Transcript Structures and Bonding

17/07/2015
Chemistry Unit C1 –
Chemistry in our World
EdExcel
Elements
17/07/2015
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
Compounds
Compounds are
different to
elements. They
contain different
atoms. Here are
some examples:
Glucose
17/07/2015
Methane
Sodium
chloride (salt)
17/07/2015
Some simple compounds…
Methane, CH4
Water, H2O
Carbon
dioxide, CO2
Key
Hydrogen
Ethyne, C2H2
Oxygen
Sulphuric
acid, H2SO4
Carbon
Sulphur
Balancing equations
17/07/2015
Consider the following reaction:
Sodium + water
Na
+
sodium hydroxide + hydrogen
Na
O
H
H
O
H
+
H
H
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”)
Balancing equations
17/07/2015
We need to balance the equation:
Sodium + water
sodium hydroxide + hydrogen
Na
O
H
Na
+
Na
H
O
O
H
Na
H
O
H
+
H
H
Now the equation is balanced, and we can write it as:
2Na(s) + 2H2O(l)
2NaOH(aq) + H2(g)
H
Some examples
2Mg
O2
2 MgO
Zn
+ 2 HCl
ZnCl2
2 Fe
+ 3Cl2
2 FeCl3
NaOH
CH4
Ca
+
+
HCl
+ 2 O2
NaCl
CO2
+
+
17/07/2015
H2
H 2O
+ 2H2O
+ 2 H2O
Ca(OH)2
+
+
H2SO4
Na2SO4
+ 2H2O
2 CH3OH
+ 3 O2
2 NaOH
2 CO2
+ 4H2O
H2
Hazard signs to learn…
Acid
Corrosive
h
i
Harmful
Irritant
17/07/2015
Toxic
Oxidising
17/07/2015
Topic 1 – The Earth’s Sea and Atmosphere
The Earth’s Atmosphere
17/07/2015
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
Carbon dioxide, water vapour
Oxygen
Nitrogen
Noble gases
17/07/2015
Evolution of the Earth’s Atmosphere
Carbon
dioxide
4 Billion years
Methane
Ammonia
Oxygen
Nitrogen
Others
Present day
atmosphere contains
78% nitrogen, 21%
oxygen, 1% noble
gases and about
0.03% CO2
3 Billion years
2 Billion years
1 Billion years
Present day
17/07/2015
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.
4 Billion years
3 Billion years
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.
2 Billion years
1 Billion years
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.
Present day
Carbon dioxide in the atmosphere
17/07/2015
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
Topic 2 – Materials from the Earth
17/07/2015
What are rocks?
17/07/2015
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
Sedimentary rocks
17/07/2015
Limestone
Sandstone
Chalk
Conglomerate
Sedimentary rocks
17/07/2015
How sedimentary
rocks are formed:
1) Weathering
2) Transportation
3) Deposition
4) Burial
Metamorphic rocks
Quartzite
Slate
Marble (made from
chalk or limestone)
17/07/2015
Metamorphic rocks
17/07/2015
Metamorphic rocks are formed by the combined effect of
heat and pressure on other rocks:
Pressure from rocks above…
…and heat from magma nearby
Igneous rocks
Granite
Pumice
17/07/2015
Obsidian
Igneous Rock
17/07/2015
Granite – a slow cooling
rock with big crystals
and rich in silica
Rhyolite – a fast cooling
rock with small crystals
and rich in silica
Basalt – a fast cooling rock with
small crystals and rich in iron
Gabbro – a slow cooling rock with
big crystals and rich in iron
Igneous rocks
17/07/2015
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
Summary
Sedimentary, igneous or
metamorphic?
Sedimentary
(e.g. sandstone, _______,
chalk)
Igneous
How they were formed
17/07/2015
Appearance
Small pieces of sediment
were ______ together by
salt and pressure from rocks
above
Usually soft, can contain
________, easily eroded
Liquid rock (______ or lava)
cooled down and turned back
into a ______
Contain ______, very hard,
never contain fossils
Other rocks were acted on by
heat and _______ over a long
time
Sometimes have tiny crystals,
no fossils, always hard and
sometimes arranged in
_______
(e.g. basalt, _______)
Metamorphic
(e.g. ______, slate)
Words to use – layers, stuck, granite, marble, fossils, limestone, crystals,
pressure, magma, solid
Conservation of mass in reactions
17/07/2015
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
H
Mg
O
H
Cl
Cl
Cl
1 x magnesium, 1 x oxygen, 2 x
hydrogen and 2 x chlorine atoms
Mg
H
Cl
H
H
C
H
O
O
O
O
H
Also 1 x magnesium, 1 x oxygen, 2
x hydrogen and 2 x chlorine atoms
Example 2 – Burning methane
H
O
C
O
O
H
H
O
O
H
H
Calcium Carbonate
17/07/2015
Calcium carbonate is a common chemical in the Earth and we’ve
already come across it in a number of forms:
Limestone
Chalk
Marble (made from
chalk or limestone)
Limestone
View video of limestone being quarried
17/07/2015
Limestone
17/07/2015
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:
Limestone + sand + soda
glass
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 _______.
Words – sand, building, sedimentary, concrete, acid rain
17/07/2015
Pros and Cons of quarrying limestone
Reasons why quarrying limestone
is a good idea
Reasons why quarrying limestone
is a bad idea
Limestone
17/07/2015
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
_______ __________:
Calcium carbonate
HEAT
calcium oxide + carbon dioxide
2) _____ is then added to produce calcium __________:
Calcium oxide
WATER
calcium hydroxide
Words – hydroxide, decomposition, carbon
dioxide, water, oxide
The “Limestone Cycle”
Step 4:
add CO2
Calcium Carbonate
CO2
(limestone)
Calcium Hydroxide solution
Step 3: add
more water
and filter
Calcium Hydroxide
17/07/2015
Step 1:
heat
Calcium Oxide
Step 2:
add a little
water
Uses of these Calcium compounds
17/07/2015
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 coalfired power station’s waste products,
helping prevent ____ _____.
Words – acid rain, alkaline, plant, scrubber, neutralise
17/07/2015
Thermal decomposition of carbonates
Limestone undergoes thermal decomposition when heated. The
same happens to other carbonates. For example, consider
copper carbonate:
Copper carbonate
(green) turns into
copper oxide (black)
Limewater
Limewater goes
cloudy due to carbon
dioxide being made
Copper carbonate
copper oxide + carbon dioxide
Topic 3 – Acids
17/07/2015
Neutralisation reactions
17/07/2015
When acids and alkalis react together they will NEUTRALISE
each other:
Sodium hydroxide
Na
Hydrochloric acid
H
OH
The sodium replaces the
hydrogen from HCl
Na
Cl
Sodium chloride
H2O
Water
Cl
Neutralisation experiment
17/07/2015
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
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 _________
Words – nitrate, neutralised, alkali, sulphate, salt, evaporating
Stomach Acid
17/07/2015
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.
Words – digestion, indigestion, acid, alkalis, bacteria
Neutralisation reactions
17/07/2015
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
Na
O
H
H
Cl
SALT + WATER
Cl
Na
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
H
O H
Making salts
17/07/2015
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
Sodium
hydroxide
Potassium
hydroxide
Calcium
hydroxide
Sulphuric acid
Nitric acid
Sodium
chloride +
water
Potassium
sulphate +
water
Calcium
nitrate +
water
Using different bases
17/07/2015
A metal oxide base:
Acid + metal oxide
natural salt solution + water
Suphuric acid + copper oxide
H2SO4(aq) + CuO(s)
heat
copper sulphate + water
CuSO4(s) + H2O(l)
heat
A metal carbonate base:
Acid + metal carbonate
natural salt soln + water + CO2
Sulphuric acid + calcium carbonate
H2SO4(aq) + CaCO3(s)
heat
heat
calcium sulphate + water + CO2
CaSO4(aq) + + H20(l) + CO2(g)
17/07/2015
Reactions of metals carbonates with acid
A metal carbonate is a compound containing a metal, carbon
and oxygen.
METAL CARBONATE + ACID
Mg
O
O
H
C
O
H
SALT + CARBON DIOXIDE + WATER
Cl
O
Cl
Cl
Mg
Cl
C
O
Copy and complete the following reactions:
1) Magnesium carbonate + hydrochloric acid
2) Calcium carbonate + hydrochloric acid
3) Sodium carbonate + sulphuric acid
H
O
H
Reactions of metal oxides with acid
17/07/2015
A metal oxide is a compound containing a metal and oxide. They are
sometimes called BASES. For example:
Mg
O
Na
Magnesium oxide
O
Al
Na
Al
Sodium oxide
Mg
O
H
O
O
Aluminium oxide
METAL OXIDE + ACID
H
O
SALT + WATER
Cl
Cl
Cl
Mg
Cl
Copy and complete the following reactions:
1) Magnesium oxide + hydrochloric acid
2) Calcium oxide + hydrochloric acid
3) Sodium oxide + sulphuric acid
H
O H
Electrolysis of Hydrochloric Acid
17/07/2015
Positive
electrode
Hydrochloric
acid
+
+
+
+
H+
Cl-
Cl-
Cl-
H+
H+
-
Negative
electrode
Testing for Hydrogen
“POP”
17/07/2015
Testing for Chlorine
17/07/2015
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.
Electrolysis of seawater
17/07/2015
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)
Sodium
chloride
solution
(seawater)
NaCl(aq)
Positive
electrode
Negative
electrode
Sodium hydroxide
(NaOH(aq))
Uses of chlorine
17/07/2015
Polyvinylchloride (PVC) is made up of lots of monomers of vinyl
chloride (chloroethene):
Cl
H
C
H
C
H
Chloroethene
monomer
Cl
H
C
H
C
H
Lots more
Chloroethene
monomers
H
H
H
H
C
C
C
C
H
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
Electrolysis of Water
Water is two atoms of hydrogen and one atom of
oxygen. It can be electrolysed to break it down:
Oxygen gas (O2)
O
Hydrogen gas (H2)
Water
H2O
Positive
electrode
H
17/07/2015
Negative
electrode
H
Testing for Oxygen
Oxygen will relight a glowing splint
17/07/2015
17/07/2015
Topic 4 – Obtaining and Using Metals
Extracting Metals
17/07/2015
Some definitions:
A METAL ORE is a mineral or mixture of
minerals from which it is “economically
viable” to extract some metal.
Most ores contain METAL OXIDES (e.g. rust = iron oxide).
To “extract” a metal from a metal oxide we need to REDUCE
the oxygen. This is called a REDUCTION reaction. To put it
simply:
Iron
ore
Iron
Oxide
“Reduce” the oxygen
to make iron
How do we do it?
Potassium
Sodium
Calcium
Magnesium
Aluminium
Carbon
Zinc
17/07/2015
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”
Iron
Tin
Carbon
Iron Oxide
Lead
Copper
Silver
Gold
Platinum
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
Extracting metals
17/07/2015
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
High reactivity (i.e anything
above carbon)
Middle reactivity (i.e.
anything below carbon)
Low reactivity
Extraction process
Examples
Extracting Aluminium
17/07/2015
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
Copper, Aluminium and Titanium
17/07/2015
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
Using impurities to strengthen Iron
17/07/2015
In pure iron all
impurities are
removed. This
makes the iron soft:
Adding 1% impurities
makes the iron much
stronger:
Alloys
17/07/2015
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
Making steel
17/07/2015
Strong
Strength
Hardness
Weak
0.5%
Steel with a low
carbon content is
easily shaped
1%
Steel with a high
carbon content is
strong but brittle
1.5%
Amount of
carbon
added (%)
Steel with chromium
and nickel is called
stainless steel
Smart Alloys
17/07/2015
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”.
Gold alloys
17/07/2015
Gold can be mixed with other metals to make alloys with
different properties. For example:
24-Carat gold
9-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” – around 9/24ths
of the atoms in these earrings
are gold atoms. Harder than
pure gold but less malleable.
Materials in a Car
Copper wires
Glass
windscreen
Plastic trim
17/07/2015
Nylon
seatbelts
Steel body
Alloy wheels
Iron or aluminium?
17/07/2015
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?
Recycling
17/07/2015
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
Rusting
17/07/2015
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
Rusting
17/07/2015
Task: To investigate what causes rusting
Tube 1 –
drying
agent
Tube 2 –
boiled
water
Tube 3 –
water + air
Tube 4 –
water + air
+ salt
Rusting
17/07/2015
Task: To investigate what causes rusting
No rust
No rust
Iron + oxygen + water
Rust
Lots of rust
hydrated iron oxide
More on Redox Reactions
17/07/2015
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
Fe2+
Fe
Cl2
2Cl-
These reactions both involve the loss of
electrons – they are Oxidation reactions
These reactions both involve the gain of
electrons – they are Reduction reactions
Reducation and Oxidation
17/07/2015
Some examples of reduction:
heat
aluminium oxide + iron
2Al(s) + Fe2O3(s)
heat
Al2O3(s) + 2Fe(s)
Lead oxide + carbon
heat
2PbO(s) + C(s)
heat
Aluminium + iron oxide
lead + carbon dioxide
2Pb(s) + CO2(s)
An example of oxidation:
Magnesium + oxygen
Mg(s) + O2(s)
heat
heat
magnesium oxide
2MgO(s)
Topic 5 – Fuels
17/07/2015
Fuels
17/07/2015
Fuels are substances that can be used to release useful
amounts of energy when they burn, e.g.
Wood
Oil
Gas
Coal
These fuels are called “fossil fuels” and
are described as being “non-renewable”.
Crude Oil
17/07/2015
Hydrocarbons and crude oil
17/07/2015
Crude oil is a mixture of HYDROCARBONS
(compounds made up of carbon and hydrogen).
Some examples:
H
C
C
H
H
H
Ethane
H
H
H
H
H
C
C
C
C
H
H
H
H
Butane
H
Increasing length
H
H
Longer chains mean…
1. Less ability to flow
2. Less flammable
3. Less volatile
4. Higher boiling point
Distillation revision
17/07/2015
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
Fractional distillation
17/07/2015
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
Burning Hydrocarbons
17/07/2015
Burning hydrocarbons will produce water, carbon dioxide and
energy:
H
H
H
O
C
O
H
Methane
+
O
O
Oxygen
C
H
O
H
O
Carbon
dioxide
+
In this reaction the hydrocarbon is oxidised.
O
O
H
H
Water
Testing for Carbon Dioxide
17/07/2015
Gas
Limewater
Limewater turns
milky/cloudy
Burning Hydrocarbons
H
Lots of
oxygen:
H
H
C
H
+
H
H
H
H
O
H
H
Methane
H
H
O
C
+
H
H
Methane
+
O
C
H
Carbon
dioxide
+
O
C
O
C
O
O
O
Oxygen
O
H
O
O
O
Oxygen
O
C
O
Oxygen
O
C
H
Little
oxygen:
O
H
Methane
Some
oxygen:
O
17/07/2015
Carbon
monoxide
+
C
Carbon
+
O
H
H
Water
H
O
H
O
H
O
H
O
H
H
H
H
Water
H
O
H
O
Water
H
H
Why Carbon Monoxide is Dangerous
17/07/2015
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!
Incomplete Combustion
17/07/2015
As well as producing carbon monoxide, incomplete combustion
can also produce soot:
Little
oxygen:
H
H
H
O
C
H
Methane
+
O
Oxygen
C
Carbon
“Soot”
+
H
O
H
O
Water
H
H
Burning Fossil Fuels
17/07/2015
Burning fossil fuels like oil and coal causes pollution.
Oil contains carbon:
H
H
H
C
H
O
O
O
O
C
O
O
H
H
O
O
H
H
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.
Global Warming
17/07/2015
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%
The Greenhouse Effect
We get heat
from the sun:
17/07/2015
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
Carbon Dioxide and Global Warming
17/07/2015
Global levels of Carbon Dioxide in PPM
Is there a
link?
17/07/2015
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.
Reducing Pollution from vehicles
17/07/2015
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:
Carbon monoxide + oxygen
Nitrogen monoxide + carbon monoxide
5) Use the train or a bus!
carbon dioxide
nitrogen + carbon monoxide
Ethanol as a biofuel
Ethanol is an important chemical. Many
countries are increasing the amount of
ethanol put into their petrol supplies:
17/07/2015
Ford Escape E85 –
runs on 85% ethanol
Ethanol is a “clean burning” energy source and produces little
or no greenhouse gases. How is it made?
The “renewable” way
Sugar
Sugar is produced from
standard crops like
sugar cane and corn
ethanol + carbon dioxide
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.
Choosing a biofuel
Does it create
pollution?
How much energy
does it release?
Biofuels
How much does
it cost? How
much land is
needed?
How easy is it to
grow/make?
17/07/2015
Is it toxic?
Does it take more CO2
to tranport it than it
takes in from the
atmosphere while
growing?
Choosing a fuel
How easily does
it burn?
How much energy
does it release?
Which fuel should
you use?
How much smoke
does it produce?
17/07/2015
Is it toxic?
Is it easy to use,
store and transport?
Hydrogen Fuel Cells
17/07/2015
Basically, a hydrogen fuel cell combines hydrogen and oxygen
to form water and release energy:
Hydrogen Fuel Cells
Advantages of fuel cells
17/07/2015
Advantages of petrol
Hydrogen fuel cells
vs Petrol
Energy from fuels
Copper
calorimeter
17/07/2015
Water
Spirit burner
Fuel
Where fossil fuels come from
17/07/2015
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.
Alkanes
17/07/2015
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:
H
H
H
C
C
H
H
Ethane
H
H
H
H
H
H
C
C
C
C
H
H
H
H
H
Butane
Alkanes are fairly unreactive (but they do burn well). The
general formula for an alkane is CnH2n+2
Drawing Alkanes
17/07/2015
Instead of circles, let’s use letters…
H
H
C
H
H
H
Methane
H
H
H
H
C
C
C
H
H
H
Propane
H
H
C
C
H
H
H
Ethane
H
H
H
H
H
H
C
C
C
C
H
H
H
H
Butane
H
Alkenes
17/07/2015
Ethane
Ethene
Butane
Butene
ALKENES
ALKANES
Alkenes are different to alkanes; they contain DOUBLE bonds.
For example:
This double bond means that alkenes have the potential to join
with other molecules – this make them REACTIVE. Alkenes
turn bromine water colourless.
Testing for alkenes
Bromine
water
Oil
Bromine goes
colourless
17/07/2015
Drawing Alkenes
H
H
H
C
C
17/07/2015
H
Ethene (n=2)
H
H
H
H
C
C
C
H
Propene (n=3)
H
H
H
H
H
H
C
C
C
C
H
H
Butene (n=4)
H
Cracking
17/07/2015
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
Cracking
Gaseous
hydrocarbon
Long chain
hydrocarbon
Heated
catalyst
17/07/2015
Liquid
hydrocarbon
This is a THERMAL DECOMPOSITION reaction,
with clay used as a catalyst
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:
1) Carbon dioxide causes the _________ effect
2) Sulfur dioxide causes _____ _____
3) Plastics are not _____________
Composition of Crude Oil
17/07/2015
Consider the following data for different fractions from
crude oil:
Amount
Amount
Supply
Demand
Petrol
Supply
Demand
Bitumen
How do people on the oil business solve this problem?
Monomers and Polymers
17/07/2015
H
H
C
C
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
Another way of drawing it…
17/07/2015
Instead of circles, let’s use letters…
H
H
C
C
H
H
H
C
H
C
H
Ethene
H
Ethene
H
H
H
H
C
C
C
C
H
H
H
H
Poly(e)thene
General formula for addition polymerisation:
n
C
C
C
C
n
e.g.
n
H
CH3
H
CH3
C
C
C
C
H
H
H
H
n
Some examples
n
n
n
17/07/2015
H
H
H
H
C
C
C
C
H
H
H
H
H
H
H
H
C
C
C
C
Cl
H
Cl
H
H
Cl
H
Cl
C
C
C
C
Br
H
Br
H
n
n
n
Uses of addition polymers
17/07/2015
Poly(ethene)
Poly(propene)
Poly(styrene)
Poly(chloroethene), PVC
Disposal of plastics
17/07/2015
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
Biodegradable carrier bags
17/07/2015
This carrier bag has been made with flax fibre from
industrial waste.