The first gases came from the eruption of Volcanoes and formed the Earth’s early atmosphere.
The main gases in the early atmosphere were:• Lots of carbon dioxide • Some nitrogen• Little or no oxygen• Water vapour• Ammonia
Volcanoes release these gases today (and so scientists think the same processes operated in the past).
C1.1 The Early atmosphere
The oceans were formed from the condensation of the water vapour to make liquid water.
C1.2 a changing atmosphere.
A simple carbon cycleThe level of carbon dioxide in the atmosphere is maintained by several processes, photosynthesis, respiration and combustion
Green plants remove carbon dioxide from the atmosphere by photosynthesis. Respiration and combustion both release carbon dioxide into the atmosphere.
These processes form a carbon cycle in which the proportion of carbon dioxide in the atmosphere remains about the same.
Carbon dioxide fell because:• Some carbon dioxide dissolved
into the oceans.• Some was absorbed by marine
creatures who stored it tin their shells as calcium carbonate which later formed carbonate rocks.
As the number of plants increased, the oxygen levels rose through photosynthesis. These plants absorb carbon dioxide too.
Carbon dioxide levels fellOxygen levels rose
C1.4 The atmosphere today.
Changes in the atmosphere occur through; Natural activities: • Volcanic activity can lead to a rise in
sulphur dioxide; lightening can lead to a rise in nitrogen oxides.
Human activity: • burning fossil fuels can lead to an
increase of carbon dioxide, carbon monoxide and sulphur dioxide.
• Deforestation lead to an increase in carbon dioxide; burning trees releases carbon dioxide (combustion), fewer trees to photosynthesise and absorb carbon dioxide; engines and furnaces release nitrogen oxides.
• Farming: increasing numbers of cattle and rice fields can lead to an increase of methane.
How do scientists use rocks to work out the composition of the Earth’s early atmosphere?
Analyse the minerals in them and look for oxides. As more oxygen was present, more oxide mineralswere formed.
Gas Formula % in dry air
Nitrogen N2 78
Oxygen O2 21
Argon Ar 0.9
Carbon Dioxide
CO2 0.04
other trace
Our atmosphere today…
C1.5 Rocks and their FormationIgneous Rocks• Example – granite.• Formed by the solidification of
magma or lava• They contain crystals whose size
depends on the rate of cooling.• Quick cooling = small crystals• Fast cooling = large crystals
metamorphic – A rock changed by pressure and heat.sedimentary – A rock formed by the deposition of sediments.thermal decomposition – The breakdown of a compound into simpler substances by heating. electrolysis – The use of electricity to split a compound. granite – A type of igneous rock that is harder than limestone and marble.igneous – A rock formed from cooled magna.limestone – A type of sedimentary rock containing calcium carbonate.limewater – A limestone product made by fully dissolving quicklime in water. It is used to test for carbon dioxide. marble – A type of metamorphic rock that is harder than limestone but softer than granite
Sedimentary rocks• Sedimentary rocks contain fossils• They are formed from compaction of
layers of rock over a long time. • They are not as strong as other rocks so
erode easily.• Examples - chalk and limestone
Metamorphic Rocks• Example – marble• Formed when heat or
pressure is applied to other rocks.
• Marble is formed from chalk or limestone being heated and pressurised.
Limestone, chalk and marble are all forms of calcium carbonate and exist in the Earths crust.
C1.6 LimestoneLimestone is made of calcium carbonate (CaCO3)It is used in:
– Building materials- glass, cement, concrete – Improving the pH of acid soil
Thermal Decomposition of Calcium Carbonate When metal carbonates are heated they break down into a metal oxide and carbon dioxide is given off
Copper carbonate copper oxide + carbon dioxide CaCO3 CaO + CO2
Problems associated with quarrying:Economic - moneySocial – the peopleEnvironmental - pollution
Limestone is heated with clay to make cementCement is added to sand and water to make mortarCement is added to sand, aggregate and water to make concrete
Advantage of quarrying…jobs and valuable building resources.
The advantages and disadvantages of quarrying.
C1.7 Thermal decomposition Ease of thermal decomposition of metal carbonates: • Most difficult to decompose is sodium carbonate (10000C), calcium carbonate (8250C), zinc
carbonate (3000C) and copper carbonate (2000C).
• Copper carbonate will start to decompose to form carbon dioxide and copper oxide. The reaction will absorb some of the heat from the fire. The carbon dioxide can help to put out the fire by reducing the amount of oxygen available for combustion.
• The mass of reactants do not change, the particles just get rearranged. • The atoms take part in a chemical reaction they are very small.• When calcium hydroxide is dissolved in water it makes Limewater.
Copper carbonate copper oxide + carbon dioxideCaCO3(s) CaO(s) + CO2(g)
Copper carbonate copper oxide + carbon dioxideZinc carbonate zinc oxide + carbon dioxide
Breaking down with heat
C1.8 Chemical reactionsWord equationsA word equation gives the names of the substances involved in a reaction. For example:
copper + oxygen → copper(II) oxideCopper and oxygen are the reactants, and copper(II) oxide is the product.
Precipitation reactions1) A simple example of conservation of mass is a precipitation reaction. 2) Transition metals form coloured compounds with other elements. Many of these are soluble in water, forming coloured solutions. If sodium hydroxide solution is then added, a transition metal hydroxide is formed. These are insoluble. They do not dissolve but instead form solid precipitates. As all the reactants and products remain in the sealed reaction container then it is easy to show that the total mass is unchanged.copper sulfate + sodium hydroxide → copper hydroxide
+ sodium sulfateCuSO4 + 2NaOH → Cu(OH)2 + Na2SO4
C1.9 Reactions of Calcium Compounds
Neutralising acids with limestone1. Calcium compounds that neutralise acids:
– Calcium carbonate (CaCO3)– Calcium oxide (CaO)– Calcium hydroxide (Ca(OH)2)
2. Uses of these alkalis1. Farmers neutralise soil2. Power stations use wet powdered CaCO3 to neutralise acidic waste gases like Sulfur dioxide and
nitrous oxides. ( below is the equation for sulfur dioxide production)S (g) + O(g) SO2 (g)
Keywords• Neutralisation reaction - reaction in which a base or an alkali reacts with
an acid.• Limewater – Solution of calcium hydroxide. It is used to test for the
presence of CO2 as it turns from colourless to cloudy.
Making Limewater1. Heating limestone - Calcium carbonate (CaCO3) turns it into Calcium oxide (CaO)
CaCO3 (s) CaO(s) + CO2 (g)
2. Adding water to CaO – vigorous reaction that creates calcium hydroxide (crumbly solid)CaO(s) + H2O (l) Ca(OH)2(s)
Testing for CO2 - limewater turns cloudy/milky as calcium carbonate forms. Ca(OH)2(s) + CO2 (g) CaCO3 (s) + H2O (l)
NB – large quantities of CO2 will dissolve to form an acid. This reacts with the CaCO3 making it colourless again!
1.10 indigestion
Indigestion remedies contain substances to neutralise excess stomach acid.
• When an acidic compound dissolves in water it produces hydrogen ions, H+. These ions are responsible for the acidity of the solution.
• When an alkaline compound dissolves in water it produces hydroxide ions, OH−. These ions are responsible for the alkalinity of the solution.
• Acids react with alkalis to form salts. These are called neutralisation reactions. In each reaction, water is also formed:
Acid + alkali → salt + water
ExampleHydrochloric acid + sodium hydroxide → sodium chloride + water
HCl + NaOH → NaCl + H2O
• Hydrochloric acid contains hydrogen ions and chloride ions dissolved in water.
• Sodium hydroxide solution contains sodium ions and hydroxide ions dissolved in water.
Hydrochloric acid is produced in the stomach to kill bacteria and to help digestion.
Hydrochloric acid produces chloride salts e.g. calcium chlorideNitric acid produces nitrate salts e.g. calcium nitrateSulfuric acid produces sulfate salts e.g. calcium sulfate
C1.11Neutralisation• You need to be able to describe the reactions of hydrochloric acid and sulfuric acid with metal hydroxides,
metal oxides and metal carbonates.
Metal hydroxides• Metal hydroxides, such as sodium hydroxide, usually dissolve in water to form clear, colourless solutions.
When an acid reacts with a metal hydroxide, the only products formed are a salt plus water. Here is the general word equation for the reaction:
acid + metal hydroxide → a salt + water• there is a temperature rise • the pH of the reaction mixture changes
Metal oxides• Some metal oxides, such as sodium oxide, dissolve in water to form clear, colourless solutions. Many of them
are not soluble in water, but they will react with acids. Copper(II) oxide is like this. When an acid reacts with a metal oxide, the only products formed are a salt plus water. Here is the general word equation for the reaction:
acid + metal oxide → a salt + water
Metal carbonates• Although sodium carbonate can dissolve in water, most metal carbonates are not soluble. Calcium carbonate
(chalk, limestone and marble) is like this. When an acid reacts with a metal carbonate, the products formed are a salt plus water, but carbon dioxide is also formed. Here is the general word equation for the reaction:
acid + metal carbonate → a salt + water + carbon dioxide• You usually observe bubbles of gas being given off during the reaction. You can show that the gas is carbon
dioxide by bubbling it through
c1.13 electrolysis
The process of electrolysis• Positively charged ions move to the
negative electrode during electrolysis. They receive electrons and are reduced.
• Negatively charged ions move to the positive electrode during electrolysis. They lose electrons and are oxidised.
ELECTROLYSIS OF Hydrochloric Acid• Produces chlorine at the positive
electrode• Produces hydrogen at the negative
electrode
ElectrolysisThe process in which electrical energy from a d.c. supply decomposes compounds
1.15 Electrolysis of Water
Water• Produces oxygen at the positive
electrode• Produces hydrogen at the
negative electrode• If the gas relights a glowing
splint, it is oxygen.
Electrolysis of Seawater• This produces chlorine gas at
the electrode.
1.16 oresGold and platinum found naturally in the environment as they are unreactive.
Most metals are found as ores (usually reacted with oxygen) in the Earths crust.
Ores are rocks which contain metals.
Extraction = getting the metal out of the rock. Sometimes you can…• Heat the rock to get the metal• Or use electrolysis.
Uses of metals.Gold= jewellery Copper = wiresSilver = jewellery
C1.26 Acid rain
Effects of acid rain- Fish numbers started to decrease.- Soils are made acid and can harm plants. - Trees damaged- Erosion of buildings made of limestone.
Causes of acid rain.- Dissolved carbon dioxide and acidic gases in
water.- Sulphur dissolved in water from fossil fuels.- Burning of fossil fuels which create sulphur.
C1.17 Extracting metal
anode – The positive electrode used in electrolysis. cathode – The negative electrode used in electrolysis. electrolysis – The use of an electric current to separate
out the elements in a compound. electrolyte – An ionic compound that conducts
electricity when in a liquid state. ore – A rock that contains a metal combined with other
elements in concentrations that make it profitable to mine.
Factors which affect how a metal is extracted are cost and position in the reactivity series
Iron is heated with carbon in a reduction reaction to extract it from its ore.
Iron oxide + carbon iron + carbon dioxide
Aluminium is extracted from its ore by electrolysis because it is more reactive.
Aluminium oxide aluminium + oxygen
C1.18 Oxidation and reduction
KeywordsReduction – occurs when oxygen is removed from a compoundCorrosion – when a metal is converted to its oxide by the action of moist airOxidation – occurs when oxygen is added to an element or compoundRusting – the corrosion of iron
Metal extraction is reduction• Most metal ores are ‘oxides’• To get the metal we must remove the oxygen• We say the compound has been reduced. It is a REDUCTION reaction• Example 1 = Iron oxide is heated with Carbon
Iron oxide + Carbon Iron + Carbon dioxide• Example 2 = Aluminium is obtained by electrolysis of aluminium oxide
Aluminium oxide Aluminium + Oxygen
Corrosion of metals is oxidation• Most metals corrode• Surface of a metal reacts with oxygen (or sometimes water)• This is called OXIDATION reaction• More reactive metals corrode more rapidly (less reactive may not corrode at all e.g. Gold)• A layer of metal oxide forms (this can stop further corrosion e.g. on Aluminium = and Al2O3 layer forms)
C1.19 Recycling metalsKeywords• Recycled metal – when a used metal is melted down and made
into something new.
Many metals can be recycled…Advantages• Natural reserves will last longer• Most use less energy to recycle that to extract. E.g. Aluminium recycling 95% more energy
efficient compared to extraction.• Reduced mining which damages landscapes and causes pollution (dust and noise)• Recycling produces less pollution. Examples supporting this are
• Lead from its ore ‘galena’ produces sulfur dioxide• Carbon dioxide is produced during extraction by electrolysis.
Disadvantages• Costs money and uses energy to collect, sort and transport metals to be recycled• This can make it more expensive to recycle some metals the extract them
The most recycled metals in the UK are Lead , Iron and Aluminium and Copper
Method1. Collecting – requires people to be willing to separate their rubbish2. Separating different metals
• Iron can be separated using a magnet (quick and easy)• Others usually separated by hand (time consuming and labour intensive)
3. Purifying – metals are melted down to form blocks
Aluminium Copper Gold Iron and SteelUseful Properties• Low density• Does not corrode
(because of layer of oxide that forms quickly)
Uses• Aeroplanes and cars
to make them lighter (cheaper to run as they need less fuel)
Useful Properties• Ductile• Low reactivity (does
not react with water)• Good electrical
conductor
Uses• Electrical cables• Water pipes
Useful Properties• Very unreactive• Does not corrode• Malleable• Remains shiny• Excellent electrical
conductor
Uses• Jewellery• Electronic devices
(printed circuit boards and connection strips)
Useful Properties• Cheap to extract by
heating with carbon• Pure iron too soft but
in alloys is very useful• Steel (Iron mixed with
carbon and other metals) is strong and hard
• MagneticUses (mainly as steel)• Bridges, cars, cutlery,
electrical goods, machinery, building frames, magnetic products
C1.20 Properties of metals
KeywordsMalleable – can be hammered into shapeConduct – allows heat or electricity to pass through itDuctile – can be stretched into wiresDensity – the mass of a substance per unit volume; the unit is usually g/cm3
Properties include:– shiny when polished; conduct heat and electricity; malleable; ductile.
C1.21 AlloysKeywordsAlloy – a metal mixed with small amounts of other metals to improve their propertiesCarats – a measure of the purity of gold with pure gold being 24 caratsFineness – another measure of purity of gold (parts per thousand)Smart material – a material that’s properties change with a change in conditionsShape Memory Alloy – an alloy that can return to its original shape when heated
Pure metal1. All atoms are the same size and therefore closely packed
together.2. This means that layers of atoms slide over each other which
makes the metal soft.3. In an alloy different atoms are added which prevent the atoms
sliding so easily = harder and stronger
Examples of AlloysAlloy steels – iron mixed with other metals• Stronger that Iron• Some resist corrosion. Stainless steel NEVER corrodes (Iron with Chromium and Nickel)Gold - Pure gold (24 carat) too soft. 24 carat gold has a fineness of 1000 parts per thousand • Copper and silver added to make it harderNitinol – Smart material made from nickel and titanium• Return to original shape when heated. • Used in repair of arteries (inserted in squashed and cold and warms with body to reshape)• Flexible glasses frames
Pure metal
Alloys
C1.22 Crude Oil
Key words• Hydrocarbons are compounds that contain
carbon and hydrogen only.• Crude oil is a complex mixture of
hydrocarbons
C1.23 Crude Oil Fractions
• Crude oil is separated into simpler, more useful mixtures by fractional distillation.
C1.23 Crude Oil Fractions
Fraction Uses
Gases Domestic heating and cooking
Petrol Car fuel
Kerosene Aircraft fuel
Diesel oil Fuel for some cars and trains
Fuel oil Fuel for ships and some power stations
Bitumen Surfacing roads and roofs
There are 6 fractions you need to know…
C1.23 Crude Oil Fractions
Fraction Length of molecule
Ease of ignition Boiling point Viscosity
Gases Short
Long
Easy
Difficult
Low
High
Runny
Thick and sticky
Petrol
Kerosene
Diesel oil
Fuel oil
Bitumen
Key words:Ignition – to set alightViscosity – How thick or runny a substance is
How do the fractions differ?
C1.24 Combustion
Key words:Combustion – a chemical reaction with oxygen (oxidation) to release energy.Complete combustion – where all the hydrocarbon is used up.Oxidation – the addition of oxygen.
+ Energy released
Any hydrocarbonTested for using limewater. CO2 will turn it cloudy if present.
C1.25 Incomplete Combustion
Keywords:• Incomplete combustion – where there is not enough oxygen for the fuel to
completely burn.• Carbon Monoxide – poisonous gas produced during incomplete combustion.
Water is formed just like in complete combustion but there are not enough oxygen atoms to form CO2. Soot and Carbon Monoxide are formed instead.
3 different equations show what can happen:
Methane + Oxygen Carbon (soot) + WaterMethane + Oxygen Carbon Monoxide + WaterMethane + Oxygen Carbon Dioxide + Carbon Monoxide + Carbon (soot) + Water
Different percentages of CO2, CO and C are produced depending on the amount of oxygen present.
C1.25 Incomplete Combustion
Problems of incomplete combustion:
• Carbon Monoxide is an odourless, colourless, toxic gas.• It reduces the amount of oxygen carried by the Red
Blood Cells.• Carbon monoxide poisoning can kill.• Soot can clog pipes carrying waste gases.• Faulty or blocked boilers can produce carbon
monoxide.
C1.26 Acid RainKey word:Acid rain – rain that is more acidic than normal.
Impurities in hydrocarbons such as sulfur react with oxygen to produce sulfur dioxide. This dissolves in rainwater to form acid rain.
4 Problems of Acid Rain:• Rivers, lakes and soils become acidic harming living organisms• Damages trees• Speeds up weathering of buildings made of limestone or marble• Corrodes metal
C1.27 Climate Change
3 gases trap heat from the Sun and keep the Earth warm – Greenhouse Effect• Carbon Dioxide• Methane• Water vapour
The Earths temperature varies.
Human activity such as burning fossil fuels may influence this
C1.27 Climate Change• The amount of carbon dioxide in the atmosphere varies due
to human activity – burning fossil fuels.
How to reduce the amount of carbon dioxide in the atmosphere:• Iron Seeding Oceans – Adding iron to the ocean encourages
algal growth which photosynthesise and absorb carbon. They are eaten by other organisms which incorporate carbon into their shells which sinks to the bottom of the ocean.
• Converting carbon dioxide back to hydrocarbons – trapping gases from power stations and reacting them to make butane or propane to use as fuels.
C1.27 Climate ChangeKey words:• Correlation – a pattern which is similar in two variables. It could be due to chance. • Causation – when one variable causes the effect in the other.
• There is a correlation between carbon dioxide levels in the atmosphere and the Earths temperature.
• Not all scientists are convinced that increasing carbon dioxide levels cause global warning.
Because…• There are fluctuations throughout history• There are other causes of global warning• There are other greenhouse gases• Future predictions are just predictions
C1.28 Biofuels
Key words:Biofuel – A fuel made by humans from animal or plant material that has recently died.Ethanol – A fuel made from sugar beet or sugar cane.Biodiesel – Diesel made from plant material.Carbon neutral – a fuel that does not add any carbon to the atmosphere overall.
Biofuels are a possible alternative to fossil fuels e.g. ethanol which could reduce demand for petrol.Advantages of Biofuels Disadvantages of Biofuels
They are renewable Growing crops for fuels requires land that could be used to grow food
Plants remove carbon dioxide from the atmosphere as they grow
Transportation of the fuels produces carbon dioxideBurning the fuels produces carbon dioxide
C1.29 Choosing Fuels4 factors that make a good fuel:• How easily it burns.• How much ash or smoke it produces.• The comparative amount of heat energy it produces.• How easy it is to store and transport.
• A fuel cell combines hydrogen and oxygen to make water and releases energy.
• Petrol, Kerosene and diesel oil are non-renewable fossil fuels made from crude oil.• Methane is a non-renewable fossil fuel from natural gas.
Advantages of using hydrogen as a fuel Disadvantages of using hydrogen as a fuel
When hydrogen burns no carbon dioxide is produced, only water vapour
Hydrogen usually produced from natural gas and the process releases carbon dioxide
Hydrogen fuel cells are more efficient than petrol engines
Hydrogen needs to be readily available first
Renewable Petrol stations would have to be converted to store and sell hydrogen tooCost of the above
C1.31 Alkanes and Alkenes
Alkanes are saturated hydrocarbons which are present in crude oil.
Learn the formula and be able to
draw each of these.
C1.31 Alkanes and Alkenes
• Alkenes are unsaturated hydrocarbons
Bromine water is used to distinguish between alkanes and alkenes
Ethene + bromine water colourless(colourless) (orange)
Ethane + bromine water orange(colourless) (orange)
Learn the formula and be able to
draw each of these.
C1.32 Cracking
Cracking involves breaking down long saturated hydrocarbons (alkanes) into smaller useful ones. Some of these small molecules are unsaturated (alkenes).
Know how to crack
paraffin in the lab.
Why is cracking needed? Crude oil has different amounts of each fraction. These don’t always match customer demand so they crack
them to match demand.
C1.33 Polymerisation
Many ethane molecules can combine in a polymerisation reaction.
Learn the formula and equation
C1.33 PolymerisationPolymer Properties Use
Poly(ethane) – polythene Flexible, cheap, good insulator
Plastic bags, plastic bottles, cling film, insulation for electrical wires
Poly(propene) – polypropene
Flexible, shatterproof, high softening point
Buckets and bowls
Poly(chloroethene) - PVC Tough, cheap, long-lasting, good insulator
Window frames, gutters, pipes, insulation for electrical wires
Poly(tetrafluoroethene) PTFE or Teflon
Tough, slippery, resistant to corrosion, good insulator
Non stick coatings for saucepans, bearings for skis, containers for corrosive substances, stain proof coating for carpets, insulation for electrical wires