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C1A Chapter
1:Rocks and
BuildingsREVISION
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Elements
} Substances made up of only one type of
atom.} The atoms are held together by chemical
bonds.
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Compounds
} Two or more different types of elementsthat are chemically joined by a chemicalbond.
}Compounds have completely differentchemical properties from the originalelements. (This is because a chemicalreaction has taken place)
} The chemical bonds makes it difficult toseparate compounds.
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Mixtures
} Two or more different types of elements
that are mixed together (i.e there is nochemical bond)
} This means that the different elementskeep their original properties.
} This makes it easy to separate themthrough use of physical methods.
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Periodic Table
}GROUPS Vertical columns that containelements that have similar chemical
properties.
} PERIODS Horizontal rows that containelements with the same number of shells
} SYMBOLS Shorthand way of writingelements. Prevents confusion betweendifferent languages.
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Chemical Bond
} This is formed in a chemical reactionwhereby the electrons from the atoms
involved are given, taken or shared.
}An ionic bond is formed when electronsare given and taken.
}A covalent bond is formed when
electrons are shared.
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Limestone
} Formed when sand/mud/remains of deadanimals and plants fall to the bottom of
the ocean. They decompose and arecemented and compacted to form alayer of rock called limestone. This processtakes millions of years.
} Limestone is mainly Calcium Carbonate(CaCO3)
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How is limestone gathered?
} It is quarried out of the ground all over theworld.
} This has many problems:
} Damage/Destruction to habitats
} Noise pollution
} Air pollution by lorries carrying it away from
the site} Ruined landscape produced that requires
a lot of money to fix.
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Uses of Limestone
} Shaped into blocks Statues and Buildings
}
Although acid rain reacts with the limestoneand dissolves it away
} Road Surfacing
}Cement
}Concrete
}Mortar
}Glass
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Cement
} Powdered Limestone + Powdered Clay
}
Heated in a kiln} Produces cement
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Concrete
}Cement + Sand + Water + Gravel
}Mixed Together
} Produces concrete
} This is a slow reaction!!!
} You can add steel rods to make
reinforced concrete} Hardness of concrete and strength of steel
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Glass
} Powdered Limestone + Sand + SodiumCarbonate
} Heated at high temperatures in a kiln
} Produces Glass
} WeatherProof + Light
} Very important building material
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Thermal DecompositionReaction
} Thermal decomposition is when onesubstance is heated strongly and
chemically changes into at least two newsubstances.
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Thermal Decomposition ofLimestone
} This process is done in a lime kiln
}
Limestone is heated strongly.} It breaks down into calcium oxide and
carbon dioxide.
}CaCO3 CaO + CO2
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Calcium Oxide (Quick Lime)
}Calcium Oxide + Water
} Produces Calcium Hydroxide
}Quick Lime + Water Slaked Lime
}CaO + H2O Ca(OH)2
} This reaction gives out a lot of heat!!!
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Calcium Hydroxide (SlakedLime)
} Slaked lime is an alkali used to neutraliseacidic fields. This is a faster way in
comparison to powdered limestone.
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Lime Water
}Calcium Hydroxide (Slaked Lime) is notvery soluble in water. However, a little bit
can be dissolved in water.
}After filtering, a colourless solution isproduced called lime water.
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Test for Carbon Dioxide
}Carbon dioxide is bubbled through thelime water.
} The carbon dioxide reacts with thecalcium hydroxide to produce calciumcarbonate and water.
} The calcium carbonate is insoluble in
water and therefore the solution turnscloudy.
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Old Mortar
} Slaked Lime + Sand + Water
}
This produces the old type of mortar.}Mortar is used for holding building
materials together.
}When the mortar is used, it is exposed toair. Carbon dioxide reacts with the slakedlime to produce calcium carbonate andwater.
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Old Mortar Continued} Ca(OH)2 + CO2 CaCO3 + H2O
} The right amount of sand needs to be used in
this mixture:} TooMuch Mortar becomes weak
} Too Little Mortar shrinks when it dries
} The mortar does not harden very quickly!
} This mortar does not harden when water ispresent because the water prevents thecarbon dioxide reacting.
} Adding volcanic ash or brick dust solves thisproblem.
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New Mortar
} Portland Cement (made in the same wayas cement but with minerals)
} Portland Cement + Sand
} This produces the modern mortar whichsets when water is added.