Transcript Chemistry_Unit_1 6649KB Jun 06 2014 10:41:53 AM

AQA Chemistry Unit 1
This PowerPoint supports section C1.4, C1.5, C1.6 and
C1.7 sections of the AQA Chemistry Unit 1 module
Crude Oil
Hydrocarbons and crude oil
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
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
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
Alkanes
Alkanes 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 COVALENT 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
General Formulae for Alkanes
Instead of circles, let’s use letters…
H
H
C
H
H
H
Methane (n=1)
H
H
H
H
C
C
C
H
H
H
Propane (n=3)
H
H
C
C
H
H
H
Ethane (n=2)
H
H
H
H
H
H
C
C
C
C
H
H
H
H
Butane (n=4)
General formula for alkanes = CnH2n+2
H
Burning Fossil Fuels
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.
Removing Sulfur
Sulfur dioxide is clearly bad for the environment so it’s a good
idea to remove as much sulfur as possible:
Vehicles can remove sulfur
from fuels before they
are burned.
Power stations can remove
sulfur dioxide from waste
gases after combustion.
Other fuel sources
Task: Identify two other fuel sources (“biofuels”) currently
being developed and find out the following:
1) What is the source called and what is it made of?
2) Why is the fuel better than coal?
3) What are the disadvantages of this fuel?
Using Crude Oil
Benefits
Drawbacks
Plastics don’t
biodegrade
Cheap to
extract
Wide range of
uses as fuel
Used to make
plastics
Crude Oil
It’s
going to
run out
Burning
fossil fuels
causes
pollution
Disposal of
materials
uses up land
fill sites
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
Ethanol
Ethanol is an important chemical. Many
countries are increasing the amount of
ethanol put into their petrol supplies:
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 and what are the
advantages and disadvanatges of each method?
The “fossil fuel” way
Ethene + steam
ethanol
The “renewable” way
Sugar
Ethene is produced by
“cracking” oil
Sugar is produced from
standard crops like
ethanol + carbon dioxide
sugar cane and corn
Making ethanol from ethene
Ethene + water
C2H + H20
ethanol
C2H5OH
Unused ethene recycled
Ethene
Reaction vessel with high
temperature and pressure
and a catalyst
Ethanol
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
Cracking
Gaseous
hydrocarbon
Long chain
hydrocarbon
Heated
catalyst
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 _____________
Alkenes
Ethane
Ethene
Butane
Butene
ALKENES
ALKANES
Alkenes are different to alkanes; they contain DOUBLE
COVALENT 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
General Formulae for Alkenes
H
H
H
C
C
H
Ethene (n=2)
H
H
H
H
C
C
C
H
H
H
H
H
H
C
C
C
C
H
H
H
Propene (n=3)
Butene (n=4)
General formula for alkenes = CnH2n
H
Monomers and Polymers
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…
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
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
Poly(ethene)
Poly(propene)
Poly(styrene)
Poly(chloroethene), PVC
Biodegradable carrier bags
This carrier bag has been made with flax fibre from
industrial waste.
Measuring Energy in Food
The energy content
in foods is measured
in Joules and calories
Foods with large carbohydrate and fat
contents have lots of energy, but too
much energy and too little exercise
could lead to obesity.
Vegetable Oils
When plants photosynthesise they produce glucose. They can
also produce vegetable oils and we can use these for food and
fuel:
Use of oil
Oily foods
Fuel
Benefits
Drawbacks
Extracting Oil
Step 1: Crush
the plant
Step 2: Remove oil
by pressing
OR step 3: Remove
oil by distillation
Why use oil for cooking?
1) Why do we use oil for cooking and not just water?
2) What are the problems associated with using oil in cooking?
Healthy and Unhealthy Oils
Unhealthy oils:
Healthy oils:
“Saturated”
“Unsaturated”
Saturated vs. Unsaturated Fats
Some oils are more healthy than others. Fish
oils contain the nutrients Omega-3 and Omega6. These oils are “unsaturated” like ethene:
H
H
C
C
H
H
Ethene
Bromine
water
Testing for double bonds:
Clearly, it is important for
scientists to be able to test if
a food contains “healthy”
unsaturated fats or
“unhealthy” saturated fats.
Here’s how it’s done:
Oil (in ethanol)
Bromine goes
colourless
Turning unsaturates into saturates
600C, Nickel catalyst
The unsaturated fat is hardened by “hydrogenation”.
Hydrogenated oils have a higher melting point and so
are solid at room temperature, making them useful for
spreads and pastries.
Emulsions
What’s an emulsion?
It’s a mixture of oil and
water, like in salad dressing…
Paint is an emulsion. Other examples:
Milk
Cream
Butterfat
Watery liquid
Butter
Why use emulsions?
Emulsions can have varying textures and this makes them
useful. Some examples:
Different
thicknesses
of cream
Paint and
mayonnaise
Emulsifiers
An emulsifier is an additive that will stop oil
and water from seperating, like in mayonnaise.
How they work:
I don’t want to
mix with you!
Water
I’m an emulsifier – I’ll
sort this out with my
hydrophobic end and
my hydrophilic end!
Oil
The water and oil drops become “coated” and insulated from
one another, which prevents them from separating.
Uses of emulsifiers in food
Emulsifiers are used:
1) In bread, to stop large _____ developing when it bakes
2) In low fat spreads, to allow the oil and water to be _____
3) In ice cream and spray cream, to ______ the foam
4) In sponge cakes, to make tiny pockets of ____
5) In chocolate, to stop melted chocolate forming _______
Words – crystals, air, holes, mixed, stabilise
The Structure of the Earth
A thin crust 10-100km thick
A mantle – has the
properties of a solid
but it can also flow
A core – made of
molten nickel and iron.
Outer part is liquid
and inner part is solid
The average density of the Earth is much higher than
the crust, so the inner core must be very dense
Movement of the Lithosphere
The Earth’s LITHOSPHERE (i.e. the _______) is split
up into different sections called ________ plates:
These plates are moving apart from each other a
few centimetres every _______ due to the
________ currents in the mantle caused by the
________ decay of rocks inside the core.
Words – radioactive, crust, convection, tectonic, year
Plate Movements
Earthquakes and
volcanic eruptions can
be common here
Oceanic Crust
Mantle
Convection
Currents
Magma
The Earth’s Atmosphere
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
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
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. Carbon from CO2
becomes locked up in sedimentary rocks as
carbonates and fossil fuels. Methane and
ammonia react with the oxygen and
nitrogen is released.
Present day
One theory about how life was formed…
The “Primordial Soup” theory:
A collection of
simple molecules
like methane
Amino acids
Dr Stanley
Miller 19302007
In 1953 I conducted an experiment that
proved that an electrical discharge can turn
methane into amino acids! This is called the
“Miller-Urey experiment”.
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) When fossil fuels are burned the carbon
contained in them reacts with _____ to form 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
Separating air
Air can be separated into the different gases that make it up.
To do this you first have to cool air down to -2000C and turn it
into a liquid:
Remove
CO2 and
H2O vapour
Liquid air
(-200OC)
Nitrogen
Fractional
distillation
Argon
Oxygen
In this chamber the air is gradually heated up again and
the different parts of air “distil” off at different
temperatures according to their boiling points
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