Making a polyester
2 marks · EasyExplain why polyesters are classified as condensation polymers, not addition polymers.
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Polyesters are formed when different types of monomers join together and a small molecule (such as water) is eliminated during each reaction. In contrast, addition polymers are made from identical monomers and no small molecule is lost.
Also accept: Polyesters form by eliminating a small molecule, usually water, at each step, whereas addition polymers do not eliminate any molecules.
Common mistakes: Referencing only monomer types but not loss of small molecule.
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Marking points
B1 · 1 mark · Mentions that polyesters are formed by elimination of a small molecule (e.g., water).
B2 · 1 mark · States that addition polymers are formed without the loss of a small molecule (or uses only one kind of monomer).
Worked solution
Polyesters are condensation polymers because when they form, a small molecule such as water is released each time two monomers join. Addition polymers are made from identical monomers and do not release a small molecule during their formation.