explaining physical properties of substances

Question 1

Sodium chloride, NaCl

mp & bp

Answer 1

giant ionic lattice structure
high melting point:
- large amount of energy required
- to overcome strong electrostatic attraction between Na+ cations and Cl- anions

smaller size = stronger EA

larger charge = stronger EA

Question 2

water, H2O

mp & bp

Answer 2

simple covalent structure
low melting point
- small amount of energy required
- to overcome the weak intermolecular forces of attraction between H2O molecules

larger Mr/ molecular size = stronger IMF

Question 3

Diamond
Graphite
(C)

mp & bp

Answer 3

giant covalent structure
high melting point
- large amount of energy required
- to overcome the strong covalent bonds of attraction between C atoms

Question 4

polyethene

mp & bp

Answer 4

macromolecules
low melting point
- small amount of energy required
- to overcome weak intermolecular forces of attraction between polyethene molecules

Question 5

polymers

mp & bp

Answer 5

melt over a range of temperatures because made up of molecules of a range of sizes

most are solid at room temp due to large size of molecules

Question 6

copper (Cu)

mp & bp

Answer 6

giant metallic lattice structure
high melting point
- large amount of energy required
- to overcome strong electrostatic attraction between Cu2+ cations and sea of delocalised electrons

Question 7

sodium chloride (NaCl)

hardness

Answer 7

giant ionic lattice structure

hard:
- large amount of energy required to overcome strong electrostatic attraction between Na+ cations and Cl- anions

brittle:
- when sufficient force is applied, layers of regularly arranged ions can slide
- bringing ions of like charges next to each other
- causing them to repel
- ionic lattice shatters

Question 8

diamond (C)

hardness

Answer 8

giant covalent structure
hard:
- large amt of energy required to overcome strong covalent bonds between C atoms

Question 9

graphite (C)

hardness

Answer 9

giant covalent structure
soft & slippery:
- small amt of energy required to overcome weak intermolecular forces of attraction between layers of C atoms
- allowing layers to slide over each other easily

Question 10

polyethene

hardness

Answer 10

macromolecules

vary greatly in hardness & flexibility because they exist in so many different combinations of atoms

Question 11

copper (Cu)

hardness

Answer 11

giant metallic lattice structure

malleable & ductile because non-directional nature of metallic bonds allow layers of regularly arranged Cu2+ cations to slide over one another without breaking the strong metallic bonds

Question 12

sodium chloride (NaCl)

electrical conductivity

Answer 12

giant ionic lattice structure

in solid state: ions held in fixed positions by strong electrostatic attraction between Na+ cations and Cl- anions. Hence no mobile ions to conduct electricity

in molten/aq states: electrostatic attraction between Na+ cations and Cl- anions is overcome. Hence ions are mobile and can conduct electricity.

Question 13

water (H2O)

electrical conductivity

Answer 13

simple covalent structure

exists as uncharged molecules, so no mobile charge carriers present to conduct electricity

Question 13

diamond
graphite
(C)

electrical conductivity

Answer 13

giant covalent structure
all 4 valence electrons of each C atom involved in covalent bonding, hence no mobile charge carriers and cannot conduct electricity

each C atom uses 3 valence electrons in covalent bonding, 4th one is delocalised -> move freely along layers to conduct electricity

Question 14

polyethene

electrical conductivity

Answer 14

macromolecule

exists as uncharged molecules, no mobile charge carriers present to conduct electricity

Question 15

copper (Cu)

electrical conductivity

Answer 15

giant metallic lattice structure

delocalised electrons move freely through metallic structure to conduct electricity