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Leaving Cert Engineering: Crystal structure & solidification

How often Crystal structure & solidification comes up on the Engineering papers, every year it was asked, and questions to try.

HL Asked on 9 of the last 9 Higher Level papers, most recently in 2025. banker

June 2028 is the first exam on the new Engineering course. These come from the 2016–2025 papers, so read them as a guide.

Crystal structure & solidification, Higher Level(7 marks)

Quick ones on Crystal structure & solidification.

(a)Crystal lattice of iron at room temperature (α-iron)?
  1. Face-centred cubic (FCC)
  2. Body-centred cubic (BCC)
  3. Close-packed hexagonal (CPH)
(b)Why are FCC metals such as copper and aluminium more ductile than BCC metals?
  1. Covalent bonds between their atoms let them stretch
  2. Fewer atoms per unit cell let the layers separate
  3. More close-packed slip planes let dislocations move
(c)The ability of an element to exist in more than one crystal structure is called?
  1. Allotropy
  2. Recrystallisation
  3. Solid solution
Show the answers

(a) Body-centred cubic (BCC)

(b) More close-packed slip planes let dislocations move

(c) Allotropy

Your turn: Higher Level questions on Crystal structure & solidification.

Higher Level

Asked on 9 of the last 9 Higher Level papers, most recently in 2025. banker

Every paper, year by year

YearWhere it came up
2025Q5
2024Q5
2023Q1(e), Q5
2022Q1(b), Q1(h), Q5
2021Q5
2019Q4
2018Q4
2017Q4
2016Q4

Links open the State Examinations Commission’s paper for that year.

More Crystal structure & solidification questions

Crystal structure & solidification, 2 marks

Glass and many plastics are amorphous. This means?

  1. Their atoms form a regular cubic lattice
  2. Each piece is one single large crystal
  3. Their particles have no regular long-range order
Show the answer

Their particles have no regular long-range order

Amorphous solids have a random arrangement, like a frozen liquid, and soften gradually. Crystalline solids such as metals have a regular repeating lattice.

Crystal structure & solidification, 3 marks

Why are close-packed hexagonal (CPH) metals such as zinc less ductile than FCC metals?

  1. They are amorphous
  2. They have few slip planes
  3. They have many slip planes
Show the answer

They have few slip planes

CPH metals (zinc, magnesium, titanium) have fewer slip systems, so dislocations cannot move as easily and they deform less before cracking. FCC metals have many.

Crystal structure & solidification, 3 marks

Carbon atoms sit in the gaps between iron atoms in austenite. This is?

  1. An interstitial solid solution
  2. A substitutional solid solution
  3. A chemical compound
Show the answer

An interstitial solid solution

Small atoms (carbon, nitrogen) fit in the spaces between larger atoms: interstitial. In substitutional solutions, e.g. zinc in copper, atoms replace each other.

Other Engineering topics

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