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(C2) OCR 21st Century GCSE: Material Choices

Material properties - Natural vs synthetic - Uses of crude oil - Hydrocarbons - Properties of hydrocarbons - Making Polymers - Modifying polymers - Nanotechnology & its uses
by

J Amuah-Fuster

on 8 July 2016

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Transcript of (C2) OCR 21st Century GCSE: Material Choices

Polymer properties and uses
OCR 21st Century GCSE: (C2) Material Choices
Types of material?
Material Properties
Sources of Materials
Object
Use
Properties needed for use
Homework
Complete a survey of
plastic
objects at home.
Look up the markings on 5 different polymers and make a table of
object
, its
use
and the
type of polymer
.
(On paper...)
Objectives
Use materials' properties to explain how they are suited to their function
Explain why some materials have been replaced
Classify materials as from Animals, Plants or Synthetic
Crude oil – a
mixture
of many different
hydrocarbons
.
These are
compounds
made up of
only carbon and hydrogen atoms
.
Nanotechnology allows individual atoms to be manipulated as in the image above
Crude Oil & Hydrocarbons
How do we measure the properties of materials and why are the results useful?
Common types of material
Metals
Ceramics
Plastic
Fibres
Rubber
Common types of material
Common types of material
Common types of material
Common types of material
The mass of a substance per unit of volume at given temperatures (e.g. water has a density of 1 gram per cubic centimetre at room temperature).


Greater densities imply heavier substances.
Material Properties
The temperature when a
solid
substance
turns

into
a
liquid
.
Melting Point

Tensile strength
is about how much it can be
stretched
before it changes shape.
Strength
Indicates the durability of the material; the ease or difficulty with which one can damage the surface.
Hardness
This is a measure of the amount of force required to bend the substance.
Stiffness
Density
The
strength under compression
, the amount it can be
squashed
before the material changes shape.
1) Complete the material properties crossword
Natural or synthetic?
Natural to Synthetic
How have polymers become more useful for specific jobs?

Why do we prefer to use synthetics (polyester, rubber, nylon) rather than leather in most shoes manufactured today?

Identify another example where a synthetic material has substituted a natural one. Why has it been more successful?
Why is crude oil important as a source of new materials such as plastics and fibres?
I can recall that crude oil consists mainly of hydrocarbons, which are chain molecules of varying lengths made from carbon and hydrogen atoms only
I can recall that only a small percentage of crude oil is used for chemical synthesis and that most is used as fuels
I understand that the petrochemical industry refines crude oil by fractional distillation; hydrocarbons are separated into fractions of different boiling points, to produce fuels, lubricants and the raw materials for chemical synthesis
I can relate the size of the forces between hydrocarbon molecules to the size of the molecules
I can relate the strength of the forces between hydrocarbon molecules in crude oil to the amount of energy needed for them to break out of a liquid and form a gas, and to the temperature at which the liquid boils
I understand that some small molecules called monomers can join together to make very long molecules called polymers, and that the process is called polymerisation
Outcomes
I can interpret information about how solid materials can differ with respect to properties such as melting point, strength (in tension or compression), stiffness, hardness and density

I can relate properties to the uses of materials such as plastics, rubbers and fibres.

I can relate the effectiveness and durability of a product to the materials used to make it.

I can interpret information about the properties of materials such as plastics, rubbers and fibres to assess the suitability of these materials for particular purposes.
Outcomes
Lesson 1:
Objectives
All: Know what is meant by a hydrocarbon and what they are used for.

Most: Understand how hydrocarbons are extracted from crude oil.

Some: Understand the link between hydrocarbon size and boiling point using intermolecular forces.
Homework
Identify at least 5 objects in your home made of different materials and answer these questions:

What was used to make them?
What physical properties do they show?
How are these properties useful for the object's function?
(On paper...)
I can recall that the materials we use are chemicals or mixtures of chemicals, and include metals, ceramics and polymers

I can recall that materials can be obtained or made from living things, and give examples such as cotton, paper, silk and wool

I can recall that there are synthetic materials that are alternatives to materials from living things

I can recall that raw materials from the Earth’s crust can be used to make synthetic materials

I can recall two examples of materials that, because of their superior properties, have replaced materials used in the past.
Outcomes
Sources of Materials
Materials can have numerous sources.
Thier properties often decide what they will be used for, but the origin of the material gives us an insight into the properties it may possess.
For this reason, we have often sourced materials from the natural world.
More recently, we have learned how to manipulate materials to create synthetic products.
Animal
Many useful materials come from plants like; wood, cotton and plant chemicals (inc. oils, dyes).

These are fairly easy to obtain. With technological developments, plants can be turned into many things.
Plant
Animal materials have been around since prehistoric humans were hunting. Use of pelts and hide for clothing, plus bones as tools and jewellery.
More animal friendly uses came with agriculture (wool and silk), but even today almost all parts of an animal are useful for something!
Mineral
Apart from living things, useful materials from the ground have driven the technological development of humans (Stone, Bronze & Iron Ages).
Synthetic
These are man-made materials that do not occur naturally. Using scientific knowledge, we can create materials that have properties that are better or different to those obtained by natural means.
make your own plastic
bioplastics
Separating crude oil using fractional distillation
Why is crude oil important?
Crude oil is separated in a
fractionating column
Temperature
decreases going up
the column
Crude oil is separated into
fractions
using the
different boiling point of different hydrocarbons
.
As it is a
mixture
, the molecules in crude oil are not chemically bonded, meaning it
can be separated
.

Each of the different hydrocarbons has its own physical properties even though it is in a mixture.

These properties are based mainly on
carbon chain length
.
Quick check
I understand that nanotechnology is the use and control of structures that are very small (the same size as some molecules; 1 to 100 nanometres in size).

I understand that nanoparticles can occur naturally (for example in seaspray), by accident (for example as the smallest particulates from combustion of fuels), and by design
Outcomes
Discuss the
advantages
and
disadvantages
of using such materials.
Polymer Circus
Complete a
table with headings

object
,
use
,
properties needed
for use,
materials
it could be made of (natural and man-made).
Describe the
properties
of the materials around the classroom.
Try to think of a
natural material

that could be used instead
e.g. cork for bottle stopper, paper bags etc.
Natural & Synthetic Polymers
Compare the properties of the two types of polymers used for a specific job and discuss what properties of the synthetic polymer make it more suitable for the use.
How would you identify a polymer as
natural
or
synthetic
?
Making polymers
Addition polymerization
Poly
ethene

(sometimes called polythene) is a
polymer
made from

ethene
.
The process used to make polyethene and other polymers is called
addition polymerization
.

This is because many
mono
mers
(
single
ethene
molecules
) are
added together
.
addition polymerization
monomer
polymer
How are plastics made?
Drawing polymers – shorthand formulae
Polymers contain
thousands
of molecules, so how can their structures be easily drawn?
Part of the polymer molecule can be drawn:
A better way
is to show a
shorthand

formula
:
The ‘n’ means that the polymer contains a very large number of the repeating unit shown in the brackets.
What’s the polymer?
What is the shorthand formula for polypropene?
The monomer is :
which can be drawn as:
1. Draw two C atoms that were in the double bond with a
single covalent bond
.
2. Draw the
brackets
and the ‘n’.
4. Add the
atoms that were attached to
each C atom
of the double bond.
3. Add the
links outside the brackets
.
poly
propene
What is the monomer of polyvinylchloride (PVC)?
What’s the monomer?
1. Draw two C atoms joined with a double
covalent bond.
2. Add the atoms attached to each C atom.
3. Draw the brackets and ‘n’.
The equation for the reaction can be drawn as:
All: Know where different materials are obtained from (giving examples).

Most: Understand how some materials are more suited for a purpose than others.

Some: Evaluate the superiority of synthetic materials over natural ones for common functions.
Objectives
Nearly all compounds in crude oil are made from atoms of
hydrogen
and
carbon.
What is a hydrocarbon?

How do the hydrocarbons vary in crude oil?


Explain why the fractional distillation of crude oil is so important.
Some fractions are used to produce
fuels
for vehicles, others are used as raw materials in chemical processes to make new materials such as
polymers
(
plastics
).
It is a thick, sticky, dark-coloured liquid.
Polymers are made from small molecules
. In most synthetic polymers, the small molecules originally come from crude oil.
Why is HDPE slightly denser than LDPE? Suggest an explanation based on the structure and arrangements of molecules.

LDPE starts to soften at the temperature of boiling water. HDPE keeps its strength at 100 Celsius. Suggest some products that would be better made of HDPE rather than LDPE and give your reasons.
Review Learning:
Physical properties
To do this
catalysts
are used. These metal compounds act in similar way to the oxygen in high-pressure process. Old branched-molecule form is called low-density polythene (LDPE) and the
new crystalline form is called high-density polythene (HDPE)
.
In some polymers molecules are jumbled up in a very irregular arrangement. In others
the molecules are arranged in neat lines
; these are called
crystalline polymers
. Increasing crystallinity might make it
stronger and denser
.
Crystalline Polymers
The
sulphur makes cross-links
between the long rubber molecules. The
molecules are locked
into a regular arrangement. This
stops them from slipping
over each other and makes the rubber
less flexible, stronger and harder
. It also gives rubber a
higher melting point
because
more energy is needed for the molecules to separate
and break out of the solid.
Cross-Links
Polythene molecules made from ethene
with a special catalyst

do not have side branches
.
Polythene made under
high pressure will have branches
, which
stop the molecules packing together neatly
.
Branching
To do this they add
plasticisers
(usually an oily liquid with small molecules).

They
sit between the chains
. They
weaken the forces between chains
,

so
less energy is needed to separate them
.
PVC is a polymer, it is used for window frames/gutters. These need to be
durable
and
hard
. But it can be used for clothes, needs to be
softer
and
flexible
.
Plasticisers
People were worried.
Evidence that they were harmful is controversial
and strongly challenged by the plastics industry.
There is
stronger
evidence that the regular use of plastic
food wrap can cut down on food poisons
.
So, what did they do?
This was made from plasticised PVC. The small plasticiser molecules were able to move through the polymer and into food.
Cling film
Charles Goodyear
added sulphur
to natural rubber and made a
stronger
,
more resistant to heat and water
.
Vulcanised Rubber
Physical properties

depend on the chain length

and

shape
of the hydrocarbon
.
Molecules are made of atoms.
Bonds
are
between

atoms
in the molecules and they are
strong
.
Forces

are

between molecules
and they can
vary with chain length and shape
.
This means some hydrocarbons are
separated easily
, some
stay close
, but
slide past each other
,

and others require
lots of energy

to melt/bend/separate the
molecules.
This process is called
vulcanisation
.
He
changed the properties
of the polymer.
I understand that it is possible to produce a wide range of different polymers with properties that make them each suited to a particular use

I understand how the properties of polymers depend on how their molecules are arranged and held together

I can relate the strength of the forces between the molecules in a polymer to the amount of energy needed to separate them from each other, and therefore to the strength, stiffness, hardness and melting point of the solid

I understand how modifications in polymers produce changes to their properties to include modifications such as:
a. increased chain length
b. cross-linking
c. the use of plasticizers
d. increased crystallinity
Outcomes
Objectives
Understand how a wide range of different polymers with different properties are made for particular uses.

Understand how the properties of polymers depend on how their molecules are arranged and held together.

Relate the strength of the forces between the molecules in a polymer to the amount of energy needed to separate them from each other, and therefore to the strength, stiffness, hardness and melting point of the solid.

Understand how polymer properties can be changed using modifications such as:
a. increased chain length
b. cross-linking
c. the use of plasticizers
d. increased crystallinity
propene (C H )
3
6
Nanotechnology
I understand that nanoparticles can be used to modify the properties of materials, and give examples including:
a. the use of silver nanoparticles to give fibres antibacterial properties
b. adding nanoparticles to plastics for sports equipment to make them stronger

I understand that some nanoparticles may have harmful effects on health, and that there is concern that products with nanoparticles are being introduced before these effects have been fully investigated.

I understand that nanoparticles of a material show different properties compared to larger particles of the same material, and that one of the reasons for this is the much larger surface area of the nanoparticles compared to their volume.
Outcomes
A microscope can show details of the individual fibres of a fabric. Silk for example has smooth fibres that slide across each other. Wool fibres have a rough surface that is covered in scales.
Put the following in order of size, starting with the largest:
fibre
,
fabric
,
atom
,
thread
,
molecule
.

Use the words above to
write four sentences that describe the decreasing structures
. The first sentence might be:
Fabrics
are made by weaving together threads
.
One nanometre is one billionth of a metre (1/1000000000)
. The molecules in fibres are big on the nanometre scale. They are very wide (1000 nm). The shape and size of the long-chain molecules in a fibre make the material what it is.
It is difficult to look much further into structure of materials using microscopes of any kind.
Molecules are very, very small
structures.
They are measured in nanometres (nm)
.
Invisible world of Molecules
Starter: can you tell what this is?
Zooming In
These are microscopic features.
When you look at a sheet of material, you can see the weave of the fabric.
Zoom, zoom, zoom!
Review your learning:
Questions
How many chemical elements are there in silk?

Is silk a hydrocarbon? Why?
Attractions betweeen side-by-side protein chains hold silk molecules together as fibres
Objectives
Understand what nanotechnology is and what the nanometre scale involves.

Understand how nanoparticles can occur.
Nanoparticles have
different properties
and therefore have
different effects on plants, animals and the environment
. It may mean that they are
more toxic to people
.

There are concerns on the medical use as they could
damage organs
. At present there are no requirements for health and safety studies for nanoparticles to be different from those for large particles.
Risks
Increases the size of forces:
Ability to walk up walls
Properties
Nano comes from the Greek word nanos, which means dwarf. The particles used are measured in nanometres (nm).

Nanotechnology is the use and control of structures called nanoparticles
.
Each nanometre is a billionth of a metre or 0.000 000 001m
.
Nanotechnology
Nanotechnology
Uses of Nanotechnology
In an Acticoat there is silver nanoparticles.
These can help with killing bacteria.
The tiny nanoparticles of silver dissolve very quickly once they are moistened.
Medicines
Increases the size of the surface area:

The surface-area-to-volume ratio is very large
sunscreen
Question Time!
Apart from anti-bacterial properties, silver has many different uses;
Which properties of silver make it good for making jewellery?
How are the particles of silver in Acticoat different from the silver particles in jewellery?
Why will nanoparticles of silver be more effective in a wound dressing than ordinary silver?
clothing
electronic paper
tennis balls and rackets
self-cleaning windows
Objectives
Understand that nanoparticles of a material show different properties compared to larger particles of the same material.

Understand that nanoparticles can be used to modify the properties of materials, and give examples.

Understand why some nanoparticles may have harmful effects on health.
All:
Some:
Most:
Their qualities have enabled better tools, weapons, medicines and quality of life.
Polymer properties and uses
Hydrogels
Molecules of butane are small with weak forces between them so butane is a _____ at room temperature.
Molecules of paraffin are bigger with slightly stronger forces so paraffin is a ________ at room temperature.
Molecules of candle wax are long with strong forces between them so candle wax is a _______ at room temperature.


Polythene is also a solid at room temperature.
What are the molecules like?
Explaining properties of hydrocarbons
If we zoom in further...
Reflects how much a substance can resist external forces before changing shape.
Natural vs. Synthetic
Wood? OR PVC?
Which is better?
Why?
Which materials occur naturally and which are synthesised (made)?
Use the video and your knowledge to
identify the materials used
for each part of the F1 car and the
useful properties
each material provides.
Why go synthetic?
Stretch your skills by explaining why the property makes the material more useful
Solid Liquid Gas
Magnification x1000
Making & modifying polymers
http://www.teachers-direct.co.uk/resources/quiz-busters/quiz-busters-game.aspx?game_id=22081
Blockbusters
Testing Materials
Describe whether each of the materials is:
hard/soft
flexible/brittle
strong/weak
heavy/light (density)
easy/hard to melt (melting point)
What properties of Chocolate make it :

Suitable
Unsuitable

For making shoes? (make two lists in your book)
Common types of material
Wood
2) List 10 materials used for any object found in houses. Write a sentence to explain why their properties make it useful.
LOW Melting Point
HIGH Density
Honey?
WEAK under compression
Boiled Potato
FLEXIBLE
Very HARD
STRONG under Tension
What physical properties do these materials have?
LOW Density
Lamp Oil?
L3: Crude Oil & Fractional Distillation
Intermolecular Forces
Plastic (polythene)
Light
Flexible
Easily moulded

Properties of materials

Plastic (polystyrene)
Light
Rigid
Good insulation

Properties of materials

Nylon
Light
Tough
Waterproof

Properties of materials

Polyester
Light
Tough
Waterproof

Properties of materials

Unvulcanised rubbers
Low tensile strength
Soft
Flexible

Properties of materials

Vulcanised rubbers
High tensile strength
Hard
Flexible

Properties of materials

Keywords:
boiling, fractions, fuels, lubricants, plastics
Hydrocarbons are separated into similar “lengths” are called “_________” and most of them are used as _____.

Some are used to make materials such as ________. Longer chains have higher _______ points. Hydrocarbons with longer chains are used as __________
Butane
Ethane
Crude oil is a mixture of HYDROCARBONS (compounds made up of carbon and hydrogen). Some examples:
Increasing length
Hydrocarbons and crude oil
Forces between molecules
As we’ve already said, longer molecules have stronger forces of attraction between them.
This tends to lead to
long-chain plastics
being:
Forces
between molecules
affect properties
Copy & Complete
fractions
plastics
boiling
fuels
Weakest force
of attraction
between

molecules
Less energy
needed to break chains apart
Lowest
boiling point
Short chain molecule
Most energy
needed to break chains apart
Higher
boiling point
Highest
High
Low
Lowest
Longer molecules

stronger force
of attraction, leading to
higher boiling points
due to the molecules needing
more energy
to
“pull” them away
from each other.
Longest chain molecule
Strongest force
of attraction
between molecules
Highest
boiling point
More energy
needed to break chains apart
Medium-size chain
Stronger force
of attraction
between molecules
How

does boiling point change with chain length?
WHY?
Stronger

Stiffer

Harder

More difficult to melt (i.e.
higher melting point
)
Butane gas


Paraffin liquid


Candle wax


Polythene
Match the diagrams to the substance names
Practice 6 mark exam question:
HMK - Chemistry
Molecules X and Y are both hydrocarbons. X has the formula C H and Y has the formula C H .




DESCRIBE how you would expect their physical properties to differ and EXPLAIN why they are so different.
(6 marks)
20
3
8
44
Investigations need an aim which should be in the form of a question…
Who can eat the most chocolate?
What is the strongest plastic bag?
What is the fastest car?
Which mascara lengthens lashes the most?
Variables
Data analysis: Planning
Planning an investigation
Who can eat the most chocolate?
What is the strongest plastic bag?
What is the fastest car?
Which mascara lengthens lashes the most?
What would you measure (dependent variable)?
What would you change (independent variable)?
What would you keep the same? (control)
What equipment would you need?
How would you investigate the questions?
What could these be?
What would it look like if you magnified it further?
This is a thread
magnified

Threads are made up of long chains of atoms = POLYMERS!!
Identify VARIABLES

Take into account the PRECISION of your measurements.
To plan an investigation you need to be able to :
The weather forecast said it was only going to be 15o C today…

But my thermometer says that it is 27.1o C!

What is precision?

Dependent variable
What are the properties that could be tested?

Independent variable
What are the polymers that could be tested?

Control variables
What should be kept the same?

Investigation - Variables
The weather forecast said it was only going to be 15o C today…

But my thermometer says that it is 27.1o C!
You will be measuring the strength of natural and synthetic threads
The equipment you will have available is…
ruler
Thread holder
Masses (100g and 10g)

The equipment - PRECISION

What polymer property are we testing?
Fair
2 Mark Exam Question

You will be investigating the strength of either nylon, cotton or polyester.

Draw a results table that you will be able to fill in next lesson

Your investigation

Tennis ball drop 2 (from 2metres)
 



1 Plot these values
2 Which timer readings are outliers, if any?
3 Calculate the mean and the range
4 Why are the values different?
5 Look at the range, are the results repeatable?

C2.4 Reliability
REPEATABLE PROCEDURE – is achieved if the quantity is measured repeatedly
REPEATABLE RESULTS – are if these repeated values are similar to each other 

Tennis ball drop 1 (from 1 metre) 
 




1 Plot these values
 
2 Which timer readings are outliers, if any?

3 Calculate the mean and the range
 
4 Why are the values different

The
shorter
the
chain
length, the
lower
the
boiling point
A substance containing
carbon
and
hydrogen
atoms
only

There are
short chain
molecules that are
lighter
and
thinner
with
lower boiling points
, and
long chain
molecules that are
darker
and
thicker
with
higher boiling points
Fractional distillation allows us to
separate crude oil
into many
useful
materials both for use as
fuel
but also as a
chemical ingredient
for making lots of other materials
Copy this diagram and annotate it with as much information about fractional distillation that you can recall
Oil Alert
Good quality equipment is used to get exact measurement
All other factors are kept the same
Close to the actual value, a precise, reliable “best estimate"
The results are repeated (and are similar to each other)
Accurate
Precise
Repeatable
Collect some results from other groups if you need to.
Conclusion
Work in groups of 2-3
Equipment per group:

100 g masses
G-clamps
Meter rulers
Wire testers x 2
Threads x 3
Calculators
Thread Strength Investigation
Discuss your Top 10 with a partner
What is the world’s strongest material?
Write a brief conclusion explaining which thread is the strongest and what your results tell you about the strength of natural and synthetic fibres .
Work out the mean
average and
the range
for each thread.
Practice Exam Questions
Crude oil is pumped out of the Earth’s crust from wells under the ground and sea.
Formed over
millions of years from dead plants and animals
.
Paraffin liquid
Candle wax
Butane gas
Polythene
Boiling point increases
as the
chain length increases
.
This is because the
forces between
longer molecules
are stronger
.
Therefore, longer molecules require
more (heat) energy to separate
them into gaseous particles
Answer
VERY LONG chains, easily tangled, strong intermolecular forces, but slides with force.
Long chains, closely packed, strong forces between chains
Medium length chains, close together, significant force between chains
Short chains, spread apart, very weak forces between molecules
Complete the table via group discussion
Fuels
Lubricants
Petroleum gas is made of small hydrocarbon molecules,
Meanwhile fuel oil is made up of large/long hydrocarbon molecules.
The longer the hydrocarbon chain, the greater the forces between the molecules.
More heat is needed to boil the longer molecules, giving them a higher boiling point
lubricants
How does POLYMERISATION happen?
Practice questions
Practice questions
(Hint: Identify the part of each polymer that has changed).
Acrylamide
Solid
Liquid
Gas
How are plastics made?
Modifying Polymers
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