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Junior Cycle Engineering: Plastics

How often Plastics comes up on the Engineering papers, every year it was asked, and questions to try.

CL Asked on 4 of the last 5 Common Level papers, most recently in 2026. most years

Plastics, Common Level(7 marks)

Quick ones on Plastics.

(a)What happens to a thermoplastic when it is heated?
  1. It stays rigid, then chars and burns
  2. It softens and can be reshaped
  3. It melts and can never set again
(b)Why can a thermosetting plastic not be recycled by melting it down?
  1. It dissolves in water when it is heated
  2. It contains too much metal to melt safely
  3. Permanent cross-links lock its chains
(c)Which of these plastics is a thermoset?
  1. Melamine
  2. Polypropylene
  3. Acrylic
Show the answers

(a) It softens and can be reshaped

(b) Permanent cross-links lock its chains

(c) Melamine

Your turn: Common Level questions on Plastics.

Common Level

Asked on 4 of the last 5 Common Level papers, most recently in 2026. most years

Every paper, year by year

YearWhere it came up
2026Q1b
2025Q2e, Q3d
2024Q1c, Q2c
2023Not asked
2022Q1b, Q3a, Q4d

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

More Plastics questions

Plastics, 2 marks

On a plastic item, what does the number inside the recycling triangle tell you?

  1. How many times it was recycled
  2. How many years it will last
  3. Which type of plastic it is
Show the answer

Which type of plastic it is

The resin code, 1 to 7, names the plastic (e.g. 1 = PET, 2 = HDPE, 5 = PP) so recycling plants can sort it. Different plastics must not be mixed when recycled.

Plastics, 3 marks

Why is silicone rubber a good material for a baking mould?

  1. It is hard, brittle and see-through
  2. It is flexible and withstands oven heat
  3. It is rigid and melts easily when warm
Show the answer

It is flexible and withstands oven heat

Silicone stays flexible over a wide range of temperatures, so it survives the oven and bends to release a cake. It is also waterproof and easy to clean.

Other Engineering topics

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