In I/GCSE Chemistry, we will learn about the atmosphere of the Earth.
Molecular structure of materials
It is possible to produce a wide range of different polymers with properties that make them suited to a particular use. The properties of solid materials depend on how the particles in these materials are arranged and how they are held together. A solid melts when the forces between its particles are broken. This requires ENERGY. The stronger the forces between the particles, the more energy is needed to break the particles out of the solid structure. THE MORE ENERGY THAT IS NEEDED, THE HIGHER THE MELTING POINT OF THE SOLID.
In I/GCSE Chemistry, different polymers have different properties, depending on the small molecules they were made from. But the properties of a polymer can also be changed. These modifications can include:
- INCREASING THE CHAIN LENGTH – Longer molecules are stronger than shorter ones. By making the chains of a polymer longer, a stronger and less flexible material is produced.
- CROSS-LINKING – Cross-links are formed by atoms bonding between the polymer molecules, so they are no longer able to move. These cross links make the material tougher and less flexible.
- PLASTICIZERS – When it comes to I/GCSE Chemistry, adding plasticizers makes a polymer softer and more flexible. A plasticizer is a small molecule that sits between the molecules and forces the chains further apart. The forces between the chains are, therefore, weaker and so the molecules can move more easily. Plasticised PVC is used to make children’s toys.
- INCREASED CRYSTALLINITY – Increasing crystalline means packing the molecules more closely together. The intermolecular forces are slightly stronger so the polymer is stronger, more dense and has a slightly higher melting point.
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