Chemistry GCSE Unit 1a

Atoms and formula

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Atoms and formula

The formula of a compound show the number and type of atoms

Atoms and symbols used to represent substances in chemical reactions


H2 = 2 x hydrogen atoms

AlCl3 = 1 x aluminium atom

            3 x chloride atoms

Represent a chemical reaction using an equation

Shows how atoms are rearranged to make new products

Always have the same on each side of the arrow (balanced equation)

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Thermal decomposition

Process of breaking something down into simpler substances by means of heating

Limewater test - if CO2 is given off the limewater will turn cloudy from clear

When we heat a metal carbonate a thermal decomposition reaction occurs

The same two products always made are a metal oxide and carbon dioxide

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Limestone cycle


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Thermal decomposition of limestone

Heated in kilns

Calcium carbonate decomposes into calcium oxide and carbon dioxide

Quicklime is vital in cement, concrete and glass

Add water to quicklime and calcium oxide changes to calcium hydroxide

Slaked lime is vital in  building materials

Limestone found in the peak district and north of england

Kilns found on side of hills or mountains near a quarry so gravity is used to move the rocks through the ovens

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Limestone is heared with sand and sodium carbonate to make glass

Made mainly from sand

First glass object dated around 4500BC 

Raw materials are sand (SiO2), limestone (CaCO3), sodium carbonate (Na2CO3)

Recycled glass makes up to 30% of new glass

Many different types of glass

Windscreens made as thin plastic coated by glass called laminated glass

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Types and uses of glass

  • Soda lime - windows
  • Boro silicate - test tubes, beakers 
  • Lead crystal - decorative glass, vases 
  • Glass fibres - fibre optics, fibre glass
  • Optical glass - cameras, reading glasses
  • Glass ceramic - opaque ovenwear
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Uses of limestone

  • Glass
  • Buildings and roads
  • Steel
  • Paper
  • Neutralisation
  • Mortar
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  • Provides jobs
  • Rock for local uses
  • Boosts local economy
  • Visitor attraction after use
  • Use limestone for products e.g make up


  • Noise pollution from explosions
  • Dust ruining landscapes
  • Visual pollution
  • Puts tourists off
  • Busy roads and lorries
  • Wildlife affected
  • Erosion
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Metals and alloys

Solid at room temperature

High melting point

Good conductors of electricity and heat

Malleable; they can be shaped

Ductile; they can be drawn into wires

Strong and dense

Found in the earth's crust combined or uncombined as pure substances

Some unreactive metals found uncombined e.g. gold, silver, copper

Metals found in pure form said to occur as 'native'

Most metals found combined in ores so have to be extracted

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Transition metals

Most common type of metals

Exhibit all common properties of metals

3/4 of periodic table is metals and 1/4 is gases


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Uses of metals

Aluminium - low density and doesn't corrode

Used for cans and car bodies because it's lighter than steel

Gold - unreactive and malleable, doesn't tarnish or change appearance

Used for jewellery and electronics

Titanium - strong but light and doesn't corrode

Mixed with other metals and used for aerospace, watches and artificial joints

Iron - hard, strong, abundant and cheap

Used in building but rusts easily which changes appearance and safety issues

Copper - good electrical conductor and ductile

Used for electric and phone wires and plumbing as not corroded by water

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Reactivity series

Metals above carbon extracted by electrolysis

Metals below carbon extracted by reduction using carbon (coke or charcoal)

Native metals do not need to be extracted


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Blast furnaces

Metals have to be extracted from ores using electricity or heat

Metals collected from a blast furnace are impure 

Alloys are a mixture of metals designed to improve the properties e.g strength

Atoms in pure iron arranged densly so layers can slide making if a soft metal

Other atoms are different sizes so when added the regular structure distorts


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Blast furnaces


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Aluminium and titanium

Aluminium - aeroplanes, foil, cans, window frames, cables, pans

99% obtained from the ore bauxite which contains aluminium oxide

Extracted by electrolysis

Andodes made from graphite

Titanium - aeroplanes, turbines, artificial joints

Titanium ore contains titanium oxide

Can't be reduced by carbon because it's too brittle

Firstly converted to titanium chloride

Reducing agent is usually sodium

Reaction carried out in an atmosphere of the noble gas argon

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Purifying copper

Copper obtained by reduction is impure

Purified by electrolysis before it can be used in wiring


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