chemistry unit c1 chemistry in our world · 2019. 11. 10. · chemistry in our world edexcel ....
TRANSCRIPT
27/11/2014 27/11/2014
Chemistry Unit C1 – Chemistry in our World
EdExcel
27/11/2014 27/11/2014
Elements If 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
27/11/2014 27/11/2014
Compounds Compounds are different to elements. They contain different atoms. Here are some examples:
Glucose
Methane
Sodium chloride (salt)
27/11/2014 27/11/2014
Some simple compounds…
Methane, CH4 Water, H2O
Carbon dioxide, CO2
Ethyne, C2H2 Sulphuric
acid, H2SO4
Key
Hydrogen
Oxygen
Carbon
Sulphur
27/11/2014 27/11/2014
Balancing equations Consider the following reaction:
Na O
H H H H
Na
O H
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”)
27/11/2014 27/11/2014
Balancing equations We need to balance the equation:
Na
O
H H
H H
Na
O H
Sodium + water sodium hydroxide + hydrogen
+ +
Na
O
H H
Na
O H
Now the equation is balanced, and we can write it as:
2Na(s) + 2H2O(l) 2NaOH(aq) + H2(g)
27/11/2014 27/11/2014
Some 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
27/11/2014 27/11/2014
Hazard signs to learn…
h i
Acid
Harmful Irritant
Corrosive
Oxidising
Toxic
27/11/2014 Topic 1 – The Earth’s Sea and Atmosphere
27/11/2014
27/11/2014 27/11/2014 The Earth’s 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
27/11/2014 27/11/2014
4 Billion years 3 Billion years 2 Billion years 1 Billion years Present day
Evolution of the Earth’s Atmosphere Carbon
dioxide
Methane Ammonia Oxygen Nitrogen Others
Present day atmosphere contains 78% nitrogen, 21% oxygen, 1% noble gases and about 0.03% CO2
27/11/2014 27/11/2014
4 Billion years 3 Billion years 2 Billion years 1 Billion years Present day
Evolution of the Earth’s Atmosphere 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.
27/11/2014 27/11/2014 Carbon dioxide in the atmosphere
The 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
27/11/2014 Topic 2 – Materials from the Earth
27/11/2014
27/11/2014
What 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
27/11/2014
Sedimentary rocks
Sandstone
Conglomerate
Limestone
Chalk
27/11/2014
Sedimentary rocks How sedimentary rocks are formed:
1) Weathering
2) Transportation
4) Burial
3) Deposition
27/11/2014
Metamorphic rocks
Slate
Marble (made from chalk or limestone)
Quartzite
27/11/2014
Metamorphic 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
27/11/2014
Igneous rocks
Granite
Pumice
Obsidian
27/11/2014
Igneous 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
27/11/2014
Igneous 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
27/11/2014
Summary 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
27/11/2014 27/11/2014 Conservation of mass in reactions
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 O
H Cl
Mg Cl Cl
H H O H 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
H O
O
O O
O H H
O H H
C O
O
Example 2 – Burning methane
27/11/2014
Calcium Carbonate Calcium carbonate is a common chemical in the Earth and we’ve already come across it in a number of forms:
Chalk Limestone
Marble (made from chalk or limestone)
27/11/2014 27/11/2014
Limestone
View video of limestone being quarried
27/11/2014
Limestone 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
27/11/2014 Pros and Cons of quarrying limestone
Reasons why quarrying limestone is a good idea
Reasons why quarrying limestone is a bad idea
27/11/2014 27/11/2014
Limestone Limestone 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 dioxide HEAT
Calcium oxide calcium hydroxide WATER
Words – hydroxide, decomposition, carbon dioxide, water, oxide
27/11/2014 27/11/2014
The “Limestone 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
H2O
H2O H2O H2O
Calcium Hydroxide solution
27/11/2014 Uses 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
27/11/2014 27/11/2014 Thermal decomposition of carbonates
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
27/11/2014
Topic 3 – Acids 27/11/2014
27/11/2014 Neutralisation reactions
When acids and alkalis react together they will NEUTRALISE each other:
OH
Sodium hydroxide
Cl H
Hydrochloric acid
The sodium replaces the hydrogen from HCl
Cl Na
Sodium chloride
H2O
Water
Na
27/11/2014
Neutralisation 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 _________
27/11/2014
Stomach 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.
27/11/2014
Neutralisation 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
Na Cl H
H O H Cl Na 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
27/11/2014
Making 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
27/11/2014
Using 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
27/11/2014 Reactions 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 Cl Mg
Cl
Cl
H H
H Cl
C
O
O
O O
O O
C
27/11/2014 Reactions of metal oxides with acid A metal oxide is a compound containing a metal and oxide. They are sometimes called BASES. For example:
Mg O Na
Na O
O
Al
Al O
O
Magnesium oxide Sodium oxide Aluminium oxide
METAL 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 O
H Cl
Mg Cl Cl
H H O H Cl
27/11/2014 Electrolysis of Hydrochloric Acid
++++
----
Positive electrode
H+
H+
H+
Negative electrode
Cl-
Cl-
Cl- Hydrochloric acid
27/11/2014
Testing for Hydrogen
“POP”
27/11/2014
Testing 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.
27/11/2014
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)
27/11/2014
Uses of chlorine Polyvinylchloride (PVC) is made up of lots of monomers of vinyl chloride (chloroethene):
Chloroethene monomer
C C
Cl H
H H
C C
Cl H
H H
Lots more Chloroethene
monomers
H
C C
H
H H
H
C C
H
H H
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
27/11/2014
Electrolysis 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)
O H H
27/11/2014
Testing for Oxygen
Oxygen will relight a glowing splint
27/11/2014 Topic 4 – Obtaining and Using Metals
27/11/2014
27/11/2014 27/11/2014
Extracting 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 Oxide Iron ore
“Reduce” the oxygen to make iron
27/11/2014 27/11/2014
Oxide Iron
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
27/11/2014 27/11/2014
Extracting metals 1) 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
27/11/2014 27/11/2014
Extracting 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
27/11/2014 27/11/2014
Copper, Aluminium and Titanium
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
27/11/2014 27/11/2014 Using impurities to strengthen Iron
In pure iron all impurities are removed. This makes the iron soft:
Adding 1% impurities makes the iron much stronger:
27/11/2014 27/11/2014
Alloys Steel 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
27/11/2014 27/11/2014 Making 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
27/11/2014
Smart 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”.
27/11/2014
Gold 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.
27/11/2014
Materials in a Car
Alloy wheels
Steel body Plastic trim
Glass windscreen
Copper wires Nylon seatbelts
27/11/2014
Iron 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?
27/11/2014
Recycling 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
27/11/2014
Rusting
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
27/11/2014
Rusting Task: To investigate what causes rusting
Tube 1 – drying agent
Tube 2 – boiled water
Tube 3 – water + air
Tube 4 – water + air
+ salt
27/11/2014
Rusting Task: To investigate what causes rusting
No rust No rust Rust Lots of rust
Iron + oxygen + water hydrated iron oxide
27/11/2014
More 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
27/11/2014
Reducation and Oxidation Some examples of reduction:
Aluminium + iron oxide aluminium oxide + iron heat
2Al(s) + Fe2O3(s) Al2O3(s) + 2Fe(s) heat
Lead oxide + carbon lead + carbon dioxide heat
2PbO(s) + C(s) 2Pb(s) + CO2(s) heat
An example of oxidation:
Magnesium + oxygen magnesium oxide heat
Mg(s) + O2(s) 2MgO(s) heat
27/11/2014 Topic 5 – Fuels
27/11/2014
27/11/2014
Fuels Fuels are substances that can be used to release useful amounts of energy when they burn, e.g.
Oil Gas Wood Coal
These fuels are called “fossil fuels” and are described as being “non-renewable”.
27/11/2014 27/11/2014
Crude Oil
27/11/2014 27/11/2014
Hydrocarbons and crude oil
Longer chains mean…
1. Less ability to flow
2. Less flammable
3. Less volatile
4. Higher boiling point
Incre
asing le
ngth
Crude oil is a mixture of HYDROCARBONS (compounds made up of carbon and hydrogen). Some examples:
Ethane
C C
H H
H
H H
H
Butane
C C
H H H
H H
H C C H
H
H H
27/11/2014 27/11/2014
Distillation 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
27/11/2014 27/11/2014
Fractional distillation Crude 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
27/11/2014 Burning Hydrocarbons Burning hydrocarbons will produce water, carbon dioxide and energy:
C
H
H
H
H O
O
O O
O H H
O H H
C O
O
Methane Oxygen + Water + Carbon dioxide
In this reaction the hydrocarbon is oxidised.
27/11/2014
Testing for Carbon Dioxide
Gas
Limewater turns milky/cloudy
Limewater
27/11/2014 Burning Hydrocarbons Lots of oxygen:
Some oxygen:
Little oxygen:
C
H
H
H
H O
O
O O
O H H
O H H
C O
O
Methane Oxygen + Water + Carbon dioxide
Oxygen +
O O
O O
O O
Methane
C
H
H
H
H
C
H
H
H
H
Carbon monoxide
C O
C O
Water +
O H H
O H H
O H H
O H H
C C
H
H
H
H
Methane
O O
Oxygen +
O H H
O H H
Water + Carbon
27/11/2014 Why 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!
27/11/2014
Incomplete Combustion As well as producing carbon monoxide, incomplete combustion can also produce soot:
Little oxygen:
C C
H
H
H
H
Methane
O O
Oxygen +
O H H
O H H
Water + Carbon
“Soot”
27/11/2014 27/11/2014
Burning Fossil Fuels Burning fossil fuels like oil and coal causes pollution.
Oil contains carbon:
C
H
H
H
H O
O
O O
O H H
O H H
C O
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.
27/11/2014
Global 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%
27/11/2014 The Greenhouse Effect We 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 LEVELS
Words – methane, radiated, absorbing, deforestation, waste, greenhouse
27/11/2014 Carbon Dioxide and Global Warming
Global levels of Carbon Dioxide in PPM
Is there a link?
27/11/2014 Reducing 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.
27/11/2014
Reducing Pollution from vehicles A 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
27/11/2014
Ethanol 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.
27/11/2014
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?
27/11/2014
Choosing 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?
27/11/2014
Hydrogen Fuel Cells Basically, a hydrogen fuel cell combines hydrogen and oxygen to form water and release energy:
27/11/2014
Hydrogen Fuel Cells
Hydrogen fuel cells vs Petrol
Advantages of fuel cells Advantages of petrol
27/11/2014
Energy from fuels
Copper calorimeter Water
Fuel
Spirit burner
27/11/2014
Where 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.
27/11/2014 27/11/2014
Alkanes Alkanes 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
H H
H
H H
H
Butane
C C
H H H
H H
H C C H
H
H H
27/11/2014 27/11/2014
Drawing Alkanes Instead of circles, let’s use letters…
Butane
H
C C
H
H H
H
C C
H
H H
H H
Methane
H
C H
H
H
Ethane
H
H
C C
H
H H
H
Propane
H
C H
H
H
C C
H
H H
H
27/11/2014 27/11/2014
Alkenes Alkenes 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
27/11/2014
Testing for alkenes 27/11/2014
Oil Bromine goes colourless
Bromine water
27/11/2014 27/11/2014
Drawing 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
H H
H
C C
H
H H
27/11/2014 27/11/2014
Cracking Shorter 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
27/11/2014 27/11/2014 Cracking
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
27/11/2014
Composition of Crude Oil Consider the following data for different fractions from crude oil:
Amount
Petrol Demand Supply
Amount
Bitumen Demand Supply
How do people on the oil business solve this problem?
27/11/2014 27/11/2014
Monomers and Polymers
C C H H
H H
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
27/11/2014 27/11/2014
Another way of drawing it… Instead of circles, let’s use letters…
Ethene
C C
H H
H H
C C
H H
H H
Ethene
H
C C
H
H H
H
C C
H
H H
Poly(e)thene
General formula for addition polymerisation:
C C n C C
n
e.g. C C n
H CH3
H H
C C n
H CH3
H H
27/11/2014 27/11/2014
Some examples
C C n
H H
H H
C C n
H H
H Cl
C C n H H
H H
C C n H H
H Cl
C C n H Cl
H Br
C C n
H Cl
H Br
27/11/2014 27/11/2014
Uses of addition polymers Poly(ethene) Poly(propene)
Poly(chloroethene), PVC Poly(styrene)
27/11/2014 27/11/2014
Disposal of plastics 1) 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
27/11/2014
Biodegradable carrier bags 27/11/2014
This carrier bag has been made with flax fibre from industrial waste.