Atoms,metal,rocks and fuel

unit one chemistry

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Crude oil

  • Crude oil is a non-renewable fuel- there is a finite amount
  • Made of dead plants and animals
  • The dead animals and plants are compressed for millons of years under the surface
  • To obtain this fuel workers have to drill deep down beneath the surface
  • The oil then needs to be distilled - fractional distillation

problems with crude oil include transporting it leading to damage to the enviroment and spills harming wildlife

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Fractional distillation

Crude ol is a mixture of small and very large molecules. They can be seperated by fractional distillation, into fractions.

  • ( 1,2,3,4 carbon molecules) fraction 1-4 - fraction fuel gas
  • (65 degrees ) fraction 5-6- petrol
  • (170 degrees) fraction 6-10- parrafin
  • ( 250 degrees) fraction 10-14- light gas oil
  • (340 degrees) fraction 14-19- diesel
  • (500 degrees ) fraction 19-35- lubricating substances
  • (over 500 degrees) - bitumen

cracking is important on this industrial scale because we break down the less useful liquids to create petrol which is in short supply.

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Breaking bonds

Hydrocarbons are molecules made up of only hydrogen and carbon. The bigger the chain length of these the higher the boiling point. Liquid becomes thicker because of the bigger chain length. This means we need energy (heat) to break intermolecular forces.

The liquids become harder to ignite because there is lese vapour coming off them which means the flame has to get close to ignite.

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Testing for alkenes and alkanes

Alkenes are unsaturated hydrocarbons having a double bond.If we shake them with bromene water , which is orange, it turns colourless as the bond adds across the double bond.

Alkanes are saturated hydrocarbons having only single bonds. These do not react with bromene which therefore stays orange. eg- ethane+bromine ------> no reaction

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Making polymers

  • Molecules which are formed by joining many smaller molecules together in a long chain are called polymers.
  • The smaller repeating ones are called monomers.
  • The reaction is called pollymerisation
  • In industry the conditions needed are high pressure and a catalyst
  • This causes the double bond in monomers to breaks and then the monomers to break and then the monomers join in a long chain

(http://upload.wikimedia.org/wikipedia/commons/9/99/Ethane-flat.png)Forces of attraction have to be broken for fractional distillation

(http://upload.wikimedia.org/wikipedia/commons/9/99/Ethane-flat.png)

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Fats

Fats repel water therefore to bind a fat and water (mayonaise) an emulsifier is needed.

  • Hydrophillic - water loving head attracts the water
  • Hydrophobic- water hating attracts th oil

The hydrophobic tail is attracted into the lump of oil ut the head isn't. The hydrophillic head is attracted to the water and pulls the oil on the tail into the water.

Other emulsifiers include detergent, soap, some paint,milk...which can be used in oil slicks when washing up.

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Combustion

When methane gas was burned waster and carbondioxide were sucked into the apparatus. This is shown by the change in the limewater from clear to cloudy which only happens when carbondioxide is present. The cobalt chloride paper turned pink which is a result of water being a product of combustion.

CH4 + 2O2--> Co2+ 2H2o

methane+ Oxygen---> carbondioxide+water

This is the equation for COMPLETE COMBUSTION because there is a plentiful supply of oxygen.

Incomplete combustion

This occurs when insufficent oxygen is availible. Eg- a closed air hole on a bunsen.

CH4 + O2 ----> C + 2H2o

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Comparing energy

energy transferred = mass of substance heated x specific heat capacity x tempreture change

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Chemical reactions

  • Reactants- starting subtances
  • Products- substances formed

Reactants -----> Products

Methane + oxygen ------> carbondioxide+ water

CH4 + 2o2 -----> Co2 + 2H20

In every chemical reaction we break bonds on one side and add bonds to another..

  • If a reastion gives out energy the surroundings increase in tempreture this is called an exothermic reaction.
  • If a reaction takes in energy the surroundings decrease in tempreture this is called an endothermic reaction.
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Paints

Thermochromic paints

  • A thermochromic pigment that changes colour at 45 degrees can be a warning (on cups or mugs).
  • A pigment that changes colour just above 0 degrees makes a good warning for road signs (freezing)

Most thermochromic paints change colour from colour to colourless. Thermochromic paints come in a range of colours. To get a larger range of colours they are mixed with different colours of normal acrlyic paints, in the same way you would mix coloured paints.

When the mixure gets hot the blue thermochromic paint becomes colourless so that all that is seen is the yellow acrlyic paint.

Phosphorescent paint

Phosphorescent pigments absorb enery from daylight. Then slowly release the energy as light ( these are someimes use in luminant watch dials). Some radioactive chemicals also glow in the dark but exposure to these may lead to cancer.

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Construction materials

Raw Building

Clay Brick

Limestone Cement

Sand glass

Iron ore Iron

Aluminium ore aluminium

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Investigating Cement and concrete

Cement - made from heating calcium carbonate (limestone) to form clacium oxide.

CaCo3 ------> CaO + Co2

When cement is mixed with sand and water to make mortar which is used for brick laying.

When cement is mixed with sand, gravel and water it forms concrete used for construction.

Concrete is strong under compression , he squashing force, but weak under tension , the pulling force. If a heavy load is put on a concrete beam it will bend very slightly , this puts it under tension and cracks will form. To cure this concrete is reinforced with steel which is strong under tension.

Unfortunately steel rods will oxidise and rust making them weak and easy to break after contact with water this means they must be carefully put in or replaced regularly.

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The limestone cycle

exothermic reaction

Calcium carbonate --------> calcuimoxide +carbon dioxide

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Problems with quarrying limestone

1. Dust pollution - covering the surrounding vegatation in a layer of dust

2. Noise pollution- loud explosions etc.

3. Damage to the enviroment- destroying natural habitats

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Rock types re-cap

Sedimentary- ware's away easily, the softest rock type and is mainly calcium carbonate (limestone) so will errode in acid rain.

Metamorphic- Changed forms limestone ----> marble ( under pressure and heat), still bad in acid rain but harder than sedimentary rock.

Igneous- cools slowly and forms interlocking crystals as it cools, an example of this is granite and is very hard.

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Comments

Vanessa-Ranae

helpful

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