C2 End Flashcards
Properties of graphene
Resembles single layer of graphene
- almost transparent
- extremely strong
- conducts electricity
Fullerenes
Large family of carbon allotropes, molecules shaped like tubes/balls
- nanotube
- buckyball
Nanotube
sheet of graphene rolled into tube
- strong
- used to reinforce some sports equipment
Buckyball
- sheet of graphene closed to make hollow ball
- used as lubricants, molecules act as tiny ball bearings
- used to deliver medical drugs directly to cells (small size = pass through cell membranes)
What happens when substances melt/boil
Forces of attraction between particles are overcome (some/all bonds between particles break)
Why do some substances have higher melting/boiling points
Stronger bonds & more bonds = more energy transferred from surroundings to break them
What happens when chemical bonds form
Stored chemical energy transferred to surroundings, usually by heating
What are the state of substances at room temp
- metals: solid
- ionic compounds: solid
- giant covalent substances: solid
- simple molecular substances: liquid/gas/solid
Relative strength of bonds in substances (strong = high boiling point)
- metals: strong
- ionic compounds: strong
- giant covalent structure: strong
- simple molecule: weak
nanoparticle
Particle between 1-100nm
Consists of just a few hundred atoms
Objects in order of size (smallest-largest)
Helium atom Methane molecule Nanoparticle Red blood cell Human hair
N’a nome très
1nm = (1 x 10)-9 m
Nano-particulate
Material made from nanoparticles
- grains
- lumps
- sheets
What does the very small size of nanoparticulates mean
& makes them useful for:
Have different properties to same substance in bulk
- new paints
- new cosmetics
- medicines
- sunscreens
What does the very large surface area to volume ratio allow it to be used for
- new catalysts to speed up industrial chemical reactions
- self-cleaning windows, ovens, clothes
How can nanoparticles enter the body
May be
- breathed in
- absorbed by skin
- passed into cells
Risks with nanoparticles
- are so tiny they can enter body easily
- take long time to break down once released into environment
- toxic substances may stick to their large surfaces
- scientists think may be harmful to health & environment, difficult to predict
Brittle substances
Cracks/breaks when external force applied
Malleable substances
Change shape without cracking/breaking when external force applied
What does a material being brittle or malleable depend on
How easily particles in substance can change their position in the lattice structure
Why are metals malleable
When large enough external force applied, layers of metal ions slide over one another
as they are held in a lattice by forces that attract them to a sea of delocalised electrons
Overall no bonds are broken as electrons free to move
Why are giant covalent structures and ionic compounds brittle
Both contain many atoms held together in a giant lattice by strong bonds (covalent/ionic)
If large enough force applied, many bonds break at once & substance breaks
Why are some simple/polymer molecules brittle
Iodine crystals, polymers
Weak intermolecular forces easily broken
If substances are in solid state & molecules arranged in a lattice
Why are some simple/polymer molecules malleable/soft/flexible (wax)
If molecules not arranged in lattice
When can a substance conduct electricity
If it has charged particles that are free to move
What state can metals conduct electricity in? Why?
In solid/liquid state
Delocalised electrons free to move through lattice
Can simple molecules / polymers / substances with giant covalent structure conduct electricity
No because no delocalised electrons
Can ionic compounds conduct electricity
When molten/in solution
Contain oppositely charged ions free to move
Not when solid
Oppositely charged ions not free to move around
