C2 End

Question 1

Properties of graphene

Answer 1

Resembles single layer of graphene

• almost transparent
• extremely strong
• conducts electricity

Question 2

Fullerenes

Answer 2

Large family of carbon allotropes, molecules shaped like tubes/balls

• nanotube
• buckyball

Question 3

Nanotube

Answer 3

sheet of graphene rolled into tube

• strong
• used to reinforce some sports equipment

Question 4

Buckyball

Answer 4

• 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)

Question 5

What happens when substances melt/boil

Answer 5

Forces of attraction between particles are overcome (some/all bonds between particles break)

Question 6

Why do some substances have higher melting/boiling points

Answer 6

Stronger bonds & more bonds = more energy transferred from surroundings to break them

Question 7

What happens when chemical bonds form

Answer 7

Stored chemical energy transferred to surroundings, usually by heating

Question 8

What are the state of substances at room temp

Answer 8

• metals: solid
• ionic compounds: solid
• giant covalent substances: solid
• simple molecular substances: liquid/gas/solid

Question 9

Relative strength of bonds in substances (strong = high boiling point)

Answer 9

• metals: strong
• ionic compounds: strong
• giant covalent structure: strong
• simple molecule: weak

Question 10

nanoparticle

Answer 10

Particle between 1-100nm

Consists of just a few hundred atoms

Question 11

Objects in order of size (smallest-largest)

Answer 11

Helium atom
Methane molecule 
Nanoparticle
Red blood cell
Human hair

Question 12

N’a nome très

Answer 12

1nm = (1 x 10)-9 m

Question 13

Nano-particulate

Answer 13

Material made from nanoparticles

• grains
• lumps
• sheets

Question 14

What does the very small size of nanoparticulates mean

& makes them useful for:

Answer 14

Have different properties to same substance in bulk

• new paints
• new cosmetics
• medicines
• sunscreens

Question 15

What does the very large surface area to volume ratio allow it to be used for

Answer 15

• new catalysts to speed up industrial chemical reactions

- self-cleaning windows, ovens, clothes

Question 16

How can nanoparticles enter the body

Answer 16

May be

• breathed in
• absorbed by skin
• passed into cells

Question 17

Risks with nanoparticles

Answer 17

• 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

Question 18

Brittle substances

Answer 18

Cracks/breaks when external force applied

Question 19

Malleable substances

Answer 19

Change shape without cracking/breaking when external force applied

Question 20

What does a material being brittle or malleable depend on

Answer 20

How easily particles in substance can change their position in the lattice structure

Question 21

Why are metals malleable

Answer 21

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

Question 22

Why are giant covalent structures and ionic compounds brittle

Answer 22

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

Question 23

Why are some simple/polymer molecules brittle

Iodine crystals, polymers

Answer 23

Weak intermolecular forces easily broken

If substances are in solid state & molecules arranged in a lattice

Question 24

Why are some simple/polymer molecules malleable/soft/flexible (wax)

Answer 24

If molecules not arranged in lattice

Question 25

When can a substance conduct electricity

Answer 25

If it has charged particles that are free to move

Question 26

What state can metals conduct electricity in? Why?

Answer 26

In solid/liquid state

Delocalised electrons free to move through lattice

Question 27

Can simple molecules / polymers / substances with giant covalent structure conduct electricity

Answer 27

No because no delocalised electrons

Question 28

Can ionic compounds conduct electricity

Answer 28

When molten/in solution
Contain oppositely charged ions free to move

Not when solid
Oppositely charged ions not free to move around