Chemistry AQA Notes,C1

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1.1 Atoms, elements and compounds
COMPOUND- a substance made of two or more types of atom chemically joined together
ELEMENT- a substance made of only one type of atom
MIXTURE- a combination of two or more elements in a way that allows each element to keep its own chemical identity.
All substances are made up of atoms
Elements contain only one type of atom
Different atoms can bond together by giving/taking/sharing electrons, to form compounds.
Atoms are made up of a tiny central nucleus surrounded by electrons
1.2 Limestone and its uses
airborne pollution = dust, gases, noise and vibration (machinery) and during blasting in quarries, and damage to countryside from
Limestone is made mainly of calcium carbonate (CaCo3)
Some types of limestone are made of the remains of tiny animals and plants which lived in the sea millions of years ago
We dig limestone out of the ground in quarries
Its main use is as a building material/ in the manufacture of iron
Powdered limestone + high temperature+ sand+ sodium carbonate= glass
powdered limestone + powdered clay + heat= cement
cement powder + water + sand +gravel= concrete
Limestone + strong heating= quicklime (calcium oxide) + carbon dioxide (thermal decomposition)
To make lots of quicklime we use a lime kiln
1) fill the kiln with crushed limestone
2) heat it strongly with a supply of hot air
quicklime comes out of the bottom of the kiln, waste gases leave at the top.
Usually the kiln rotates to ensure that the limestone is thoroughly mixed with the stream of hot air and it therefore decomposes
1.3 Decomposing carbonates
Calcium is in group two, as is magnesium, so we can expect magnesium carbonate to have the same properties as calcium carbonate
(they both decompose)
The behaviour of carbonates
Calcium carbonate (2) / Magnesium Carbonate (2) / Zinc Carbonate/ Copper Carbonate DECOMPOSE (Y)
Potassium Carbonate(1) / Sodium Carbonate (1) DO NOT DECOMPOSE (N)
From looking at these results we could say that they suggest that group two decompose, and group one does not. However we cannot
assume this for all of each group.
This investigation shows that when many carbonates are heated in a Bunsen flame they decompose,; they dorm the metal oxide and
carbon dioxide (calcium carbonate). Sodium and potassium do no decompose at the temperature in the Bunsen flame.
Word Equations VS Symbol Equations
Symbol equations are BETTER, because: 1) word equations are only useful if everyone who needs to read them speak the same language
2) word equations do not tell us quantities of the substances involved
3) word equations can get very complex when lots of chemicals are involved
All symbol equations must be BALANCED this means that there is the same amount of atoms in each side.
The general equation for thermal decomposition of a metal carbonate
metal carbonate =heat> metal oxide+ carbon dioxide
The mass of reactants is the same as the mass of the products in a chemical reaction
1.4 Quicklime and slaked lime
Limestone +heat = quicklime
quicklime + water= slaked lime (calcium hydroxide) + heat
calcium oxide +water= calcium hydroxide
EXOTHERMIC reaction.
Calcium hydroxide is not very soluble, but can dissolve a little in water, after filtering a colourless solution called lime water
calcium hydroxide + water= lime water (left over calcium hydroxide)
We can use lime water to test for carbon dioxide
when carbon dioxide is bubbles through clear lime water, the solution turns cloudy.
This is because calcium carbonate is formed, which is insoluble in water
calcium hydroxide + carbon dioxide => calcium carbonate + water
slaked lime + sand + water=. Mortar

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Calcium carbonate + water
the amount of sand is very important, too little, the mortar shrinks as it dries, too much, the mortar is too weak. This method has been
used for thousands of years
1.5 Cement, concrete and glass
Lime mortar is very strong, but can't be used in places where water prevents it from reacting with carbon dioxide (swimming
pools/fountains) The Romans realised that in order to make it work in wet conditions, they would have to add brick dust/ volcanic ash..…read more

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At the high temp blast furnace=> the co2 reacts again with coke = carbon monoxide
3) Carbon monoxide reacts with iron oxide, removing oxygen, reducing it to molten iron, which flows to the bottom of the blast
Fe2O3 + 3CO => 2Fe + 3CO2
a) Some is left in moulds to cool= cast iron ( 96 % iron)= very important to industrial revolution- 1700s and 1800s Abraham Darby
family- improved/developed ways of making iron.…read more

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These properties= many uses: buildings, cars, trains, transport.
strength=useful as construction metals.
good conductors= heating and electrical wiring.
Example of transition metal- Copper. not particularly strong bent/shaped easily. conducts heat/electricity well doesn't react with
water. ideal for water pipes or electrical wires.
Extraction of Copper ­
extracted from a Copper Ore by two methods
1) involves sulphuric acid, producing copper sulphate solution before extracting the copper.
2) smelting. Copper Ore heated strongly in air => crude copper.…read more

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Complexing agents increase uptake of crop.
2)Crops grow on soil containing metal concentration
3)Plant material is burned, possible production of electricity.
4)Small volume of plant ash (bio-ore) high amount of metal
5)Smelt bio-ore to yield metal.
Recycling Fridges ­ Recycling is easier than extracting metals. It is not always easy to recycle metals because they are combined with
other materials.
1)Firstly, chemicals need to be removed from the cooling system of the fridge.…read more

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OR CH + 5O 3CO + 4HO
Notice how we need 5 molecules of oxygen for the propane to burn. This creates 3 molecules of Carbon Dioxide and 4 molecules of water.
The equation is therefore BALANCED!!!
As well as hydrocarbons all fossil fuels, (coal, oil and natural gas), contain other substances. When we burn the fuel different
compounds are produced which can cause problems for us.
Impurities of sulphur= major problems.…read more

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Plant fuels- Fossil fuels used to produce electricity and drive our cars have big disadvantages: production of CO and other pollutants.
They are also non-renewable; once they run out we can't replace them. Plants could be one answer to this problem
Plants that make sugar can be used to produce ethanol by fermenting the sugar using yeast. The ethanol can then be added
to fuel to make gasohol.…read more


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