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Limestone-Using it

  • Cement factories create a lot of dust, which can cause breathing problems.
  • Energy is needed to produce cement and quicklime...the energy comes from burning fossil fuels.
  • Uses:
  • Dyes, paints and medicines; housing and roads
  • Limestone products are used to neutralise acidic soil damaged by acid rain
  • Used in power station chimneys to neutralise sulfur dioxide (a cause of acid rain)
  • Quarrying provides jobs...and brings money into the local economy...this can lead to local improvements e.g. transport.
  • Once quarrying is complete, restoration is required to repair the land.
  • Limestone is widely available and is cheaper than granite and marble.
  • Some Limestone is quite hard-wearing but still attractive.
  • Limestone, concrete and cement don't rot, are fire-resistant and can not be gnawed by insects either.
  • Concrete does not corrode but can crack...and so should be reinforced with steel bars.
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Limestone-Quarrying and Reactions

  • Limestone is QUARRIED out of the ground, and is great for making into blocks for BUILDINGS.
  • Advantages:
  • Hated with powdered clay to form cement.
  • Mixed with sand and water to make mortar.
  • You can also mix cement with sand and aggregate to make comcrete.
  • Disadvantages:
  • Makes huge ugle holes in the landscape.
  • Creates noise pollution and creates dust.
  • Destroys habitats.
  • Lorries transport the Limestone away...these created noise and air pollution.
  • Produce unsightly waste materials.
  • Limestone is mainly CALCIUM CARBONATE...CaCO3.
  • When heated...thermally decomposes to make calcium oxide CaO and carbon dioxide CO2.
  • Reacts with acid to make...a calcium salt, carbon dioxide and water.
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Atoms, Elements; The Periodic Table

  • Nucleus of an atom has a positive charge because of the protons.
  • Atoms have no overall charge...they are neutral.
  • Number of protons is EQUAL to the number of electrons in an atom.
  • If electrons are added or removed, the atom becomes CHARGED, and is then an ion.
  • Elements consist of one type of atom only.
  • Elements with similar properties are displayed in COLUMNS.
  • Top number...is the mass number (number of protons+neutrons)
  • Bottom number...is the atomic number (number of protons=number of electrons)
  • Number of neutrons=mass number-atomic number
  • Refer to pg 19 of AQA textbook for Periodic Table Guide
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Compounds

  • When different elements react with eachother, atoms form chemical bonds with other atoms...to form compounds.
  • A compound formed from a METAL and a NON-METAL consists of ions. METAL atoms LOSE electrons to form POSITIVE IONS; NON-METAL atoms GAIN electrons to form NEGATIVE IONS. Opposite charges mean that they are strongly attracted to eachother, this is called IONIC BONDING.
  • A compound formed from NON-METALS consists of molecules. Each atom shares an electron with another,  this is called COVALENT BONDING. Each atom has to make enough covalent bonds to fill its outer shell.
  • Compounds can be SMALL molecules like water, or can be HUGE like giant lattices.
  • The PROPERTIES of a compound are completely DIFFERENT from the properties of the original elements.
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Getting metals from rocks

  • A metal ore is a rock which contains enough metal to make it worthwhile extracting the metal from it.
  • In many cases the ore is an oxide of the metal.
  • Most metals can be extracted from their ores using a chemical reaction.
  • The profitability of metal extraction can chagne over time:
  • If the market price of a metal drops, it may not be worthwhile to extract it
  • If the price increases, then it may be worth extracting more of it.
  • Technology improves, it becomes possible to extract more metal than was possible originally.
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Reactivity Series

Potassium-Aluminium...extracted by electrolysis (higher than carbon).

Zinc-Copper...extracted by reduction using carbon (lower than carbon).A list of elements from most reactive to least reactive: potassium, sodium, lithium, calcium, magnesium, aluminium, zinc, iron, copper, silver and gold. (http://a.files.bbci.co.uk/bam/live/content/zb7y4wx/small)

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Properties of metals

ALL METALS...are strong, can be bent or hammered; and can conduct heat and electricity.

Transition metals: strong but bendible measn can be widely used. Conductivity makes them great for making things like like electrical wires.

Metals are useful as structural materials, but some corrode when exposed to air or water, and so need to be protected.

Metals can get "tired" when stresses and strains are repeatedly put on them over time. The is called "metal fatigue" and can lead to metals breaking...potentially dangerous.

For exact properties of individual metals...refer ti pg 39 of AQA textbook.

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Alloys

Alloys are two metals mixed together in order to make the metal stronger for use.

  • Pure iron is too bendy and so scientists add small amounts of carbon to it to strngthen it.

Alloy Properties:

  • Different elements have different sized atoms. Different sized atoms upset eachother's layers within the metal, making it more difficult for them to slide over eachother.
  • Most metals used today are alloys:
  • Bronze=copper+tin
  • Cupronickel=copper+nickel
  • Gold alloys are used to make JEWELLERY.
  • Aluminium alloys are used to make AIRCRAFT.

Alloys can now be designed for specific uses.

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Fractional Distillation of Crude Oil 1

  • Crude oil is a mixture of hydrocarbons (consists of two elemetns of compunds that aren't chemically bonded to echother.
  • Crude oil is a mixture of many different compounds (most are hydrocarbon molecules)
  • Hydrocarbons are fuels made of carbon and hydrogen.
  • No chemical bonds between different parts of the mixture, so keep individual properties such as: condensing points.
  • Parts of a mixture can be separated out by physical methods into fractions by distillation. Each fraction contains molecules with a similar number of carbon atoms to each other.
  • All the fractions of crude oil are called alkAnes.
  • Alkanes are made up of chains of carbon atoms surrounded by hydrogen atoms.
  • e.g. Methane...CH4
  •        Ethane...C2H6
  •        Propane...C3H8
  •        Butane...C4H10
  • Carbon atoms form four bonds, as hydrigen atoms only form 1.
  • When an atom has formed all the bonds it can... it is saturated.
  • General formula for alkanes: CnH2n+2
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Fractional Distillation of Crude Oil 2

Fractionating column works continuously with heated crude oil piped in at the bottom. See pg 43.The top of the column is cool (25 degrees celsius). Fractions taken from here have small molecules, low boiling points, are very volatile, flow easily and ignite easily. Crude oil enters at the bottom of the column and is heated to 350 degrees celsius. Fractions taken here have large molecules, high boiling points, are not very volatile, and don't flow or ignite easily. From top to bottom the fractions are: Refinery gases (bottled gas), gasoline (petrol), naptha (used for making chemicals), kerosene (aircraft fuel), diesel oil (fuel for cars, and lorries, etc), fuel oil (fuel for ships, power stations), residue (bitumen for roads and roofs). (http://www.bbc.co.uk/staticarchive/d1fc03f39806642998b1bd6ea1dda2c8e2e2b674.gif)

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Properties and Uses of Crude Oil

  • Shorter molecules...more runny the hydrocarbon
  • Shorter molecules...more volatile (gas at lower temperature); lower the boiling point
  • Shorter molecules...more flammable the hydrocarbon
  • Uses of crude oil: pg 46
  • Problems with crude oil: 47-50
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Questions

Questions I found difficult in revision summary:

  • Which elements properties are more similar to magneium's: calcium or iron?
  • Symbol equation for the thermal decomposition of limestone?
  • Products produced when limestone reacts with acid?
  • What is calcium hydroxide used for?
  • Name 3 building materials made from limestone?
  • Why is aluminium an expensive metal?
  • What is electrolysis? Describe the process?
  • Name of process when plants extract metals from soil?
  • General formula for an alkane?
  • Is a shorter chain hydrocarbon more viscous? Volatile?
  • 3 ways of reducing acid rain?
  • Has the theory of global dimming been proven?

Check your answers in pg 18-50 in AQA Textbook

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