Grade 9 Science Related Reading/Chemistry
Grade 9 Chemistry
9M.4: Polymers and Materials
Polymers
Task 1 - Pre- Reading Activity
A world of plastic
How many different uses of plastic can you spot?
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Grade 9 Science Related Reading/Chemistry
Task 2 – Reading Activity
What are polymers?
Polymers are very large molecules made when hundreds of
monomers join together to form long chains.
The word ‘polymer’ comes from the Greek words poly (meaning ‘many’)and
meros (meaning ‘parts’). The monomers in a polymer are joined
How the monomers in a
polymerare joined
together?
_____________________
_____________________
_____________________
together by covalent bonds between atoms. Many polymers are formed
from alkenes, which are a family of hydrocarbon molecules with the general
formula CnH2n. Many polymers are formed from alkenes, which are a family
of hydrocarbon molecules with the general formula CnH2n. The simplest alkene
is ethene (C2H4). The second simplest alkene is propene (C3H6). Polyethene
(sometimes called polythene) is a polymer made from ethene. The process by
which polyethene and other polymers is made is called addition polymerization.
This is because many monomers (ethene molecules) are added together.
Write the name of two
simple alkenes.
_____________________
_____________________
_____________________
What is Plastic?
Plastics are synthetic polymers that can be shaped by heat or pressure.
properties of plastics
Plastics are all different, but they show a few general properties:
 they do not conduct electricity and are poor conductors of heat
 they are unreactive – most are not affected by water or air, and many are not affected by chemicals
Their unreactivity makes plastics durable and able to safely contain and protect many substances.
However, it also means that they persist in the environment for a long time.
The properties of a plastics depend greatly on how the polymer chains are arranged:
 branching chains make plastics light, soft and easy to melt
(e.g. low-density polyethene) They are called thermo softening
plastics. They have weak intermolecular forces –
these let the chains slide past each other
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Grade 9 Science Related Reading/Chemistry
 lined-up chains make plastics dense, rigid and harder to melt
(e.g. high-density polyethene). . They are called thermosetting
plastics (or ‘thermosets’). They have strong intermolecular forces
(cross-links) –these hold the chains firmly in place
Turning plants into plastic
A team of scientists from a Dutch university has discovered a way of
turning gases made from plant matter into the building blocks of
common plastics.
They used a new kind of iron catalyst made from nanoparticles to
produce the alkenes ethene and propene from biogas (a gas made
from plants). These hydrocarbons can be used to make the polymer
chains that form plastics.
Alkenes are usually derived from crude oil, which is a non-renewable
resource. However, this new method means that plastics with the
same chemical structure, and therefore properties as traditional plastics,
can be produced using biomass, a renewable resource.
Natural polymers, such as starch found in potatoes and corn, can also be
used to make bioplastics. However, these have only limited use as they
are not as strong and durable as petro plastics.
However, some people say that using biomass in this way is not as environmentally friendly as it
sounds. Growing the plants takes up valuable space that could be used to grow crops to feed
people. Also, forests might be cut down to make room to grow the plants. The research, which is
published in the journal Science, is still at an early stage. It now requires larger-scale testing, so it
will not reach the market for several years.
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Grade 9 Science Related Reading/Chemistry
Task 3 – Post Reading Activity
Q1:Write the monomer of the polymers in the flow chart below
Q2: Use the text “Turning Plants into Plastic “ as reference and answer the following questions
1.By which process is ethene converted into a polymer?
______________________________________________________________________________
2. Write an equation to show this and name the polymer formed.
______________________________________________________________________________
3. Are these new plastics biodegradable? Explain your answer.
______________________________________________________________________________
4. Are they sustainable? Explain your answer.
______________________________________________________________________________
5. What are the benefits and drawbacks of these new types of bioplastics made from biogas?
______________________________________________________________________________
6. What are the benefits and drawbacks of bioplastics made from starch?
______________________________________________________________________________
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Grade 9 Science Related Reading/Chemistry
Q3: Read the words in the box. Read the sentences. Fill in each blank with the word or phrase that
best completes the sentence.
Low
monomers
thermosets
high
polymers
thermoplastic
1. Plastics are synthetic _____________that can be made into any kind of shape.
2. Polymers are made when lots of _________________ join together.
3. Polymers containing cross links are tough, rigid and have a _________ melting
point.
4. Polymers without cross links are soft , stretchy and have a __________ melting
point.
5. ____________ are plastics that can be moulded and shaped after they have made.
6. ____________ are plastics that must be moulded and shaped when they are being
made.
Q4: Sort the list of materials below into Synthetic and natural polymers.
Starch,
protein ,
polyethene
polyester
, rubber ,
Natural Polymers
DNA,
kevlar,
nylon,
silk ,
polystyrene,
Synthetic Polymers
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