ist as gases at room temperature5 hydrogen, helium, carbon,

o%ygen, nitrogen, fluoride, neon, chloride, argon, %enon, !rypton, and radon.

• "%amples of covalent lattices include diamond (an allotrope of carbon),

graphite (an allotrope of carbon) and silicon dio%ide (0i>9, or sand.)

'xplain the relationship between the properties of conductiity and hardness and

the structure of ionic, coalent molecular and coalent networ( structures.

,roperty "etallic

Crystal

$onic Crystal Covalent

networ7

Covalent

molecular

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crystal crystal

&hemical

bonding

'etallic #onic &ovalent &ovalent

'elting point -igh -igh Hery high +ow

"lectrical

conductivity

0olid5 high

+iquid5 high

0olid5 nil

+iquid5 high

>ther

properties

'alleable

2uctile

+ustrous

-ard

;rittle

Hery hard 0oft

;rittle

"%amples &opper

$luminium

0odium

chloride

Kinc o%ide

0ilicon dio%ide

0ilicon carbide

#ce

0ucrose

#odine

0tudents5

%erform a first&hand inestigation to compare the properties of some common

elements in their elemental state with the properties of the compounds/ of these

elements e.g. magnesium and oxygen/.


Choose resources and process information from secondary sources to construct and

discuss the limitations of models of ionic lattices, coalent molecules and coalent

and metallic lattices.

• 'odels can oversimplify the process and lead to a misunderstanding

• They lac! detail due simplicity

• Lnable to predict why certain materials have certain properties eg. electrical properties

• #f detail were to be added, it would complicate the model. -ence, the model will lose

its purpose of conveying its intended information.

%erform an inestigation to examine the physical properties of a range of common

substances in order to classify them as metallic, ionic or coalent molecular or

coalent networ( substances and relate their characteristics to their uses.


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8.3 Metals

1. "etals have been extracted and used for many thousands of years

Students learn to:

0utline and examine some uses of different metals through history, including

contemporary uses, as uncombined metals or as alloys

• Copper 1irst metal used during the &opper $ge (=888:888;&), which itself is

the first half of the larger ;rone $ge (=888888;&.) They were e%tracted from

copper ore such as malachite (CuCO$.Cu(OH)2) using moderately hot fires and

carbon in the form of charcoal. &opper was used for ornaments, weapons, coo!ing

implements due to coppers high thermal conductivity, and copper pipes for waterdue to coppers resistance to erosion. &ontemporary uses of copper include hot water

pipes and tan!s due to coppers resistance to erosion in high temperatures, copper

wiring due to its extremely high electrical conducitivty (second only to silver.) and

air condition units due to its ability to dissipate heat. &opper also forms a large

variety of alloys, allowing it to remain relevant today. >ne of the disadvantages of

copper is that it is fairly soft, producing wea! weapons.

+ron8e $n alloy of copper and tin that led to the second half of the ;rone $ge

(:888888;&.) The addition of tin to copper produced the harder alloy brone.

;rone had several advantages to copper5 it had a lower melting point so was easier

to wor! with and cast3 it was harder, ma!ing better weapons and armor3 cutting tools

made of brone, such as a%es, maintained their edge well and were easily

resharpened3 and brone is very durable.

$ron The first traces of iron came from meteorites, but the e%traction and prolific

use of iron did not come about until higher temperature furnaces were made with

bellows. This happened around 888;&, mar!ing the beginning of the #ron $ge (888

;&.) The ore hematite ( e2O$) was mi%ed with charcoals and heated to reduce

the ore into iron. This was then repeatedly heated to red and hammered to e%pel the

impurities in the metal, leaving wrought iron. $t around =88;&, the &hinese

constructed more powerful furnaces that could produce molten iron that could be used

to produce cast iron.

&luminium 'ost abundant metal in the earths crust but also e%tremely difficult to

e%tract from its ore bau%ite, which contains the mineral gibbsite ( l(OH)$).

$luminium only became more abundant when an appropriate electrolytic e%traction

method arose in the Cth century. $luminiums low density and resistance to

corrosion (due to the buildup of a layer of aluminium o%ide) means that it is used in

many applications such as roofing, window frames and aircraft construction.

$luminiums high thermal and electrical conductivity also ma!es it good for frying

*evin +iang &-


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pans, and its malleability ma!es it suitable for uses such as utensils, drin! cans and

ca!e tins.

Describe the use of common alloys including steel, brass and solder

and explain how these relate to their properties

Steel' #ron containing other elements. &arbon, most prominently. -owever, other

elements such as nic!el, tin and chromium are also used, such as in stainless steel (8

9=B chromium,


25/61

alloying technology, has allowed a wide variety of alloys to be created and used.

• &heaper means of e%tracting metals ma!es it more affordable and thus economically

feasible for metals such as aluminium to find wider uses.

Students:

"ather, process, analyse and present information from secondary sources on the

range of alloys produced and the reasons for the production and use of these alloys

• $lloying allows the properties of metals to be modified for specific needs, such as

stainless steel to prevent rusting. $lloying in general will ma!e pure metals such as

aluminium, copper and iron much harder due to the introduction of irregularities to

the metal lattice, preventing ions from easily slipping over one another. $lloying can

also be used to reduce the cost of materials by introducing cheaper metals to fill up

the bul!5 for instance, L0 coins are made up of C@B inc and a copper coating.

#nalyse information to relate the chronology of the 2ronze #ge, the Iron #ge and

the modern era and possible future deelopments

+ron8e &ge 06999:1999+C The ;rone $ge collectively describes the &opper

$ge (=888:888;&) and the subsequent ;rone $ge (:888888;&).

&hronologically, the ;rone $ge stands between the 0tone $ge, before the use of

metals became commonplace, and the #ron $ge. This is because copper was the firstto be e%tracted and recognised, due to its low temperatures required to e%tract the

metal from its ore.

$ron &ge 01999:1+C The #ron $ge describes the period of time directly before

the 'odern $ge. While iron wor!ing emerged in the centuries before the #ron $ge,

the #ron $ge mar!s the wider !nowledge of iron wor!ing and e%traction across the

globe.

"odern &ge 01CE onwards While the #ron $ge is remar!ed to have ended at

;&, iron and steel continued to be the dominant metals and there were no dramaticchanges in the way we used metals until the Cth century. 2iscoveries of metals in the

Cth century led to the development of alloying and more alloy metals being produced

and used.

2. Metals difer in their reactivity with other chemicals and thisinuences their uses

Students learn to:

3 Describe obserable changes when metals react with dilute acid, water and oxygen

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• &cids 'ost metals will react with cold dilute acids to form a salt and hydrogen gas.

Thus the metal is o%idised to an ion while the hydrogen ion is reduced to gas. +ess

reactive metals will react less with acids3 lead reacts only with warm dilute acids, while

metals that are less reactive (copper, silver, gold, mercury) will not react at all.

*etal ' cid & Salt ' +ater

• E.g. ,n (s) ' 2HCl (aq) & ,nCl2 (aq) ' H2 (g)

The ionic equation ,n ' 2H ' & ,n 2' (aq) ' H2 (g)

(ater >nly the most reactive metals such as sodium and calcium will react with cold

water to produce a hydro%ide salt and hydrogen gas. Travelling down the activity series,

metals become less and less reactive with water3 from hot water (to produce an o%ide salt

and hydrogen gas) to steam (to produce an o%ide salt and hydrogen gas) to no reaction at

all.

Example' Cold water 94a (s) I 9-9> (l) M 2NaOH (aq) ' H2 (g)

Example' %ot water *g (s) ' H2O (l) & *gO (s) ' H2 (g)

Example' Steam ,n (s) ' H2O (g) & ,nO (s) ' H2 (g)

Example' o reaction u (s) & u (s)

• 3xygen 'ost metals will react with o%ygen to form o%ides (e%cept silver, gold,

platinum.) 'etals such as sodium and potassium react readily with o%ygen and burn

easily. 'etals lower on the reactivity series can burn to form o%ides if finely divided.

0ome metals lower on the activity series such as copper will react slowly with o%ygen

when heated but not burn.

The general equation is *etal ' Ox!gen & *etal Oxide

• E.g. 2*g (s) ' O2 (g) & 2*gO (s)

3 Describe and 4ustify the criteria used to place metals into an order of actiity based on

their ease of reaction with oxygen, water and dilute acids

• #n all cases above, certain metals are less reactive with acids, o%ygen and water than other

metals, often requiring e%ternal energy in the form of heat in order for an reaction to occur.

#n analysing the order of reactivity, an overall scale of the reactivity of metals can be

formed.

• 1or e%ample, the reactivity series in general will describe metals from easily o%idised to

no reaction with o%ygen at all.

• $nother criteria of the order of the activity series is the tendency for one metal to displace

another in solution.

3 Identify the reaction of metals with acids as requiring the transfer of electrons

• The reaction of metals with acids is referred to as a redo% reaction

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• "g. Kn (s) I 9-&l (aq) N Kn&l9 (aq) I -9 (g)

o Fiving the net ionic equation to be5 Kn (s) I 9-I (aq) N Kn9I (aq) I-9 (g)

o Where Kn is o%idised to Kn9I (loses 9 electrons) and -I is reduced to -9 (gains 9

electrons), hence5

o >%idation reaction5 Kn (s) N Kn9I (aq) I 9e

o ?eduction reaction5 9-I (aq) I 9e N -9 (g)

3 0utline examples of the selection of metals for different purposes based on their

reactiity, with a particular emphasis on current deelopments in the use of metals

• $ lac! of reactivity in metals such as gold and silver allows them to retain their lustre to

ma!e ;ewellery.

• The lac! of reactivity and e%cellent electrical conductivity of gold allows for very useful

applications in electronic circuits and computers.

• The intense light produced in the burning of magnesium due to its high reactivity with

o%ygen is used in photographic flashbulbs and firewor7s.

• &alciums high reactivity allows it to be used in removing oxygen* sulfur and

phosphorus from steels and in vacuums.

• The reactivity of inc ma!es it suitable for use in batteries such as dry cells.

• +ess reactive metals such as tin are often used as coating on more reactive metals such

as iron to protect it from corrosion and reacting with chemicals such as the food being

stored in cans.

• &oppers lac! of reactivity with water and resistance to corrosion means that it has been

used in the plumbing industry for hot water pipes.

3 0utline the relationship between the relatie actiities of metals and their positions on the

%eriodic )able

• The most reactive metals e%ist on the left3 Froup is more reactive than Froup 9.

This is because there are fewer electrons in the valence shell, therefore3 less energy is

required for the element to lose its electrons in chemical reactions.

'etals become more reactive moving down the group3 caesium is more reactive than

rubidium. This is because each element down a group has one more valence shell. $s the

atomic radius increases, the further the valence electrons are from its nucleus, hence3 the

nuclear attraction between the electrons and the nucleus become wea!er, requiring less

energy to remove a valence electron.

3 Identify the importance of first ionisation energy in determining the relatie reactiity of

metals

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• The first ionisation energy of an element is the minimum amount of energy required to

remove the first electron from one mole of the element as a gas. #t is given as !ilooules

per mole (!O/mol). #n essence the first ionisation energy of an element determines how

easily it is for the element to lose electrons.

The reactivity of metals is largely determined by the tendency for metals to be o%idisedinto cations through the loss of electrons3 thus the ease with which the metal loses

electrons directly affects its reactivity.

Students:

Perform a rst-hand investigation incorporating informationfrom secondary sources to determine the metal activity series

Refer to prac book.

Construct word and balanced formulae equations for the

reaction of metals with water, oxygen, dilute acid

• &cids 0ome metals react with dilute acid to form a salt and hydrogen gas.

Kn (s) I 9-&l (aq) M Kn&l9 (aq) I -9 (g)

• (ater 0ome metals react with either liquid water to form hydro%ides and hydrogen gas

or steam to form o%ides and hydrogen gas. #t can be argued that in the former, the metal isdisplacing the hydrogen from solution.

94a (s) I 9-9> (l) M 94a>- (aq) I -9 (g)

• 3xygen 0ome metals react with o%ygen to form o%ides.

9'g (s) I >9 (g) M 9'g> (s)

Construct half-equations to represent the electron transferreactions occurring when metals react with dilute hydrochloricand dilute sulfuric acids

Hydrochloric acid: Kn (s) I 9-&l (aq) N Kn&l9 (aq) I -9 (g)

• >%idation reaction5 Kn (s) N Kn9I (aq) I 9e

• ?eduction reaction5 9-I (aq) I 9e N -9 (g)

•

0ulfuric acid5 'g (s) I -90>


29/61

• >%idation reaction5 'g (s) N 'g9I (aq) I 9e

• ?eduction reaction5 9-I (aq) I 9e N -9 (g)

3. As metals and other elements were discovered, scientists recognisedthat patterns in their physical and chemical properties could be used toorganise the elements into a Periodic Table

Students learn to:

5 Identify an appropriate model has been deeloped to describe atomic structure

• The ? 0eparated elements into metals and nonmetals.

@ohann obereiner* 1>)? Frouped elements into triads based on similar properties,

such as chlorine, bromine and iodine (fluorine had yet to be discovered). 4oticed the

linear progression of atomic masses within triads.

@ohn ewlands* 1>A5 Proposed the la- o octaes, wherein properties of elements

repeat periodically after seven elements (the noble gases had yet to be discovered.)

>rdered elements by atomic mass.

#othar "eyer* 1>A? >rdered elements by atomic mass. Plotted the properties of

elements as a function of their mass and so demonstrated the periodicity of elements.#t is

interesting to note that 'eyers AEC publication of his Periodic Table was a revised

version of a table he had published in AE


30/61

'xplain the relationship between the position of elements in the %eriodic )able, and:

'lectrical conductiity

Ionisation energy

#tomic radius

*elting point

2oiling point

Combining power alency/

'lectronegatiity

6eactiity

Electrical conductivity 2ecreases from left to right.

$onisation energy 2ecreases from top to bottom due to more electron shells, thus a

greater distance between the nucleus and the valence shell and hence wea!er electrostatic

attraction between them. 2ecreases from left to right due to a greater number of protons in

the nucleus, thus causing the valence shell to hold on more strongly to its electrons.

&tomic radius #ncreases from top to bottom due to more electron shells. 2ecreases

from left to right due to a greater number of protons in the nucleus, thus increasing the

electrostatic forces between the nucleus and the electrons and causing the valence shell to

contract.

"elting point #ncreases from top to bottom due to a greater number of electrons, thus

increasing the strength of dispersion forces between molecules. $dditionally, melting point

increases due to an increase in metallic character. #ncreased from left to right up to Froup

#H, then decreases. Periodic minima (lowest point) corresponding to the noble gases.

+oiling point #ncreases from top to bottom due to a greater number of electrons, thus

increasing the strength of dispersion forces between molecules. $dditionally, melting point

increases due to an increase in metallic character. #ncreases from left to right up to Froup

#H, then decreases. Periodic minima (lowest point) corresponding to the noble gases.

Combining power 0valency #ncreases from left to right up to Froup #H, then

decreases.

Electronegativity 2ecreases from top to bottom due to increased atomic radius.

#ncreases from left to right due to decreasing atomic radius.


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Students:

Process information from secondary sources to develop aPeriodic Table by recognising patterns and trends in the

properties of elements and use available evidence to predict

the characteristics of unknown elements both in groups andacross periods

Completed using the trends above

se computer-based technologies to produce a table and agraph of changes in one physical property across a period anddown a group

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. !or e"cient resource use, industrial chemical reactions mustuse measured amounts o# each reactant

Students learn to

!ene the mole as the number of atoms in exactly "#g ofcarbon-"# $%vogadro&s number'

• $ mole of a substance describes an amount that contains an e%act number of

individual items. #n the case of chemical substances, this is the amount of particles

(atoms or molecules) in the substance.

• This number of atoms is called &vogadroBs number, and is defined to be the number

of atoms in e%actly 9g of carbon9, or carbon containing E neutrons, or E.899 %

8G9:.

Compare mass changes in samples of metals when theycombine with oxygen to measure and identify the mass

• When a metal reacts with o%ygen to form an o%ide, a new substance is formed that

contains all of the metal as well as a certain amount of o%ygen. Thus the metal o%ide

would weigh more, because it would weigh e%actly as much as the metal that we

began with in addition to the o%ygen.

• 1or e%ample, suppose we begin with 8g of magnesium and burn it. The magnesium

o%ide that resulted would weigh E.Eg. Therefore, the mass of the o%ygen used is

E.Eg.

!escribe the contribution of (ay-)ussac to the

understanding of gaseous reactions and apply this to anunderstanding of the mole concept

• /ay-#ussacBs #aw states that ratio of gases between the reactants and products of areaction can be e%pressed as simple whole numbers.

• ;ecause we understand that moles react in simple whole number ratios, one can

conclude that equal volumes of gases contain the same number of molecules.

*ecount %vogadro&s law and describe its importance indeveloping the mole concept

•

&vogadroBs #aw states that gases of the same volume under the same temperatureand pressure have the same number of particles.

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• Thus equal volumes of gases will possess the same number of moles. ;ecause the

ratio of moles is crucial to chemical reactions, this connection means that volume is

also important.

• $t 8D& and 88!Pa, the volume is 99.@*. $t 9=D& and 88!Pa, the volume is

9


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reactions involving a metal and relate this to anunderstanding of the mole

Refer to worksheets

$. The relative abundance and ease o# e%traction o# metalsinuences their value and breadth o# use in the community

Students learn to:

!ene the terms mineral and ore with reference toeconomic and non-economic deposits of natural resources

• $ mineral is a pure crystalline compound that occurs naturally in the earths crust.

• $n ore is a compound or mi%ture of compounds from which it is economic (or

commercially profitable) to e%tract a desired substance such as a metal

• 'inerals can share names with ores. 1or e%ample, iron (###) o%ide ( e2O$), or

hematite, is a mineral and also a common ore of iron, usually with impurities in it,

ma!ing it a mi%ture.

Describe the relationship between the commercial prices of common metals, their

actual abundances and relatie costs of production.

• $s the abundance increases, the supply increases. 0imilarly, if the relative costs of

production increase, less metals are being e%tracted for the same cost of e%traction

• The abundance of metals in the earths crust, and the number of ore deposits mined

affects the availability and price.

• 1or instance, iron e%ists as =B of the earths crust highly abundant.

&opper e%ists at 8.8=B of the earths crust, but is concentrated in ore such as

chalcopyrite (&u1e09) and malachite

• The cost of mining and e%traction. 1or instance, aluminium e%traction requires a lot of

energy and thus is highly e%pensive.

• The useful properties of metals. 1or instance, titanium has many important

applications due to its biocompatibility, low density and high strength, and so is more

e%pensive.

0xplain why ores are non- renewable resources

• The amount of metals that e%ist on the earth as ores is fi%ed, and the ore itself that can

be used to e%tract the metal forms at geological rates. -ence in our current timeframe

as humans, there is a limited quantity of ore available to use.

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!escribe the separation processes, chemical reactions andenergy considerations involved in the extraction of copperfrom one of its ores

"ining &opper ore is mined. &opper e%ists mostly in the form

chalcopyrite (CueS2) at about 8.EB purity. &opper also e%ists in other sulfide

forms, such as chalcocite (Cu2S ). The remaining bul! is mostly silicate and o%ide

waste.

Froth flotation The copper ore is concentrated to improve the efficiency of

later smelting and so conserve energy per ton of copper produced. The copper ore is

crushed and the copper sulfide is wetted to become hydrophobic. The ore is then put

into a mi%ture of water and oildetergent frothing agents !nown as collectors. $ir is

bubbled through this mi%ture to create a layer of bubbles to which the hydrophobic

copper sulfides adhere and are removed. The waste, or gangue, settles out via

sedimentation and can be removed. The new mi%ture is about 9= :8B rich in copper.

•


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made the anode. The copper is o%idised at the anode to form free copper ions that are

then reduced and deposit at the copper cathode.

6ecount the steps ta(en to recycle aluminium

• Waste aluminium is collected and transported to aluminium recycling plants.

• The specific compositions of individual waste items, such as cans, are

analysed and the specific alloy determined. Waste is then sorted according to

the alloy type.

• 0hredding the aluminium and then heating remove impurities in the waste,

such as lacquer on cans.

• The metal is melted down at temperatures of EE8D& (the melting point of

aluminium) and then cast into ingots.

Students:

Discuss the importance of predicting yield in the identification, mining and

extraction of commercial ore deposits

• The advantages of predicting the yield of a certain ore deposit includes5

• 2etermining whether mining the land will draw profit or not

• &omparisons between theoretical yield and the commodity allow problems to

be identified in the e%traction process.

• #dentifies the longevity of a deposit and predicts whether there may be

shortages of that metal in the future.

1ustify the increased recycling of metals in our society andacross the world

• ?ecycling requires less of an energy input (=B of e%traction in the case of aluminium,

A88'O as opposed to E= 888'O per tonne).• #t is 88B recyclable

• +ess energy also means less greenhouses gases produced.

• ?educes the rate at which new areas are mined.

• &onserves ore deposits and our worldwide supply of aluminium.

• Waste products of e%traction are reduced for instance, carbon dio%ide is produced

in the electrolysis of alumina.

• +ess metal goes to waste dumps and so reduces the rate at which countries accumulate

waste that needs to be stored.

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%nalyse information to compare the cost and energyexpenditure involved in the extraction of aluminium from itsore and the recycling of aluminium

• ?ecycling of aluminium5

• >ver @8B of aluminium cans in $ustralia are recycled.

• $luminium waste is sorted according to the alloy type, and then melted at

temperatures of around EE8D&, or the melting point of aluminium.

The composition of the molten aluminium is analysed and adusted as

necessary to produce the correct alloy required. They are then cast into ingots.

• "nergy concerns5

• $luminium e%traction The ;ayer process requires = 888 'O per tonne of

aluminium produced, and the -all -eroult process requires =8 888 'O per

tonne of aluminium produced. This totals E= 888 'O per tonne.• ?ecycling ?equires only A88 'O per tonne of aluminium produced. This is

less than =B of the amount of energy required to e%tract it from bau%ite. This

is the main incentive for recycling aluminium and e%plains its popularity.

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8. !ater

&. 'ater is distributed on (arth as a solid, li)uid and gas

Students learn to:

Define the terms solute, solent and solution

• $ solute is the substance that dissolves into the solvent, and is in much smaller

quantity.

• $ solvent is the substance that the solute dissolves into, and is much greater in

quantity.

• $ solution is a homogenous mi%ture of solutes and solvents.

• The solvent dissolves the solute to form a solution.

2dentify the importance of water as a solvent

• Water is called the 6universal solvent.6 This is because more substances dissolve in

water than any other liquid on "arth, including acids.

• Waters ability to dissolve a large range of compounds means that it is e%tremely

important in many biological and physical processes.

• Water is used in all aspects of living organisms to facilitate biological

processes in aqueous solutions. This includes diluting waste and transporting

nutrients and waste through the body. This occurs by a number of processes.

iffusion is the process by which the random movement of dissolved particles

in solution causes them to eventually move along their concentration gradient

from areas of high concentration to areas of low concentration, thus

transporting them. This can be seen in the transportation of glucose from the

plants to the other parts of the organism.

• $queous solutions relying on waters ability to dissolve compounds is used in

many areas of life, including household cleaning agents and acids used in

industry.

Compare the state, percentage and distribution of water inthe biosphere, lithosphere, hydrosphere and atmosphere

+iosphere Water is e%tremely important in the structure of living organisms, such

as blood vessels and supporting cells.

#ithosphere Water e%ists in the lithosphere mainly as water of crystallisation in

minerals such as copper sulfate pentahydrate (CuSO4.H 2O). #t also e%ists as a liquid as

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ground water, ma!ing up less than B.

%ydrosphere Water e%ists mainly as C@B as salt water in seas and oceans, 9B in

polar icecaps and 8.@B as fresh water.

• &tmosphere Water e%ists as a gaseous state water vapour, or steam, in the

atmosphere. The concentration of water vapour in the atmosphere can vary between 8to =B.

3utline the signicance of the di4erent states of water on0arth in terms of water as

# constituent of cells and its role as both a solent and a raw material in

metabolism

# habitat in which temperature extremes are less than nearby terrestrialhabitats

%n agent of weathering of rocks both as liquid andsolid

% natural resource for humans and other organisms

• +iological functions of water Water ma!es up about @8B of all living bodies. #n

the human body in particular, but indicative of functions in many organisms, water5

•

Photosynthesis Water is a reactant in the production of glucose.• -ydrolysis Water brea!s down large molecules into smaller submolecules,

such as starch into individual glucose molecules.

• 2ilution of waste products in the human body, such as urea.

• $ transport system for both waste products and nutrients, such as urea or

o%ygen. ;lood is basically water.

• -ydrostatic s!eleton $s a means of supporting biological structures in a

way similar to how our s!eletons hold us up. #n human bodies, this is also

apparent in structures such as the eyeball.

• -eat distribution and regulation through sweat.• >smosis that shifts the concentration of solutions such as those in cell

membranes.

1undamental for enymes to function.

%abitats The high heat capacity of water means that bodies of water such as the

sea or la!es have far narrow temperature bands than other geological areas. This

means that bodies of water are usually warmer than the surroundings in winter and

cooler in the summer. These marginal shifts in temperature also provide a stable

environment for aquatic organisms to live.

/eological process Water contributes heavily to the shaping of the landscape. This

occurs in two ways5 weathering and erosion. (eathering is the process by which

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roc!s are bro!en down, and erosion is the movement of roc!s and soil across the

landscape.

(eathering

• Chemical weathering water reactions with compounds in the

ground over long periods of time to form new compounds.• Water containing suspended impurities acts li!e sandpaper over roc!s.

• Flaciers scrape over roc!s and gradually wear them away.

Water seeps into the crac!s of roc!s and then freees, e%panding and

widening crac!s and eventually causing them to brea!.

Erosion 'oving bodies of water such as rivers and rainfall downhill causes

loose minerals and soil to move, usually downhill. #t is interesting to note that

erosion of salts into the ocean is what caused the ocean to become saltwater.

• & natural resource >ther than for drin!ing and washing, water has many

functions in society5• +eisure swimming, beaches, water sports, ices!ating.

• #ndustry as a reactant or product, or for cooling machinery.

• $griculture irrigating crops and watering livestoc!.

• "lectrical power generation through hydroelectricity or tidal power.

• Transport 0hips and barges, allowing goods in the past to be moved down

river for trade.

Students:

Perform an investigation involving calculations of thedensity of water as a liquid and a solid using density mass.volume

Refer to prac book

%nalyse information by using models to account for thedi4ering densities of ice and liquid water

• #n ice, there are more hydrogen bonds between water molecules. $s hydrogen bonds

are directional, meaning that they prefer specific orientations, the water molecules are

pushed apart and so there are less water molecules per unit volume in ice than in

liquid water.

• #n the lattice of ice, each o%ygen atom in the water molecule is bonded to four

hydrogen atoms two covalently (the atoms in its molecule), and two by hydrogen

bonding. This forms a tetrahedral structure with the o%ygen at the center and the

hydrogens at the vertices. This array is an opencage, reducing the density of ice.

• #n liquid water, the hydrogen bonding occurs almost randomly between particles ofwater. Water molecules are also closer together due to less hydrogen bonds.

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