9780008160869

Page 100

Bonding, Structure and Properties of Matter

Metals and Special Materials You must be able to: Recall the structure and uses of graphene and fullerenes Understand the bonding within and between polymer molecules Describe when and why metallic bonding occurs Explain the properties of pure metals and alloys.

• • • •

Graphene • • • •

Graphene is a form of carbon. It is a single layer of graphite (see page 99). The atoms are arranged in a hexagonal structure, just one atom thick. Graphene has some special properties. It is very strong, a good thermal and electrical conductor and nearly transparent.

Fullerenes • • •

• •

Carbon can also form molecules known as fullerenes, which contain different numbers of carbon atoms. Fullerene molecules have hollow shapes, including tubes, balls and cages. The first fullerene to be discovered was buckminsterfullerene, C60: – It consists of 60 carbon atoms. – The atoms are joined together in a series of hexagons and pentagons. – It is the most symmetrical and, therefore, most stable fullerene. Carbon nanotubes are cylindrical fullerenes with some very useful properties. Fullerenes can be used: – to deliver drugs in the body – in lubricants – as catalysts – for reinforcing materials, e.g. the frames of tennis rackets, so that they are strong but still lightweight.

Structure of Buckminsterfullerene

Carbon atom

Strong covalent bond

Structure of a Nanotube

Strong covalent bond

Carbon atom

Polymers • • • • • •

100

Polymers consist of very large molecules. Plastics are synthetic (man-made) polymers. The atoms within the polymer molecules are held together by strong covalent bonds. The intermolecular forces between the large polymer molecules are also quite strong. This means that polymers are solid at room temperature. Poly(ethene), commonly known as polythene, is produced when lots of ethene molecules are joined together in an addition polymerisation reaction. It is cheap and strong and is used to make plastic bottles and bags.

Addition Polymerisation

H n

H C

H

C H

H

H

C

C

H

H

n

GCSE Combined Science Revision Guide

227841 AQA Higher Tier Combined Science All-in-One_P088_105.indd 100

6/29/16 11:17 AM


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