C6 Global Challenges Flashcards
What are natural materials?
Chemicals, or mixtures of chemicals that come from living things (cotton & paper- plants, silk & wool- animals).
What are synthetic materials?
Chemicals, or mixtures of chemicals, which have been produced by chemical synthesis.
Describe in terms of intermolecular forces and bonds how crude oil needs different boiling points to break it up.
When crude oil is heated the molecules are supplied with extra energy; thus the molecules moves about more. Eventually, a molecule may have enough energy to overcome the intermolecular term-54forces that keep it with the other molecules. The covalent bonds are much stronger meaning you don’t end up with small molecules. The intermolecular forces are easier to break in smaller molecules in comparison to larger ones. Meaning more energy is needed to break larger hydrocarbons out of crude oil.
What is crude oil made of?
Hydrocarbons- compounds made entirely of hydrogen and carbon atoms. Their properties change as the chain get longer. There are strong covalent bonds between the carbons and hydrogens within each hydrocarbon molecule. There are intermolecular forces of attraction between different hydrocarbon molecules. Only a small percent of it is used for chemical synthesis the rest if used for fuel.
What are the uses of crude oil?
It is used for fuels, to make plastics such as polyethylene, small amounts of hydrocarbons are used to make new compounds for use in thinks such as plastics, medicines, fertilisers and even food.
How is crude oil separated?
Into fractions by fractional distillation depending on the chain length. Smaller molecules have a lower boiling point, very volatile, flow easily and are easy to ignite. Vis Versa
What happens in fractional distillation?
The crude oil is heated at 400°C for the hydrocarbons to be evaporated, this passes into a fractional distillation column at the bottom. The vapour moves up the FD column and cools. Its hotter and the bottom and cooler at the top. Each fraction condenses when it has cooled below its boiling point (the larger hydrocarbon molecules with a high boiling point condense lower down the column, and the smaller molecules with a low boiling point condense higher up). Other gases will leave at the top of the tower. The fractions can then be used as fuels, lubricants and the raw materials for chemical synthesis
What are the properties and uses of polythene?
It has a low density, so is light, and is flexible and easily moulded. It can be used for plastic bags and containers.
What are the properties and uses of polystyrene?
It has a low density, so is light, and it is stiff and water resistant. It is also a thermal insulator. It can be used for coffee cups, meat trays, egg cartons and in the protection of appliances.
What are the properties and uses of nylon?
It has a low density, so is light, and it is tough and waterproof. It also blocks UV light. It can be used for clothing and climbing ropes.
What are the properties and uses of polyester?
It has a low density, so is light, and is tough and waterproof. It can be used for clothing and bottles.
What is polymerisation?
The chemical process during which hydrocarbon monomers are joined to make longer strings of molecules (polymers).
How can polymerisation be used?
Polymers have different physical properties depending on how their molecules are arranged and held together, meaning they have different uses. For example, Carrier bags (strong and waterproof), window frames (unreactive and doesn’t rot), non-stick frying pans. Heat-resistant polymers such as melamine resin and polypropene are used to make plastic kettles.
Why have polymers replaced natural materials for some uses?
They have more benefits in comparison to the traditional materials. For example, synthetic fibers like nylon are used to replace fabrics as they are lighter, more durable, water- resistant and cheaper. The main down-side is that they aren’t breathable making them uncomfortable.
What happens if polymer chains are packed close together or spread out?
If the polymer chains are packed close together, it will have a high density.
If a polymer chains are spread out the material will have a low density
What happens if the polymer chains are held together by weak forces?
If polymer chains are held together by weak forces then they are free to slide over each other. The bonds holding the atoms together are strong but the forces between molecules are weak. This means that the material (plastic) can be stretched easily (is flexible),will have a low melting point won’t be stiff, won’t be hard.
What happens if the polymer chains are held together by strong forces?
If a polymer chain is held together by strong forces then they have high melting points and can’t easily be stretched as the crosslinks hold the chains firmly together. Crosslinks are chemical bonds between the polymer chains and hold them in a regular structure. It means it will be very strong, stiff hard and have a high melting point.
Why is rigid PVC used in windows?
It is weather-resistant, strong, and durable; making window frames more secure. And do not need constant painting.
What is natural rubber?
A mass of long-chain molecules, where the molecules are held together by very weak intermolecular forces. This makes it flexible and gives it a low melting point (less energy is needed to separate the molecules).
What is vulcanised rubber?
A mass of tangled molecules, held together by cross-links, giving it strong covalent bonds between the molecules. This makes it more rigid, and gives it a high melting point (more energy is needed to separate the molecules). It is used for conveyor belts and car tyres.
How does chain length affect affect a polymer?
Depending on the length shorter chains will have weaker forces of attraction between molecules (compared to long chains) so the polymer chains can easily slide past each other, making the material flexible.
It will also have weak forces of attraction, it requires less energy to separate the molecules out of the solid structure and into a liquid formation, therefore it will have a low(er) melting point than a long chained polymer
Vis Versa.
What is the effect of increasing or decreasing the chain length?
Making a polymer chain longer will mean it will be less flexible, a higher melting point, stiffer and stronger.
Making a polymer chain shorter will mean it will be flexible, low melting point, less stiff and weaker.
What is the effect of cross-links?
These agents chemically bond the polymer chains linking them together.
These cross-links between the molecules mean that the molecules are locked in a regular arrangement which stops the chains from uncoiling and slipping over each other. The result of this is that is makes the rubber less flexible, stronger , stiffer and harder.
It also gives the rubber a high melting point because more energy is needed for the molecules to separate and break out of the solid thus more heat resistant.
What is vulcanisation?
A type of cross-linking, where sulphur atoms join rubber molecules. This creates vulcanised rubber.
What is the effect of adding plasticisers?
Plasticisers are usually an oily liquid with small molecules which can be added to polymers during their manufacture.
The small molecules sit between the polymer chains, they push the polymer chains further apart, which weakens the forces between them.
This means that less energy is needed to separate them and they slide over each other more easily.
What is the effect of making a polymer crystalline?
In a crystalline polymer, the molecules are lined up in a regular way (in neat lines) as in a crystal. It has straight chains with no branches so that the chains can fit close together. This means that the forces between the molecules are slightly stronger and more energy is needed to separate them so it has a higher melting point. As more chains are packed in, it has a higher density, and is stronger. The branches stop the molecules from packing neatly.
Batch
Certain Times. Flexible, Low Start-up Cost. But is Labour Intensive and changing quality e.g Drugs.
Continuous
All the time. Specific, Automatic (less labour), Consistent quality, Huge start up costs. e.g. Haber Process.
