Transcript C1 At least a C!!!. - Life Learning Cloud

Revision Notes C1
C1.1 Fundamental ideas
Atomic Number = The number of protons in each atom of
an element e.g. oxygen = 8.
Mass Number = The number of protons AND neutrons in
each atom of an element e.g. oxygen = 16.
Mass Number will always be the bigger number.
In an atom the number of protons = number of electrons.
(This is why atoms are always neutral…no overall charge)
Number of neutrons = Mass number - Atomic number
C1.2 Limestone and it uses
Limestone is a rock made of calcium The limestone cycle:
carbonate (CaCO3). Metal carbonates
undergo thermal decomposition (they
break down when heated) producing
carbon dioxide:
CaCO3 → CaO + CO2
A rotary kiln does this on a huge scale to
make calcium oxide from limestone.
Metal carbonates also react with acid to
make a salt, water and carbon dioxide
CaCO3 + 2HCl → CaCl2 + H2O + CO2
We test for carbon dioxide gas by
bubbling it through limewater and seeing
Cement is a mixture of clay and calcium oxide.
if it goes cloudy. Limewater is calcium
When mixed with sand and water it makes
hydroxide and reacts with CO2 to make
mortar. If we add small stones as well it becomes
calcium carbonate which is insoluble.
concrete. Concrete hardens over time as it reacts
Ca(OH)2 + CO2 → CaCO3 + H2O.
with CO2 to become CaCO3 again. Concrete can
Calcium hydroxide is made by adding
be made even stronger by reinforcing it with
water to calcium oxide
steel rods. Limestone is quarried in areas of
CaO + H2O → Ca(OH)2
countryside. This can be a nuisance as it scars the
These reactions represent the limestone
landscape and creates a lot of noise and dust but
cycle opposite (except the one with acid)
creates lots of jobs bringing money to an area.
C1.3 Metals and their uses
Aluminium is a very light metal. It is extracted by
electrolysis of aluminium oxide. This is very
expensive as it needs a lot of electricity. Aluminium
Three ways of extracting
is unreactive as the metal forms a protective coating
metals from their ores.
of aluminium oxide. Recycling aluminium is very
1. Reduction with carbon
important as it saves energy/fuel, conserves ores
2. Electrolysis
and does not waste space in landfill.
3. Displacement
Titanium is much stronger than aluminium but
1. Any metals lower than
even more expensive to make as it is
carbon in the reactivity series
extracted by displacement with Mg.
can be obtained by reduction
Copper is extracted by smelting:
with carbon. The metal oxide
Copper Sulfide + Oxygen → Copper + Sulfur Dioxide
is reduced (loses oxygen) to
The copper is then purified by electrolysis to
give the metal and CO2.
make very pure copper for electrical wiring.
Iron Oxide + Carbon → Iron + Carbon Dioxide Low-grade ores contain small amounts of
Zinc Oxide + Carbon → Zinc + Carbon Dioxide copper. We extract the copper from these by
using bacteria (bioleaching) or plants to absorb
Iron is obtained from iron oxide by heating
the copper into their roots (phytomining). We
with carbon in a blast furnace. Steel is an
harvest and burn the plants to get the copper.
alloy of iron as the metal contains more
Both of these green methods take a long time.
than one element (iron + carbon). Alloys are
much stronger than the pure metal. Stainless We can make an alloy of any metal to
steel is very useful as it does not corrode.
change it’s properties (eg strength)
An ore is a rock that contains enough of
the metal to make it worth extracting
C1.4 Fuels from Crude Oil
Fractional distillation separates crude oil into
fractions containing similar sized hydrocarbon
molecules. The crude oil is vaporised at high
temperature and passed into a fractionating
column. The column is hot at the bottom and
cool at the top. As the vapour rises up the
column, different fractions condense at their
boiling point and are collected. Big hydrocarbons
have high boiling points and are
Burning hydrocarbons in oxygen produces carbon
collected at the bottom of the column.
dioxide and water.
Small hydrocarbons have low boiling
ALKANE + OXYGEN
CARBON DIOXIDE + WATER
points and are collected at the top
We can use this show this with this equipment:
of the column.
i) The carbon dioxide will turn the limewater
cloudy
ii) The water will condense in the U-tube and
cause any indicator to change colour.
Alkanes are hydrocarbons – they contain
carbon and hydrogen only.
Monkeys Methane CH4
Eat
Ethane
C 2H6
Peanut
Propane C3H8
Butter
Butane
C4H10
Alkanes have the formula CnH(2n+2)
C1.4 Green Chemistry
Burning fossil fuels releases carbon dioxide, CO2.
Carbon dioxide is a greenhouse gas. It traps heat
in the earth’s atmosphere and causes global
warming.
Burning diesel also produces particulates (soot) –
these small carbon particles.
Burning hydrocarbons in oxygen produces carbon
dioxide and water.
ALKANE + OXYGEN
CARBON DIOXIDE + WATER
We can show this with the set-up below:
i) The carbon dioxide will turn the limewater
cloudy
ii) The water will condense in the U-tube and
cause any indicator to change colour.
C1.5 Products from Oil
Cracking = Big alkane
Octane
How? Heat and catalyst
Small alkane + Small Alkene
Hexane + Ethene
Why? Turn useless big alkanes into small alkanes
(fuel) and alkenes (to make polymers and ethanol)
Unsaturated – alkene - C=C double bonds
Bromine water tests for these. This is
orange but goes colourless if C=C present.
If bromine water stays orange its alkane –
saturated – C-C bonds only
Polymerisation:
Many small molecules (monomers)
joined together
to make very large molecules (polymer)
Smart polymers have
properties which change
depending on their
surroundings e.g. shrink as
they warm up
Plastic waste is a big problem. We can:
1. Burn it to provide energy (but that’s dirty)
2. Recycle and make into other products
3. Dump as landfill (not very green)
Plastics from crude oil do not break down. We
can make biodegradable plastics from plants (PLA
- cornstarch) which do break down. These are
also renewable (unlike plastics from crude oil) but
people may starve as less land used to grow food.
Ethanol : From plants or oil?
Hydration (from oil):
Ethene + Steam
Ethanol
monomer
polymer
ethene
poly(ethene)
n is a very large number
Fermentation (from plants):
Glucose
Ethanol + Carbon dioxide
C1.6 Plant Oils
2 methods of extracting plant oils
1. Pressing
2. Steam Distillation
Unsaturated means C=C double bonds
Bromine water tests for these. This is
orange but goes colourless if C=C present.
Cooking with oils (frying):
Good: Nice taste and texture
Energy rich
Nutrients eg Vitamin E
Quick (higher temperature)
Bad: Make you fat if eat too much
Hardening: Turn oils to solid fat (margarine)
Why? Make spreadable
How? Hydrogen / 60oC / Nickel catalyst
Unsaturated
C=C
Emulsions: Mixture of two immiscible
liquids (oil and water).
Examples: Mayonnaise, Milk, Paint
Why? Nicer, thicker texture. Good
coating ability (dipping chips in sauce)
How? Add emulsifier – chemical that
forces oil and water to mix…
Hydrophilic
head
attracted to
water
Hydrophobic tail
attracted to oil Emulsifier
Emulsion
Unsaturated fats (C=C) good for you
Saturated fats (C-C only) bad for you
Monounsaturates have one C=C
Polyunsaturates have more than one C=C
E numbers are food additives…chemicals added
as emulsifiers, preservatives or for colour
Saturated Hardening oils increases melting point so solid at
C-C
room temperature
C1.7 Our changing planet
primordial
soup
Volcanoes formed our early atmosphere which
was mainly water vapour and carbon dioxide.
The water vapour condensed and formed the
oceans. The carbon dioxide has been ‘locked up’
Radioactive decay in the core releases
heat which causes convection currents in in carbon sinks (sedimentary rock, fossil fuels,
the mantle. Tectonic plates can move on oceans). Plants also changed carbon dioxide
into oxygen during photosynthesis.
these currents.
Wegener believed South America and Africa
The carbon cycle balances the amount
were joined together a long time ago. He
of carbon dioxide in the atmosphere.
believed this because:
Burning fossil fuels is upsetting the
1. Coastlines fit together like a jigsaw
carbon cycle causing
2. Similar layers of rock on both coastlines.
global warming and making
3. Similar fossils on both coastlines.
the sea more acidic.
Fractional distillation is used
In the Miller-Urey experiment they showed it was
to separate the gases in air.
possible to make organic compounds from simple
They are cooled to make liquid
molecules in the early atmosphere (hydrogen,
air (the solid carbon dioxide
ammonia, water and methane) but they cannot
and water are removed) and
make living things. Other possibilities are meteors
then warmed up slowly so
or developed in volcanic vents under the sea.
they boil one at a time.
The edges of tectonic plates are called plate boundaries. We can get earthquakes or volcanic
eruptions at these but it is difficult to predict them as we cannot see under the earth’s surface.