C3

Question 1

if there is a higher melting and boiling point what does that mean

Answer 1

there are stronger forces operating between particles

Question 2

what is sublimation

Answer 2

when a solid heats up and changes directing into a gas without going through the liquid phase

Question 3

what is a compound

Answer 3

2 or more elements chemically combined

Question 4

what is the difference between covalent and ionic bonding

Answer 4

covalent is sharing electrons and ionic is transferring

Question 5

when are ionic compounds formed

Answer 5

when metals and non metals react

Question 6

how is a giant lattice/structure formed

Answer 6

when ionic bonds between the charged particles result in an arrangement of ions

Question 7

why do ionic compounds have high melting and boiling points

Answer 7

because it takes a lot of energy to break up a giant lattice as there are many strong ionic bonds to break

Question 8

when can ionic compounds carry electrical charge

Answer 8

when they melt and become liquid and their ions are free to move anywhere in the liquid

or when they are dissolved in water

Question 9

how does dissolving an ionic compound in water allow it to be a conductor

Answer 9

water molecules separate the ions from the lattice so they are free to move around

Question 10

what is covalent bonding

Answer 10

when non metals react together, their atoms share pairs of electrons to form molecules

Question 11

what are macromolecules

Answer 11

giant covalent structures where huge numbers of atoms are held together by a network of covalent bonds

Question 12

what is the giant covalent structure of diamond

Answer 12

each carbon atom forms 4 bonds with its neighbours resulting in a rigid giant covalent lattice

Question 13

what bonds are broken when a substance melts or boils

Answer 13

the weak intermolecular forces are broken/ overcome. the covalent bonds are not broken

Question 14

what is the hardest known natural substance and what is its boiling point

Answer 14

diamond and 4827c

Question 15

how can artificial diamonds be formed

Answer 15

by heating pure carbon under huge heat and pressure

Question 16

what are properties of substances with giant covalent structures

Answer 16

high melting and boiling points

insoluble in water

hard and don’t conduct electricity (except granite)

Question 17

what is the difference between diamond and graphite

Answer 17

in diamond the carbon atoms are bonded to 4 other carbon atoms but in graphite it’s only 3 bonds

Question 18

why do layers in giant structures slide over each other easily

Answer 18

there are no covalent bonds between layers only weak intermolecular forces which is why graphite is soft and slippery

Question 19

why does graphite conduct electricity

Answer 19

because it only has 3 carbon bonds so it has delocalised electrons which move freely along the layers

Question 20

why do larger molecules have higher melting and boiling points

Answer 20

because the intermolecular forces increase with the size of the molecules

Question 21

what are polymers

Answer 21

very long chain molecules with stronger intermolecular forces

Question 22

what are allotropes

Answer 22

different forms of the same element in the same state e.g diamond and graphite are allotropes of carbon

Question 23

what are fullerenes

Answer 23

hollow shaped molecules of carbon

Question 24

what are carbon nanotubes

Answer 24

cylindrical fullerenes (thin cylinders with lengths greater than diameter)

Question 25

what are useful properties of carbon nanotubes

Answer 25

high tensile strength (use in reinforcing composite materials eg those used in tennis rackets)

high electrical and thermal conductivity as their bonding gives them delocalised electrons

Question 26

what are uses of fullerenes

Answer 26

their cage like structure can be used to deliver drugs or radioactive atoms into the body to treat cancer

can be used as lubricants and catalysts because of large SA:V ratio (nanoparticles)

Question 27

what is graphene

Answer 27

a layer of interlocking hexagonal rings of carbon atoms just one atom thick

Question 28

how can you get graphene from graphite

Answer 28

stick a piece of tape over graphite, pull it off and look under a powerful electron microscope as one layer of graphite is graphene

Question 29

what are the properties of graphene

Answer 29

better conductor of heat and electricity than graphite

low density

most reactive form of carbon

strong considering mass

Question 30

what are the future uses of graphene

Answer 30

could be used to make quicker and more powerful computer chips

flexible electronic displays e.g. watching a film on your sleeve

Question 31

what is the structure of metals

Answer 31

made of atoms in a regular pattern built layer upon layer

Question 32

how do you grow silver crystals in a test tube

Answer 32

place a copper wire in a boiling test tube containing silver nitrate solution and silver crystals will appear on wire

Question 33

what do the outer electrons of metals do in a giant structure

Answer 33

they form a sea of delocalised electrons surrounding the positive metal ions

Question 34

what is one nanometer equal to

Answer 34

1x10-9m or 1 billionth of a metre

a human hair is 80,000 nm wide

Question 35

what is a micrometer equal to

Answer 35

1x10-6m

e.g. pollutants, pollen, dust

Question 36

in nanoparticles what does a higher SA:V ratio indicate

Answer 36

the higher the ratio the greater proportion of atoms exposed at the surface of the particles