Edexcel IGCSE Chemistry Synthetic polymers questions

What You Need To Know

Synthetic polymers questions can test recall, explanation, calculations, practical method, or data handling. For this subtopic, you should be able to:

• 4.44 know that an addition polymer is formed by joining up many small molecules called monomers
• 4.45 understand how to draw the repeat unit of an addition polymer, including poly(ethene), poly(propene), poly(chloroethene) and (poly)tetrafluoroethene
• 4.46 understand how to deduce the structure of a monomer from the repeat unit of an addition polymer and vice versa
• 4.47 explain problems in the disposal of addition polymers, including: their inertness and inability to biodegrade the production of toxic gases when they are burned.
• 4.48C know that condensation polymerisation, in which a dicarboxylic acid reacts with a diol, produces a polyester and water
• 4.49C understand how to write the structural and displayed formula of a polyester, showing the repeat unit, given the formulae of the monomers from which it is formed including the reaction of ethanedioic acid and ethanediol: ``` O O || || nH—O—C—C—O—H + nH—O—CH2CH2—O—H → [ O O || || —C—C—O—CH2CH2—O— ]n + 2nH2O ```
• 4.50C know that some polyesters, known as biopolyesters, are biodegradable

How To Answer Synthetic polymers Questions

1. Start by identifying exactly which specification point the question is testing.
2. Use the command word carefully: state and identify need a direct answer, while describe and explain need linked detail.
3. For tables, graphs, diagrams, and practical questions, quote the relevant observation or reading before drawing a conclusion.
4. When a question asks for a calculation, show the key substitution and include units where they are needed.

Example Questions With Worked Explanations

Example 1: Explaining the Chemistry

Question 1

The diagram shows some important conversion processes used in the oil industry.

Explain why the disposal of polymers such as poly(chloroethene) is difficult.

Final answer

• They are inert / unreactive, so they are non-biodegradable and do not naturally break down.
• Or: when polymers such as poly(chloroethene) are burned, they produce toxic fumes.

Mark scheme points

1. M1 State that the polymer is inert / unreactive.
2. M2 Link this to the polymer being non-biodegradable / not naturally breaking down / taking a long time to break down.
3. M3 Alternative route: state that the polymer is burned.
4. M4 Link burning to the production of toxic fumes.

Explanation

There are two ways to score full marks here, and either one is enough.

• One route is to explain that these polymers are inert / unreactive. Because of this, they are non-biodegradable and do not naturally break down. This is why disposal in landfill is difficult.
• The other route is to explain that when they are burned, they produce toxic fumes. That makes disposal by incineration difficult.

To secure both marks, make sure you include both parts of one route: the property and the consequence. For example, “they are inert” on its own is not enough, and “they produce toxic fumes” needs to be linked to burning.

If you use the landfill idea, “take a long time to break down” is also acceptable.

Common mistakes

• Writing only “they are inert” without saying they are non-biodegradable or do not break down.
• Writing only “burning is bad” without stating that toxic fumes are produced.
• Talking about recycling or cost of disposal instead of the accepted mark-scheme points.
• Saying the polymer is biodegradable; this is the opposite of the correct idea.
• Examiners reported that a very common full-mark answer was that burning polymers such as poly(chloroethene) produces toxic fumes. That statement was already more than enough for 2 marks.

Practise This Subtopic

Build a focused practice set on synthetic polymers, with questions selected from this part of the Edexcel IGCSE Chemistry specification.