Making Crude Oil Useful
Crude oil is made from 'Hydrocarbons' (contains ONLY hydrogen and carbon molecules)
Fractional distillaton: fractions that exit at the bottom of the column have high boiling points. The column gets cooler towards the top and fractions that exit here have low boiling points.
Crude oil can be separated because different hydrocarbons have different size molecules.
Fractions with stronger intermolecular forces require more energy to break the bonds and so have high boiling points.
Therefore fractions with weaker intermolecular forces are easily separated and require less energy so have low boiling points.
Problems extracting crude oil: transporting crude oil- oil slicks can damage birds' feathers and cause death. Can be political problems, e.g one country being dependant on another country for oil.
Cracking: process that turns large alkane molecules into smaller alkane and alkene molecules. Alkenes have double bonds which makes them ideal for making polymers.
Complete combustion: is when a fuel burns with plenty of oxygen
hydrocarbon + oxygen → carbon dioxide + water (general formula)
More energy is released in complete combustion than in incomplete combustion.
During incomplete combustion, carbon monoxide and carbon are made.
hydrocarbon + oxygen → carbon monoxide + carbon + water (general formula)
Incomplete combustion occurs when oxygen supply is limited.
Air: Nitrogen - 78% Oxygen 21% 0.035% Carbon Dioxide
The Atmosphere: It is thought that early atmosphere consisted of mostly carbon dioxide and water vapour, with a smaller proportion of ammonia, NH3.
For photosynthesis, plants absorb carbon dioxide from the atmosphere and release oxygen as a by-product. Photosynthesis increased the proportion of oxygen in the atmosphere until it reached today’s level, 21 per cent.
One theory is that the water vapour condensed to form oceans and carbon dioxide dissolved in the water. The % of nitrogen slowly in creased and little was removed (due to it being unreactive)
Atmospheric pollution: needs to be controlled beause- sulphur dixoide (a pollutant) causes difficulties for people w/ asthma. Can also cause acid rain which damages wildlife and buildings.
alkAnes are hydrocarbons with SINGLE covalent bonds only
alkEnes have DOUBLE covalent bonds between carbon atoms.
POLYMERISATION: addition polymerisation is where many alkene monomers react to give a polymer. The process requires high pressure and a catalyst.
Nylon has some desirable properties. It does not let ultraviolet light pass through it, and it is:
Unfortunately, nylon does not let water vapour pass through it either. This means nylon waterproof clothing traps sweat
Gore-Tex has the desirable properties of nylon, but is also 'breathable'. It lets water vapour from sweat pass to the outside, but it stops rain drops from passing to the inside
Proteins and Carbohydrates:
protein molecules permanently change shape when food is cooked. This is called 'denaturing'. Also causes the texture to change.
Potatoes are easier to eat if cooked because- starch grains swell up and spread out. The cell walls rupture so the rigid structure is lost causing a softer texture.
Baking power: when heated breaks down to gice carbon dioxide which helps cakes to rise
sodium hydrogencarbonate → sodium carbonate + carbon dioxide + water
2NaHCO3 → Na2CO3 + CO2 + H2O
Emulisfiers: molecules with a hydrophillic (water loving) head and hydroPHOBIC (water hating) tail.
Emulsifiers stop water and oil separating because the head bonds to water and the tail to oil. The hydrophillic head is attracted to water molecules (which surrond the oil) keeping them together.
Esters: alcohol + acid → ester + water
These esters are used to make perfumes.
A solvent is a liquid that dissolves substances.
The substance that dissolves is called the solute and the mixture formed by a solvent and solute is called a solution.
Volatile liquids evaporate easily. This is because there are only weak attractive forces between particles in the substance. These forces are overcome easily, so particles with enough energy can escape from the liquid.
Water doesnt dissolve nail varnish. attraction between water and nail varnish particles is weaker than the attraction that joins water to water and the attraction that joins nail varnish to nail varnish. The attractive force between water and nail varnish particles is too weak to break those other bonds.
Paints and Pigments
Emulsion paints are water-based. Their solvent is water and they dry when the water evaporates.
Oil paints contain pigment dispersed in oil, which may be dissolved in a solvent. The solvent evaporates away when the paint dries. This leaves the pigment and oil behind. The oil oxidises to form a hard film.
In a colloid, particles of one substance are mixed and dispersed with particles of another substance - but they are not dissolved in it. The components do not separate out because their particles are small enough not to settle at the bottom.
Thermochromic pigments are sensitive to temperature.
Phosphorescent pigments glow in the dark. They are able to absorb light energy and store it. This stored energy is released as light energy over a period of time.
Designer Polymers (2)
One of the useful properties of polymers is that they are unreactive, so they are suitable for storing food and chemicals safely. Unfortunately, this property makes it difficult to dispose of polymers.
Chemists are developing new types of polymers.However, it is possible to include chemicals that cause the polymer to break down more quickly.Some polymers are water-soluble, which means they dissolve in water.
Strong covalent bonds join atoms to each other in individual polymer molecules.
The properties of solid materials like polymers depend on:
- how their molecules are arranged
- the strength of the forces between these molecules.