The Earth's Structure
- Crust: bit we live on, surrounded by atmosphere, thin layer.
- Mantle: properties of a solid, but flows very slowly, radioactive decay here (causing mantle to flow in convection currents).
- Core: made of iron and nickel.
- Earth's surface: made up of tectonic plates which drift due to convection currents.
- Most plates move a few cm per year.
- Occasionally they move very suddenly...earthquake!
- Volcanoes and earthquakes can occur at the boundaries of 2 tectonic plates.
- It is IMPOSSIBLE to predict exactly how the plates will move.
- Scientists can only say what is LIKELY.
- Some clues suggest an approaching volcanic eruption. Molten rock rises into chambers near the surface, causing the ground to bulge slightly (mini-earthquakes). But sometimes the molten rock cools down instead of erupting...so can be a false alarm!
Evolution of the atmosphere
- Phase 1:
- Earths surface molten...any atmosphere just "boiled away" in the heat.
- As cooled...thin crust formed...volcanoes kept erupting (gave out gas)
- Atmosphere mostly CO2, NO OXYGEN. Also, water vapour, methane and ammonia.
- Oceans formed when water vapour condensed.
- Phase 2:
- Green plants + algae evolved.
- Early CO2 dissolved into the oceans. Plants absorbed CO2 and produced O2.
- As plants and marine life die and become buried under layers of sediment, the carbon within them became "locked up" in sedimentary rocks as fossil fuels.
- When we burn fosisl fuels, the "locked up" carbon is released, concentration of CO2 in atmosphere increases!
- Phase 3:
- Build-up of O2 killed some organisms, but allowed more complex organisms to evolve.
- O2 created OZONE LAYER, which blocked harmful rays from the sun and enabled even more complex organisms to evolve.
- Quite a lot less CO2 now than in Phase 1.
- What is cracking?
- General formula for alkenes?
- What are polymers?
- 4 uses of Polymers?
- Why are oils distilled after being extracted?
- What is hydrogenation?
- Why not add emulsifiers to food?
- Example of an emulsion?
- What does an emulsifier do?
- What can be found beneath the earth's crust?
- Name the 2 gases that make up the earth today?
- Why do we fractionally distill air?
- Primordial soup theory states that the earth's atmosphere used to be rich in nitrogen, hydrogen, ammonia and methane. Lightning struck, resulting in the formation of amino acids. Amino acids collected in a "soup" (body os water in which life came from). Amino acids combined to produce organic matter, which evolved into living organisms. In the 1950s, experiements were carried out, and found that amino acids were made, but not as many as there are on earth.
- Earth's crust, oceans and atmosphere are the ultimate source of minerals and resources...we can get everything we need from them! For us to get these things, we fractionally distill air (separate it in a fractionating column) for use in industry etc.
- Increase in CO2 is causing gloal warming
- Oceans are a natural store of CO2. The extra CO2 we release is making them to acidic...bad news for coral and shellfish...also means that in the future, won't be able to absorb any more CO2.
- Alfred Wegener found fossils of similar species on opposite sides of the Atlantic Ocean.
- The accepted explanation for this is that there used to be land bridges linking continents which had now sunk.
- Wegner noticed that the coastlines of Africa and South America match like jigsaw pieces.
- In 1915, Wegner offically published his theory of "continental drift" (used to be one "supercontinent" which broke up into smaller pieces)
- "Continental drift" theory wasn't accepted for many years...
- Few scientists supported Wegner as they didn't see how the theory was possible...used inaccurate data and other evidence contradicted Wegner.
- In 1950s, new evidence was found in the ocean floor which supported Wegner's theory.
- By 1960s, Geologists were convinced tectonic plates in the earth caused the growing movement between continents.
- Emulsions are mae of lots of one liquid SUSPENDED to another.
- Emulsions can be OIL-IN-WATER or WATER-IN-OIL.
- Emulsions are THICKER than water or oil.
- Used in foods including...salad cream and moisturisers.
- EMULSIFIERS are molecules with one part attracted to the water (hydrophilic), and the other to the oil (hydrophobic).
- Stop emulsions from separating...so gives them a longer shelf-life.
- Allow food companies to produce foods lower in fat, but still with good texture.
- BUT some people are allergic to certain emulsifiers.
- Ethene (C2H4) can be hydrated with steam in the presence of a catalyst, to make ethanol.
- This is a CHEAP process...and little is wasted.
- Ethene is from crude oil...a non-renewable resource, this means it will become EXPENSIVE.
- Alcohol is made by fermentation.
- Raw material for fermentation is sugar, which is converted into ethanol using yeast.
- This is a cheaper process...(simpler equipment and lower temperature)
- It's renewable...sugar is grown as a major crop around the world.
- Ethanol produced like this can be used as a CHEAP FUEL.
- However...ethanol like this is NOT very concentrated + needs to be purified
Using Alkenes to make Polymers
- Best thing to do with ALKENES is POLYMERISATION.
- This means JOINING together lots of small alkene molecules (monomers)...to form large molecules (polymers).
- e.g. Ethene.....to Polyethene.
Different polymers have different properties:
- Depend what it is made from.
- Affected by the TEMPERATURE and PRESSURE of polymerisation.
- Flexibility and density vary depending on the above factors.
Uses: of different polymers:
- Light + stretchable...plastic bags
- Tooth fillings, hydrogel wound dressings
- Biodegradable packaging materials
- Memory foam
Polymers are cheap, but don't rot...they're hard to get rid of!!!
- Oils can be EXTRACTED from fruits and nuts for FOOD or FUEL.
- To extract the oil, the plant material is CRUSHED + PRESSED between 2 metal plates.
- The plant and it's oils are separated either by a centrifuge or a solvent.
- Distillation refines the oil by removing water and impuritues.
Vegetable oils provide a lot of ENERGY, VITAMIN E and ESSENTIAL FATTY ACIDS; so are used in FOODS. HIGHER BOILING POINTS, DIFFERENT FLAVOURS so used in COOKING. PRODUCE FUELS...including biodiesel (provide lots of energy)
- UNSATURATED oils contain double CC bonds.
- UNSATURATED oils can be HYDROGENATED (hardened by reacting them with hydrogen in the presence of nickel catalyst at 60 degrees. Makes them have higher melting points, so useful for spreads.
- These reduce the amount of cholestrol in the blood, much better than saturated oils.
- Cooking with oils (sats, unsats or trnas fats (partially hydrogenated), makes them more fattening.
Cracking Crude Oil
- Long-chain hydrocarbons produced from fractional distillation are made smaller by CRACKING.
- CRACKING is a THERMAL DECOMPOSITION REACTION.
- Heat long-chain hydrocarbon to vaporise it
- Vapour is passed over Aluminium oxide powdered catalyst (400-700 degrees)
- Long-chains split on the surface of the specks or the catalyst.
- Most products are alkanes but some are unsaturated...called alkenes.
- Double bonds between 2 carbon atoms
- Unsaturated because they can make more bonds
- General formula: CnH2n
- First 2 called...Ethene and Propene
- Alkenes decolourise bromine water because the double bond opens up to form bonds with the bromine.