AQA Chemistry Unit 1

1
AQA Chemistry Unit 1
2
Atoms

• All substances are made of atoms
• An element contains only one type of atom
• A compound contains more than one type of atom
  chemically bonded together
• There are about 100 different elements in the
  Periodic Table

3
The protons and neutrons exist in a dense core at
the centre of the atom. This is called the
nucleus.
The electrons are spread out around the edge of
the atom. They orbit the nucleus in layers called
shells.
4
Mass number the number of protons and neutrons
7
Li
3
Atomic number the number of protons

• So lithium has
• 3 protons
• 7-3 4 neutrons
• 3 electrons (atoms are neutral so always have the
  same number of protons and electrons)

5
This electron arrangement is written as 2,8,8.
1st shell holdsa maximum of2 electrons
2nd shell holdsa maximum of8 electrons
3rd shell holdsa maximum of8 electrons
6
The Periodic Table

• Columns are called GROUPS
• Elements in the same group have the same number
  of electrons in their outer shell
• This gives them similar chemical properties
  (think about the reactions of Group I metals in
  water!)
• Group 0 The Noble Gases full outer shells so
  are unreactive and do not form bonds.

7
Chemical Reactions

• Metal and a non-metal IONIC BONDING
• Metal loses electrons and becomes a positive ion
• Non-metal gains electrons and becomes a negative
  ion
• Non-metals together COVALENT BONDING
• Atoms share pairs of electrons to form molecules

8

• Word equations
• Each reactant goes on the left separated by a
  
• An arrow ? represents them reacting together
• Each product goes on the right separated by a

Magnesium Hydrochloric acid ? Magnesium
chloride Hydrogen

• Symbol equations
• There must be the same number of each atom on
  both sides of the equation
• You can ONLY put big numbers in front of the
  substances

Mg HCl ? MgCl2 H2
9
Conservation of Mass

• The mass of the products equals the mass of the
  reactants
• e.g. CaCO3 ? CaO CO2
• 100g ? ? 44g

10
Limestone Cycle
This is the test for CO2 gas!
Thermal Decomposition CO2 gas released
Bubble CO2 through
Add water
Add more water
This is an alkali and can be used to neutralise
acids
11
Uses of Limestone

• As a building material (buildings, statues etc)
• Mortar calcium hydroxide, sand and water
• Cement calcium oxide, clay and water
• Concrete cement and aggregate

12
Carbonates

• Other metal carbonates will thermally decompose
  in a similar way to produce the metal oxide and
  carbon dioxide
• Carbonates react with acids to produce a neutral
  salt, water and carbon dioxide
• calcium nitric ? calcium water
  carbon
• carbonate acid nitrate
  dioxide

Limestone buildings are damaged by acid rain
because of this!
13
Metals

• An ORE contains enough metal to make it
  economical to extract
• Unreactive metals like gold are found NATIVE
• Other metals are found as compounds (often
  oxides) and require chemical reactions to extract
  them
• Metals less reactive than carbon can be extracted
  by REDUCTION with carbon
• Metals more reactive than carbon are extracted
  using ELECTROLYSIS

14
The reactivity of a metal determines how it is
extracted.
Metals above carbon in the reactivity series must
be extracted using electrolysis. Electrolysis can
also be used to purify copper.
potassium
increasing reactivity
sodium
calcium
magnesium
aluminium
(carbon)
Metals less reactive than carbon can be extracted
from their ores by reduction using carbon, coke
or charcoal.
zinc
iron
lead
(hydrogen)
copper
Platinum, gold, silver and copper can occur
native and do not need to be extracted.
silver
gold
platinum
15
Extraction

• Reduction/smelting
• iron oxide carbon ? iron carbon
  dioxide
• 2Fe2O3 3C ? 4Fe
  3CO2
• Electrolysis
• Aluminium must be molten
• Large amounts of heat and electrical energy make
  this very expensive

16
At the negative electrode Al3 3e- ? Al
(reduction)
At the positive electrode 2O2- ? O2 4e-
(oxidation)
17
Copper

• Purified by electrolysis
• Bioleaching uses bacteria to separate copper from
  copper sulphide the leachate contains copper
  which can be separated by filtering
• Phytomining plants grow in soil containing
  copper. Plants are burned and copper is collected
  from the ash.

18
Impact of Extracting Metals

• Quarrying

• Recycling

• Advantages
• Useful products
• Money to local economy
• Local jobs
• Improved roads and transport links
• Disadvantages
• Scars landscape
• Noise and dust pollution
• Loss of habitats

• Uses less energy and less fossil fuels than
  extraction
• Conserves fossil fuels and reduces CO2 emissions
• Saves money
• Conserves resources
• Reduces landfill

19
Properties of Metals

• Strong
• Malleable
• Ductile
• Good conductors of heat and electricity
• Different properties make metals useful for
  different things

20
Alloys

• Mixture of metals
• Pure metals are often too soft mixture changes
  structure so layers cant slide which makes them
  stronger
• Iron from blast furnace is too brittle so

Type of Steel Properties Uses
Low carbon steel (0.1 C) Easily shaped Car bodies
High carbon steel (1.5 C) Very hard Inflexible Cutting blades Bridges
Stainless steel (chromium added) Corrosion resistant Cutlery Containers for corrosive substances
21
Crude Oil

• Mixture of hydrocarbons (compounds containing
  carbon and hydrogen ONLY)
• Most are ALKANES, CnH2n2 (saturated)
• Methane, CH4 Monkeys
• Ethane, C2H6 Eat
• Propane, C3H8 Peeled
• Butane, C4H10 Bananas

22
Fractional Distillation

• The longer the carbon chain the
• Higher the bp
• Higher the viscosity
• Lower the flammability

23
Combustion of Fuels
Product Problem? Solution
Water No
Carbon dioxide Yes greenhouse gas, contributes to global warming Use alternative fuels?
Carbon monoxide Yes - toxic Catalytic converters
Sulphur dioxide Yes causes acid rain Sulphur impurities can be removed before fuel is burned. Gas scrubbers in power stations
Nitrogen oxides Yes causes acid rain Catalytic converters
24
Cracking

• Hydrocarbons can be cracked to make smaller, more
  useful molecules
• This requires heat and a catalyst and is an
  example of thermal decomposition

25
ALKENES

• Alkenes contain a carbon-carbon double bond
• CnH2n (unsaturated)
• Ethene, C2H4
• Propene, C3H8
• To test for an alkene bromine water is added and
  decolourises

26
Making Ethanol

• Ethene from crude oil

• Sugar cane

• React with steam
• Catalyst
• Cheap
• Continuous process
• Produces 100 ethanol
• Non-renewable
• Requires high temp

• Fermentation with yeast
• Renewable
• Lower temp
• Simpler equipment
• Requires land and can cause food shortages in
  poorer countries
• Only produces 15 ethanol
• Batch process

27
Polymerisation

• Many alkene monomers react together to form a
  polymer
• This requires pressure and a catalyst

Repeating unit
28
Polymers

• Disposal

• New developments

• Most are non-biodegradable
• Increases landfill and litter
• Reuse and recycling are encouraged
• Biodegradable plastics made from corn starch are
  being developed

• New packaging materials
• Waterproof coatings for fabrics
• Dental polymers
• Wound dressings
• Hydrogels
• Smart materials

29
Plant Oils

• Can be extracted from fruits, seeds and nuts
• Vegetable oils have higher boiling points than
  water so food can be cooked at higher
  temperatures
• Quicker
• Different flavours
• Increases energy the food releases (higher in
  fat!)

30
Fats

• Saturated

• Unsaturated

• Higher boiling points (tend to be solids at room
  temp)
• Unhealthy

• Contain CC can be tested for using bromine
  water
• Better for us
• Can be turned into margarine by adding hydrogen
  at 60oC with a nickel catalyst
• This adds across some of the double bonds and
  increases the melting point

31
Emulsions

• Oil does not dissolve in water
• It can form an emulsion if an emulsifier is added
  to stop it separating
• e.g. mayonnaise is a mixture of oil and vinegar
  with egg acting as the emulsifier

hydrophillic end
hydrophobic end
32
Earths Structure
Crust is split into tectonic plates These move
due to convection currents in the mantle caused
by heat released from radioactive
processes Large movements can cause earthquakes
and volcanoes
33
Wegeners Theory of Continental Drift

• Jigsaw like fit of continents
• Rocks containing similar fossils on Africa and
  South America
• Others didnt believe him ? - they said there
  could have been a land bridge and didnt think it
  was possible for the continents to move
• In the 1950s new evidence was found that proved
  him right! ?

34
The Earths Atmosphere
35
History

• First billion years intense volcanic activity
  created the early atmosphere and oceans
• One theory early atmosphere was mainly carbon
  dioxide, water vapour and small proportions of
  methane and ammonia.
• Miller-Urey is one theory for how life was formed
  hydrocarbons, ammonia and lightning created
  amino acids.

36
Development

• Most of the carbon from the carbon dioxide in the
  air became locked up in sedimentary rocks as
  carbonates and fossil fuels
• Some dissolved in the oceans
• The level of carbon dioxide is increasing again
  due to burning fossil fuels

37
Fractional Distillation of Air

• Air is filtered to remove dust
• Cooled to -200oC
• Water vapour condenses and is removed
• Carbon dioxide freezes and is removed
• Liquified air is then heated slowly in the column
  and the gases are separated