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C2 REVISION POWERPOINT
Suitable for:
Yr 11 Dual award
Yr 11 separate Science
Revision websites:
http://www.creative-chemistry.org.uk/
http://www.bbc.co.uk/schools/gcsebitesize/science/aqa/
http://www.s-cool.co.uk/gcse/chemistry
http://www.docbrown.info/page20/AQAscience2C.htm#Trip
e
C2 REVISION CHECKLIST
STRUCTURE AND BONDING
C2.1 Structure and Bonding
An ion is a charged particle which has either lost of gained electrons
Metal atoms lose electrons to become positive ions
Non-metals atoms gain electrons to become negative ions
Ionic bonds form between metal and non metal atoms
Ions have charges relating to the number of electrons lost or gained
Ionic bonding is described as the transfer of electrons
Ionic bonding can be represented using a dot and cross diagram
  
Examples of ionic compounds include sodium chloride, potassium bromide, magnesium oxide.
The ionic formula e.g MgO can be worked out from the charges on the ions
The electrostatic attraction between the positive and negative ions s known as the ionic bond
  
Covalent bonds form between non-metal atoms
Examples of covalent molecules include water, carbon dioxide, ammonia, methane
Covalent bonding can be represented using a dot and cross diagram
  
Ionic substances have high melting points.
Ionic substances a hard and brittle
Ionic substances are soluble in water
Ionic substances conduct electricity when molten or in solution
Ionic substances form a giant ionic lattice (crystal structure)
  
Covalent molecules have low boiling points
Covalent molecules do not conduct electricity
Covalent molecules are normally gases at room temperature
  
C2.1 STRUCTURE AND BONDING
C2.1 Structure and Bonding
Ionic substances have a high melting point because of the electrostatic attraction (force) between
the positive and negative ions.
This attraction occurs because opposite charges attract.
Ionic substances conduct electricity when molten or in solution because the ions are free to move
  
Covalent molecules are gases at room temperature and have low boiling points due to the weak intermolecular
forces between molecules.
Covalent molecules do not conduct electricity because they are neutral molecules and have no charge
  
Atoms that share electrons can also form giant structures or macromolecules. Diamond and
graphite
(forms of carbon) and silicon dioxide (silica) are examples of giant covalent structures (lattices) of
atoms. All the atoms in these structures are linked to other atoms by strong covalent bonds and so
they have very high melting points.
Diamond and graphite are giant covalent structures.
These giant covalent substances have very high melting points.
This is because of the strong covalent bonds, lots of energy is needed to break these bonds.
Diamond and graphite are allotropes of carbon. This means they are both made of carbon but have
different properties & structure.
Graphite is a non metal but can conduct electricity.
This is because graphite has free(delocalised electrons) HT
Graphite has free electrons because each carbon atom is covalently bonded to 3 others
leaving 1 electron free per carbon atom.
Graphite has strong covalent bonds and weak intermolecular forces between layers.
Graphite is slippery and can rub off in layer this is why it is used in pencil lead
In diamond, each carbon atom forms four covalent bonds with other carbon atoms in a giant
covalent
structure, so diamond is very hard.
  
  
  
  
C2.3.1 Atomic structure
Atoms can be represented as shown in this example:
Mass number 23
Na
Atomic number 11
The relative masses of protons, neutrons and electrons are:
Name of particle Mass
Proton 1
Neutron 1
Electron Very small
The total number of protons and neutrons in an atom is called its
mass number.
Atoms of the same element can have different numbers of
neutrons; these atoms are called isotopes of that element.
The relative atomic mass of an element (Ar)
compares the mass of atoms of the element
with the 12C isotope. It is an average value for
the isotopes of the element. (HT only)
The relative formula mass (Mr) of a compound is
the sum of the relative atomic masses of the
atoms in the numbers shown in the formula.
The relative formula mass of a substance, in grams,
is known as one mole of that substance.
  
  
  
  
  
C2.3.2 Analysing substances
Elements and compounds can be detected and
identified using instrumental methods. Instrumental
methods are accurate, sensitive and rapid and are
particularly useful when the amount of a sample
is very small.
Chemical analysis can be used to identify additives
in foods. Artificial colours can be detected and
identified by paper chromatography.
Gas chromatography linked to mass spectroscopy (GC-MS) is an
example of an instrumental method:
■ gas chromatography allows the separation of a mixture of
compounds
■ the time taken for a substance to travel through the column can be
used to help identify the substance
■ the output from the gas chromatography column can be linked to a
mass spectrometer, which can be used to identify the substances
leaving the end
of the column
mass spectrometer can also give the relative molecular mass of
each of the
substances separated in the column. (HT only)
  
  
  
■ the
  
C2.3.3 Calculations
The percentage of an element in a compound can
be calculated from the relative mass of the element
in the formula and the relative formula mass of the
compound.
  
The empirical formula of a compound can be
calculated from the masses or percentages
of the elements in a compound. (HT Only)
  
The masses of reactants and products can be
calculated from balanced symbol equations.
  
Even though no atoms are gained or lost in a chemical reaction, it is
not always possible to obtain the calculated amount of a product
because:
■ the reaction may not go to completion because it
is reversible
■ some of the product may be lost when it is
separated from the reaction mixture
■ some of the reactants may react in ways different
from the expected reaction.
The amount of a product obtained is known as the yield. When
compared with the maximum theoretical amount as a percentage, it
is called the
  
  
C2.3.4 Rates of reaction
The rate of a chemical reaction can be found by measuring the
amount of a reactant used or the amount of product formed over
time:
Rate of reaction = amount of reactant used
time
Rate of reaction = amount of product formed
time
  
Chemical reactions can only occur when reacting particles collide with each
other and with sufficient energy. The minimum amount of energy particles
must have to react is called the activation energy.
  
Increasing the temperature increases the speed of the reacting particles so
that they collide more frequently and more energetically. This increases
the rate of reaction.
  
Increasing the pressure of reacting gases increases the frequency of
collisions and so increases the rate of reaction.
  
Increasing the concentration of reactants in solutions increases the
frequency of collisions and so increases the rate of reaction.
  
Increasing the surface area of solid reactants increases the frequency of
collisions and so increases the rate of reaction.
Catalysts change the rate of chemical reactions but are not used up during
the reaction. Different reactions need different catalysts. Catalysts are
important in increasing the rates of chemical reactions used in industrial
  
  
C2.3.5 Exothermic and Endothermic reactions
When chemical reactions occur, energy is transferred to or from the
surroundings.
An exothermic reaction is one that transfers energy to
the surroundings. Examples of exothermic reactions
include combustion, many oxidation reactions and
neutralisation. Everyday uses of exothermic reactions
include self-heating cans (eg for coffee) and hand warmers.
An endothermic reaction is one that takes in energy
from the surroundings. Endothermic reactions include
thermal decompositions. Some sports injury packs
are based upon endothermic reactions.
If a reversible reaction is exothermic in one direction,
it is endothermic in the opposite direction. The same
amount of energy is transferred in each case.
  
  
  
  
C2.6 Acids, Bases and Salts
The pH scale goes from 0 to 14, and pH 7 is a neutral solution.
Acid + Alkali  Salt + water (Neutralisation reaction)
Acid + Base  Salt + water (Neutralisation reaction)
Acid + Metal  Salt + Hydrogen
Metal oxides and hydroxides are bases. Soluble
hydroxides are called alkalis.
The particular salt produced in any reaction between
an acid and a base or alkali depends on:
■ the acid used (hydrochloric acid produces
chlorides, nitric acid produces nitrates, sulfuric
acid produces sulfates)
■ the metal in the base or alkali.
Hydrogen ions, H+(aq), make solutions acidic and
hydroxide ions, OH–(aq), make solutions alkaline.
The pH scale is a measure of the acidity or
alkalinity of a solution.
In neutralisation reactions, hydrogen ions react with
hydroxide ions to produce water. This reaction can
be represented by the equation:
H+(aq) + OH–(aq) H2O(l)
  
  
  
  
  
C2.3.7 Electrolysis
When an ionic substance is melted or dissolved in water, the ions are
free to move about within the liquid or solution.
Passing an electric current through ionic substances that are molten,
for example lead bromide, or in solution breaks them down into
elements.
This process is called electrolysis and the substance that is broken
down is called the electrolyte.
During electrolysis, positively charged ions move to the negative
electrode, and negatively charged ions move to the positive electrode.
Electrolysis is used to electroplate objects. This maybe for a variety
of reasons and includes copper plating and silver plating.
At the negative electrode, positively charged ions
gain electrons (reduction) and at the positive electrode, negatively
charged ions lose electrons (oxidation). If there is a mixture of ions,
the products formed depend on the reactivity of the elements
involved.
Aluminium is manufactured by the electrolysis of a molten mixture
of aluminium oxide and cryolite. Aluminium forms at the negative
electrode and
oxygen at the positive electrode. The positive electrode is made of
carbon, which reacts with the oxygen to produce carbon dioxide.
The electrolysis of sodium chloride solution produces hydrogen and
  
  
  
  
  
PURE substances have different
STRUCTURES depending on the type of
BONDING they have
IONIC
COVALENT
eg sodium
chloride
(salt)
METALLIC
eg copper
SIMPLE
MOLECULAR
GIANT
MOLECULAR
eg carbon
dioxide, water
eg diamond,
graphite
The structure of a substance decides what its
PHYSICAL PROPERTIES will be.
IONIC
C of metals and non-metals (eg
Ionic substances are compounds
sodium chloride, copper oxide, magnesium sulphide etc)
They are made of IONS: atoms which have lost or gained
electrons giving them a positive or negative CHARGE
Positive
sodium ion
Na+
Negative
chloride ion
Cl-
The + ions and – ions STRONGLY ATTRACT each other
to make a regular crystal structure
Because of the very STRONG BONDS between the IONS,
ionic compounds have HIGH MELTING & BOILING
POINTS
Strong ionic
bond
Sodium chloride
melts at over 800°C
Ionic
compound
Melting
point (°C)
Iron chloride
677
Potassium chloride
770
Sodium chloride
801
Copper oxide
1446
Calcium oxide
2707
As ionic compounds are made of CHARGED IONS, they can
CONDUCT ELECTRICITY but ONLY if the ions can
MOVE.
If it is
MOLTEN the
ions can move
MEL
T
+
- + - +
- + - + - + - +
+
800°C
- +
+ - +
+ -
-
+
-
+
If it is
DISSOLVED the
ions can move
DISSOLV
E
-
+ - +
+
+ -
-
-
+
20°C
H2O
+
MOLTEN IONIC
COMPOUND
-
+ -
-
+
+
-
+
-
+
+
+
-
MOLTEN ionic compounds CONDUCT
ELECTRICITY
When salt is put in water, H2O molecules pull the ions
apart to make a solution. This lets the ions move around.
H20
molecule
Ions free
to move
around
PURE WATER
SOLID
SALT
SALT SOLUTION
DISSOLVED ionic compounds also CONDUCT
ELECTRICITY
SIMPLE MOLECULAR
SUBSTANCES
These are substances like carbon dioxide CO2, water H2O
and methane CH4 which are always made of simple
molecules whether they are SOLIDS, LIQUIDS OR GASES
H atom
O atom
Whole thing
= H2O
molecule
MOLECULES ONLY WEAKLY ATTRACT EACH OTHER
VERY STRONG bonds
BETWEEN ATOMS
(so molecule is very hard
to break up)
WEAK bonds
BETWEEN
MOLECULES
(so molecules are easy
to separate)
SOLI
D
LIQUI
D
GAS
Simple molecular substances can only be a liquid or a solid
when the temperature is LOW enough for the WEAK
BONDS to pull the molecules together
This means simple molecular substances have LOW
melting and boiling points
Compound
Mpt
(°C)
Bpt
(°C)
State at
room temp
Water H2O
0
100
Liquid
Butane C4H10
-138
-0.5
Gas
Methane CH4
-182
-164
Gas
Carbon dioxide CO2
-
-78
Gas
Oxygen O2
-218
-183
Gas
Hydrogen H2
-259
-252
Gas
Solid
oxygen at 240°C
Liquid oxygen
boiling at 183°C
As the bonds between the molecules are weak, simple
molecular substances are weak and soft when solid.
As the molecules are NOT CHARGED simple molecular
substances DON’T CONDUCT ELECTRICITY when
solids, liquids or gases.
GIANT MOLECULAR
SUBSTANCES
In these materials strong covalent bonds join atoms together
with other atoms of the same type to make giant structures,
rather than little groups.
DIAMON
D
Carbon
atom
Only
STRONG
bonds
Every C
atom
joined to 4
others
(this is only part of
the structure - the
same pattern
carries on in every
direction)
SILICA (Silicon dioxide SiO2) has a similar structure to
diamond
Every Si
atom joined
to 4 O
atoms
Silica is the main substance in ROCKS. Pure silica is called
QUARTZ
Because all the atoms in Giant Structures are joined by
STRONG BONDS they:
• Have HIGH melting / boiling points
• Are usually HARD and STRONG
Because all the atoms in Giant Structures are
UNCHARGED, they will not conduct electricity.
GRAPHITE – a special case
Common form of carbon found in soot, charcoal, pencil leads etc
Carbon atoms each
joined to 3 others with
STRONG bonds to make
hexagonal sheets of
atoms
WEAK
BONDS
STRONG
BONDS
The sheets of atoms are
joined to other sheets by
WEAK bonds
As the bonds
between the
layers of
atoms are
weak, they
can easily
slide over
each other
As the C atoms are only bonded
to 3 others, the extra electrons
form clouds of ‘free electrons’
between the layers
GRAPHITE - Properties
The STRONG BONDS between
the ATOMS mean it has HIGH
MELTING and BOILING POINTS
The WEAK BONDS between the
LAYERS mean it is SOFT and
SLIPPERY as the layers SLIDE over
each other easily (used in pencils
and as a solid lubricant)
The FREE ELECTRONS between the layers mean that
graphite CONDUCTS ELECTRICITY (used as sliding
contacts in electric motors)
METAL
S held together by strong bonds in
In a metal the atoms are
regular structures.
This means most metals have high melting and boiling
points and are hard and strong
In a metal the atoms LOSE SEVERAL OF THEIR OUTER
ELECTRONS which drift around between the metal ions
as FREE ELECTRONS.
As they have LOST a
few electrons, the
atoms become
POSITIVE IONS
HIGHER TIER
ONLY
Free (“delocalised”)
electrons
The large number of free electrons makes all metals
are GOOD CONDUCTORS of electricity AND heat.
The regular structure
means the layers of atoms
can fairly easily slide over
each other without
breaking the bonds
(though not as easily as
graphite) and so metals
are MALLEABLE (bend
rather than snap)
HIGHER TIER ONLY
IONS
ONLY
SUMMARY Descriptions
IONIC
Crystals
Dissolve in water
eg sodium chloride
(salt)
SIMPLE
MOLECULAR
Usually Gases
eg CO2, H2O
MOLECULE
S ONLY
IONS +
FREE
ELECTRON
S
ATOMS
joined into
GIANT
MOLECUL
ES
METALLIC
Strong malleable
solids
Don’t dissolve
eg copper
GIANT MOLECULAR
Hard strong solids
Don’t dissolve
eg diamond
(graphite – special case)
SUMMARY - PROPERTIES
Structure Property
Reason
Ionic
HIGH mpt/bpt
CONDUCT: Solid NO
Molten YES Dissolved YES
Strong bonds between IONS
Ions can’t move
Ions can move to carry current
Covalent – LOW mpt/ bpt (often gas at
room temp). Soft when solid
Simple
molecular
CONDUCT: Never
Bonds between MOLECULES
very weak.
Molecules aren’t charged
Covalent – HIGH mpt/bpt. Hard & strong Strong bonds between all ATOMS
giant
No free charges/electrons
molecular
CONDUCT: Never
Covalent graphite
HIGH mpt/bpt
Soft & slippery
CONDUCT: YES (fairly well)
Strong bonds between ATOMS
Weak bonds between LAYERS
Free electrons between layers
Metallic
HIGH mpt/bpt. Hard & strong Strong bonds between IONS
Malleable
Regular structure, layers slide
CONDUCT: YES (very well) Free electrons between ions
KEY WORDS
Describe the following keywords to each other.
Atom
Ion
Ionic compound
Electron
Free ions
Attraction
Electrolysis is splitting up
substances using
electricity
(Lysis is latin for splitting)
WHAT IS
ELECTROLYSIS?
Electric
current is used to
breakdown a substance made
up of ions ( ionic compounds)
An
electrolyte is the name for
the substance being broken
down
ELECTROLYSIS OF AN IONIC SOLUTION YOUTUBE

An ionic compound can be split back into its elements
through electrolysis.
E.g NaCl Sodium chloride
(An ionic compound can be turned back into its
atoms sodium and chlorine.)

Positive
Anode
Don’t get stressed
in the exam:
Remember PANIC
Negativ
e
Is
Cathode
ELECTROLYSIS OF MOLTEN NACL
+
ANODE
+
CATHODE
The metal goes to
the cathode and the
non metal goes to
the anode.
Na+
ClNa+
-
Na+
Cl-
ClNa+
-
Cl-
+
positive electrode
(anode)
-
(cathode)
Zn+
Zn+
Clmolten zinc
chloride (ions free
to move)
negative electrode
ClZn+
Cl-
ClZn+
ClZn+
Zn+
Zn+
Cl-
Cl-
ClZn+
The
positively
charged zinc
ions are
attracted to
the negative
electrode
+
-
Zn+
Zn+
ClCl-
Cl-
Zn+
ClZn+
Cl-
Zn+
+
The
negatively
charged
chloride ions
are attracted
to the positive
electrode
-
+ +
ZnZn
Zn+Zn+
Cl-
Zn+
Cl-
ClCl-
Cl-
Compound
Sodium
Bromide
Potassium
Iodide
Calcium
Fluoride
Magnesium
Oxide
Lithium
Chloride
Anode
Cathode
= bromide ion
Electrolysis of
lead bromide
= lead ion
Cathode
Anode
= bromide ion
At the cathode:
Pb+ gains electrons to form
lead metal.
= lead ion
It is REDUCED.
Cathode
Anode
At the anode:
Br- loses electrons to form
bromine gas.
It is OXIDISED.
O.I.L.R.I.G.
Oxidation
is loss
of electrons
Reduction is
gain of electrons
Cathode
Negative
Anode
Positive
Positive ions
attracted
Negative ions
attracted
REDUCTION
happens here (
positive ions gain
electrons)
OXIDATION
happens here
(negative ions lose
electrons
What happens when the ionic compounds are
dissolved in water?
Here, water molecules break up into HYDROGEN
IONS, H+ and HYDROXIDE IONS OH-
H2O  H+ + OHSo, in an ionic solution (eg sodium chloride solution), there will
be FOUR types of ion present:
TWO from the ionic compound and TWO from the water (H+
OH-)
SODIUM CHLORIDE
SOLUTION NaCl (aq)
H+
OH-
Cl
-
Na+
OHH+
Na+
Cl
-
H+
OH-
Na+
Cl
-
+
IONIC
SOLUTION
H+
OH-
Cl
-
Na+
OHH+
Na+
Cl
-
H+
Na+
OH-
Cl
-
Which ions gain or lose electrons (“get discharged”)
and which stay in solution?
IONIC SOLUTIONS: At the CATHODE
Na+
sodium ION,
missing 1
electron
H+
+
hydrogen
ION, missing
1 electron
As HYDROGEN is
LESS
REACTIVE than
SODIUM, it is
discharged.
The sodium ions
stay in solution.
At CATHODE: 2H+ + 2e-
H2
H
Hydrogen
ATOM,
NEUTRAL
which
ions?
Na+
H+
H
H
Na+
+
IONIC SOLUTIONS: At the CATHODE – halogen
hydroxide
compounds
chloride ION,
Cl
-
O H ION, from
extra 1
electron
+
O
H
Cl
Cl
-
H
O
O H
Cl
-
O H
Cl
Cl
-
which
ions?
Cl
-
At ANODE:
Cl2
water extra
electron
Cl
chlorine ATOM,
NEUTRAL
If the – ion is a
HALOGEN (Cl, Br,
I) it is discharged
and chlorine (or Br
or I) is given off and
the OH - ions stay
in solution
2Cl-
2e- +
IONIC SOLUTIONS: CATHODE – non halogen compounds
nitrate ION,
NO3-
extra 1 electron
hydroxide ION,
- from water,
OH
O H
extra electron
O
Oxygen
atom
+
NO3H
O
NO3H
O
which
ions?
NO3-
O H
NO3-
If the – ion is NOT a halogen
(eg nitrate, sulphate etc) then
the HYDROXIDE ions from
the water are discharged to
make WATER and OXYGEN
gas. The other ions stay in
solution.
O H
At CATHODE: 4OH4e-
2H2O + O2 +
RULES FOR IONIC
SOLUTIONS
+ ANODE
Attracts – ions (‘Anions’)
If – ions are HALOGENS ie
chloride Clbromide Briodide Ithe HALOGEN is produced.
If – ions are NOT
HALOGENS
Eg sulphate SO42-,
nitrate NO3carbonate CO32OXYGEN is produced.
- CATHODE
Attracts + ions (‘Cations’)
If + ions (metals) are MORE
REACTIVE than hydrogen
K, Na, Ca, Mg, Zn, Fe
Then HYDROGEN is
produced
If + ions (metals) are LESS
REACTIVE than hydrogen
Cu, Ag, Au
Then the METAL is
produced
(REACTIVITY: K+ Na+ Ca2+ Mg2+ Al3+ Zn2+ Fe3+ H+ Cu2+ Ag+ Au3+ )
Compound
State
potassium chloride molten
aluminium oxide
copper chloride
molten
Ions
K+
ClAl3+ O2-
2+ Cl- H+ OHCu
solutio
n
sodium bromide
+ solution Na Br H+ OH-
silver nitrate
+
solution Ag NO3 H+ OH-
potassium chloride solution K+ Cl- H+ OHzinc sulphate
+
solution Zn SO42 H+ OH-
Cathode (-) Anode (+)
potassium
chlorine
aluminium
oxygen
copper
chlorine
hydrogen
bromine
silver
oxygen
hydrogen
chlorine
hydrogen
oxygen
(REACTIVITY: K+ Na+ Ca2+ Mg2+ Al3+ Zn2+ Fe3+ H+ Cu2+ Ag+ Au3+ )
ELECTROLYSIS makes a CIRCUIT
Complete electric circuit:
Current carried by:
ELECTRONS in
electrodes/wires
+
+
-
-
IONS in the electrolyte
To DOUBLE the MASS of
substance discharged at
electrodes:
2 x CURRENT (2x batt. voltage)
2 x TIME current flows for
(Q = I t)
OILRIG
Cl
Cl
Cl
Cl
-
-
-
Oxidation is
loss, reduction
is gain
‘OILRIG’
-
- ions LOSING electrons
to become atoms is
called ‘OXIDATION’
(even though oxygen
may not be involved)
Na+
Na+
Na+
Na+
+ ions GAINING
electrons to become
atoms is called
‘REDUCTION’
INDUSTRIAL USES OF
ELECTROLYSIS
1. To extract
reactive metals such as ALUMINIUM,
sodium, magnesium etc from their compounds. This is
EXPENSIVE due to the large amounts of electrical
energy needed. Aluminium is extracted from bauxite
(Al2O3).
2. Electrolysis of BRINE (salt solution) to produce
see below
CHLORINE (for disinfectants and plastics)
HYDROGEN (for ammonia fertilisers, margarine)
SODIUM HYDROXIDE (for soap and cleaning agents)
see below
3. Purifying copper. The copper for wiring etc needs
to
be more pure than that produced in a blast furnace.
Electrolysis is used to convert impure copper to pure
copper
INDUSTRIAL ELECTROLYSIS OF
BRINE
Chlorine
Hydrogen gas
gas
BRINE
(NaCl solution)
CATHODE
H+ and Na+
ANODE
OH- and Cl2Cl-
2e-
OH- left in
solution so
concentration
grows
+ Cl2
Sodium chloride
solution (neutral)
slowly changed to
sodium hydroxide
solution (alkaline)
2H+ + 2eNa+ left in
solution so
concentration
grows
H2
Industrial chlorine production from electrolysis
of brine
Mass number
Number of
protons and
neutrons
Atomic number
Number of
protons
Atomic Structure
Cl
17
35
Proton
Neutron
Electron
Relative mass
1
1
negligible
Charge
+
0
-
location
nucleus
nucleus
shells
Atoms of the same element
can have different
numbers of neutrons - these
atoms are called
isotopes of that element.
Same atomic number
Different mass number
The relative atomic mass of an element (Ar)
compares the mass of atoms of the element with the
12C isotope. It is an average value for the isotopes
of the element.
The relative formula mass (Mr) of a compound is
the sum of the relative atomic masses of the atoms
in the numbers shown in the formula.
The relative formula mass of a substance, in grams,
is known as one mole of that substance
10 Questions
Using the following information about Cl and Mg
answer the question below…
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
Cl
17
35
Mg
12
24
What is the mass number of this chlorine atom?
What is the atomic number of this chlorine atom?
How many protons neutrons and electrons does this chlorine
atom have?
What is the electron configuration of a chlorine atom?
What is the relative mass of an electron?
What is the charge on a neutron particle?
Where in the atomic structure are electrons located?
What is the relative atomic mass of chlorine?
Using 35Cl and 37Cl as examples explain what is meant by an
isotope.
What is the relative formula mass (Mr) of MgCl2?
Atomic Structure
Ionic bonding
Metal and non-metal – electron transfer
Metals lose electrons and become positive ions.
Non-metals gain electrons and become negative
ions.
Metals in group 1 form ions with a +1 charge
Metals in group 2 form ions with a +2 charge
…
Non-metals in group 6 form ions with -2 charge
Non-metals in group 7 form ions with -1 charge
sodium chloride
magnesium oxide
calcium chloride
Writing formulae
The charges on the positive and
negative ions need to balance out
Na+ Cl NaCl
2+
2Mg O
 MgO
2+
Ca Cl Cl
 CaCl2
Properties of ionic compounds
• Ionic compounds have regular
structures (giant ionic lattices)
in which there are strong
electrostatic forces in all
directions between oppositely
charged ions.
• These compounds have high melting points
and high boiling points because of the large
amounts of energy needed to break the many
strong bonds.
• When melted or dissolved in water, ionic
compounds conduct electricity because the
ions are free to move and carry the current
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
10 Questions
Do ionic bonds transfer or share electrons?
Ionic bonds exist between..
(a) Metals and Non-metals,
(b) Non metals and Non-metals
(c) Metals and Metals
Elements in group 7 form ions with what charge?
Elements in group 3 form ions with what charge?
Ionic compounds are held together by strong E _ _ _ _ _ _ _ _ _ _ _ C
forces in all directions between oppositely charged ions.
Under what 2 conditions will ionic compounds conduct electricity?
Draw a diagram to show the electron arrangement in a fluorine ion.
Draw a diagram to show the electron arrangement in a magnesium
ion.
What is the electron configuration of a fluorine ion?
What is the formula of calcium fluoride?
Ionic bonding
Covalent bonding - molecules
Hydrogen - H2 (g)
Chlorine - Cl2 (g)
Oxygen - O2 (g)
Properties of covalent compounds
•
A covalent bond is a shared pair of electrons
•
Substances that consist of simple molecules
are gases, liquids or solids that have
relatively low melting points and boiling points
•
They have only weak forces between the
molecules (intermolecular forces). It is
these intermolecular forces that are
overcome, not the covalent bonds, when the
substance melts or boils. Intermolecular
forces are much weaker than covalent bonds.
The forces within the molecules (the covalent
bonds) can be referred to as intramolecular
forces.
•
They do not conduct electricity because the
molecules do not have an overall electric
charge. No free electrons or ions.
Methane – CH4 (g)
Hydrogen chloride
HCl (g)
Water – H2O (l)
Ammonia – NH3 (g)
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
10 Questions
Do covalent bonds transfer or share electrons?
covalent bonds exist between..
(a) Metals and Non-metals,
(b) Non metals and Non-metals
(c) Metals and Metals
Elements in group 7 form covalent compounds with how many bonds?
Elements in group __ form covalent compounds with 3 bonds?
Why do covalent compounds NOT conduct electricity?
Are covalent bonds strong or weak?
Draw a diagram to show the electron arrangement in a carbon atom.
Draw a dot-cross diagram to show the bonding between 2 fluorine
atoms
Draw a dot-cross diagram to show the bonding present in CH4?
How many bonds does carbon form in CO2?
Covalent bonding - molecules
Covalent bonding - Giant
Diamond (carbon only)
Fullerenes (carbon
only)
Carbon can also form
fullerenes with
different numbers of
carbon atoms. They
are used for drug
delivery into the body,
lubricants, catalysts,
and in nanotubes for
reinforcing materials,
eg tennis rackets.
In graphite, each
carbon atom bonds to
three others, forming
layers. The layers are
free to slide over each
other because there
are no covalent bonds
between the layers and
so graphite is soft and
slippery.
Graphite (carbon only)
All the atoms in these
structures are linked
to other atoms by
strong covalent bonds
and so they have very
high melting points.
In diamond, each
carbon atom forms
four covalent bonds
with other carbon
atoms in a giant
covalent
structure, so diamond
is very hard.
Silicon dioxide (Si + O)
Sand
Giant covalent structures are also called
macromolecules.
In graphite, one electron from each carbon atom
is delocalised. These delocalised electrons
allow graphite to conduct heat and electricity.
1.
2.
3.
4.
5.
6.
7.
8.
9.
10 Questions
How many bonds do carbon atoms form in diamond?
How many bonds do carbon atoms form in graphite?
Why is graphite soft and slippery?
Why can graphite conduct electricity?
What can diamond not conduct electricity?
What is the chemical name for sand?
Giant covalent structures are also called __________?
Do giant covalent structures have high or low melting
points?
Explain your answer to question 8.
HT only
10. Give a use for fullerenes.
Covalent bonding - Giant
Metallic bonding
Positive ions in a sea of delocalised electrons
Metals
• Metals consist of giant structures of atoms
arranged in a regular pattern.
• The electrons in the highest occupied energy
levels (outer shell) of metal atoms are
delocalised and so free to move through the
whole structure.
• a structure of positive ions with electrons
between the ions holding them together by
strong electrostatic attractions.
• Metals conduct heat and electricity because
of the delocalised electrons in their
structures.
• The layers of atoms in metals are able to
slide over each other and so metals can be
bent and shaped.
Alloys
• Alloys are usually made from two or more
different metals. The different sized atoms
of the metals distort the layers in the
structure, making it more difficult for them
to slide over each other and so make alloys
harder than pure metals.
• Conduction depends on the ability of
electrons to move throughout the metal.
Different sized atoms do not form a regular
pattern.
force
heat
Shape memory
Alloys can return to
their original shape
after being deformed,
eg Nitinol used in
dental braces.
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
10 Questions
What type of bonding do metals have?
Draw a diagram to show the arrangement of atoms in a
metal.
Do metals have a regular or irregular structure?
What is the main purpose of alloying metals?
What are alloys called that can return to their original
shape?
How can we return them to their original shape?
What happens to valence (outer) electrons in a metal?
What forces of attraction hold metal atoms together?
Why can metals conduct electricity?
Draw a diagram to show the bonding present in solid
sodium.
Metallic bonding
Polymers and Nanoscience
High density polymer –
chains close together
The melting point of a thermosoftening polymer
is determined by the strength of the
INTERMOLECULAR FORCES
•
•
Low density polymer chains far apart
•
Nanoscience is the science of very small
particles and looks at the properties of
nanoparticles.
These are particles with in the range of
0·1nm to 100nm. The name 'nano' means 10-9.
A nanoparticle is about 100 atoms
Advantages
Some do not melt when
heated, these are called
thermosetting polymers.
These cross-links make the
material tougher and less
flexible.
Some will soften easily, and
can be moulded into shape
before they are cooled
down, these are called
thermosoftening polymers.
•
•
Large surface area
makes them
effective catalysts.
Nanotubes can be
used in small scale
circuits as
nanowires.
Disadvantages
•
•
So small they can
enter the skin and
therefore the
bloodstream.
Easily become
airborne, breathing
in can potentially
damage the lungs.
Nanoparticles are present in sun screens
May be used to develop faster computers,
lighter construction materials and new coatings
10 Questions
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
Are hydrocarbons tightly packed together in HD or LD
polystyrene?
Some plastics melt when heated, what do we call them?
Some plastics do not melt when heated, what do we call them?
Why do they not melt?
What is the melting point of a thermosoftening plastic
determined by?
When we grind solids up into small particles, what happens to
the surface area of the solid?
What is nanoscience?
Approximately how many atoms are in a nanoparticle?
State one advantage and one disadvantage of nanoparticles?
State one use for nanoparticles.
Polymers and Nanoscience
Elements and compounds can be detected and
identified using instrumental methods.
Advantages
•
•
•
GC, GC-MS
Disadvantages
Highly accurate and
sensitive.
They are quicker.
Enable very small
samples to be
analysed
•
•
•
Equipment is very
expensive.
Takes specialist
training to use.
results can ONLY
be analysed by
comparison with
known data
Chemical analysis can be
used to identify additives
in foods. Artificial colours
can be detected/identified
by paper chromatography
A
B
C
D
Components in a mixture can be identified by the
distance they move relative to the solvent. This
is the Rf value: Distance moved by component
Distance moved by solvent
Relative abundance
Analytical techniques
Retention time
Different substances, carried by a gas, travel
through a column packed with a solid material at
different speeds, so that they become
separated the number of peaks on the output of
a gas chromatograph shows the number of
compounds present. The position of the peaks on
the output indicates the retention time.
The output from the gas
chromatography column
can be linked to a mass
spectrometer, which can
be used to identify the
substances leaving the
end of the column by
relative molecular mass
The molecular mass is
given by the molecular
ion peak.
1.
10 Questions
How can you separate…
a)
b)
c)
2.
3.
4.
5.
6.
7.
8.
9.
10.
A solid from a liquid
A liquid from a gas
A liquid from a liquid
What is an E-number?
State one advantage and one disadvantage of chromatography.
What do we call the filter paper after the chromatography
experiment has ended?
What colours are present in blank inks?
What does the Rf value represent?
What do the initials GC-MS stand for?
Give an example of a typical carrier gas in a GC-MS.
What is the period of time a gas remains in the column of a GC-MS
called?
Give a use for chromatography.
Analytical techniques
Calculations and moles
The relative atomic mass of an element (Ar)
compares the mass of atoms of the element
with the 12C isotope. It is an average value for
the isotopes of the element
The relative formula mass (Mr) of a compound
is the sum of the relative atomic masses of the
atoms in the numbers shown in the formula.
The relative formula mass of a substance, in
grams, is known as one mole of that substance.
Percentage of element in a compound
Yield
The amount of a product obtained is known as
the yield. When compared with the maximum
theoretical amount as a percentage, it is called
the percentage yield.
Reacting masses - What mass of calcium oxide
will I get when 20 g of limestone is decomposed?
CaCO3

40+12+(3x16)
100g
CaO
40+16
56g
+
CO2
12+(2x16)
44g
As 20g is less than 100g the reaction needs to
be scaled down by a factor of:
20 = 0.20
So, mass of CaO = 56x0.20 = 11.2g
100
Empirical formula is the simplest ratio of atoms
in a compound. Molecular formula is the actual
ratio of atoms. e.g. What is the empirical
formula of a compound containing 40.0% sulfur
and 60.0% oxygen by mass?
1.
2.
Divide through by
Ar
40 : 60
32
16
Get molar ratio
1.25 : 3.75
3.
=
Get simplest whole
number ratio by
dividing through by
the smallest
1.25 : 3.75
1.25
1.25
1 : 3 SO3
10 Questions
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
What is the definition for the relative formula mass of a
compound?
What is the Ar of Cl?
What is the Mr of Na2O?
What is the percentage of Na in Na2O?
What is the Mr of (NH4)2SO4?
What is the percentage of O in (NH4)2SO4?
What is the yield of a substance?
What mass of magnesium oxide will I get when 42 g of
magnesium carbonate is decomposed?
Only 18g of magnesium oxide was formed, what is the yield?
A hydrocarbon contains 75% carbon and 25% hydrogen by
mass, what is the empirical formula?
Calculations and moles
Reaction kinetics
For a reaction to occur:
• Step 1: Energy must be SUPPLIED to break
bonds.
• Step 2: Energy is RELEASED when new
bonds are made.
A reaction is EXOTHERMIC if more energy is
RELEASED then SUPPLIED (hotter). If more
energy is SUPPLIED then is RELEASED then the
reaction is ENDOTHERMIC (older).
Even though no atoms are gained or lost in a
chemical reaction, it is not always possible to
obtain the calculated amount of a product
because:
•
the reaction may not go to completion
because it is reversible.
•
some of the product may be lost when it is
separated from the reaction mixture
•
some of the reactants may react in ways
different from the expected reaction.
In some chemical reactions, the products of the
reaction can react to produce the original
reactants. Such reactions are called reversible
reactions and are represented:
A
+
B
ammonium
chloride
NH4Cl (s)
C
+
ammonia +
D
hydrogen
chloride
NH3 (g) + HCl (g)
The change from blue hydrated copper sulphate
to white anhydrous copper sulphate is one of the
most commonly known reversible reactions.
hydrated
copper sulphate
anhydrous + steam
copper sulphate
CuSO4.5H2O (s)
CuSO4 (s) + 5H2O (l)
If a reversible reaction is exothermic in one
direction, it is endothermic in the opposite
direction. The same amount of energy is
transferred in each case.
10 Questions
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
For a reaction to occur why is energy supplied?
Why is energy released during a reaction?
If more energy is supplied than released is the reaction exothermic
or endothermic?
If a reaction is endothermic will the surroundings get warmer or
colder?
A reaction requires a lot of heat to take place, it is endothermic or
exothermic?
Is breaking bonds an endothermic or exothermic process?
Give 2 reasons why a yield is not always 100%?
What is the symbol for a reversible reaction?
Give an example of a reversible reaction.
If a reversible reaction is exothermic in 1 direction what must it be
in the other?
Reaction kinetics
Reaction rates
Amount of
product
formed
Fast rate
of reaction
here
Slower rate of reaction here due
to reactants being used up
Reactions occur when particles collide with
sufficient energy. The minimum amount of
energy required for particles to react on
collision is called the activation energy.
Factors affecting reaction rate
Slower reaction
Time
Reaction can be followed by:
• Loss in mass if gas produced.
• Measuring volume of a gas produced every min.
• Appearance/disappearance of colour.
• Change in pH etc.
Concentration: Increasing concentration
increases number of collisions and increases rate
Temperature: Particles have more energy and
move faster and collide more often. More
particles have energy greater than the
activation energy so more successful collisions
Catalyst: Catalysts change the rate of chemical
reactions but are not used up during the
reaction. Different reactions need different
catalysts. Catalysts are important in increasing
the rates of chemical reactions used in
industrial processes to reduce costs.
Pressure: Increasing pressure increases the
number of collisions as the particles are closer.
Surface area: Increases the number of
collisions as there is more surface exposed
1.
2.
3.
4.
5.
6.
10 Questions
What equipment can be used to measure the mass of a product?
In terms of reactants how do we know when a reaction is completed?
State 2 ways in which a reaction can be followed.
Define activation energy.
How do catalysts effect the activation energy?
How does this change the rate of a reaction?
Describe how the following factors effect the rate of a reaction in
terms of amount (frequency) of collisions and energy of collisions?
7.
8.
9.
10.
Increasing the temperature.
Decreasing the concentration.
Increasing the pressure of gaseous reactants.
Grinding up solid calcium carbonate into a powder.
Reaction rates
Acids and Bases
Acid
Formula
Salts
hydrochloric
HCl
chlorides
sulphuric
H2SO4
sulphates
nitric
HNO3
nitrates
1
2
3
4
5
6
Red
7
•
9
10
11
Green
Increasingly acidic
•
•
•
8
Reactions occur when particles collide with
sufficient energy. The minimum amount of
energy required for particles to react on
collision is called the activation energy.
12
13
14
Purple
Increasingly basic
Acids give H+ in water
Bases accept H+
Alkalis are soluble bases and give OH- in
water
Bases include, metal oxides, metal
hydroxides, metal carbonates
Common Acids
Common Bases
hydrochloric acid - HCl
sodium hydroxide - NaOH
sulphuric acid - H2SO4
potassium hydroxide - KOH
nitric acid - HNO3
ammonia – NH3
acid
+
metal

salt
+
hydrogen
acid
+
base

salt
+
water
acid
+
carbonate  salt
+
H 2O
+
CO2
Neutralisation
An acid can be neutralised by a base
H+ (aq) + OH- (aq)  H2O (l)
Base
Acid
Salt
Calcium
hydroxide
Hydrochloric
acid
Calcium
chloride
Magnesium
oxide
Nitric acid
Magnesium
nitrate
Calcium
carbonate
Sulphuric acid
Calcium
sulphate
1.
2.
3.
4.
5.
6.
7.
10 Questions
What scale is used to measure how acidic or alkaline a substance is?
What in the name and formula of the acid that can be used to make
magnesium chloride from magnesium ribbon?
What is the definition of an acid?
What is the difference between an alkali and a base?
What gas is formed when an acid reacts with a metal?
How can we test for this gas?
What is the name of the salt formed when Na2O reacts with HNO3?
Balance and complete the following reactions:
1.
__Mg (s) + __HCl (aq)  __MgCl2 (aq) + __H2 (g)
2.
__Al2O3 (s) + __HCl (aq)  __AlCl3 (aq) + __H2O (l)
3.
__Na2O (s) + __H2SO4 (aq) 
Acids and Bases
Salts
Soluble salts
• Metal can be reacted with an acid until the
metal is used up.
• Excess metal can be filtered off.
• Water can be evaporated from the solution
and the salt left to crystallise
• Disadvantage: not all metals are suitable;
some are too reactive and others are not
reactive enough.
acid
+
metal
acid
+
acid
+
base

salt
+
water
acid
+
alkali

salt
+
water

salt
carbonate  salt
+
+
H 2O
hydrogen
+
CO2
Ammonia dissolves in water to produce an
alkaline solution. It is used to produce ammonium
salts. Ammonium salts are important as
fertilisers.
•
•
•
•
Place a known volume of alkali in a beaker
Add an indicator
Add acid dropwise until the solution is
neutral. Record the amount of acid required.
Mix the same volume of alkali and acid,
evaporate off some of the water and leave to
crystallise
Insoluble salts
• Insoluble salts can be made by mixing
appropriate solutions of ions so that a
precipitate is formed.
•
The precipitate can be separated using filter
paper, washed with distilled water and left
to dry.
•
All nitrates are soluble, all sodium salts are
soluble.
Precipitation can be used to remove unwanted
ions from solutions, for example in treating
water for drinking or in treating effluent.
10 Questions
Nickel sulphate (a soluble salt) can be made by adding an excess of insoluble nickel oxide
to sulphuric acid until no further reaction occurs.
1.
2.
3.
4.
5.
6.
Give an observation that would show you that the reaction is complete?
What equipment could be used to removed the excess nickel oxide?
What is the name of this separation method?
How you could produce crystals of nickel sulphate from nickel sulphate solution?
What other reactant could be added to H2SO4 to make nickel sulphate?
What is the formula of nickel (II) sulphate?
Silver chloride is an insoluble salt which is formed as a precipitate when silver nitrate and
sodium chloride solutions are mixed together.
7.
8.
9.
10.
Write a word equation for this reaction.
What is the formula of silver (I) chloride?
After mixing the reactants how could the insoluble salt be separated?
Lead nitrate and sodium sulphate are reacted together in solution. Name the two salts
made in this reaction?
Salts
Electrolysis – Molten
When ionic compounds are melted
or dissolved in water the ions can
move.
This means that molten ionic
compounds and solutions of ionic
compounds conduct electricity.
Br2 +
Anode
Br-
Br-
-
Positive ions (CATIONS) move to
the negative electrode
(CATHODE).
Cathode
Negative ions (ANIONS) move to
the positive electrode (ANODE).
Pb2+
The solution or melt that is
electrolysed is called the
ELECTROLYTE.
Electrolysis of molten compounds
All ionic compounds contain positive and negative
ions. We can predict the ions present from the
formula and the charges on the ions using the
formula and the data sheet.
e.g. lead bromide
PbBr2  Pb2+ + 2Br-
During electrolysis:
• The CATIONS move to the negative
electrode where they GAIN electrons
• The ANIONS move to the positive electrode
where they LOSE electrons
Br- ions move to the anode and lose electrons:
2Br-  Br2 + 2e-
OF ELECTRONS
Pb2+ ions move to the cathode and gain electrons:
Pb2+ + 2e-  Pb
O xidation
R eduction
Is
Is
L oss
G ain
1.
2.
3.
4.
5.
6.
7.
10 Questions
Why can’t ionic solids conduct electricity?
What is the name given to the positive electrode?
What is a compound split up into using electrolysis?
What is the solution or melt that is electrolysed called?
What does the acronym O I L R I G stand for?
Br- ions reach the positive electrode and loose electrons to form
bromine gas, is this process oxidation or reduction?
What ions are present in calcium iodide and which electrode would each
ion go to?
Balance and complete the following reactions:
1.
__Ca2+ + __e-  __Ca
2.
__Cl-  Cl2 + __e-
3.
__CaCl2  __Ca2+ + __Cl-
Electrolysis – Molten
Electrolysis - Solutions
At the negative electrode, positively charged
ions gain electrons (reduction) and at the
positive electrode, negatively charged ions lose
electrons (oxidation).
If there is a mixture of ions, the products
formed depend on the reactivity of the elements
involved.
Brine
Compounds: sodium chloride (NaCl) and water (H2O)
Ions: Na+ + Cl- (Anode) --- OH- + H+ (Cathode)
Positive electrode
2Cl-  Cl2 + 2e-
Negative electrode
2H+ + 2e-  H2
When the chloride ions and hydrogen ions have
been discharged……NaOH is left behind
Products in the electrolysis of brine:
• Chlorine (Cl2) - used in bleach and plastics.
• Hydrogen (H2) - used in the hydrogenation
of vegetable oil to make butter.
• Sodium hydroxide (NaOH) - used in soap.
Electroplating
Electrolysis is used to electroplate objects. This may be
for a variety of reasons and includes copper plating and
silver plating.
Passing a current through a solution containing Cu2+ ions
or Ag+ ions will result in the silver or copper being
deposited on the cathode.
Extraction of aluminium
•
Bauxite – aluminium ore containing aluminium oxide
•
Aluminium oxide has a very high melting point
•
The electrolysis takes place when the aluminium
oxide is molten. It is dissolved in molten cryolite to
reduce the temperature at which it melts.
•
This reduces energy costs
•
The cathode and anode are made of graphite
Negative electrode
3Al+ + 3e-  Al
Positive electrode
2O2-  O2 + 4e-
Oxygen is released at the anode where it reacts
with the graphite to form carbon dioxide.
Therefore the anode needs to be replaced often
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
Electrolysis - Solutions
What is the chemical formula of salt in the sea?
What ions are present in brine?
What are the 3 products made when brine undergoes electrolysis?
Give a use of each one.
What ions move towards the anode?
What ions move towards the cathode?
What gas discharged at the anode (write the ionic equation as well)?
What gas discharged at the cathode (write the ionic equation as
well)?
What ions are left in solution?
What is the name of the compound left in the solution
When bauxite undergoes electrolysis what metal is formed and why
does the carbon anode need to be frequently replaced?
Electrolysis – Molten
Mark Scheme
Atomic Structure
1. 35
2. 17
3. 17 protons, 18 neutrons, 17 electrons
4. 2,8,7
5. 0
6. 0
7. shells (or) orbitals
8. 35.5
9. Isotopes - Atoms of the same element that
have different numbers of neutrons
35Cl – 18 neutrons
37Cl – 20 neutrons
Ionic bonding
1. Transfer
2. (a) Metals and Non-metals
3. -1
4. +3
5. Electrostatic
6. Molten (l) or in solution (aq)
10. MgCl2
=
=
=
=
9. [2,8]10. CaF2
(1xMg)
(1x24)
24
95
+
+
+
(2xCl)
(2x35.5)
71
7.
8.
Mark Scheme
Covalent bonding - molecules
1. Share
2. (b) Non metals and Non-metals
3. 1
4. 5
5. They do not conduct electricity because the
molecules do not have an overall electric
charge. (or) No free electrons or ions.
6. Strong
7.
8.
9.
10. 4
Covalent bonding - Giant
1. 4
2. 3
3. In graphite, each carbon atom bonds to
three others, forming layers. The layers are
free to slide over each other because there
are no covalent bonds between the layers
and so graphite is soft and slippery.
4. In graphite, one electron from each carbon
atom is delocalised. These delocalised
electrons allow graphite to conduct heat and
electricity.
5. No delocalised electrons.
6. Silicon dioxide
7. Macromolecules
8. High
9. Giant covalent structures are linked by
strong covalent bonds and so they have very
high melting points.
10. They are used for drug delivery into the
body, lubricants and catalysts.
Mark Scheme
Metallic bonding
1. Metallic
2.
1.
2.
3.
4.
5.
6.
7.
8.
Regular
To make them harder
Shape memory alloys
Heat them up
The outer electrons of metal atoms are
delocalised and so free to move through the
whole structure.
Strong electrostatic attractions.
Metals conduct heat and electricity because
of the delocalised electrons.
Positive ions in a sea of delocalised electrons
Polymers and Nanoscience
1. High Density (HD)
2. Thermosoftening
3. Thermosetting
4. Cross-links in the structure
5. The melting point of a thermosoftening
polymer is determined by the strength of
the INTERMOLECULAR FORCES
6. Gets bigger
7. Nanoscience is the science of very small
particles and looks at the properties of
nanoparticles.
8. A nanoparticle is about 100 atoms
9. Advantages:
• Large surface area makes them effective
catalysts.
• Nanotubes can be used in small scale
circuits as nanowires.
Disadvantages:
• So small they can enter the skin and
therefore the bloodstream.
• Easily become airborne, breathing in can
potentially damage the lungs.
10. Sun screens (or) Bandages - others
Mark Scheme
Analytical techniques
1. (a) Filtering
(b) take the lid off
(c) chromatography
2. Codes for chemicals which can be used as
food additives for use within the EU.
3. Advantages:
• Highly accurate and sensitive.
• They are quicker.
• Enable very small samples to be analysed
Disadvantages:
• Equipment is very expensive.
• Takes specialist training to use.
• results can ONLY be analysed by
comparison with known data.
4. Chromatogram
5. All colours
6. Distance compound travels up chromatogram
7. Gas Chromatography – Mass Spectrometry
8. He (or) N2 (or) H2
9. Retention time
10. Separating a mixture of liquids (or) Money
and cheques can be proven as fakes using
this scientific technique - others
Calculations and moles
1. The relative formula mass of a substance, in
grams, is known as one mole of that
substance.
2. 35.5
3. Na2O
= (2xNa)
+
(1xO)
= (2x23)
+
(1x16)
= 46
+
16
= 62
4. % of Na = (46/62) x 100 = 74.2%
5. Mr of (NH4)2SO4 = 132
6. % of O = (64/132) x 100 = 48.5%
7. The amount of a product obtained is known
as the yield.
8. MgCO3 
MgO +
CO2
(24+12+48)
(24+16)
84g
40g
42g
20g
18
9. Yield = ( /20) x 100 = 90%
10.
C
H
75/
25/
12
1
6.25
25
1
4
CH4
Mark Scheme
Reaction kinetics
1. To break bonds
2. Bonds are made
3. Endothermic
4. Colder
5. Endothermic
6. Endothermic
7. Yield is never 100% because:
•
The reaction may not go to completion
because it is reversible.
•
Some of the product may be lost when it is
separated from the reaction mixture
•
Some of the reactants may react in ways
different from the expected reaction.
8.
9.
NH4Cl (s)
10. Endothermic
NH3 (g) + HCl (g)
Reaction rates
1. Balance (or) Scales
2. There are no reactants remaining
3. Amount of product formed (and) Amount of
reactant used.
4. Reactions occur when particles collide with
sufficient energy. The minimum amount of
energy required for particles to react on
collision is called the activation energy.
5. Catalysts lower the activation energy.
6. Speeds it up
7. Rate increases as frequency and energy of
collisions increases.
8. Rate decreases as only the frequency of
collisions decreases.
9. Rate increases as only the frequency of
collisions increases.
10. Rate increases as the surface area is
increased, therefore increasing the
frequency of collisions increases.
Mark Scheme
Acids and Bases
1. pH scale
2. Hydrochloric acid (HCl)
3. Acids give H+ in water
4. Alkalis are soluble bases and give OH- in
water.
5. Hydrogen
6. Squeaky pop (heard when an ignition source
is brought near).
7. Sodium nitrate
Salts
1. Temperature would stop rising – other
2. Filter paper + filter funnel + conical flask
3. Filtering
4. Leave to evaporate
5. Nickel metal, Ni (s)
6. NiSO4
7.
8.
Mg (s) + 2HCl (aq)  MgCl2 (aq) + H2 (g)
9.
Al2O3 (s) + 6HCl (aq)  2AlCl3 (aq) + 3H2O (l)
8. AgCl
9. Filtering
10. lead sulphate (and) sodium nitrate
10. Na2O (s) + H2SO4 (aq)  Na2SO4 (aq) + H2O (l)
silver
nitrate
+
sodium
chloride

silver
chloride
+
sodium
nitrate
Mark Scheme
Electrolysis – Molten
1. Ions cannot move
2. Anode (Remember PANIC: Positive Anode
Negative Is Cathode).
3. Elements
4. Electrolyte
5. OILRIG – Oxidation Is Loss, Reduction Is
Gain (of electrons).
6. Oxidation
7. Ca2+ would go to the cathode, I- would go to
the anode.
8.
Ca2+ + 2e-  Ca
9.
2Cl-  Cl2 + 2e-
10. CaCl2  Ca2+ + 2Cl-
Electrolysis - Solutions
1. NaCl
2. Na+, H+, OH-, Cl3. Hydrogen, chlorine, sodium hydroxide.
4. Negative ions (OH-, Cl-)
5. Positive Ions (H+, Na+)
6. Chlorine, 2Cl-  Cl2(g) + 2e7. Hydrogen, 2H+ + 2e-  H2(g)
8. Na+ and OH9. Sodium hydroxide
10. Aluminium. Oxygen is released at the anode
where it reacts with the graphite to form
carbon dioxide. Therefore the anode needs
to be replaced often.