Chemistry unit 1 - AQA GCSE

1. C1 1.1 ATOMS, ELEMENTS & COMPOUNDS
• All substances are made of atoms
• Elements are made of only one type of atom
• Compounds contain more than one type of atom
• Compounds are held together by bonds
• Each element has its own
symbol in the periodic table
• Columns are called GROUPS.
• Elements in a group have
similar properties
• Rows are called PERIODS
• The red staircase splits
metals from non-metals
An atom is
made up of
a tiny
nucleus
with
electrons
around it

2. C1 1.2 ATOMIC STRUCTURE
• Atoms contain PROTONS, NEUTRONS & ELECTRONS
• Protons and Neutrons are found in the NUCLEUS
• Electrons orbit the nucleus
• ATOMIC NUMBER  the number of protons in the nucleus
 the periodic table is arranged in this order
• MASS NUMBER  the number of protons plus neutrons
Number of neutrons = Mass Number – Atomic Number
Any atom contains equal numbers of
protons and electrons
PARTICLE RELATIVE
CHARGE
RELATIVE
MASS
Proton +1 (positive) 1
Neutron 0 (neutral) 1
Electron -1 (negative) 0

3. C1 1.3 ELECTRON ARRANGEMENT
• Electrons are arranged around the nucleus in SHELLS (or energy levels)
• The shell closest to the nucleus has the lowest energy
• Electrons occupy the lowest available energy level
• Atoms with the same number of electrons in the outer shell belong to the same GROUP in
the periodic table
• Number of outer electrons determine the way an element reacts
• Atoms of the last group (noble gases) have stable arrangements and are unreactive
This is how we draw atoms
and their electrons
Low energy shell
High energy shell
Sodium

4. C1 1.4 FORMING BONDS
• Atoms can react to form compounds in a number of ways:
i) Transferring electrons  IONIC BONDING
ii) Sharing electrons  COVALENT BONDING
IONIC BONDING
• When a metal and non-metal react
• Metals form positive ions
• Non-metals from negative ions
• Opposite charges attract
• A giant lattice is formed
COVALENT BONDING
• When 2 non-metals bond
• Outermost electrons are shared
• A pair of shared electrons forms a bond
CHEMICAL FORMULAE
• Tells us the ratio of each element in the
compound
• In ionic compounds the charges must cancel
out:
E.g. MgCl2
We have 2 chloride ions for every magnesium ion

5. H2 + O2  H2O
Add a 2 to the products side to make the oxygen
balance
H2 + O2  2H2O
This has changed the number of hydrogen atoms
so we must now adjust the reactant side:
2H2 + O2  2H2O
C1 1.5 CHEMICAL EQUATIONS
• Chemical equations show the reactants (what we start with) and the products (what we
end up with)
• We often use symbol equations to make life easier
CaCO3  CaO + CO2
MAKING EQUATIONS BALANCE
Equations MUST balance
We can ONLY add BIG numbers to the front of
a substance
We can tell elements within a compound by BIG
letters
CaCO3  this is a compound made of 3 elements
(calcium, carbon and oxygen)
Ca = 1
C = 1
O = 3
Ca = 1
C = 1
O = 3
• This is balanced – same number of each type of
atom on both sides of the equation
• We can check this by counting the number of each
type on either side
H = 2
O = 2
H = 2
O = 1
H = 2
O = 2
H = 4
O = 2

6. C1 2.1 LIMESTONE & ITS USES
• Limestone is made mainly of Calcium Carbonate
• Calcium carbonate has the chemical formulae CaCO3
• Some types of limestone (e.g. chalk) were formed from the remains of animals and plants
that live millions of years ago
USE IN BUILDING
We use limestone in many buildings by cutting
it into blocks.
Other ways limestone is used:
Cement = powdered limestone + powdered clay
Concrete = Cement + Sand + Water
HEATING LIMESTONE
Breaking down a chemical by heating is
called THERMAL DECOMPOSITION
Calcium  Calcium + Carbon
Carbonate Oxide Dioxide
CaCO3  CaO + CO2
ROTARY LIME KILN
This is the furnace used to heat lots of calcium carbonate and turn it into calcium oxide
Calcium oxide is used in the building and agricultural industries

7. C1 2.2 REACTIONS OF CARBONATES
• Buildings made from limestone suffer from damage by acid rain
• This is because carbonates react with acid to form a salt, water and carbon dioxide
Calcium + Hydrochloric  Calcium + Water + Carbon
Carbonate Acid Chloride Dioxide
CaCO3 + 2HCl  CaCl2 + H2O + CO2
TESTING FOR CO2
• We use limewater to test for CO2
• Limewater turns cloudy
• A precipitate (tiny solid particles) of calcium
carbonate forms causing the cloudiness!
HEATING CARBONATES
Metal carbonates decompose on heating
to form the metal oxide and carbon
dioxide
MgCO3  MgO + CO2

8. C1 2.3 THE LIMESTONE REACTION CYCLE
• Limestone is used widely as a building material
• We can also use it to make other materials for the construction industry
Calcium Carbonate + Heat  Calcium Oxide
Calcium Oxide + Water  Calcium Hydroxide (Limewater)
Calcium Carbonate
Calcium Oxide
Calcium Hydroxide
Calcium Hydroxide
Solution
Step 1: Add Heat
CaCO3  CaO + CO2
Step 2: Add a bit of water
CaO + H2O  Ca(OH)2
Step 3: Add more water & filter
Ca(OH0)2 + H2O  Ca(OH)2 (aq)
Step 4: Add CO2
Ca(OH)2 + CO2  CaCO3 + H2O
Limestone

9. C1 2.4 CEMENT & CONCRETE
CEMENT
Made by heating limestone with clay in a kiln
MORTAR
Made by mixing cement and sand with water
CONCRETE
Made by mixing crushed rocks or stones (called aggregate), cement and sand with water
C1 2.5 LIMESTONE ISSUES
BENEFITS
• Provide jobs
• Lead to improved roads
• Filled in to make fishing lakes or for
planting trees
• Can be used as landfill sites when finished
with
DRAWBACKS
• Destroys habitats
• Increased emissions
• Noisy & Dusty
• Dangerous areas for children
• Busier roads
• Ugly looking

10. C1 3.1 EXTRACTING METALS
• A metal compound within a rock is called an ORE
• The metal is often combined with oxygen
• Ores are mined from the ground and then
purified
Whether it’s worth extracting a particular metal
depends on:
 How easy it is to extract
 How much metal the ore contains
The reactivity series helps us decide the best way
to extract a metal:
 Metals below carbon in the series can be
reduced by carbon to give the metal element
 Metals more reactive than carbon cannot be
extracted using carbon. Instead other
methods like ELECTROLYSIS must be used
THE REACTIVITY SERIES

11. C1 3.2 IRON & STEELS
• Iron Ore contains iron combined with oxygen
• We use a blast furnace and carbon to extract it (as it’s less reactive than carbon)
• Carbon REDUCES the iron oxide;
Iron (III) Oxide + Carbon  Iron + Carbon Dioxide
• Iron from the blast furnace contains impurities:
 Makes it hard and brittle
 Can be run into moulds to form cast iron
 Used in stoves & man-hole covers
• Removing all the carbon impurities gives
us pure iron
 Soft and easily shaped
 Too soft for most uses
 Need to combine it with other elements
• A metal mixed with other elements
is called an ALLOY
E.g. Steel  Iron with carbon and/or
other elements
There are a number of types of steel
alloys:
Carbon steels
 Low-alloy steels
 High-alloy steels
 Stainless steels

12. C1 3.3 ALUMINIUM & TITANIUM
Aluminium Titanium
Property • Shiny
• Light
• Low density
• Conducts electricity and energy
• Malleable – easily shaped
• Ductile – drawn into cables and wires
• Strong
• Resistant to corrosion
• High melting point – so can be used at
high temperatures
• Less dense than most metals
Use • Drinks cans
• Cooking foil
• Saucepans
• High-voltage electricity cables
• Bicycles
• Aeroplanes and space vehicles
• High-performance aircraft
• Racing bikes
• Jet engines
• Parts of nuclear reactors
• Replacement hip joints
Extraction Electrolysis
• Aluminium ore is mined and extracted.
• Alumminium oxide (the ore) is melted
• Electric current passed through at high
temperature
 Expensive process – need lots of heat and
Displacement & Electrolysis
• Use sodium or potassium to displace
titanium from its ore
• Get sodium and magnesium from
electrolysis
 Expensive – lots of steps involved, &

13. C1 3.4 EXTRACTING COPPER
COPPER-RICH ORES
These contain lots of copper. There are 2 ways to
consider:
1. Smelting
• 80% of copper is produced this way
• Heat copper ore strongly in a furnace with air
Copper + Oxygen  Copper + Sulphur
Sulphide Dioxide
• Then use electrolysis to purify the copper
• Expensive as needs lots of heat and electricity
2. Copper Sulphate
• Add sulphuric acid to a copper ore
• Produces copper sulphate
• Extract copper using electrolysis or displacement
LOW GRADE COPPER ORES
These contain smaller amount of
copper. There are 2 main ways:
1. Phytomining
• Plants absorb copper ions from
low-grade ore
• Plants are burned
• Copper ions dissolved by adding
sulphuric acid
• Use displacement or electrolysis
to extract pure copper
2. Bioleaching
• Bacteria feed on low-grade ore
• These produce a waste product
that contains copper ions
• Use displacement or electrolysis to
extract pure copper

14. C1 3.5 USEFUL METALS
TRANSITION METALS
• Found in the central block of the periodic table
Properties:
• Good conductors of electricity and energy
• Strong
• Malleable – easily bent into shape
Uses:
• Buildings
• Transport (cars, trains etc)
• Heating systems
• Electrical wiring
Example: Copper
1. Water pipes – easily bent into shape, strong,
doesn’t react with water
2. Wires – ductile and conduct electricity
COPPER ALLOYS
Bronze – Copper + Tin
- Tough
- Resistant to corrosion
Brass – Copper + Zinc
- Harder but workable
ALUMINIUM ALLOYS
• Alloyed with a wide range of other
elements
• All have very different properties
• E.g. in aircraft or armour plating!
GOLD ALLOYS
• Usually add Copper to make
jewellery last longer

15. C1 3.6 METALLIC ISSUES
EXPLOITING ORES
Mining has many environmental consequences:
• Scar the landscape
• Noisy & Dusty
• Destroy animal habitats
• Large heaps of waste rock
• Make groundwater acidic
• Release gases that cause acid rain
RECYCLING METALS
• Recycling aluminium saves 95% of the energy
normally used to extract it!
• This saves money!
• Iron and steel are easily recycled. As they are
magnetic they are easily separated
• Copper can be recycled too – but it’s trickier as
it’s often alloyed with other elements
BUILDING WITH METALS
Benefits
• Steel is strong for girders
• Aluminium is corrosion resistant
• Many are malleable
• Copper is a good conductor and not
reactive
Drawbacks
• Iron & steel can rust
• Extraction causes pollution
• Metals are more expensive than
other materials like concrete

16. C1 4.1 FUELS FROM CRUDE OIL
CRUDE OIL
• A mixture of lots of different compounds
[A mixture is 2 or more elements or compounds that are not
chemically bonded together]
• We separate it into substances with similar boiling points
• These are called fractions
• This is done in a process called fractional distillation
HYDROCARBONS
Nearly all the compounds in crude oil are hydrocarbons
Most of these are saturated hydrocarbons called alkanes
Methane
CH4
Ethane
C2H6
Propane
C3H8
Butane
C4H10
General formula for
an alkane is CnH(2n+2)

17. C1 4.2 FRACTIONAL DISTILLATION
This is the process by which crude oil is separated
into fractions
 These are compounds with similar sized chains
 Process relies on the boiling points of these
compounds
 The properties a fraction has depend on the size
of their hydrocarbon chains
SHORT CHAINS ARE:
 Very flammable
 Have low boiling points
 Highly volatile (tend to turn into gases)
 Have low viscosity (they flow easily)
Long chains have the opposite of these!
Crude oil fed in at the bottom
Temperature decreases up the
column
Hydrocarbons with smaller chains
found nearer the top

18. C1 4.3 BURNING FUELS
COMPLETE COMBUSTION
Lighter fractions from crude oil make good fuels
They release energy when they are oxidised 
burnt in oxygen:
propane + oxygen  carbon dioxide + water
POLLUTION
Fossil fuels also produce a number
of impurities when they are burnt
These have negative effects on the
environment
The main pollutants are summarised
below
Sulphur Dioxide
• Poisonous gas
• It’s acidic
• Causes acid rain
• Causes engine
corrosion
Carbon Monoxide
• Produced when not
enough oxygen
• Poisonous gas
• Prevents your blood
carrying oxygen
around your body
Nitrogen Oxide
• Poisonous
• Trigger asthma
attacks
• Can cause acid rain
Particulates
• Tiny solid particles
• Contain carbon and
unburnt hydrocarbon
• Carried in the air
• Damage cells in our
lungs
• Cause cancer

19. C1 4.4 CLEANER FUELS
Burning fuels releases pollutants that spread throughout the atmosphere:
CATALYTIC CONVERTERS
• Reduces the carbon monoxide
and nitrogen oxide produced
• They are expensive
• They don’t reduce the amount of
CO2
GLOBAL DIMMING
• Caused by particulates
• Reflect sunlight back into space
• Not as much light gets through to the
Earth
CARBON MONOXIDE
Formed by incomplete combustion
GLOBAL WARMING
• Caused by carbon dioxide
• Causing the average global temperature to
increase
SULPHUR DIOXIDE
• Caused by impurities in the fuel
• Affect asthma sufferers
• Cause acid rain  damages plants & buildings
Carbon + Nitrogen  Carbon + Nitrogen
Monoxide Oxide Dioxide

20. C1 4.5 ALTERNATIVE FUELS
These are renewable fuels  sources of energy that could replace fossil fuels (coal, oil &
gas)
BIODIESEL ETHANOL HYDROGEN
+ • Less harmful to animals
• Breaks down 5 × quicker
• Reduces particulates
• Making it produces other useful
products
•‘CO2 neutral’ – plants grown to
create it absorb the same amount
of CO2 generated when it’s burnt
• Easily made by
fermenting sugar cane
• Gives off CO2 but the
sugar cane it comes
from absorbs CO2 when
growing
• Very clean – no
CO2
• Water is the only
product
- • Large areas of farmland required
• Less food produced  Famine
• Destruction of habitats
• Freezes at low temps
• Large areas of
farmland required
• Less food produced as
people use it for fuel
instead!
• Hydrogen is
explosive
• Takes up a large
volume  storage
becomes an issue

21. C1 5.1 CRACKING HYDROCARBONS
CRACKING  Breaking down large hydrocarbon chains into smaller, more useful ones
SATURATED OR UNSATURATED?
We can react products with bromine water
to test for saturation:
Positive Test:
Unsaturated + Bromine  COLOURLESS
hydrocarbon Water
= ALKENES
Negative Test:
Saturated + Bromine  NO RECTION
Hydrocarbon Water (orange)
= ALKANES
CRACKING PROCESS
1. Heat hydrocarbons to a high temp;
then either:
2. Mix them with steam; OR
3. Pass the over a hot catalyst
EXAMPLE OF CRACKING
Cracking is a thermal decomposition reaction:
C10H22 C5H12 + C3H6 + C2H4
ALKENES
• These are unsaturated hydrocarbons
• They contain a double bond
• Have the general formula  CnH2n
Decane Pentane Propene Ethene
800o
C

22. C1 5.2 POLYMERS FROM ALKENES
PLASTICS  Are made from lots of monomers joined together to make a polymer
HOW DO MONOMERS JOIN TOGETHER?
• Double bond between carbons ‘opens up’
• Replaced by single bonds as thousands of monomers join up
• It is called POLYMERISATION
MONOMERS POLYMER
Ethene
Poly(ethene)
n
Simplified way
of writing it:
‘n’ represent a large
repeating number

23. C1 5.3 NEW & USEFUL POLYMERS
DESIGNER POLYMER  Polymer made to do a specific job
Examples of uses for them:
• Dental fillings
• Linings for false teeth
• Packaging material
• Implants that release drugs slowly
Light-Sensitive Plasters
• Top layer of plaster
peeled back
• Lower layer now exposed
to light
• Adhesive loses stickiness
• Peels easily off the skin
SMART POLYMERS  Have their properties changed by light, temperature or other
changes in their surroundings
Hydrogels
• Have cross-linking chains
• Makes a matrix that
traps water
• Act as wound dressings
• Let body heal in moist,
sterile conditions
• Good for burns
Shape memory polymers
• Wound is stitched loosely
• Temperature of the body
makes the thread tighten
• Closes the wound up with
the right amount of force

24. C1 5.4 PLASTIC WASTE
NON-BIODEGRADABLE
• Don’t break down
• Litter the streets and
shores
• Harm wildlife
RECYCLING
• Sort plastics into different types
• Melted down and made into new
products
• Saves energy and resources…BUT
• Hard to transport and
• Need to be sorted into specific
types
DISADVANTAGES OF
BIODEGRADABLE PLASTICS
• Farmers sell crops like corn to
make plastics
• Demand for food goes up
• Food prices go up  less can
afford it  STARVATION
• Animal habitats destroyed to
make new farmland
• Unsightly
• Last 100’s of years
• Fill up landfill sites
BIODEGRADABLE PLASTICS
• Plastics that break down easily
• Granules of
cornstarch are
built into the
plastic
• Microorganisms
in soil feed on
cornstarch
• This breaks the
plastic down

25. C1 5.5 ETHANOL
There are 2 main ways to make ethanol
2) ETHENE
Hydration reaction  water is added
Ethene + Steam  Ethanol
C2H4 + H2O  C2H5OH
+ Continuous process – lots made!
+ Produces no waste products
- Requires lots of heat and energy
- Relies on a non-renewable resource
1) FERMENTATION
Sugar from plants is broken down by
enzymes in yeast
Sugar + Yeast  Ethanol + Carbon Dioxide
80% of ethanol is made this way
+ Uses renewable resources
-Takes longer to produce
- CO2 is given off
A molecule of ethanol
HH-C-C-O
H
H
H
H
USES FOR ETHANOL
• Alcohol
• Perfume
• Rocket Fuel
• Solvents
• Antiseptic wipes

26. C1 6.1 EXTRACTING VEGETABLE OIL
There are 2 ways to extract vegetable oils from plants:
2) DISTILLATION
1. Plants are put into water and boiled
2. Oil and water evaporate together
3. Oil is collected by condensing (cooling
the gas vapours)
Lavender oil is one oil extracted this way
1) PRESSING
1. Farmers collect seeds from plants
2. Seeds are crushed and pressed
3. This extracts oil from them
4. Impurities are removed
5. Oil is processed to make it into a
useful product
FOOD AND FUEL
Vegetable oils are important foods:
• Provide important nutrients (e.g. vitamin E)
• Contain lots of energy  so can also be used
as fuels
• Unsaturated oils contain double bonds (C=C)
 they decolourise Bromine water
Food Energy
(kJ)
Veg Oil 3900
Sugar 1700
Meat 1100
Table for info only – don’t
memorise it!

27. C1 6.2 COOKING WITH VEGETABLE OILS
COOKING IN OIL
• Food cooks quicker
• Outside becomes crispier
• Inside becomes softer
• Food absorbs some of the oil
• Higher energy content
• Too much is unhealthy
HARDENING VEGETABLE OILS
• Reacting vegetable oils with HYDROGEN
hardens them  increases melting points
• Makes them solid at room temperature 
makes them into spreads!
• Double bonds converted to single bonds
C=C  C-C
• Now called a HYDROGENATED OIL
• Reaction occurs at 60o
C with a nickel
catalyst
+
60o
C + Nickel catalyst
Double bonds converted to
single bonds
Margarine

28. C1 6.3 EVERYDAY EMULSIONS
Oils do not dissolve in water
Emulsion  Where oil and water are
dispersed (spread out) in each
other
 These often have special
properties
EMULSION EXAMPLES
1. Mayonnaise
2. Milk
3. Ice cream
4. Cosmetics – face cream, lipstick etc
5. Paint
EMULSIFIERS
• Stop water and oil separating out
into layers
• Emulsifiers have 2 parts that make
them work:
1.Hydrophobic tail – is attracted
to oil
2.Hydrophilic head – is attracted
to water. It has a negative
charge
Oil
droplet
Emulsifier
molecule
Water
-

29. C1 6.4 FOOD ISSUES
E NUMBER
Additives approved for use in Europe
EMULSIFIERS
• Improve texture and taste of foods
containing fats and oils
• Makes them more palatable (tasty)
and tempting to eat!
FOOD ADDITIVES
Substance added to food to:
• Preserve it
• Improve its taste
• Improve its texture
• Improve its appearance
VEG OILS
Unsaturated Fats:
• Source of nutrients like vitamin E
• Keep arteries clear
• Reduce heart disease
• Lower cholesterol levels
ANIMAL FATS
Saturated Fats:
• Are not good for us
• Increase risk of heart disease
• Increase cholesterol
E.g. chocolate!

30. C1 7.1 STRUCTURE OF THE EARTH
Atmosphere:
Most lies within 10km of the
surface
Rest is within 100km but it’s hard
to judge!
Crust:
Solid
6km beneath
oceans
35km beneath land
Core:
Made of nickel and iron
Outer core is liquid
Inner core is solid
Radius is 3500km
Mantle
Behaves like a solid
Can flow very slowly
Is about 3000km deep!

31. C1 7.2 THE RESTLESS EARTH
MOVING CONTINENTS
The Earth’s crust and upper mantle are cracked into a number of
pieces  TECTONIC PLATES
These are constantly moving - just very slowly
Motion is caused by CONVECTION CURRENTS in the mantle,
due to radioactive decay
PANGAEA
If you look at the continents they roughly fit together
Scientists think they were once one large land mass called
pangaea, which then broke off into smaller chunks
PLATE BOUNDARIES
Earthquakes and volcanoes
happen when tectonic plates
meet
These are very difficult to
predict

32. C1 7.3 THE EARTH’S ATMOSPHERE IN THE PAST
PHASE 1:PHASE 1:
Volcanoes = Steam & CO2
• Volcanoes kept eruptingVolcanoes kept erupting
giving outgiving out Steam andand CO2
• The early atmosphere wasThe early atmosphere was
nearly all COnearly all CO22
• TheThe earth cooledearth cooled andand
water vapourwater vapour condensedcondensed
to form theto form the oceansoceans
Like
this for
a billion
years!
PHASE 2:PHASE 2:
Green Plants, Bacteria
& Algae = Oxygen
• Green plants, bacteriaGreen plants, bacteria
and algae ran riot in theand algae ran riot in the
oceans!oceans!
• Green plants steadilysteadily
converted CO2 into O2
by the process ofby the process of
photosynthesis
• Nitrogen released byreleased by
denitrifying bacteria
• Plants colonise the land.
Oxygen levels steadily
increase
PHASE 3:PHASE 3:
Ozone Layer = Animals
& Us
• TheThe build up of Obuild up of O22
killed off earlykilled off early
organisms - allowingorganisms - allowing
evolution of complexevolution of complex
organismsorganisms
• TheThe O2 created thecreated the
Ozone layer (O3) whichwhich
blocks harmfulblocks harmful UV rays
from the sunfrom the sun
• Virtually no COVirtually no CO22 leftleft

33. C1 7.4 LIFE ON EARTH
No one can be sure how life on Earth first
started. There are many different theories:
MILLER-UREY EXPERIMENT
• Compounds for life on Earth came from
reactions involving hydrocarbons (e.g.
methane) and ammonia
• The energy for this could have been
provided by lightning
OTHER THEORIES
1. Molecules for life (amino acids) came on
meteorites from out of space
2. Actual living organisms themselves arrived
on meteorites
3. Biological molecules were released from
deep ocean vents
The experiment completed
by Miller and Urey

34. C1 7.5 GASES IN THE ATMOSPHERE
THE ATMOSPHERE TODAY:
The main gases in the atmosphere today are:
1. Nitrogen  78%
2. Oxygen  21%
3. Argon  0.9%
4. Carbon Dioxide  0.04%
CARBON DIOXIDE:
• Taken in by plants during photosynthesis
• When plants and animals die carbon is
transferred to rocks
• Some forms fossil fuels which are
released into the atmosphere when burnt
The main gases in air
can be separated out
by fractional
distillation.
These gases are
useful in industry

35. C1 7.6 CARBON DIOXIDE IN THE ATMOSPHERE
The stages in the cycle are shown below: Carbon moves into and out
of the atmosphere due to
• Plants – photosynthesis &
decay
• Animals – respiration &
decay
• Oceans – store CO2
• Rocks – store CO2 and
release it when burnt
CO2 LEVELS
Have increased in the
atmosphere recently
largely due to the
amount of fossil fuels
we now burn