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Chemistry in Society

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Title: Chemistry in Society


1
Unit 3 Chemistry in Society Plastics and Polymers
Lots of types were used at the London 2012
Olympics
2
  • Scenario - Howard was in charge of designing a
    new toy car for an infant (3-6 years old.)
  • He had the choice of using metal, wood or
    plastic in his design. Howard decided to use
    plastic. Why?

3
Properties of Plastics (Polymers)
  • Plastics are used for so many jobs because they
    have many useful properties. Properties of
    materials describe what they are like and how
    they behave.
  • For example, a plastic shampoo bottle has the
    following properties
  • Flexible the shampoo can be squeezed out of the
    bottle.
  • Watertight the shampoo will not leak.
  • Shatterproof the bottle will not break if
    dropped.
  • Light this also make it cheaper to transport.
  • Plastics are good heat insulators this means
    plastic doesnt let heat escape. Plastics are
    also good electrical insulators
  • Plastics can be coloured (any colour) at the
    manufacture stage unlike metal and wood.

Why is plastic used to make shampoo/shower gel
bottles?
4
Hydrogels
  • Hydrogels are smart materials.
  • Hydrogels can change structure in response to
    their environment.
  • Hydrogels are used in nappies and contact lenses
    (amongst other things)

5
Kevlar
  • Kevlar is an incredibly strong yet lightweight
    fibre.
  • Kevlar is strong because of its bonding. (higher)
  • Kevlar is used in a range of things including
    stab vests, motorcycle equipment and now even
    football boots.

6
Water Soluble Polymers
  • Water soluble polymers are plastics that dissolve
    in water.
  • In the past high temperatures were needed to
    dissolve the polymer but advances in recent years
    means lower temperatures are successful too.
  • Water soluble polymers are used in hospital
    laundry bags and washing up liquitabs

7
Special Polymer Name Special Property
Kevlar Bulletproof (very strong yet lightweight)
Biopol Biodegradable plastic (breakdowns down naturally)
Poly(ethenol) Soluble in water (i.e. it dissolves in water)
Hydrogels can change its structure in response to salt concentration, pH and  temperature.
8
Advantages and Disadvantages of Plastics
Advantages
Disadvantages
The main advantage plastics is also the reason
why plastic is such a problem. It lasts forever.
(doesnt biodegrade) Plastics are
reusable. Plastics are usually shatterproof and
are see-through. Light-weight and odourless.
Burning plastics can be very dangerous as they
give off toxic and poisonous fumes. Different
plastics give off different types of fumes. All
plastics give off carbon monoxide. Made from
Crude Oil which is a finite resource. (i.e. its
running out) Plastics dont biodegrade (i.e.
they dont break down naturally)
9
  • Reminder
  • An addition reaction occurs when something adds
    across a double bond.
  • During an addition reaction the carbon to carbon
    double bond is broken.

10
How are Addition Polymers are made?
  • Plastics are made up of huge long chain molecules
  • called polymers.
  • Polymers are made when many small molecules,
    called
  • monomers, join together.
  • These monomers (usually alkenes) must contain a
  • carbon double bond and join together to form
  • saturated polymers.
  • This process is called addition polymerisation
    (only
  • carbons bonded together i.e. carbon backbone)

11
Making poly(ethene)
  • (mono means one, poly means many)
  • Monomer name ethene Polymer name poly(ethene)
  • Monomer structure
  • Polymer structure
  • Repeating unit

whiteboard example
12
Making poly(propene)
  • Monomer name propene Polymer name
    poly(propene)
  • Monomer structure
  • Polymer structure
  • Repeating unit

whiteboard example
13
Making poly(styrene)
  • Monomer name Polymer name
  • Monomer structure
  • Polymer structure
  • Repeating unit

whiteboard example
14
  • Reminder
  • In a condensation reaction two molecules join and
    a small molecule (often water) is removed.
  • Making an ester is an example of a condensation
    reaction.

15
How are Condensation Polymers are made?
Some examples of condensation polymers are nylon,
poly(ester), proteins, starch and
cellulose. Poly(ester) and nylon are synthetic
(man-made) while the others mentioned above are
natural. The monomers used to make condensation
polymers have two functional groups at each end
of the molecule they are bifunctional. A
small molecule is also produced when a
condensation polymer is formed. This process is
called condensation polymerisation (other
elements as well as carbon are bonded together
in the molecules backbone)
16
Making a poly(ester)
  • Carboxylic acid Alcohol Ester Water
  • Therefore
  • Diacid Diol Poly(ester) Water
  • Monomer structures
  • Polymer structure

whiteboard example
17
Making Starch
  • Starch is a natural condensation polymer made
    when many glucose monomers join together.
  • Starch, like other natural polymers, are
    biogradeable (break down/decompose naturally)
  • Monomer structure (glucose)
  • Polymer structure

whiteboard example
18
Metals
19
Metallic Bonding
  • Metallic bonding unsurprisingly only appears
    in metal elements.
  • Metallic bonding occurs between metal ions
    (positively charged) and delocalised outer shell
    electrons (negative) opposite attract.
  • delocalised means the electrons are common to
    all of the ions (not just one atom i.e. they hop
    from one to another)

20
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21
The main properties of metals
  • Strength metals that are strong are used to
    make car bodies, bike frames, ships hulls etc.
  • Malleability (mouldable) this means that they
    can be shaped by hammering or rolling and can be
    bent without breaking. For example car chassis.
  • Conduction of electricity all metal elements
    conduct electricity. Non metals (except carbon in
    graphite form) do not. Copper is used in
    household wires, aluminium wires are used in
    overhead power lines.

22
  • Conduction of heat metals are good conductors
    of heat. We use metals like aluminium, iron and
    copper for cooking pots and pans.
  • Density If we had two pieces of metals the same
    size, the higher density metal will be heavier
    than the lower density one. e.g.
  • Lead is highly dense and was useful in old
    divers suits (i.e. theyd sink!)
  • Aluminium less dense and is used to make planes.

23
Alloys
  • The properties of metals can be changed and
    improved by making alloys. (i.e. make it stronger
    or shine more etc.
  • An alloy is a mixture of two or more metals. (in
    some cases some non-metals are also added)
  • The usual way to make an alloy is to melt
    together the elements that make it up.
  • Bronze, brass and stainless steel are examples of
    common everyday alloys.

24
reacts with...
extraction method
acid
water
oxygen
  • Lithium
  • Potassium
  • Calcium
  • Sodium
  • Magnesium
  • Aluminium
  • Zinc
  • Iron
  • Nickel
  • Tin
  • Lead
  • Copper
  • Silver
  • Mercury
  • Gold

This will act as a summary
25
Ores
  • Unreactive metals such as silver and gold are
    found
  • uncombined this is why panning for gold can
    happen.
  • In nature most metals are found in compounds
    these
  • compounds are known as ores.
  • Metals can be extracted from their ores in a
    variety of
  • ways.
  • Extraction with heat only gold, silver and
    mercury.
  • Extraction with heat carbon
  • Extraction with electricity

26
Extraction Heating with Carbon
  • Some metal ores have to be heated with carbon.
  • This is because the metal ore (usually a metal
    oxide)
  • needs the carbon to be able to pull the oxygen
    away
  • from the metal.
  • This leaves the pure uncombined metal. Carbon
  • dioxide is formed too.

METAL OXIDE CARBON METAL CARBON
DIOXIDE
27
Iron and the Blast Furnace
iron(III) oxide
Stage
3
iron(III) oxide
2
1
28
Extraction of Metals using electricity
  • More reactive metals (Al and above) are too
    volatile and therefore dangerous to extract via
    heat carbon.
  • Instead we use electricity to attract the ______
    metal ion to the _________ electrode.

positive
negative
29
Metals and Oxygen Important !!!
  • Metal Oxygen Metal oxide
  • For example
  • Magnesium Oxygen Magnesium Oxide
  • All of the metals above __________ in the
  • reactivity series react with oxygen.

gold
30
Metals and Water Important !!!
  • Metal Water Metal Hydroxide
    Hydrogen
  • Example
  • Potassium Water ____________
    __________
  • Formula equation
  • All of the metals above __________ in the
    reactivity series
  • react with water. (hint - every metal with m at
    end !!)

Potassium Hydroxide
Hydrogen
whiteboard example
aluminium
31
Metals and Acid Important !!!
  • Metal Acid Salt Hydrogen
  • Example
  • Zinc Hydrochloric Acid _________
    _________
  • Formula equation
  • All of the metals above _________ in the
    reactivity series
  • react with acid.

Zinc Chloride
Hydrogen
whiteboard example
hydrogen
32
The Reactivity Series
  • A reactivity series of metals is a league table
    which puts the metals in order of how reactive
    they are.
  • The reactivity series is also known as the
    electrochemical series.
  • The most reactive metals are at the top and the
    least reactive are at the bottom.

33
Electrolysis
  • Electrolysis is the splitting (lysis) up of a
  • compound using electricity (electro).

Electro
lysis
34
Oxidation and Reduction
Copper Chloride Example
whiteboard example
35
Word bank atoms, copper, gain, electrons, ions,
lose, solution, negative, positive
ions
  • The chlorine ______ (in solution) lose electrons
    forming
  • chlorine _______. We see these as gas at the
    ________
  • electrode.
  • The copper ions (in solution) ______ electrons
    forming
  • copper atoms. We see these as solid at the
    _______
  • electrode.
  • 2Cl- Cl2 2e- and
    Cu2 2e- Cu
  • These are called ion-electron equations.

atoms
positive
gain
negative
36
  • OILRIG

Oxidation Is Loss (of electrons)
Reduction Is Gain (of electrons)
37
  • In the copper chloride example
  • Reduction
  • Oxidation
  • Ion electron equations are found in the data
    booklet where they are written as reduction
    reactions.
  • Reducing agents help reduction to occur by
    providing electrons.

whiteboard example
38
Electrochemical Series
  • Metals _______ electrons to obtain a full outer
  • electron shell. This makes the metal stable.
  • The electrochemical series is a list of metals
  • arranged in rank order of how easily the metal
  • atoms lose electrons.
  • The electrochemical series in your data booklet

lose
39
Experiment Measuring a voltage between two
metals.
Voltmeter
v
/ other metals
A cell can be made when two different metals are
connected in contact with an electrolyte. In
this cell the electrolyte is sodium chloride. An
electrolyte is always an ionic compound and it
completes the circuit as it allows the ions flow.
40
lose
  • When metals ________ their electrons, they
  • do so with a certain force.
  • This force is known as voltage.
  • When two different metals are connected
  • together in a cell (a battery), the metal with
  • the higher force pushes its electrons on to
  • the other metal. (bully rule)
  • No voltage is obtained when the same metal is
  • connected together. i.e. two pieces of copper
  • metal.

41
Important
The further apart the metals are in the
electrochemical series, the higher the voltage.
Electrons flow along the wire from the metal
higher in the electrochemical series to the
metal lower down.
42
  • In which direction will electrons flow in the
    following?
  • A magnesium/iron cell?
  • _____ to _____ through the _____.
  • A silver/aluminium cell?
  • _____ to _____ through the _____.
  • A Cu/Sn cell?
  • _____ to _____ through the _____.

wires
wires
wires
43
Combining Batteries, Oxidation and Reduction
  • Remember the metal higher up in the
    electrochemical
  • series loses its electrons more easily i.e.
    oxidation.
  • Write the ion electron equations and label them
    reduction
  • / oxidation for the following batteries
  • Tin Silver Cell
  • Magnesium Zinc Cell
  • Sodium Gold Cell
  • Lead Iodide Cell

44
REDOX Reactions
  • Oxidation cannot happened without reduction and
  • vice versa.
  • Therefore reactions in electric cells (batteries)
    can
  • be described as REDOX.
  • Rechargeable batteries and fuel cells are
    technologies
  • which use REDOX reactions.

45
Writing REDOX equations
  • Zinc Copper Cell
  • OXidation
  • REDuction
  • REDOX equation -
  • i.e. the oxidation and reduction equations have
    been
  • combined and the electrons have been cancelled.

whiteboard example
46
  • Potassium Iodine Cell
  • Oxidation
  • Reduction
  • Redox Equation -
  • If the number of the electrons is NOT the same on
  • each side of the equation then you need to
    multiply
  • the equations to find a common factor.

whiteboard example
47
Examples
  • Write the REDOX equations for the following
  • (show all working please)
  • Magnesium Tin Cell Nickel Chloride Cell
  • Gold Zinc Cell Iron (III) Tin Cell
  • Lithium Aluminium Cell Aluminium Copper
  • Copper Silver Cell Mercury Silver Cell
  • Calcium Bromide Cell Sodium Lead Cell

48
Fertilisers
49
Growth of Plants
  • To grow well, plants require some essential
    elements. These are called NUTRIENTS.
  • Nutrients are made from water soluble compounds.
  • The most important nutrients that plants require
    are Nitrogen, Phosphorus and Potassium (often
    referred to as NPK)
  • These nutrients are often added in the form of
    FERTILISERS

Why do we use fertilisers?
50
Name Chemical Formulae of Fertilisers
  • Ammonium Nitrate (NH4)(NO3-)
  • Ammonium Phosphate (NH4)3(PO43-)
  • Potassium Nitrate K(NO3-)
  • Potassium Phosphate K3(PO43-)
  • i.e. compounds that contain potassium, phosphorus
  • and/or nitrogen

51
Problems with fertilisers
  • Many fertilisers are very soluble, sometimes too
    soluble.
  • If it rains, fertilisers are carried off of the
    land into streams, rivers and lochs.
  • In lochs, high nitrate (NO3-) levels encourage
    algae growth.
  • The algae decrease the amount of oxygen dissolved
    in the water thus killing fish and other marine
    life.
  • High nitrate levels in drinking water
  • make it unfit for human consumption.

52
Nitrogen Fixation and the Nitrogen Cycle
  • Some plants can absorb nitrogen directly from the
    air. e.g. peas, beans and clover. (leguminous
    plants)
  • Leguminous plants have nodules which contain
    nitrifying bacteria.
  • Most plants cant do this and require to absorb
    nitrogen in the form of nitrogen compounds.

53
The Haber Process
  • The Haber Process is the industrial method used
    to make
  • ammonia.
  • N2(g) 3H2(g) 2NH3(g)
  • (this is a reversible reaction)
  • Ammonia is used in the manufacture of nitric
    acid.
  • An iron catalyst, a high temperature (500oC) and
    high pressure (about 150-300atms) are used to
    increase the reaction rate.
  • Nitrogen is obtained by the distillation of air
    and hydrogen is obtained from methane (natural
    gas)

structure from whiteboard
54
The Ostwald Process
  • The Ostwald Process is the industrial method used
    to make
  • Nitric Acid. (HNO3)
  • NH3(g) O2(g) NO(g) H20
  • NO(g) O2(g) NO2(g)
  • NO2(g) H2O(l) HNO3(aq)
    NO(g)
  • A platinum catalyst and a high temperature 9000C
    are required to make the first stage happen.
  • Nitric acid is used in the manufacture of
    fertilisers, explosives and plastics.
  • The reaction is exothermic which means it only
    has to be heated once as it keeps itself going.

step 1
step 2
step 3
55
Percentage Composition
  • The percentage composition allows us to
  • calculate the percentage of each element in
  • a compound.
  • Percentage composition is also known as
  • percentage by mass.

56
  • Percentage of element Mass of Element
  • in a compound (in
    Compound)

  • x100

  • Total mass of
  • Compound


formula mass
57
Worked Example
  • Calculate the percentage by mass of oxygen
  • in aluminium oxide (Al2O3).
  • Formula mass (total mass) of Al2O3
  • Percentage of oxygen in Al2O3

whiteboard example
58
Worked Example 2
  • Calculate the percentage by mass of nitrogen
  • in ammonium nitrate (NH4NO3).
  • Formula mass (total mass) of NH4NO3
  • Percentage of nitrogen in NH4NO3

whiteboard example
59
Examples
  1. Calculate of iron in Fe2O3
  2. Calculate of sulphur in SO2
  3. Calculate of lithium in LiOH
  4. Calculate of oxygen in LiOH
  5. Calculate of hydrogen in LiOH
  6. Calculate of oxygen in H2SO4
  7. Calculate of nitrogen in HNO3
  8. Calculate of sulphur in magnesium sulphite
  9. Calculate of sodium in sodium sulphate
  10. Calculate of aluminium in aluminium nitrate.
  11. Calculate of carbon in hydrogen carbonate
  12. Calculate of zinc in zinc (III) ethanoate

60
Nuclear Chemistry
61
Particle Mass Charge Location
Proton 1 ve Nucleus
Neutron 1 0 Nucleus
Electron 0 -ve Electron shells
Mass Number
16
O
Symbol
8
Atomic Number
62
isotopes
Isotopes are atoms of the same element (same
number of protons) but have different number of
neutrons. This means for isotopes, the atomic
number stays the same but the mass number
changes. Many elements exist as 2 or more
isotopes.
63
Isotopes Protons Electrons Neutrons
28 14 Si
25 14 Si
31 14 Si
27 14 Si
64
Radioactivity
  • Radioactivity results from unstable isotopes of
    elements
  • spontaneously decaying with the emission of
    radiation. This makes
  • the isotopes become more stable.
  • Isotopes that emit radiation are known as
    radioisotopes.
  • What makes a nucleus unstable?
  • Protons are positively charged and it is thought
    that the neutrons
  • prevent the protons repelling each other.
  • If an atom has too many or too few neutrons for
    the number of
  • protons, the atom will be unstable and therefore,
    radioactive.
  • Very large atoms (atomic number gt 83) are always
    unstable.

65
Types of Radiation
  • There are three types of radiation
  • Alpha (a)
  • Beta (ß)
  • Gamma (?)
  • Alpha and beta are made up of particles
  • Gamma radiation is made of waves and has no
  • mass.

66
Alpha Radiation
  • The particles that make up alpha radiation are
    helium nuclei
  • (i.e. 42He)
  • Alpha decay Example
  • i.e.
  • when a nucleus emits an alpha particle its atomic
    number will
  • decrease by two and its mass will fall by 4.

whiteboard example(s)
67
Beta Radiation
  • The particles that make up beta radiation are
    electrons
  • (i.e.0-1e) Beta particles are formed when
    neutrons break up
  • into protons and electrons.
  • Beta decay Example
  • i.e.
  • The atomic number increases by 1 but the mass
    number will
  • remain unaffected.

whiteboard example(s)
68
Gamma Radiation
  • Since gamma rays have no mass and no charge,
  • their emission has no effect on the mass number
  • or the atomic number of the radioisotope. The
  • atom does however lose energy.

69
Artificial Radioisotopes
  • For nuclear reactions to occur, the bombarding
  • particles must have a high energy to overcome the
  • forces of repulsion from the nuclei.
  • Example 1 Cobalt 60 - Neutron Capture
  • Cobalt 60 is used in cancer therapy and is made
    in
  • nuclear reactors where a target of stable cobalt
    59
  • molecules are bombarded by neutrons.

whiteboard example
70
  • Example 2 Nitrogen 14 - Proton Capture
  • When nitrogen 14 is bombarded with protons the
  • following reaction could happen.

whiteboard example
71
Half Life
  • Radioactive decay happens at random.
  • However over time this averages out and a
  • value can be calculated half life.
  • Half life is the time required for something
  • to fall to half its initial value (in particular,
  • the time for half the atoms in a radioactive
  • substance to decay)

72
Half life Calculation Example 1
A sample of a radioisotope has a half life of 14
days. After 56days what mass of the original 80g
sample remained?
whiteboard example
73
Half life Calculation Example 2
A radioisotope of carbon had an initial radiation
reading of 200 counts per minute. 24 days later
the reading was found to be 50 counts per
minute. How many half lives occurred in 24days.
whiteboard example
74
Half life Calculation Example 3
A radioisotope has a half life of 700 years. How
long will it take for 96g of a sample to decay
to 12g?
whiteboard example
75
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