C2.3 Properties Of Materials
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What are allotropes
Different forms of elements in the same state but different atomic arrangements
Give 2 examples of allotropes of carbon
Diamond and graphite
Give 2 differences between Diamond and Graphite
Diamond is transparent and very hard Graphite is Grey-Black and soft
Describe the structure of diamond
Layers of carbon atoms held together by strong covalent bonds to form a lattice/regular structure
Describe the structure of graphite
Layers of Carbon atoms held together by strong covalent bonds to form a lattice/regular structure. Able to conduct electricity due to the delocalised electrons being able to flow around freely
What is graphene?
A carbon allotrope that resembles a single layer of graphite.
Describe graphene
Almost transparent Extremely strong Conducts electricity
What do fullerenes form?
A large family of carbon allotropes The molecules are shaped like tubes or balls
What does a nanotube resemble?
a sheet of graphene rolled into a tube
What are nanotubes used for?
They are strong and used to reinforce some sports equipment.
What does a buckyball resemble?
a sheet of graphene closed to make a hollow ball. carbon atomsmay be in pentagons as well as hexagons.
Uses of Buckyballs
Lubricants, with molecules acting like tiny ball bearings
Which 3 types of substance are usually solid at RT?
Metals Ionic compounds Giant Covalent
Which type of substance is NOT solid at RT?
-Simple molecular substances -usually in liquid or gas state at RT or -solid but easily melted
What is sublimation?
When a solid becomes a gas straight away without becoming a liquid
Why are some substance brittle? - GCS
• Giant Covalent structures contain many atoms held together in a lattice by strong covalent bonds. • If a large enough force is applied, many covalent bonds break at once
Why are some substances brittle? - Ionic compounds
Oppositely charged ions are held together in a lattice by strong ionic bonds. If large enough force is applied, many ionic bonds break at once
Which 2 types of substances are brittle?
• Ionic compounds - Giant covalent structures
Why do metals conduct electricity?
their delocalised electrons are free to move throughout the lattice
Why don’t simple molecules or giant covalent structures conduct electricity
they do not have any delocalised electrons
When do ionic compounds conduct electricity? Why?
In molten or in solution the ions are free to move in the liquid state or when dissolved in a solvent
What is a metalloid
An element that has properties for both metals and non-metals.
What is a nanoparticle
• A particle between 1 nm and 100 nm across and consists of just a few hundred atoms
what is a nanoparticulate?
a material made from nanoparticles