Polymers

• Starter: What do the following substances have in common? How are they different?–Plastic kettle–Plastic soldiers–A light plastic bottle–A heavy plastic pipe

• Extension: What is a polymer? How are they made?

Similarities Differences

Polymerisation recap

• Watch the demonstration using atomscope to recap polymerisation

Learning outcomes

• State that the properties of polymers depend on what they are made from and the conditions under which they are made.

• Describe how thermosoftening plastics are different from thermohardening.

HT Only: Explain the properties of thermosoftening polymers in terms of intermolecular forces.

Key words

• Thermosetting • Thermosoftening• Cross linking• Intermolecular forces• Low density poly(ethene)LDPE• High density poly(ethene)HDPE

What causes this difference?

Plastic kettle Melted plastic army men

• _______________ polymers melt when heated.

• _____________ polymers do not melt when they are heated.

Copy and complete the sentences below with either the words

‘thermosoftening’ or ‘thermosetting’

Thermosoftening

Thermosetting

So, are these plastics thermosoftening or thermosetting?

Plastic kettle Melted plastic army men

Thermosoftening Thermosetting

• __________________ polymers consist of individual, tangled polymer chains.

• _______________ polymers consist of polymer chains with cross-links between them so that they do not melt when they are heated.

Copy and complete the sentences below with either the words

‘thermosoftening’ or ‘thermosetting’

Thermosoftening

Thermosetting

Thermosoftening Thermosetting

So, are these plastics thermosoftening or thermosetting?

Thermoplastics in art and technology

Watch this video and listen to see what kind of plastic the artist uses:

Design & Technology - Thermoplastics - BBC Learninghttp://www.youtube.com/watch?v=VDHWNNRXiXo

Why do you think she uses this kind of plastic?

How are these different?

Why might this be?

• The bottles on the left are made of Low Density Polyethelene (LDPE), which is lighter but less strong.

• The pipe on the right is made of High Density Polyethelene (HDPE), which is heavier and stronger.

Diagrams from:http://www.steinwall.com/ART-polyethylene.html

Task

Draw labelled diagrams showing:

1. thermosoftening plastics

2. thermosetting plastics

3. LDPE (low density polyethene)

4. HDPE (high density polyethene)

GCSE Bitesize diagrams can be found on:http://www.bbc.co.uk/schools/gcsebitesize/science/add_aqa/bonding/structure_propertiesrev3.shtml