T2 bonding, structure and the properties of matter

Question 1

what is ionic bonding

Answer 1

electrostatic attraction between positive and negative ions

relatively strong attraction

Question 2

how are ionic compounds held together

Answer 2

in a giant lattice

regular structure that extends in all directions in a substance

electrostatic attraction between positive and negative ions holds the structure together

Question 3

state properties of ionic substances

Answer 3

high melting and boiling points (strong electrostatic forces between oppositely charged ions)

don’t conduct electricity when solid (ions in fixed positions)

conduct when molten or dissolved in water - ions are free to move

Question 4

give 5 examples of positive and negative ions

what is important when working out a formula of an ionic compound

Answer 4

P: Na+ Mg2+ Al3+ Ca2+ Rb+
N: Cl- Br- SO2-4 No-3 OH-

ionic compounds are electrically neutral

Question 5

how are ionic compounds formed?

Answer 5

reaction of a metal with a non-metal

electron transfer occurs - metal gives away its outer shell electrons to non-metal

Question 6

what is a covalent bond

Answer 6

shared pair of electrons between 2 atoms

Question 7

describe the structure and properties of simple molecular covalent substances

Answer 7

don’t conduct electricity (no ions)
small molecules
weak intermolecular forces
low melting and boiling points

Question 8

how do intermolecular forces change as the mass/size of the molecule increases

Answer 8

increase

causes melting/boiling points to increase as well (more energy needed to overcome these forces)

Question 9

what are polymers? What are thermosoftening polymers?

Answer 9

very large molecules with atoms linked by covalent bonds

special type of polymers, melt/soften when heated, no bonds between polymer chains. Strong intermolecular forces ensure that the structure is solid at room temperature, forces are overcome with heating - polymer melts

Question 10

what are giant covalent substances

give examples

Answer 10

solids, atoms covalently bonded together in a giant lattice
high melting/boiling points - strong covalent bonds
mostly don’t conduct electricity
diamond, graphite, silicon dioxide

Question 11

name the allotropes of carbon

Answer 11

diamond
fullerenes
graphite
nanotubes
graphene

Question 12

describe and explain diamond

Answer 12

four, strong covalent bonds for each carbon atom
very hard, strong bonds
very high melting point
doesn’t conduct

Question 13

describe and explain graphite

Answer 13

three covalent bonds for each carbon atom
layers of hexagonal rings
high melting points
layers free to slide as weak intermolecular forces between layers,
soft, can be used as lubricant
conduct thermal and electricity due to one delocalised electron per each carbon atom

Question 14

describe and explain fullerenes

Answer 14

hollow shaped molecules
based on hexagonal rings but may have 5/7 carbon rings
C60 has spherical shape, simple molecular structure (buckminsterfullerene)

Question 15

describe and explain nanotubes

Answer 15

cylindrical fullerene with length to diameter ratio
high tensile strength (strong bonds)
conductivity (deloc electrons)

Question 16

describe and explain graphene

Answer 16

single layer of graphite

Question 17

what is metallic bonding

Answer 17

forces of attraction between delocalised electrons and nuclei of metal ions

Question 18

describe properties of metals

Answer 18

high melting/boiling points (strong forces of attraction)

good conductors of heat and electricity (delocalised electrons)

malleable, soft (layers of atoms can slide over each other whilst maintaining the attraction forces)

Question 19

what are alloys

why are they harder than pure metals

Answer 19

mixtures of metal with other elements, usually metals

different sizes of atoms distorts the layers so they can’t slide over each other, making them harder than pure metals

Question 20

describe the properties of simple covalent structures

Answer 20

low boiling and melting points due to weak intermolecular forces between molecules

poor conductivity when solid as no ions to conduct

poor conductivity when molten as no ions

mostly gases and liquids

Question 21

describe the properties of ionic structures

Answer 21

high melting/boiling points due to giant lattice of ions with strong forces between oppositely charged ions

poor conductivity when solid as ions can’t move

good conductivity when molten as ions are free to move

crystalline solids

Question 22

describe the properties of giant covalent structures

Answer 22

high boiling/melting points due to many strong covalent bonds between atoms

poor conductivity when solid in diamond and sand as electrons can’t move
good in graphite as free delocalised electrons between layers can move

poor conductivity when molten

generally solids

Question 23

describe the properties of metallic structures

Answer 23

high melting/boiling points as strong electrostatic forces between positive ions and delocalised electrons

good conductivity when solid as delocalised electrons are free to move through the structure

good conductivity when molten

generally shiny metal solids

Question 24

what are the limitations of the simple model

Answer 24

shows particles as spheres

doesn’t take into account different sizes of particles

no forces are shown

spheres are shown as solid

Question 25

what does the amount of energy needed to change state from solid to liquid or liquid to gas depend on

Answer 25

strength of the forces between the particles of the substance

nature of the particles involved depends on the type of bonding and the structure of the substance

the stronger the forces between the particles, the higher the melting/boiling point of the substance

Question 26

a pure substance will melt or boil at…

Answer 26

a fixed temperature

a mixture will melt over a range of temperatures

Question 27

3 states of matter

Answer 27

solid, liquid and gas

Question 28

what is nanoscience

Answer 28

science that studies particles that are 1-100nm in size

Question 29

state the uses of nanoparticles

Answer 29

medicine (drug delivery systems)
electronics 
deodorants
sun creams (better skin coverage and more effective protection against cell damage)

Question 30

what are fine and coarse particles

Answer 30

fine particles (soot) 100-2500 nm diameter
coarse particles (dust) 2500-10^5 nm diameter

Question 31

why do nanoparticles have different properties to those for the same materials in bulk

Answer 31

high surface area to volume ratio