C1B
help to revise
- Created by: Dr Afzal
- Created on: 19-04-10 17:41
Cracking Crude Oil (Splitting up long chain hydroc
Long-Chain hydrocarbons form floopy liquids like tar which arn't useful,
so break you break up longer molecules from fractional distillation- Some products are useful like fuels
Cracking
You crack (break molecules) by heating them
1) First step is to heat the long chain hydrocarbons to turn it into gas
2) Then the gas (vapour) is passed over a catalyst
3) Aluminium oxide is the catalyst used
4) The long-chain molecules split apart or "crack" on the surface of the of catalyst
5) Most of products = Alkanes + Alkenes
Alkenes
Alkenes are hydrocarbons which have a double bond between two of the carbon atoms
They are known as unsaturated because they can make more bonds- The double bond can open up
1st three alkenes= ethene, propene, butene
All alkenes have the formula= Cn H2n
Ethene to Ethanol
Ethene will react with steam to make ethanol
The reactions needs a temperature of 300 c and a pressure of 70 atmospheres
Phosphoric acid is used as catalyst
Using Alkenes to make Polymers
Polymerisation- (joining together small akene molecules (monomers) to form very large molecules)- Polymers
E.g. Many ethene molecules can be joined up to produce polythene
Monomers have double bonds
Polymers don't have double bonds
Polymer Physical Properties
The physical properties of a polymer depend on what it's made from
E.g Temperature and pressure of polymerisation-
Polyethene made at 200 c (temp) and 2000 atmospheres is flexible and has a low density
But polyethene made at 60 c (temp) and a few atmosphere pressure with a catalyst is rigid and dense
POLYMERS ARN'T BIODEGRADABLE IT'S DIFFICULT TO GET RID OF THEM, USE THEM AS MUCH AS POSSIBLE THEN RECYLE THEM
Polymer Uses
Light and stretchable polymers (polythene)- Plastic bags
Waterproof coatings for fabrics are made from polymers
Dental polymers are used in tooth fillings
Polymer hydrogel wound dressings keep wound moist
Memory foam- Polymer material that gets softer as it gets warmer
Plants and Oils
Some fruits and seeds contains a lot of oil, these oils can be extracted and used for food or for fuel
To get the oil out the plant material is crushed
Then you have to press the crused plant material between metal plates and squash the oil out
Oil seperated by a centrifugue
Distillation refines oil
Vegetable oil provides a lot of energy, contains vitamin E and contain fatty acids- Needs for metabolic processes
Emulsions
You can mix oil with water to make an emulsion- emulsions made up of lots of droplets
Emulsions are thicker than either oil and water
The physical properties of emulsions made them suited to lots of uses in foods
The more oil the more thik the emulsion is
Emulsions also have non food uses- moisturising lotions
Vegetable Oils can be used to Produce Fuels
Vegetable Oils provide a lot of energy- Sutiable for fuel
Useful fuel made from vegetable oils -Biodiesel (renewable fuel)
Biodiesel produce much less sulfur dioxide pollution than engines burning diesel or petrol
Biodiesel is biodegradable and less toxic than normal diesel
Biodiesel engines release the same amount of carbon dioxide as ordinary diesel engines
Biodiesel comes from plants but normal diesel comes from crude oil
Using Plant Oils
Oils and fats are either saturated or unsaturated- Contain long chain molecules with lots of carbon atoms
Unsaturated oils contain double bonds between some of the Carbon atoms in their carbon chains
C=C double bonds can be detected by reacting with bromine or iodine
Unstaturated oil decolourise bromine water or iodine water
Monosaturated fats contain one C=C double bond some where in their carbon chains, polyunsaturated fats contain more than one C=C double bond
Unsaturated Oils can be Saturated
Unsaturated Vegetable oils are liquid at room temperature
Can be hardened by reacting them with hydrogen in presence of a nickel catalyst at about 60 c- CALLED HYDROGENATION
Hydrogen reacts with the double bonded carbons and opens out the double bonds
Hydrogenated Oils have higher melting points than unsaturated oils
Partially hydrogenating vegetable oil means end up trans fats- very bad for you
Vegetable Oils in Foods can affect Health
Vegetable oils tend to be unsaturated, while tend to be saturated
Saturated fats increase the amount of cholesterol in blood which can block up arteries and increase risk of heart disease
Natural unsaturated fats such as olive oil and sunflower oil reduce the amount of blood cholesterol
Food Additives
Food manufacturers add various chemical compounds to improve its appearence, taste etc- ADDITIVES
Additives in UK have "E" numbers, e.g. E127
Artificial can be detected by Chromotography
1) Extract colour from each food sample by placing in it a small cup with few drops of solvent
2) Put spots of each coloured solution on a pencil baseline on filter paper
3) Roll up the sheet and put it in a beaker with some solvent
4) The solvent seeps up the paper, taking the food dyes with it. different dyes form different spots in different places
Food Additives- Benefits and Drawbacks
Preservatives- help food stay fresh
Colourings and Flavourings- make food look and taste better
Emulsifiers and stabilisers- stop emulsions like mayonaise from spreading out
Sweeteners- can replace sugar in some processed foods- helpful to diabetics and dieters
Some synthetic additives are identical to natural substances
Some additives are of natural origin e.g lecithin from soya beans
Continental Drift
Alfred Wegner came across some work listing the fossils of very similar plants and animals which had been found on opposites sides of the Atlantic Ocean
But Wegner also noticed that the coastlines of Africa and South America seemed to join together like a jigsaw
Fossil's had been found un wrong places
Wengner said that about 300 million years ago, there had been one supercontinent. This Landmass, Pangaea broke into smaller chunks which moved apart and are still moving
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