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Chemistry Unit C1 – Chemistry Unit C1 – Chemistry in our WorldChemistry in our World
EdExcel
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ElementsElementsIf a solid, liquid or gas is made up of only one type of atom we say it is an element. For example, consider a tripod made up of iron:
These atoms are ALL iron – there’s nothing else in
here
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CompoundsCompoundsCompounds are different to elements. They contain different atoms. Here are some examples:
Glucose
Methane
Sodium chloride (salt)
19/04/2319/04/23Some simple Some simple compounds…compounds…
Methane, CH4 Water, H2O
Carbon dioxide, CO2
Ethyne, C2H2Sulphuric
acid, H2SO4
Key
Hydrogen
Oxygen
Carbon
Sulphur
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Balancing equationsBalancing equationsConsider the following reaction:
Na
O
H HH H
Na
OH
Sodium + water sodium hydroxide + hydrogen
+ +
This equation doesn’t balance – there are 2 hydrogen atoms on the left hand side (the “reactants” and 3 on the right hand side (the “products”)
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Balancing equationsBalancing equationsWe need to balance the equation:
Na
O
H H
H H
Na
OH
Sodium + water sodium hydroxide + hydrogen
+ +
Na
O
H HNa
OH
Now the equation is balanced, and we can write it as:
2Na(s) + 2H2O(l) 2NaOH(aq) + H2(g)
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Some examplesSome examples
Mg + O2
Zn + HCl
Fe + Cl2
NaOH + HCl
CH4 + O2
Ca + H2O
NaOH + H2SO4
CH3OH + O2
MgO
ZnCl2 + H2
FeCl3
NaCl + H2O
CO2 + H2O
Ca(OH)2 + H2
Na2SO4 + H2O
CO2 + H2O
2
2
2 3
2
2
2
2 3
2
2
2
2
2 4
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Hazard signs to learn…Hazard signs to learn…
h i
Acid
Harmful Irritant
Corrosive
Oxidising
Toxic
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The EarthThe Earth’’s Atmospheres Atmosphere
Carbon dioxide, water vapour
Oxygen Nitrogen Noble gases
For the last 200 million years the atmosphere has remained roughly the same – it contains 78% nitrogen, 21% oxygen, 1% noble gases and about 0.03% CO2
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4 Billion years 3 Billion years 2 Billion years 1 Billion years Present day
Evolution of the EarthEvolution of the Earth’’s s AtmosphereAtmosphere
Carbondioxide
Methane Ammonia Oxygen Nitrogen Others
Present day atmosphere contains 78% nitrogen, 21% oxygen, 1% noble gases and about 0.03% CO2
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4 Billion years 3 Billion years 2 Billion years 1 Billion years Present day
Evolution of the EarthEvolution of the Earth’’s s AtmosphereAtmosphere
Volcanic activity releases CO2, methane, ammonia and water vapour into the atmosphere. The water vapour condenses to form oceans.
Some of the oxygen is converted into ozone. The ozone layer blocks out harmful ultra-violet rays which allows for the development of new life.
Green plants evolve which take in CO2 and give out oxygen by photosynthesis, increasing the amount of oxygen in the atmosphere. Carbon from CO2 becomes locked up in sedimentary rocks as carbonates and fossil fuels and is dissolved into the sea. Methane and ammonia react with the oxygen and nitrogen is released.
19/04/2319/04/23Carbon dioxide in the Carbon dioxide in the atmosphereatmosphereThe amount of CO2 in the atmosphere is affected by 3
things: 1) Geological activity moves carbonate rocks deep into the Earth and they release ______ _______ into the atmosphere during volcanic activity.
2) Human activity - When fossil fuels are burned the carbon contained in them reacts with _____ to form CO2. Furthermore, deforestation means that less _____ are around to take in CO2.
3) Increased CO2 in the atmosphere causes a reaction between it and _______. These reactions do not remove ALL of the new CO2 so the greenhouse effect is still getting _______!
Words – oxygen, seawater, carbon dioxide, worse, trees
19/04/23What are rocks?
Rocks are made from a combination of minerals and can be hard or soft depending on how the minerals are arranged.
Rocks can be found here…
…and here…
…and here…
…and here
19/04/23Sedimentary rocks
How sedimentary rocks are formed:
1) Weathering
2) Transportation
4) Burial
3) Deposition
19/04/23Metamorphic rocks
Metamorphic rocks are formed by the combined effect of heat and pressure on other rocks:
Pressure from rocks above…
…and heat from magma nearby
19/04/23Igneous Rock
Granite – a slow cooling rock with big crystals and rich in silica
Basalt – a fast cooling rock with small crystals and rich in iron
Rhyolite – a fast cooling rock with small crystals and rich in silica
Gabbro – a slow cooling rock with big crystals and rich in iron
19/04/23Igneous rocks
Igneous rocks are formed when lava or magma cools down and solidifies
If the lava or magma cools QUICKLY it has SMALL crystals
If the lava or magma cools SLOWLY it has BIG crystals
19/04/23Summary
Sedimentary, igneous or metamorphic?
How they were formed Appearance
Sedimentary
(e.g. sandstone, _______, chalk)
Small pieces of sediment were ______ together by salt and pressure from rocks above
Usually soft, can contain ________, easily eroded
Igneous
(e.g. basalt, _______)
Liquid rock (______ or lava) cooled down and turned back into a ______
Contain ______, very hard, never contain fossils
Metamorphic
(e.g. ______, slate)
Other rocks were acted on by heat and _______ over a long time
Sometimes have tiny crystals, no fossils, always hard and sometimes arranged in _______
Words to use – layers, stuck, granite, marble, fossils, limestone, crystals, pressure, magma, solid
19/04/2319/04/23Conservation of mass in Conservation of mass in reactionsreactions
In any reaction the total mass of products is the same as the total mass of the reactants
Example 1 – Magnesium oxide and hydrochloric acid
Mg OH Cl
Mg ClCl
HH OH Cl
1 x magnesium, 1 x oxygen, 2 x hydrogen and 2 x chlorine atoms
Also 1 x magnesium, 1 x oxygen, 2 x hydrogen and 2 x chlorine atoms
C
H
H
H
HO
O
OO
OH H
OH H
CO
O
Example 2 – Burning methane
19/04/23Calcium Carbonate
Calcium carbonate is a common chemical in the Earth and we’ve already come across it in a number of forms:
ChalkLimestone
Marble (made from chalk or limestone)
19/04/23Limestone
Limestone is a __________ rock made up of mainly calcium carbonate. It’s cheap and easy to obtain. Some uses:
1) Building materials – limestone can be quarried and cut into blocks to be used in _______. However, it is badly affected by ____ ____.2) Glass making – glass is made by mixing limestone with _____ and soda:
3) Cement making – limestone can be “roasted” in a rotary kiln to produce dry cement. It’s then mixed with sand and gravel to make _______.
Limestone + sand + soda glass
Words – sand, building, sedimentary, concrete, acid rain
19/04/23Pros and Cons of quarrying limestone
Reasons why quarrying limestone is a good idea
Reasons why quarrying limestone is a bad idea
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LimestoneLimestoneLimestone has a number of uses when it undergoes chemical reactions. There are two reactions to know:
1) Firstly, a THERMAL _________________ reaction is used to break the calcium carbonate down into calcium ______ and _______ __________:
2) _____ is then added to produce calcium __________:
Calcium carbonate calcium oxide + carbon dioxideHEAT
Calcium oxide calcium hydroxideWATER
Words – hydroxide, decomposition, carbon dioxide, water, oxide
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The The ““Limestone CycleLimestone Cycle””
Calcium Carbonate
(limestone)
Calcium Oxide
Calcium Hydroxide
Step 1: heat
Step 2: add a little water
Step 3: add more water and filter
Step 4: add CO2
CO2
CO2
Calcium Hydroxide solution
19/04/23Uses of these Calcium compounds
Calcium carbonate (limestone), calcium oxide and calcium hydroxide have a number of uses:
1) Neutralising acidic soil – calcium carbonate, calcium hydroxide and calcium oxide are _______ and can be used to ________ soil acidity to help ______ growth.
2) Removing pollutants – calcium carbonate can be used as a “_______” to remove acidic gases from a coal-fired power station’s waste products, helping prevent ____ _____.
Words – acid rain, alkaline, plant, scrubber, neutralise
19/04/2319/04/23Thermal decomposition of Thermal decomposition of carbonatescarbonates
Limestone undergoes thermal decomposition when heated. The same happens to other carbonates. For example, consider copper carbonate:
Limewater
Copper carbonate (green) turns into copper oxide (black)Limewater goes cloudy due to carbon dioxide being made
Copper carbonate copper oxide + carbon dioxide
19/04/23Neutralisation reactionsWhen acids and alkalis react together they will NEUTRALISE each other:
OH
Sodium hydroxide
ClH
Hydrochloric acid
The sodium replaces the hydrogen from HCl
ClNa
Sodium chloride
H2O
Water
Na
19/04/23Neutralisation experiment
In this experiment we mixed sodium hydroxide (an _____) and hydrochloric acid together and they ________ each other. The equation for this reaction is…
Sodium hydroxide + hydrochloric acid sodium chloride + water
Words – nitrate, neutralised, alkali, sulphate, salt, evaporating
A ____ was formed during the reaction, and we could have separated this by __________ the solution. The salt that we formed depended on the acid:
• Hydrochloric acid will make a CHLORIDE• Nitric acid will make a _________• Sulphuric acid will make a _________
19/04/23Stomach Acid
Words – digestion, indigestion, acid, alkalis, bacteria
Hydrochloric acid is used in the stomach to help _______ and to kill ______. If we eat too many “rich” foods our stomachs create too much ____ – this is called ______. This acid needs to be neutralised by taking indigestion tablets. Indigestion tablets contain substances such as _______ that neutralise excess stomach acid.
19/04/23Neutralisation reactions
A neutralisation reaction occurs when an acid reacts with an alkali. An alkali is a metal oxide or metal hydroxide dissolved in water.
ACID + ALKALI SALT + WATER
NaClH
H OH ClNa O
H
Copy and complete the following reactions:
1) Sodium hydroxide + hydrochloric acid
2) Calcium hydroxide + hydrochloric acid
3) Sodium hydroxide + sulphuric acid
4) Magnesium hydroxide + sulphuric acid
19/04/23Making salts
Whenever an acid and alkali neutralise each other we are left with a salt, like a chloride or a sulphate. Complete the following table:
Hydrochloric acid
Sulphuric acid
Nitric acid
Sodium hydroxide
Sodium chloride + water
Potassium hydroxide
Potassium sulphate + water
Calcium hydroxide
Calcium nitrate + water
19/04/23Using different bases
A metal oxide base:
Suphuric acid + copper oxide copper sulphate + water
heat
H2SO4(aq) + CuO(s) CuSO4(s) + H2O(l)heat
Sulphuric acid + calcium carbonate calcium sulphate + water + CO2
heat
H2SO4(aq) + CaCO3(s) CaSO4(aq) + + H20(l) + CO2(g)heat
A metal carbonate base:
Acid + metal oxide natural salt solution + water
Acid + metal carbonate natural salt soln + water + CO2
19/04/23Reactions of metals carbonates with acid
A metal carbonate is a compound containing a metal, carbon and oxygen.
METAL CARBONATE + ACID SALT + CARBON DIOXIDE + WATER
Copy and complete the following reactions:
1) Magnesium carbonate + hydrochloric acid
2) Calcium carbonate + hydrochloric acid
3) Sodium carbonate + sulphuric acid
Mg H ClMg
Cl
Cl
HH
H Cl
C
O
O
OO
OO
C
19/04/23Reactions of metal oxides with acidA metal oxide is a compound containing a metal and oxide. They are
sometimes called BASES. For example:
Mg O NaNa
O
O
Al
AlO
O
Magnesium oxide
Sodium oxide Aluminium oxideMETAL OXIDE + ACID SALT + WATER
Copy and complete the following reactions:
1) Magnesium oxide + hydrochloric acid
2) Calcium oxide + hydrochloric acid
3) Sodium oxide + sulphuric acid
Mg OH Cl
Mg ClCl
HH OH Cl
19/04/23Electrolysis of Hydrochloric Acid
++++
----
Positive electrode
H+
H+
H+
Negative electrode
Cl-
Cl-
Cl-Hydrochloric acid
19/04/23Testing for Chlorine
Chlorine “bleaches” damp indicator paper. It is also a toxic gas so don’t breathe it! This leads to problems when it comes to large-scale manufacture of chlorine gas.
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Positive electrode
Negative electrode
Electrolysis of seawater
Sodium chloride solution (seawater)
NaCl(aq) Sodium hydroxide (NaOH(aq))
Seawater is a mixture of water and salt (sodium chloride) and we can electrolyse it to produce chlorine and other useful products:
Chlorine gas (Cl2) Hydrogen gas (H2)
19/04/23Uses of chlorine
Polyvinylchloride (PVC) is made up of lots of monomers of vinyl chloride (chloroethene):
Chloroethene monomer
C C
Cl
H
HH
C C
Cl
H
HH
Lots more Chloroethene
monomers
H
C C
H
HH
H
C C
H
HH
Polyvinylchloride (PVC)
Chlorine is also used in the manufacture of bleach. Sodium hydroxide is reacted with chlorine to form sodium hypochlorite (bleach):
Cl2 + 2 NaOH → NaCl + NaClO + H2O
19/04/23Electrolysis of Water
Positive electrode
Negative electrode
Water
H2O
Water is two atoms of hydrogen and one atom of oxygen. It can be electrolysed to break it down:
Oxygen gas (O2) Hydrogen gas (H2)
OH H
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Extracting MetalsExtracting Metals
A METAL ORE is a mineral or mixture of minerals from which it is “economically viable” to extract some metal.
To “extract” a metal from a metal oxide we need to REDUCE the oxygen. This is called a REDUCTION reaction. To put it simply:
Most ores contain METAL OXIDES (e.g. rust = iron oxide).
Some definitions:
Iron OxideIron ore
“Reduce” the oxygen to make iron
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OxideIron
How do we do it?How do we do it?Potassium
Sodium
Calcium
Magnesium
Aluminium
Carbon
Zinc
Iron
Tin
Lead
Copper
Silver
Gold
Platinum
Metals ABOVE CARBON, because of their high reactivity, are extracted by ELECTROLYSIS, which is very expensive!Metals BELOW CARBON are extracted by heating them with carbon in a BLAST FURNACE. This is a “displacement reaction”
These LOW REACTIVITY metals won’t need to be extracted because they are SO unreactive you’ll find them on their own, not in a metal oxide
Carbon
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Extracting metalsExtracting metals1) What is an ore?
2) In what form are metals usually found in the Earth?
3) How do you get a metal out of a metal oxide?
4) What is this type of reaction called?
Type of metal Extraction process Examples
High reactivity (i.e anything above carbon)
Middle reactivity (i.e. anything below carbon)
Low reactivity
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Extracting AluminiumExtracting Aluminium
Aluminium has to be extracted from its ore by electrolysis. This is because aluminium is very ___________ and so it cannot be extracted using ______. The amount of energy and _____ required to extract aluminium and other metals is very high and so ________ is a much better option.
Words – reactive, recycling, money, carbon
19/04/2319/04/23Copper, Aluminium and Copper, Aluminium and TitaniumTitanium
Metal Uses and why Extraction method
Problems
Copper Electrical wires – good
conductor
Electrolysis Limited supply
Gold Jewellery – attractive and
resistant to corrosion
None needed – its unreactive
so you find it in the Earth as
gold
Limited supply and very
expensive
Aluminium and titanium
Planes – light and corrosion
resistant
Complicated and expensive
Expensive and difficult to
extract
19/04/2319/04/23Using impurities to strengthen Using impurities to strengthen IronIron
In pure iron all impurities are removed. This makes the iron soft:
Adding 1% impurities makes the iron much stronger:
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AlloysAlloysSteel is an “alloy” – i.e. a mixture of metals. Here are other alloys:
Gold mixed with copper
Aluminium mixed with magnesium and copper
Aluminiun mixed with chromium
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Making steelMaking steel
Amount of carbon added (%)0.5% 1%
Strong
Weak
1.5%
Strength
Hardness
Steel with a low carbon content is easily shaped
Steel with a high carbon content is strong but brittle
Steel with chromium and nickel is called stainless steel
19/04/23Smart Alloys
A “smart alloy” is one that can “remember” its original state after being bent or stretched.
These glasses are made from a “smart” material – if they are bent they will return to their original shape. They could be made from an alloy called “nitinol” (an alloy of nickel and titanium) which can be bent but then returned to its original shape simply by heating to its “transformation temperature”.
19/04/23Gold alloys
Gold can be mixed with other metals to make alloys with different properties. For example:
24-Carat gold
“Pure gold” – 99.99% of the atoms in this bar are gold atoms (fineness off 999.9). Pure and malleable but soft.
9-Carat gold
“9 carat gold” – around 9/24ths of the atoms in these earrings are gold atoms. Harder than pure gold but less malleable.
19/04/23Materials in a Car
Alloy wheels
Steel bodyPlastic trim
Glass windscreen
Copper wires
Nylon seatbelts
19/04/23Iron or aluminium?
Aluminium:
Does not corrode
Less dense so it’s lighter
Iron:
Cheaper than aluminium
Magnetic so easily recycled
Most cars are made from steel (an alloy of carbon)
From 2015 95% of a car will have to be made from recycled material. What are the advantages of this?
19/04/23Recycling
Why recycle metals?
1) Less space will be needed for landfill sites
2) Recycled metals only need about 1/10th of the energy to produce compared to producing new metals
3) Recycling saves on raw materials
4) Less excavation and mining costs
19/04/23Rusting
Rust is a hydrated form of iron oxide. It is formed when iron and/or steel combines with oxygen and water in an oxidation reaction:
Iron + oxygen + water hydrated iron (III) oxide
19/04/23Rusting
Task: To investigate what causes rusting
Tube 1 – drying agent
Tube 2 – boiled water
Tube 3 – water + air
Tube 4 – water + air
+ salt
19/04/23Rusting
Task: To investigate what causes rusting
No rust No rust Rust Lots of rust
Iron + oxygen + water hydrated iron oxide
19/04/23More on Redox Reactions
Basically, during a redox reaction electrons are either lost or gained:
The Golden Rule: OILRIG
Oxidation Is Loss (of electrons)
Reduction Is Gain (of electrons)
For example:
Fe Fe2+
2Cl- Cl2
These reactions both involve the loss of electrons – they are Oxidation reactions
Fe2+ Fe
Cl2 2Cl-
These reactions both involve the gain of electrons – they are Reduction reactions
19/04/23Reducation and Oxidation
Some examples of reduction:
Aluminium + iron oxide aluminium oxide + ironheat
2Al(s) + Fe2O3(s) Al2O3(s) + 2Fe(s)heat
Lead oxide + carbon lead + carbon dioxideheat
2PbO(s) + C(s) 2Pb(s) + CO2(s)heat
An example of oxidation:
Magnesium + oxygen magnesium oxideheat
Mg(s) + O2(s) 2MgO(s)heat
19/04/23Fuels
Fuels are substances that can be used to release useful amounts of energy when they burn, e.g.
Oil GasWood Coal
These fuels are called “fossil fuels” and are described as being “non-
renewable”.
19/04/2319/04/23Hydrocarbons and crude Hydrocarbons and crude oiloil
Longer chains
mean…
1. Less ability to
flow
2. Less flammable
3. Less volatile
4. Higher boiling
point
Incre
asin
g le
ng
th
Crude oil is a mixture of HYDROCARBONS (compounds made up of carbon and hydrogen). Some examples:
Ethane
C C
HH
H
HH
H
Butane
C C
HH H
HH
H C C H
H
HH
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Distillation revisionDistillation revision
This apparatus can be used to separate water and ink because they have different _____ ______. The ______ will evaporate first, turn back into a _______ in the condenser and collect in the _______. The ink remains in the round flask, as long as the _______ does not exceed ink’s boiling point. This method can be used to separate crude oil.
Words – temperature, boiling points, water, beaker, liquid
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Fractional distillationFractional distillationCrude oil can be separated by fractional distillation. The oil is evaporated and the hydrocarbon chains of different lengths condense at different temperatures:
Fractions with low boiling points condense at the top
Fractions with high boiling points condense at the bottom
19/04/23Burning HydrocarbonsBurning hydrocarbons will produce water, carbon dioxide and energy:
C
H
H
H
HO
O
OO
OH H
OH H
CO
O
Methane Oxygen+ Water+Carbon dioxide
In this reaction the hydrocarbon is oxidised.
19/04/23Burning HydrocarbonsLots of oxygen:
Some oxygen:
Little oxygen:
C
H
H
H
HO
O
OO
OH H
OH H
CO
O
Methane Oxygen+ Water+Carbon dioxide
Oxygen+
OO
OO
OO
Methane
C
H
H
H
H
C
H
H
H
H
Carbon monoxid
e
CO
CO
Water+
OH H
OH H
OH H
OH H
CC
H
H
H
H
Methane
OO
Oxygen+
OH H
OH H
Water+Carbon
19/04/23Why Carbon Monoxide is Dangerous
Basically, carbon monoxide “sticks” to red blood cells instead of oxygen, causing anybody inhaling it to essentially suffocate:
CO 1) Carbon Monoxide is breathed in
2) The molecule “sticks” to red blood cells instead of oxygen
3) The red blood cells transport the “carboxyhaemoglobin” molecule to the rest of the body and the body’s cells are starved of the oxygen needed for respiration.
Carbon monoxide is odourless, colourless and non-irritating so it’s very difficult to detect!
19/04/23Incomplete Combustion
As well as producing carbon monoxide, incomplete combustion can also produce soot:
Little oxygen:
CC
H
H
H
H
Methane
OO
Oxygen+
OH H
OH H
Water+Carbon
“Soot”
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Burning Fossil FuelsBurning Fossil FuelsBurning fossil fuels like oil and coal causes pollution.
Oil contains carbon:
C
H
H
H
HO
O
OO
OH H
OH H
CO
O
Carbon dioxide is a “greenhouse gas” – it helps cause global warming
Coal contains carbon, sulfur and other particles:
sulfur + oxygen sulfur dioxide
Sulfur dioxide causes acid rain. Other particles can cause “global dimming” – sunlight is absorbed by the particles in the atmosphere.
19/04/23Global Warming
Facts:
1) The 10 warmest years of the last century have all occurred within the last 15 years
2) Sea level has risen by between 12 and 24cm in the last 100 years
3) Rainfall has risen by 1%
19/04/23The Greenhouse EffectWe get heat from the sun:
A lot of this heat is _______ back into space.
However, most of it is kept inside the Earth by a layer of gases that prevent the heat escaping by _______ and then re-radiating it back again.This is called the _________ Effect. It has always been around, but is
currently being made worse due to:
1) Burning (releasing CO2)
2) __________ (removing trees that remove CO2)
3) Increased micro organism activity (from rotting ______)
4) Cattle and rice fields (they both produce _______)
These changes will cause GLOBAL WARMING and RISING SEA LEVELSWords – methane, radiated, absorbing, deforestation, waste, greenhouse
19/04/23Reducing the amount of Carbon Dioxide
Scientists are trying to reduce the amount of carbon dioxide in the atmosphere through a number of possibilities:
1) “Iron seeding” – this is the process where iron is intentionally put in seawater to help produce more phytoplankton which then increases photosynthetic activity, therefore reducing the amount of CO2 in the atmosphere.
Aerial view of phytoplankton near Argentina
2) Converting CO2 into hydrocarbons – carbon dioxide can be converted into hydrocarbons and then stored in the Earth by putting it in such places as old oil fields or coal beds.
19/04/23Reducing Pollution from vehiclesA number of suggestions:
1) Buy a new, smaller, cleaner car
2) Buy a “hybrid” car
3) Convert your car to run on biodiesel
4) Make sure your car has a catalytic converter:
5) Use the train or a bus!
Carbon monoxide + oxygen carbon dioxide
Nitrogen monoxide + carbon monoxide nitrogen + carbon monoxide
19/04/23Ethanol as a biofuel
Ethanol is an important chemical. Many countries are increasing the amount of ethanol put into their petrol supplies:
Ethanol is a “clean burning” energy source and produces little or no greenhouse gases. How is it made?
Ford Escape E85 – runs on 85% ethanol
The “renewable” way
Sugar ethanol + carbon dioxide
Sugar is produced from standard crops like sugar cane and
corn
What’s the point?
When ethanol burns it only produces small amounts of carbon dioxide. Making more cars run on ethanol means having less cars that need petrol.
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Does it take more CO2 to tranport it
than it takes in from the atmosphere while growing?
Choosing a biofuel
Does it create pollution?
How much does it cost? How much land is
needed?
Is it toxic?
How much energy does it release?
Biofuels
How easy is it to grow/make?
19/04/23Choosing a fuel
How easily does it burn?
How much smoke does it
produce?Is it easy to use,
store and transport?
Is it toxic?
How much energy does it release?
Which fuel should you use?
19/04/23Hydrogen Fuel Cells
Basically, a hydrogen fuel cell combines hydrogen and oxygen to form water and release energy:
19/04/23Hydrogen Fuel Cells
Hydrogen fuel cellsvs Petrol
Advantages of fuel cells Advantages of petrol
19/04/23Where fossil fuels come from
Petrol, kerosene and diesel oil are non-renewable fossil fuels that come from crude oil.
Methane is a non-renewable fossil fuel found in natural gas.
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AlkanesAlkanesAlkanes are chemicals found in crude oil. They are SATURATED HYDROCARBONS. What does this mean?
HYDROCARBONS are molecules that are made up of hydrogen and carbon atoms
SATURATED means that all of these atoms are held together by single bonds, for example:
Ethane
Alkanes are fairly unreactive (but they do burn well). The general formula for an alkane is CnH2n+2
C C
HH
H
HH
H
Butane
C C
HH H
HH
H C C H
H
HH
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Drawing AlkanesDrawing AlkanesInstead of circles, let’s use letters…
Butane
H
C C
H
HH
H
C C
H
HH
H H
Methane
H
C H
H
H
Ethane
H
H
C C
H
HH
H
Propane
H
C H
H
H
C C
H
HH
H
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AlkenesAlkenesAlkenes are different to alkanes; they contain DOUBLE bonds. For example:
Ethane Ethene
Butane Butene
This double bond means that alkenes have the potential to join with other molecules – this make them REACTIVE. Alkenes turn bromine water colourless.
ALK
AN
ES
ALK
EN
ES
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Drawing AlkenesDrawing Alkenes
Propene (n=3)
H
C H
H
H
C C
H
H
Ethene (n=2)
H
H
C C
H
H
Butene (n=4)
H
C C
H
HH
H
C C
H
H H
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CrackingCrackingShorter chain hydrocarbons are in greater demand because they burn easier. They can be made from long chain hydrocarbons by “cracking”:
Butane
Ethane
For example, this bond can be “cracked” to give these:
Ethene
19/04/2319/04/23CrackingCracking
This is a THERMAL DECOMPOSITION reaction, with clay used as a catalyst
1) Carbon dioxide causes the _________ effect
2) Sulfur dioxide causes _____ _____
3) Plastics are not _____________
Cracking is used to produce plastics such as polymers and polyethanes. The waste products from this reaction include carbon dioxide, sulfur dioxide and water vapour. There are three main environmental problems here:
Long chain hydrocarbon
Heated catalyst
Gaseous hydrocarbon
Liquid hydrocarbon
19/04/23Composition of Crude Oil
Consider the following data for different fractions from crude oil:
Amount
PetrolDeman
dSupply
Amount
Bitumen
Demand
Supply
How do people on the oil business solve this problem?
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Monomers and PolymersMonomers and Polymers
C CHH
HH
Ethene
Here’s ethene again. Ethene is called a MONOMER because it is just one small molecule. We can use ethene to make plastics…
Step 1: Break the double bond
Step 2: Add the molecules together:
This molecule is called POLYETHENE, and the process that made it is called POLYMERISATION
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Another way of drawing it…Another way of drawing it…Instead of circles, let’s use letters…
Ethene
C C
HH
HH
C C
HH
HH
Ethene
H
C C
H
HH
H
C C
H
HH
Poly(e)thene
General formula for addition polymerisation:
C Cn C C
n
e.g. C Cn
H CH3
HH
C Cn
H CH3
HH
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Some examplesSome examples
C Cn
H H
HH
C Cn
H H
HCl
C CnH H
HH
C CnH H
HCl
C CnH Cl
HBr
C Cn
H Cl
HBr
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Uses of addition polymersUses of addition polymersPoly(ethene) Poly(propene)
Poly(chloroethene), PVC
Poly(styrene)
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Disposal of plasticsDisposal of plastics1) Landfill sites - most plastics do not _________ which means that landfill sites are quickly filled up. Research is being carried out on __________ plastics.
2) Burning – this releases carbon dioxide which causes the ________ effect, as well as other ________ gases.
3) _______ – the best option, but difficult because of the different types of plastic
Words – recycling, greenhouse, decompose, biodegradable, poisonous