Chemistry Module C2: Material Choices

James McConnell
Note by , created about 5 years ago

An overview of Chemistry Module C2 for UK GCSE.

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Page 1

Natural & Synthetic

A material is a mixture of chemicals, made up of billions of atoms. Natural materials come from natural things, such as paper and silk from plants and wool and silk from animals. However, most materials we use nowadays are synthetic, meaning man-made alternatives starting with materials from the Earth's crust.

The process of using natural wool from sheep to create products. This is a natural material.

C2: Material Choices

Welcome to this study guide overview for GCSE Chemistry Module C2. You can take a quiz on this module by clicking here.

Fractional Distillation

Crude Oil is a natural material, often found in the sea or underground. It is refined in a process called Fractional Distillation in order to make a variety of valuable products. The Crude Oil starts as a thick black liquid containing many hydrocarbons (compounds made entirely of hydrogen and carbon). This is then heated intensely to evaporate the hydrocarbons and then pumped into a Fractional Distillation tower.

Each evaporated hydrocarbon fraction has a different boiling point dependant on how strong the bonds are within each molecule. As gases they naturally rise upwards through the tower which is coller at the top. Once they reach their boiling point the fraction condenses and is run off from the side of the tower. Any gases that remain at the top are also collected to become bottled gases.

A diagram of Fractional Distillation and the uses of each fraction that runs off after condensing. Source: BBC Bitesize

The most important part of Fractional Distillation to know is the information given in the diagram about boiling points, volatility, and the ease of flow and ignition. The higher it comes out of the tower, the lower the boiling point and the better it will be at all the latter three listed.

Material Properties

All materials have different properties and therefore must be tested on for suitability to ensure they are effective and durable. Tests include boiling points, melting points, strength and flexibility.

Modern monomer technology has allowed scientists to develop materials which are fit for purpose by combining the small hydrocarbon molecules (monomers) to make long chains of molecules, called polymers.

These synthetic polymer materials have replaced natural materials in many instances due to superior properties. For example, paper bags are practically non-existent due to polythene 'plastic' carrier bags which are waterproof and much stronger. Wooden window frames have been replaced with polychloroethene (PVC) because it is un-reactive and doesn't rot therefore lasts much longer.

Above: Polymerisation technology combines small molecules, monomers, to make long chains called polymers. Below: A carrier bag that was produced by Polymerisation techniques 

Modifying Properties

The properties of a solid material depends largely on the the covalent bonds between atoms and the links between each molecule. Rubber is a good example of this because it has strong covalent bonds meaning each molecule is very tough, although it has very weak links between molecules which allow it to stretch. This also means rubber has a very low boiling point.

Vulcanisation is a process that can be applied to molecules to make them stronger because it strengthens the covalent bonds and the links between molecules by cross-linking. The reverse of this can be achieved by adding plasticisers, which are small molecules that sit between molecules to push them apart and thus make the links weaker and easier to move. These processes are often applied to rubber to create varying types of wheels for cars.

Formula 1 tyres have varying properties to work better in different conditions.

Crystalline polymers can be created by packing molecules closer together which creates stronger intermolecular forces, and makes the polymer denser, stronger, and gives a higher melting point.

Before (left) and after (right) crystallisation of a polymer. The process makes it stronger, denser, and have a higher melting point.

Nanotechnology

View a short presentation on this topic here.

Nanotechnology is another way of modifying properties but on a much smaller scale: 1-100 nanometres in fact. The word literally means technology on a nano scale, with nano being the Greek word for dwarf. The 'nano' prefix has become common in technology, including the iPod Nano. The Nanoscale particles are more common than you might think, including in sea spray and carbon particulates (see Module C1). Their properties are very different to large molecules.

A common example of nanotechnology is silver nanoparticles which are put in some clothing to give them antibacterial properties such as reducing smell. Nano metals are also used in golf clubs to make the 'sweet spot' larger which makes golf easier and - apparently - more enjoyable!

However, there are currently some major concerns about nanotechnology. Some people think it could cause cancer related health risks, and some athletes argue it gives an unfair advantage.

Take the quiz by clicking here.

Think you know C2 now?

Natural & Synthetic

Fractional Distillation

Material Properties

Modifying Properties

Nanotechnology