Chemistry Unit 1 Chemistry Revision
Atoms, elements and compounds
 An atom has a tiny nucleus in its centre, surrounded by electrons.
The arrangement of electrons in atoms
 The atoms of the unreactive noble gases all have very
stable arrangements of electrons.
Forming bonds
When atoms from different elements react together they
make compounds. The formula of a compound shows the
number and type of atoms that have bonded together to
make that compound.
When metals react with non-metals, charged particles
called ions are formed.
 Metal atoms form positively charged ions. Non-metal
atoms form negatively charged ions. These oppositely charged ions attract each other in ionic bonding.
 Atoms of non-metals bond to each other by sharing electrons. This is called covalent bonding.
Rocks and Building Materials
Limestone (CaCO3)
 Thermal Decomposition  Calcium Carbonate  Calcium Oxide + Carbon Dioxide
 Quicklime (CaO) + Water (H2O)  Calcium Hydroxide (Ca(OH)2)
Other Reactions
Limewater turns cloudy in the test for carbon dioxide gas.
Metal carbonates decompose on heating to form the metal oxide and carbon dioxide.
Compounds involving limestone
Cement is made by heating limestone with clay in a kiln.
Mortar is made by mixing cement and sand with water.
Concrete is made by mixing crushed rocks or small stones called aggregate, cement and sand with water.
Limestone Benefits:
 More jobs are created
 Valuable natural resource used to make glass and concrete
Limestone disadvantages
 Quarrying creates noise and traffic
 Disfigure environment
Metals and their uses
Extracting metals
Metal Ore: If there is enough of the metal to make it worth extracting, it
metal ore.
Unreactive metals like gold are found in their natural state
Extraction
Metal Oxide + Carbon  Metal + Carbon Dioxide
Metals below carbon are extracted through reduction. Metals that are
reactive than carbon are extracted using electrolysis.
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Iron and steels
iron
 Carbon reduces the iron oxide (often haematite) forming molten
and carbon dioxide.
 Iron from the blast furnace is very brittle as it contains 96% iron and some impurities such as carbon.
Used to make wood-burning stoves, manhole covers on roads, and engines.
 Iron becomes useful when small amounts of other elements are added, such as chromium and nickel.
Alloy Steels
 Are expensive and contain about 1-5% other elements
Aluminium and titanium
Aluminium and titanium are both strong and they don’t corrode.
Properties of Aluminium
 Shiny
 Very good conductor
 Used for:
o Drinks cans
o Aeroplanes and space vehicles
Extraction
Electric current is passed through molten aluminium oxide at high temperatures which is expensive because of
the energy uses.
Properties of Titanium
 Silvery white metal.
 Very strong
 Melts at 1660oC
 Used for:
o Bodies of high-performance aircraft and racing bikes
o Parts of nuclear reactors
Extraction
Titanium is extracted by sodium and magnesium which are extracted by electrolysis.
Useful metals
Transition metals are mostly strong, ductile, malleable and good conductors.
 Copper alloys: bronze (copper and tin) and brass (copper and zinc)
o Bronze is tough and resistant to corrosion
 Aluminium alloys: They have different properties: some are used for aircraft while others are used for
armour plating.
 Gold alloys: when alloyed with copper it is very hard and does not wear easily, so it is used for jewellery.
Metallic issues
 Scar landscapes.
 Water can be affected by mining, as rain drains through exposed ores and slag heaps of waste, acidifying
it.
 Sulphur dioxide that is produced causes acid rain.
 Recycling
o Recycling aluminium saves energy (95% energy saving).
o Iron and steel can be recycled, saving 50% energy.
o Copper is recycled so that we do not use up the Earth’s reserves of the metal.
Crude Oil and Fuels
Crude oil is a mixture of lots of different chemical compounds, with different boiling points, mostly hydrocarbons,
which are mostly alkanes.
 Alkanes are saturated hydrocarbons:
Fractional distillation
The column is very hot at the bottom and decreases in
temperature as you ascend. The different compounds in
the
crude oil vapour condense at different points on the
fractionating column.
Burning fuels
 Lighter fractions from crude oil are volatile and are
very
useful as fuels.
 They combust to make carbon dioxide and water.
The
carbon and hydrogen of the hydrocarbon are
oxidised during the reaction.
Environmental problems
 Carbon particulates can cause global dimming.
 Carbon monoxide is poisonous and it is particularly serious for people who have heart problems.
 Sulphur dioxide and nitrogen oxides acidify rain in the clouds.
Alternative fuels
 Biofuels are made from animal or plant products
Advantages
 Biodiesel is renewable resource and is almost carbon neutral.
Disadvantages
 Using large areas of land to grow crops for could result in famine.
 Forests may need to be cut down to make room for biofuel crops which also destroys habitats.
Ethanol
Ethanol is made by fermenting sugar from sugar beet or sugar cane
Products from oil
Cracking hydrocarbons
Long chain hydrocarbons can be broken down in a process called cracking. The hydrocarbon is heated up and
passed over a hot nickel catalyst at 500 degrees Celsius.
 Test to see if hydrocarbon is saturated:
o Saturated hydrocarbon + orange-yellow bromine water produces an orange-yellow solution
o Unsaturated hydrocarbon + orange-yellow bromine water produces a colourless solution.
Making polymers from alkenes
Polymers are made up of joined monomers in a process called polymerisation. The double bond between the
carbon atoms opens up, and is replaced by single bonds.
New and useful polymers
Scientist are researching new biodegradable plastics which rot away when they are dumped. Granules of cornstarch are added to the plastics so micro-organisms can feed on them.
Disadvantages
 Using food crop for plastics can raise the same issues as when it is used for biofuels (famine, destruction
of rainforests).
Ethanol
 Ethanol is an alcohol: C2H5OH.
Fermentation
We can ferment sugar from plants to produce ethanol (C6H12O6 ––> 2C2H5OH + 2CO2) 30o to 40o and normal
pressure passed over a catalyst which are the enzymes in yeast
Hydration
Ethanol for industrial use as a fuel or solvent can be made from ethene gas (C2H4 + H2O  C2H5OH) 300o at high
pressure, catalyst: concentrated Phosphoric Acid
Plant Oils
Extracting vegetable oils
 Plants turn glucose into oils which we can extract to make biofuels
Crushing and Pressing
The seeds are removed and crushed to extract the oil. Then the impurities are removed.
Steam
The plants are put into water and boiled. The oil and water evaporate together and are collected through
distillation.
Cooking with vegetable oils
Vegetable oils boil at much higher temperatures than water therefore food can be cooked at a much higher
temperature. Therefore the food will absorb the oil and contain much more energy.
Unsaturated vegetable oils
Unsaturated vegetable oils are usually liquids at room temperature. By adding hydrogen molecules (which replace
the carbon-carbon double bonds with single bonds) we can increase the boiling and melting points of these
compounds. By reacting it with hydrogen gas, using a nickel catalyst at 60oC.
Emulsions
Oil and water do not mix, but when an emulsifier is added, it turns the oil into lots of tiny bubbles which spread
out in the water, creating an emulsion. Common emulsifiers are egg yolk and honey. An emulsifier has two ends
which stop the water and the oil from separating
Saturated and Unsaturated Fats
 Saturated fats are likely to cause heart disease by clogging up your arteries with fat.
 Unsaturated fats are very good for you as they reduce the chance of clogging up the arteries.
Earth and Environment
Structure of the Earth
 Crust: 5-70km
 Mantle: 3000km, behaves like a solid, but it can flow in parts slowly.
 Core: 3000km, made of a mixture of the magnetic metals, nickel and iron. The outer core is a liquid and
the inner core is a solid.
The restless Earth
 The tectonic plates move and separate due to convection currents in the mantle. The currents are driven
by radioactive processes. If they suddenly slip past each other, an earthquake will occur.
 Huge stresses build up at plate boundaries, which can make the plates buckle and deform, and mountains
may be formed.
The Earth’s atmosphere in the past
The atmosphere today is 80% nitrogen, 20% oxygen and smaller proportions of various other gases. During the
first billion years of the Earth’s existence there was intense volcanic activity. This activity released the gases that
formed the early atmosphere and water vapour that condensed to form the oceans
One theory suggests that during this period the Earth’s atmosphere was mainly carbon dioxide and there would
have been little or no oxygen gas (like the atmospheres of Mars and Venus today)
Life of Earth
Miller and Urey conducted an experiment to see the molecules of life (e.g. amino acids) could be made from the
gases in the early atmosphere.
 They used a mixture of water, ammonia, methane and hydrogen to model the early atmosphere, and
used a high voltage to produce a spark to provide the energy needed for a reaction.
 After a week, a brown soup was produced which contained 11 different amino acids.
Gases in the atmosphere

Carbon dioxide is taken up by plants during photosynthesis. Carbon Dioxide is absorbed by the oceans.
Dead bodies of living things built up at the bottom of vast oceans, eventually forming sedimentary
carbonate rocks like limestone. They are also trapped in sedimentary things as carbonates and fossil fuels.
Separation
Fractional distillation can be used to separate atmospheric gases these gases. Firstly, the air must be
cooled to a temperature below -200oC. At this low temperature, solid carbon dioxide and water are both
removed from the mixture, and dust is filtered out. As the liquid is warmed up, the nitrogen boils off first
at -196
Boiling points:
 Nitrogen: -196
 Oxygen: -183
 Argon: -186