5: Exam Questions

Question 1

How does a metal (in terms of internal structure) show plastic behaviour?

Answer 1

1) atomic planes, 2) can slip

Question 2

How does a long chain polymer (in terms of internal structure) show plastic behaviour?

Answer 2

1) cross-linked chains, 2) chains slip

Question 3

Describe metallic bonding, and the elastic behaviour (talk about bonding)

Answer 3

1) metal atoms form +ve ions, 2) they are close packed in planes, 3) when given a small displacement restorative force so ions return when force is removed

Question 4

Why are metals good electrical conductors?

Answer 4

many / high density of ;
free / delocalised;
electrons which act as movement of charge carriers / transfer (negative) charge

Question 5

Explain the term polycrystalline relating to a metal

Answer 5

1) many small crystals 2) whose close packed planes have different alignments / grain boundaries

Question 6

Steel alloy containing carbon is less ductile than iron. Why? Explain the term ductile.

Answer 6

1) (ductile): can be drawn into a wire ;2+3) any 2 further points: in metal dislocation identified ; free to move through a regular crystal ; slip occurs easily / atomic planes slide over each other ; in alloy impurity atom pins dislocation ; slip more difficult so less ductile

Question 7

Steel has metallic bonding, diamond has covalent. Use this to describe the difference in hardness

Answer 7

1+2) any 2 points: metals have free electrons / delocalised electrons / non-directional bonds ; which hold + ions in lattice / + ions can slip / dislocate ; 3+4) any 2 points: in diamond bound / localised electrons ; form strong ; directional bonds ; giant lattice hence hard to displace / move atoms