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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.
• ?efer to prac boo!
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.
). <hough 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.
• ?efer to prac boo!
#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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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/.
• ?efer to prac boo!
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.
• ?efer to prac boo!
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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
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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,
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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>
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• >%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
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'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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Plan and perform an