Types of Plastics and Their Properties

This page delves into the different types of plastics and their properties, which is crucial information for AQA GCSE Chemistry paper 1 revision.

The page introduces two main categories of plastics:

1. Thermosoftening plastics (thermoplastics): These plastics soften when heated and can be reshaped.

2. Thermosetting plastics: These do not soften when heated and are used in applications where heat resistance is important.

Example: Thermosetting plastics are used in items like kettles, plugs, and laptop chargers due to their heat resistance.

The page then focuses on the effect of heat on thermoplastics. When heat is applied, the weak bonds between the polymer chains break, allowing the chains to slide over each other. This results in the plastic becoming malleable and able to be reshaped.

Vocabulary: Malleable - Able to be shaped or molded easily.

The structural differences between thermoplastics and thermosetting plastics are also explained. Thermosetting plastics have cross-linking between polymer chains, which gives them their heat-resistant properties.

Examples of Addition Polymerisation

This page provides specific examples of addition polymerisation, which is essential knowledge for WJEC Chemistry Bonding, structure and properties topics.

Four main examples of addition polymerisation are presented:

1. Polythene (polyethene): Formed from ethene monomers.
2. Polypropene: Formed from propene monomers.
3. Polyvinylchloride (PVC): Formed from vinyl chloride monomers.
4. Polytetrafluoroethene (PTFE): Formed from tetrafluoroethene monomers.

Highlight: In all these examples, the double bond in the monomer is broken during polymerisation, creating a spare bond that joins the molecules together.

For each example, the page shows the chemical structure of the monomer and the resulting polymer. This visual representation helps students understand how the monomers link together to form the polymer chain.

Definition: A monomer is a small reactive organic molecule containing a carbon-carbon double bond.

The page emphasizes that all these examples are addition polymerisation reactions, where only one product (the polymer) is formed.

Vocabulary: Saturated hydrocarbon - A hydrocarbon compound where all carbon atoms are joined by single bonds.

Properties and Uses of Plastics

This final page focuses on the properties and uses of different types of plastics, which is crucial information for WJEC Chemistry knowledge organisers.

The page begins by emphasizing the importance of plastics and how they can be engineered for specific uses based on their properties.

Two main categories of plastics are reiterated:

1. Thermosoftening plastics (thermoplastics): These soften when heated and can be reshaped.
2. Thermosetting plastics: These do not soften when heated and are used where heat resistance is important.

Example: Thermosetting plastics are used in items like kettles, plugs, and laptop chargers. Examples include melamine, bakelite, and polyurethanes.

The page then provides detailed information on the properties and uses of common thermosoftening plastics:

1. Polypropylene:

   • Properties: Light, hard but scratches easily, tough, good chemical resistance, resists work fatigue.
   • Uses: Medical equipment, laboratory equipment, containers with built-in hinges, plastic seats, string, rope, kitchen equipment.

2. Polystyrene:

   • Properties: Light, hard, stiff, transparent, brittle, good water resistance.
   • Uses: Toys (especially model kits), packaging, plastic boxes and containers.

3. Low Density Polyethene (LDPE):

   • Properties: Tough, good chemical resistance, flexible, fairly soft, good electrical insulator.
   • Uses: Packaging, especially bottles, toys, packaging film and bags.

4. High Density Polyethene (HDPE):

   • Properties: Hard, stiff, able to be sterilized.
   • Uses: Plastic bottles, tubing, household items.

Highlight: The properties of each plastic are closely linked to its uses, demonstrating how materials are chosen for specific applications based on their characteristics.

This information is particularly useful for understanding the practical applications of chemistry in everyday life, a key aspect of GCSE Chemistry summary notes.

Page 5: Plastic Properties and Applications

This final section categorizes plastics and details their specific properties and applications in various industries.

Definition: Thermosoftening plastics can be reshaped when heated, while thermosetting plastics maintain their shape.

Example: Polypropylene is used in medical equipment and laboratory containers due to its chemical resistance.

Highlight: Different types of polyethylene (LDPE and HDPE) serve distinct purposes based on their properties.

Addition Polymerisation and Alkene Reactions

This page introduces the concept of addition polymerisation and the reactions of alkenes. It covers key processes in GCSE Chemistry and is essential for understanding polymer formation.

Addition polymerisation is the process of creating long-chain molecules (polymers) from small reactive molecules (monomers). This process is crucial in the production of many common plastics.

Definition: Addition polymerisation is a process where monomers with carbon-carbon double bonds link together to form a polymer.

The page also discusses the reactions of alkenes, focusing on addition reactions. Two important reactions are highlighted:

1. Reaction with Hydrogen (Hydrogenation): This reaction converts unsaturated alkenes into saturated alkanes.

2. Reaction with Bromine Water: This reaction serves as a test for the presence of alkenes.

Example: When bromine water is added to an alkene, the brown color of the bromine water turns colorless, indicating the presence of a carbon-carbon double bond.

The formation of polythene from ethene is presented as an example of addition polymerisation. This process involves breaking the double bond in ethene molecules, allowing them to join together and form long chains of carbon atoms.

Highlight: The resulting polymer, polythene, is a saturated hydrocarbon with all single bonds between carbon atoms.