Transcript Slide 1

Lots of types
were used
at the London
2012 Olympics
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?
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;
1. Flexible – the shampoo can be squeezed out of the bottle.
2. Watertight – the shampoo will not leak.
3. Shatterproof – the bottle will not break if dropped.
4. Light – this also make it cheaper to transport.
• Plastics are good heat insulators – this means plastic doesn’t let
heat escape. Plastics are also good electrical insulators
• Plastics can be coloured (any colour) at the manufacture stage
unlike metal and wood.
Hydrogels
• Hydrogels are smart materials.
• Hydrogels can change structure in
their environment.
response to
• Hydrogels are used in nappies and contact lenses
(amongst other things)
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.
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’
‘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.
Advantages and Disadvantages of Plastics
The main advantage plastics is
also the reason why plastic is
such a problem. It lasts forever.
(doesn’t biodegrade)
Burning plastics can be very
dangerous as they give off toxic
and poisonous fumes.
Plastics are reusable.
Different plastics give off
different types of fumes. All
plastics
give
off
carbon
monoxide.
Plastics are usually shatterproof
and are see-through.
Light-weight and odourless.
Made from Crude Oil which is a
finite resource. (i.e. it’s running
out)
Plastics don’t biodegrade (i.e.
they don’t break down naturally)
Reminder;
An addition reaction occurs when something
adds across a double bond.
During an addition reaction the carbon to
carbon double bond is broken.
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’)
Making poly(ethene)
(mono means one, poly means many)
Monomer name; ethene Polymer name; poly(ethene)
Monomer structure;
Polymer structure;
Repeating unit;
Making poly(propene)
Monomer name; propene Polymer name; poly(propene)
Monomer structure;
Polymer structure;
Repeating unit;
Making poly(styrene)
Monomer name;
Monomer structure;
Polymer structure;
Repeating unit;
Polymer name;
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.
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 molecule’s
‘backbone’)
Making a poly(ester)
Carboxylic acid + Alcohol
Ester + Water
Therefore;
‘Diacid’ + ‘Diol’
Monomer structures –
Polymer structure –
Poly(ester) + Water
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 –
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)
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.
• 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. they’d sink!)
Aluminium less dense and is used to make planes.
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.
Lithium
Potassium
Calcium
Sodium
Magnesium
Aluminium
Zinc
Iron
Nickel
Tin
Lead
Copper
Silver
Mercury
Gold
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.
1. Extraction with heat only – gold, silver and mercury.
2. Extraction with heat + carbon
3. Extraction with electricity
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
Iron and the Blast Furnace
Stage
3
2
1
Extraction of Metals using electricity
More reactive metals (Al and above) are too volatile and
therefore dangerous to extract via heat + carbon.
positive metal
Instead we use electricity to attract the ______
negative electrode.
ion to the _________
Metals and Oxygen
Metal + Oxygen
Metal oxide
For example;
Magnesium + Oxygen
Magnesium Oxide
All of the metals above __________ in the
reactivity series react with oxygen.
Metals and Water
Metal + Water
Metal Hydroxide + Hydrogen
Example;
Potassium + Water
Potassium
Hydrogen
Hydroxide + __________
____________
Formula equation:
All of the metals above __________ in the reactivity series
react with water. (hint - every metal with m at end !!)
Metals and Acid
Metal + Acid
Example;
Zinc + Hydrochloric Acid
Salt + Hydrogen
Zinc
Hydrogen
Chloride + _________
_________
Formula equation:
All of the metals above _________ in the reactivity series
react with acid.
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.
Electrolysis
Electrolysis is the splitting (lysis) up of a
compound using electricity (electro).
Oxidation and Reduction
Copper Chloride Example
Word bank; atoms, copper, gain, electrons,
ions, lose, solution, negative, positive
ions (in solution) lose electrons forming
The chlorine ______
atoms We see these as gas at the ________
positive
chlorine _______.
electrode.
gain electrons forming
The copper ions (in solution) ______
negative
copper atoms. We see these as solid at the _______
electrode.
2Cl-
Cl2 + 2e-
and
Cu2+ + 2e-
These are called ion-electron equations.
Cu
OILRIG
Oxidation
Reduction
Is
Is
Loss
Gain
(of electrons)
(of electrons)
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.
Electrochemical Series
Metals _______
lose
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
Experiment – Measuring a voltage between two metals.
Voltmeter
/ 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.
When metals ________
their electrons, they
lose
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.
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.
In which direction will electrons flow in the following?
•
A magnesium/iron cell?
wires
_____ to _____ through the _____.
•
A silver/aluminium cell?
_____ to _____ through the _____.
wires
•
A Cu/Sn cell?
_____ to _____ through the _____.
wires
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
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.
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.
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.
Examples
Write the REDOX equations for the following;
(show all working please)
Magnesium Tin Cell
Gold Zinc Cell
Lithium Aluminium Cell
Copper Silver Cell
Calcium Bromide Cell
Nickel Chloride Cell
Iron (III) Tin Cell
Aluminium Copper
Mercury Silver Cell
Sodium Lead Cell
• 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
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
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.
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 can’t do this and require to
absorb nitrogen in the form of nitrogen
compounds.
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)
The Ostwald Process
The Ostwald Process is the industrial method used to make
Nitric Acid. (HNO3)
NH3(g) + O2(g)
NO(g) + O2(g)
NO2(g) + H2O(l)
NO(g) + H20
NO2(g)
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.
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’.
Percentage of element
in a compound
Mass of Element
(in Compound)
x100
Total mass of
Compound
Worked Example
Calculate the percentage by mass of oxygen
in aluminium oxide (Al2O3).
Formula mass (total mass) of Al2O3 ;
Percentage of oxygen in Al2O3;
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;
Examples
1) Calculate
2) Calculate
3) Calculate
4) Calculate
5) Calculate
6) Calculate
7) Calculate
8) Calculate
9) Calculate
10) Calculate
11) Calculate
12) Calculate
%
%
%
%
%
%
%
%
%
%
%
%
of
of
of
of
of
of
of
of
of
of
of
of
iron in Fe2O3
sulphur in SO2
lithium in LiOH
oxygen in LiOH
hydrogen in LiOH
oxygen in H2SO4
nitrogen in HNO3
sulphur in magnesium sulphite
sodium in sodium sulphate
aluminium in aluminium nitrate.
carbon in hydrogen carbonate
zinc in zinc (III) ethanoate
Particle
Proton
Mass
1
Charge
+ve
Location
Nucleus
Neutron
Electron
1
0
0
-ve
Nucleus
Electron
shells
16
8
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.
Isotopes
28
14
Si
25
14 Si
31
14
Si
27
14
Si
Protons
Electrons
Neutrons
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 > 83) are always unstable.
Types of Radiation
There are three types of radiation;
1) Alpha (α)
2) Beta (β)
3) Gamma (γ)
Alpha and beta are made up of particles;
Gamma radiation is made of waves and has no
mass.
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.
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.
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.
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.
Example 2 – Nitrogen 14 - Proton Capture
When nitrogen 14 is bombarded with protons the
following reaction could happen.
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)
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?
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.
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?