Question 1: Define addition polymerisation and explain how it differs from condensation polymerisation.

Answer: Addition polymerisation is a chemical process where monomers with double bonds link together to form a long chain polymer, releasing no other molecules. It differs from condensation polymerisation, which involves the formation of polymers with the release of small molecules like water.

Question 2: Describe the general mechanism of addition polymerisation, including the role of free radicals.

Answer: The mechanism involves the initiation, propagation, and termination steps. Free radicals are generated in initiation and react with the monomer's double bond to form a reactive site, which then reacts with additional monomers in propagation. Termination occurs when two free radicals combine, ending the chain growth.

Question 3: Identify the monomer used to produce polyethene.

Answer: Ethene (ethylene)

Question 4: What type of bond is formed between monomers during addition polymerisation?

Answer: Single covalent bonds

Question 1: Calculate the number of monomer units in a polyethene chain with a molecular weight of 28,000 g/mol. (Molecular weight of ethene = 28 g/mol)

Answer: Number of monomers = 28,000 g/mol ÷ 28 g/mol = 1000 monomer units

Question 2: If 50 grams of ethene gas are used in the production of polyethene, how many moles of ethene are involved? (Molecular weight = 28 g/mol)

Answer: Moles of ethene = 50 g ÷ 28 g/mol ≈ 1.79 mol

Question 1: Describe a simple experiment to test the tensile strength of a plastic polymer produced by addition polymerisation. Include variables to be controlled and safety precautions.

Answer: Prepare samples of the polymer and use a tensile testing machine to measure the force required to break each sample. Control variables include sample size, temperature, and humidity. Safety precautions involve wearing safety goggles and gloves, and ensuring the machine is operated by trained personnel.

Question 2: Explain why polymers like polyethene are used in packaging and what properties make them suitable for this purpose.

Answer: Polymers like polyethene are lightweight, flexible, resistant to moisture and chemicals, and have good barrier properties, making them ideal for packaging to protect products and reduce weight.

Question 1: A sample of polyvinyl chloride (PVC) has a density of 1.4 g/cm³. If a block made of PVC measures 10 cm x 5 cm x 2 cm, calculate its mass.

Answer: Volume = 10 cm × 5 cm × 2 cm = 100 cm³; Mass = Volume × Density = 100 cm³ × 1.4 g/cm³ = 140 g

Question 2: Discuss the environmental impact of widespread use of addition polymers and suggest one sustainable alternative or solution.

Answer: Addition polymers are non-biodegradable and contribute to pollution and landfill accumulation. One sustainable solution is developing biodegradable plastics or recycling existing polymers to reduce environmental harm.

Question 1: Explain the process of addition polymerisation of ethene to produce polyethene. Include the role of catalysts if applicable. (6 marks)

Answer: The process begins with the activation of ethene monomers, often using a catalyst like a Ziegler-Natta catalyst, which helps generate free radicals or coordinate bonds. The double bonds in ethene open up, allowing monomers to link together in a chain through single covalent bonds. The chain grows as more monomers add on in a chain reaction. The process continues until termination, where free radicals combine or react with other species, ending the chain growth.

Question 2: Identify two advantages and two disadvantages of using addition polymers in industry.

Answer: Advantages: 1) Lightweight and durable 2) Resistant to chemicals and moisture. Disadvantages: 1) Non-biodegradable leading to environmental pollution 2) Derived from non-renewable resources.