Download Pre exam Higher C1 topic (2017) PPTX

C1 Revision
The periodic table of elements
• The periodic table of elements shows us metals
(left) and non-metals (right)
• Each group has similar chemical properties
Atoms
• The smallest particle of an
element
• Atoms have the same
amount of positive and
negative charges so they are
neutral
Type of sub-atomic particle Relative charge
Proton
Neutron
Electron
+1 positive
0 (neutral)
-1
Mass number
Atomic number
• Atomic number = number of protons
• No. of protons = no. of electrons
• The mass number = no. of protons + neutrons
Therefore
• No. of neutrons = mass no. – atomic no.
Arrangement of electrons
• Electrons are arranged around the nucleus of
atoms in shells
• The first shell can hold up to 2 electrons
• The second shell can hold up to 8 electrons
• The third shell can hold up to 8 electrons
• Then the fourth shell fills up
Lithium
2,1
Electrons and the periodic table
• Elements in the same group all have the same
number of electrons in their outer shell. This
means that they share similar properties
• Group 1 elements all have 1 electron in the outer
shell – they are all very reactive
• Group 0 elements (noble gases) have full outer
shells – they are unreactive
Group 1 – alkali metals
• Alkali metals are all soft, stored in oil, low density,
react with oxygen and all react violently with
water and form alkaline (pH>7) solutions.
Lithium + water  lithium hydroxide + hydrogen
Sodium + oxygen sodium oxide
Forming compounds
• When atoms of different types of elements join
together they form ‘compounds’
• When metals react with non-metals they lose or
gain electrons & form ions
• Metals lose electrons and become positive ions (+)
• Non-metals gain electrons – negative ions (-)
• Oppositely charged ions are attracted to each other
and form an ionic bond
Forming compounds
• when non-metals react with non-metals they
share electrons
• This is called covalent bonding
• A covalent bond is a shared pair of electrons
Cl
Cl
solid
line
covalent bond
Cl – Cl
Cl
– Cl
Chemical equations
• These show us the reactants (on the left) and the
products (on the right)
calcium carbonate  calcium oxide + carbon dioxide
CaCO3  CaO
+ CO2
• No atoms are lost or made in the reaction and so
the total mass of the products is equal to the total
mass of the reactants- conservation of mass
Limestone
• Calcium carbonate (CaCO3)
• Limestone can be heated with clay to make cement
• Cement is mixed with sand and water to make
mortar
• Cement is mixed with water, sand and crushed rock
to produce concrete
• Useful as a building material but is damaged by acid
rain
• When carbonates react with acids, carbon dioxide
is given off as well as making a salt and water.
Limestone reactions
1. Calcium carbonate  calcium oxide + carbon dioxide
CaCO3 
CaO +
CO2
2. Calcium oxide + water  calcium hydroxide
Calcium hydroxide is an alkali ( Limewater). It can be used to
neutralise acids. It is used by farmers to neutralise acidic soil, and
to neutralise acidic industrial gases.
3. Calcium hydroxide + carbon dioxide  calcium
carbonate + water
This is the test for carbon dioxide.
Other Carbonates
• The carbonates of magnesium, copper, zinc, calcium
and sodium can be thermally decomposed too
• They always form a metal oxide and carbon dioxide
Magnesium carbonate  magnesium oxide + carbon dioxide
Advantages of using limestone and
producing building materials form it
advantages
Disadvantages
Can build houses and
roads from it
Neutralise acidic soil
Neutralises sulphur
dioxide in power station
chimneys
Jobs for local people
Landscape can be
restored after use
Makes the landscape ugly
Dust pollution
Sound pollution from
blasting
Destroys animal habitats
To make cement needs
energy which is got from
burning fossil fuels- global
warming
Advantages of limestone + its products
over other materials
Advantages
Disadvantages
Widely available
Concrete is ugly looking
Cheaper than granite/marble
Concrete has a low tensile
More hardwearing than marble strength
Concrete can be poured into
moulds
Doesn’t rot like wood
Doesn’t corrode like metals
Can be reinforced with steel
Extracting metals
• Metals are found naturally in the Earth’s crust
• They are often chemically combined with
other elements – this is called the ore
• Whether it is worth extracting a metal
depends on:
1. How easy it is to extract it from its ore
2. How much metal the ore contains
Extracting metals
• The way we extract a metal depends on its place in
the reactivity series
Most reactive
Least reactive
Potassium
Sodium
Calcium
Magnesium
Aluminium
Carbon
Zinc
Iron
Tin
Lead
Copper
Silver
Gold
Platinum
electrolysis
carbon
reduction
Other
methods
Copper
• Pure copper is a good conductor of electricity, does
not react with water and can be shaped easily
• Copper can be removed from its ore by smelting
( heating in a furnace)
• The copper produced is purified using electrolysis
• This involves passing an electrical current through a
copper solution
Metal ions are
positive so pure
copper forms at the
negative electrode
Copper
• Copper-rich ores are running out
• New methods are used to extract copper from low
grade ores
• Phytomining – using plants to extract copper
• Bioleaching – using bacteria to extract copper
• Scrap iron can be dipped into a solution of a copper
salt to extract copper ( displacement)
• Solutions can be electrolysed
Aluminium
• Aluminium is a very low density metal
• Because it is higher than carbon in the reactivity
series it is extracted using electrolysis
• Electrolysis is very expensive because lots of energy
is needed to get temperatures high enough to melt
the ore and electricity is needed to split the ore
• This is why we recycle aluminium
Titanium
• Titanium is very strong and has a very high melting
point
• It is used for replacement hip joints
• It cannot be reduced using carbon because it is
more reactive
• It is reduced (using sodium or magnesium) but this
process is very complicated and has lots of steps
and large amounts of energy are needed which
means the titanium is very expensive
Iron
• Iron ore contains iron combined with oxygen
• Iron is extracted using carbon reduction
• It is heated in a blast furnace
Iron (III) oxide + carbon  iron + carbon dioxide
• Iron straight from the blast furnace still contains some
impurities (it is about 96% iron) – it is very brittle and is
called cast iron. It can be used to mould different
shapes
• Removing the impurities gives us pure iron – this is too
soft for most uses
Iron
• To make iron stronger we can add small amounts of
other elements
• A metal that is mixed with other elements is called
an alloy
• Low carbon steel is easily shaped
• High carbon steel is hard
• Stainless steels are resistant to corrosion
Why recycle metals( or plastics)
• Recycling does NOT involve using up valuable
limited resources
• Is cheaper than extraction due to needing less
energy
• NO MORE damage on the landscape
• Stops filling up landfill sites
alloys
• Steel is an alloy of iron containing carbon
• Alloys are harder than pure copper, gold iron
and aluminium. The “added” atoms distort
the layers
Crude oil
• Crude oil is a mixture of a large number of
compounds. They are NOT chemically combined
together
• We separate the different compounds by fractional
distillation
• This involves separating the different fractions
depending on their boiling points
Fractional distillation of crude oil
Crude oil
• Crude oil contains compounds made of only
hydrogen and carbon – hydrocarbons
• Most of the hydrocarbons are alkanes
• The general formula for alkanes is CnH(2n+2)
• Alkanes are saturated hydrocarbons because they
only have single C-C bonds
Propane
C3H8
AlkAnes
Methane
Ethane
Propane
Monkeys Eat Peanut Butter
Butane
Combustion
• When hydrocarbons are burned they react with
oxygen(OXIDATION) & release energy
• complete combustion – plenty of oxygen
e.g. Propane + oxygen  carbon dioxide + water
• Incomplete combustion happens when there is not
enough oxygen – carbon monoxide (CO) (a toxic
gas) is produced instead of carbon dioxide
Products of combustion
Pollutant
Environmental problem
Sulphur dioxide
Acid rain
Oxides of nitrogen
Acid rain
Carbon dioxide
Global warming
particulates
Global dimming
Sulphur can be removed from the fuel before it is burned. Sulphur
dioxide is removed from the waste gases before it is released e.g
power stations
Cracking
• After fractional distillation of crude oil, we are left
with lots of less useful long-chain hydrocarbons
• Long-chain hydrocarbons can be broken down into
smaller ones by a process called cracking
• This involves heating the fraction until it vapourises
then passing it over steam or a hot catalyst
• The products always include smaller alkanes( used
as fuels) and alkenes
Cracking hexane
(800°C + hot catalyst)
Hexane  butane + ethene
C6H14  C4H10 + C2H4
Alkenes ( double “e” double bond)
Ethene
C2H4
Propene
C3H6
Alkenes have the general formula CnH2n
Alkenes are Unsaturated as they have a
double bond
Butene
C4H8
Testing alkanes and alkenes
• Bromine water reacts with
alkenes and forms a colourless
solution
• Bromine water stays orange in
alkanes
Biofuels
• This includes biodiesel and ethanol which are
made from plant material
• They are made from renewable resources
• Almost carbon neutral
• But plant crop may be destroyed due to poor
weather conditions
• Using up land that should be growing crops to
feed us
Polymers
• Alkenes molecules can be used to make plastics
• Small molecules are called monomers
• Lots of monomers joined together make polymers
monomers
polymer
Polymers
n
A repeating unit of poly chloroethene (PVC)
New polymers
• New plastics with special properties are being
developed
• Dental fillings, waterproof fabrics and light sensitive
plasters are made with special polymers
• Smart polymers such as shape memory polymers
‘remember’ their original shape and will return to it
when heated e.g. stitches closing a wound using
body heat
Plastic waste
• Many polymers are not biodegradable – this means
microorganisms cannot break them down
• New biodegradable polymers have been developed
using starch and plant products that
microorganisms can break down
• This reduces the amount of plastics in landfills
Ethanol
• This is the type of alcohol found in
alcoholic drinks
• Its formula is C2H5OH
• Ethanol can be made by fermentation of sugar from
plants with yeast
Glucose (sugar)  ethanol + carbon dioxide
• Ethanol can also be produced by reacting ethene
(from cracking crude oil) with steam using a
catalyst
Ethene + steam  ethanol
Vegetable oil
• Some fruits, seeds and nuts are rich in oils that can
be extracted
• The plant material is crushed and the oil is removed
by pressing or distillation
• Vegetable oils provide nutrients and have a high
energy content
• Vegetable oils have higher boiling points than water
so foods can be cooked at higher temperatures
than by boiling
• Food cooks faster and has different flavours
• Food cooked in vegetable oil releases more energy
when it is eaten but has a higher calorie content
Making Margarine
Most modern margarines are made from plant oils. The oil is
heated and hydrogen is pumped through it. This is called
hydrogenation
Nickel catalyst
Vegetable oil + hydrogen
→
margarine
60 C
Some of the carbon-to-carbon double bonds in the plant oils
are broken and extra hydrogen atoms are added. This hardens
the oil to make it a solid at room temperature (its melting point
has been raised..
This is useful as spreads or for use in cakes and pastries.
Emulsions
• Oil does not mix with water
• An emulsifier is a special molecule that can be used
to mix them and stop them separating creating an
emulsion
• Emulsifiers work by having one end that dissolves in
water (hydrophilic) and one that dissolves in oil
(hydrophobic)
• Emulsions include ice cream
and mayonnaise
Structure of the Earth
Crust: thin
Mantle:
thickest
section
Core: middle
• The Earth is made up of many layers
• The Earth is surrounded by the atmosphere
Where did the mountains come from?
Before Wegener developed his theory, it was
thought that mountains formed because the
Earth was cooling down, and in doing so
contracted. This was believed to form wrinkles,
or mountains, in the Earth’s crust. If the idea
was correct, however, mountains would be
spread evenly over the Earth's surface. We know
this is not the case.
Alfred Wegener
Continental drift.
Wegener proposed idea that the
continents were all joined together at
one time and slowly moved apart
His evidence included:
Jigsaw pattern of coastlines
Identical fossils and ages on the coasts of south America and
Africa
Matching rock types and ages
But how did they move? He couldn’t explain it and many
other scientists believed they were locked in place and maybe
there were land bridges in the past that have now gone
Tectonic plates
• The crust and mantle are broken up into large pieces
(tectonic plates)
• They move a few centimetres per year due to
convection currents caused by radioactive reactions in
the mantle
• Earthquakes are caused when plate boundaries meet
and push together, mountains are also formed here.
The modern atmosphere
• The Earth’s atmosphere
has been the same for
about 200 million years
Air
Air is a mixture of gases with different boiling
points. These can be separated out using
fractional distillation
The early atmosphere
• About 4.5 billion years ago when the Earth formed
volcanoes released carbon dioxide, water vapour
and small amounts of ammonia & methane – this
formed the first atmosphere( similar to Venus and
Mars)
• As the Earth cooled the water vapour condensed,
fell as rain & this formed the first oceans
• When life evolved plants used the carbon dioxide &
released oxygen during photosynthesis
How did it all begin( maybe)?
The Miller-Urey experiment simulated a
lightning spark in a mixture of gases of the
early atmosphere
A week later, more than 2% of the carbon
in the system had formed compounds from
which proteins in living cells are made
Carbon
• Most of the carbon dioxide from the Earth’s early
atmosphere has been taken up by plants, which
were eaten by animals
• This means that most of the carbon is ‘locked’ in
sedimentary rocks and in fossil fuels
• Carbon dioxide also dissolved in oceans
• Over the past 200 million years the amount of
carbon dioxide in the atmosphere has not changed
much – however we are now burning fossil fuels
and releasing carbon dioxide