C2.3
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What are allotropes
Allotropes are different forms of an element in the same state but with different atomic arrangements
An example of allotropes
Diamond and graphite
What causes the differences in allotropes
Structure and bonding
What is graphene
A single layer of graphite
What is a nanotube
A sheet of graphene rolled into a tube
what is a buckyball
A ball of carbon atoms that are small and can pass through cell membranes.
What happens when a substance melts of boils
Forces between its particles are broken
Why do some substances have a high melting and boiling point
They have a high melting point as they have many strong bonds
How many bonds are broken from solid -> liquid and liquid -> gas
Some bonds break when solid -> liquid All remaining bonds break when liquid -> gas
What happens when a substance condenses or freezes
Bonds form
What determines whether a substance will be brittle or malleable
How easily particles in th substance can change positions in the lattice
are metals malleable or brittle
Metals are malleable even though there are strong metallic bonds. This is because metal ions slide over each other but because the delocalised electrons are free to move no bonds are broken overall.
are giant covalent structures and ionic structures malleable or brittle
Covalent structures contain lots of atoms held together in a giant lattice by strong covalent bonds. If a large force is applied many covalent bonds break at once and the substance breaks. This is the same as ionic substances
are polymers malleable or brittle
Polymers are attracted to each other by weak intermolecular forces which are easily broken. If the substance is in a lattice they may be brittle.
Why do some substances conduct electricity
Some substances conduct electricity if it has free to move charged particles metals conduct in solid and liquid state as they have delocalised electrons. Simple molecules and polymers can’t.
Why can ionic compounds conduct electricity when dissolved
Because their ions are free to move.
What is a nanoparticle
A nanoparticles is a particle between 1nM and 100nM across.
How much is 1nM in m
1 x 10 to the -9m
Why do nanoparticles have different properties
They have different properties because they have a very large SA:VOL ratio
Uses of nanoparticles
.New paints .New cosmetics/medicines (sunscreens) .New catalysts speeding up chemical reactions .Self cleaning items.
Risks of nanoparticles
So small that they can be breathed in, absorbed by skin or pass into cells. They may take long times to break down once released into the environment and toxic substances may stick to their surfaces.