Transcript File

C1 Core Chemistry
Atoms, Elements
& Compounds
Elements and Compounds
Everything in the Universe is made up from atoms.
Things are either elements or compounds:
Elements:
 one type of atom only
 sometimes joined
Compounds:
 different types of atom
 always chemically joined
Structure of the Atom
+1
0
-1
N
Shells
7
Li
3
Mass number =
number of protons +
number of neutrons
E
Atomic number
= number of protons
= number of electrons
E
N P NP
N P
N
E
neutrons = mass number – atomic number
We normally use crosses or
dots to show electrons...
Rules for drawing electrons
1. Start putting
electrons in the inside
shell and work
outwards
2. 2 electrons can go into
the first shell
3. 8 electrons can go into
all other shells
X
XX
X
X X
X
2 electrons
max
Si
X X
X
X
XX
X
8 electrons
max
Electrons and the Periodic Table
The number of electrons in
the outside shell determine
Hwill be in
which group they
on the periodic table tells.
Metals
Non-Metals
Forming
Bonds
Ionic Bonding
X
Li
X
F
X
Metal atoms
Lose electrons
Non-metal atoms
Gain electrons
What is formed? See next page......
X
Li
-1
+1
X
Metal atom
Lose electrons
Become positive
X
F
Non-metal atom
Gain electrons
Become negative
The neutral atoms have become oppositely
charged ions that are attracted to each other
Covalent Bonding
 Non-metal atoms only
 Atoms share electrons
 A molecule is formed
Chemical
Equations
magnesium + oxygen
magnesium oxide
Reactants
Products
2Mg(s)
Mg
+
Mg
(s) = solid
(l) = liquid
(g) = gas
(aq) = aqueous
O2(g)
O
O

2MgO(s)

Mg
O
Mg
O
Balancing Rules
The number of atoms on both sides of the
arrow must be the same
Only put numbers in front of elements or
compounds when balancing!!!
H
Li
O
H

2LiOH
+
Li
O
H
Li
O
H
H2
H H
H
O
Li
+ 2H2O
H
2Li
Both sides have the same
number of each type of atom
Uses of
Limestone
What is Limestone?
The chemical name for limestone is calcium carbonate.
It has the formula CaCO3
It can be used to produce building materials such as lime
mortar, cement and concrete
Metal
Carbonates
metal
+ acid
carbonate

carbon
salt + water +
dioxide
magnesium + hydrochloric  magnesium + water + carbon
carbonate
acid
chloride
dioxide
We can test for carbon dioxide because it turns
lime water cloudy
Carbon dioxide
Thermal Decomposition
When metal carbonates are heated they break
down to make a metal oxide and carbon dioxide.
metal carbonate  metal oxide + carbon dioxide
This is a themal decomposition reaction
which means breaking something down using heat.
e.g.
copper carbonate  copper oxide + carbon dioxide
CuCO3(s)
 CuO(s)
+
CO2(g)
Calcium oxide is produced on a large scale by heating
limestone (calcium carbonate) in a rotating lime kiln.
Limestone
Cycle
The limestone cycle shows how calcium carbonate
can react to make other substances:
Step 3:
add CO2
(lose H2O)
Limestone
calcium carbonate
CaCO3
Slaked Lime/
Limewater
calcium hydroxide
Ca(OH)2
Step 1: heat
(lose CO2)
Step 2:
add water
Quicklime
calcium oxide
CaO
Step 1
calcium carbonate
CaCO3
calcium oxide + carbon dioxide
CaO
+
CO2
Step 2
calcium oxide + water
CaO
+ H2O
calcium hydroxide
Ca(OH)2
Step 3
calcium
+ carbon
hydroxide dioxide
Ca(OH)2
+ CO2
calcium
+
carbonate
CaCO3
+
water
H2O
Quarrying
Limestone
To get limestone it must be quarried (dug) from
the ground using heavy machinery...
Advantages of Quarrying
Disadvantages of Quarrying
Limestone has many uses
Noise pollution
Creates jobs for the local
community
Dust pollution
Destroys habitats
Improves transport links to
Carbon dioxide released by
community
digging machinery leads to
No quarrying (digging)
global warming
Extracting
Metals
Non-reactive metals are
found in their native state.
The metal just has to be
mined from the ground
e.g. gold
Most metals are found in
ores as a compound
(usually metal oxides).
Here the metal must be
extracted from the ore
Potassium
Aluminium
Carbon
Iron
Copper
Silver
Gold
Most
reactive
Metal oxides below
carbon in the reactivity
series can be extracted
using carbon.
Least
reactive
metal oxide + carbon
E.g.
iron oxide + carbon
Heat
Heat
metal + carbon dioxide
iron + carbon dioxide
This type of extraction is called a reduction reaction
because oxygen is removed from the compound.
Iron and
Steel
Extracting Iron & Making Steel
Iron is extracted from iron oxide
by reducing it with carbon.
Carbon
The reaction is heated in a blast
furnace.
This produces cast iron which is
brittle because it contains carbon
impurities which must be removed.
The pure iron can then be mixed
with other elements to make steel.
Cast
Pure Metals vs Alloys
Pure metals:
 One type of atom only
 Regular layers
 Layers can slide easily
 Malleable (soft)
Pure Metal e.g. iron
Alloys:
 Mixture of metals
 Distorted layers
 Cannot slide easily
 Much harder
Alloy e.g. steel
Aluminium &
Titanium
Properties of Al and Ti:
Strong
Don’t corrode (oxide
layer protects metal)
Low density (light)
High melting point
(especially titanium)
Metal
Oxide layer
Al and Ti are very reactive so they cannot be
extracted using carbon
Electrolysis is used to extract them instead. This
requires lots of heat and electricity!!
Extracting
Copper
Copper can be extracted from high grade ores in 3
ways:
1. Smelting – Heating copper ore with carbon
2. Displacement – Using cheap, scrap iron to
displace the copper from a copper solution
3. Electrolysis – Using electricity
Phytomining (plants) & bioleeching (bacteria) can be
used to extract copper from low grade ores.
Phytomining
Bioleeching
Plants (or bacteria)
absorb metal from
soil as they grow
Advantages
Plants/bacteria containing
metal are burnt and metal
is extracted from ash
Disadvantages
Uses low grade copper ore Very slow process (plants
need to grow)
Heat energy can be used
Large amount of land used
Little energy required
Plants could have been
No quarrying (digging)
used for food
Using
Metals
Transition metals are found in the middle block of
the periodic table.
They are malleable, have high melting points, and
conduct electricity and heat.
Some are resistant to corrosion but others can be
galvanised using a reactive metal such as zinc.
Transition Metals
Smart Alloys
Smart alloys, or shape memory alloys (SMAs) change
their shape under different conditions.
e.g. dental braces made from nitinol (alloy of Ni &Ti)
Why recycle metals?
Conserve natural resources
Use less energy resources
Reduce CO2 and SO2 emissions
that contribute towards global
warming and acid rain
Crude Oil
What is Crude Oil?
Crude oil is a mixture of
hydrocarbons.
Hydrocarbons are
compounds that are only
made up of hydrogen and
carbon.
The main group of
hydrocarbons found in crude
oil are called alkanes.
Alkanes
Name
Formula
Methane
CH4
Ethane
C2H6
Propane
C3H8
Butane
C4H10
Structure
Formula
Name
CH4
Methane
Example; n=8
C2H6
Ethane
C8H2x8+2
= C8H18 (Octane)
C3H8
Propane
C4H10
Butane
C5H12
Pentane
C6H14
Hexane
The general formula
for alkanes is CnH2n+2
Alkanes are saturated
because they only
contain single bonds
Properties
of Alkanes
Short vs Long Alkanes
Physical
Property
Viscosity
(thickness)
Short alkanes
Low – molecules
slide past each
other easily
Long alkanes
High – Molecules become
tangled up
Low – often gases High – more heat energy
Boiling point at room
needed to separate
(liquid gas)
temperature
molecules
Flammability Very flammable
Not as flammable
Uses of alkanes
Short chains – used for
fuels because they are
very flammable
Long alkanes – used as
lubricants for engines
because they have very
high boiling points.
Fractional
Distillation
Fractional distillation
separates crude oil into
groups of alkanes that
are a similar size.
Alkanes in these groups
(fractions) have similar
properties.
Each fraction has a
specific use.
E.g. petrol used in cars,
bitumen used for tarmac
Process
1. Crude oil is heated and
vaporised and fed into a
large column
2. Different sized alkanes
have different boiling
points
3. This causes them to
condense at different
temperatures:
 Short alkanes condense at
top where it is cool
 Long alkanes condense at
bottom where it is hot
Burning
Fuels
Combustion
Hydrocarbons such as
alkanes can be used as
fuels (petrol, diesel,
kerosene, methane)
Fuels are substances that
can be burnt to produce
energy.
When fuels burn they
react with oxygen in a
process called combustion.
Products from Combustion
Turns pink 
water produced
Turns cloudy  carbon
dioxide produced
Types of Combustion
Combustion can either be complete (plenty of
oxygen) or incomplete (lack of oxygen)
Complete Combustion
Water and carbon dioxide
are produced:
hydrocarbon + oxygen  water + carbon dioxide
C3H8
+ 5O2

4H2O +
3CO2
Incomplete Combustion
Poisonous carbon monoxide
(CO) is produced instead of
carbon dioxide (CO2):
hydrocarbon + oxygen  water + carbon monoxide
C3H8
+ 3.5O2  4H2O +
3CO
Pollution from
Combustion
Global Warming
Carbon dioxide (CO2) is
produced which contributes
towards global warming.
Consequences:
 Melting ice caps
 Floods
Reduced by:
 Using alternative fuels
Acid Rain
Sulphur impurities in crude oil
are converted to sulphur dioxide
(SO2) which leads to acid rain.
Consequences:
 Kills aquatic life
 Kills trees
Reduced by:
 Removing sulphur from fuel
 Catalytic convertors
Solid Carbon Particulates
Solid carbon particulates
can also be produced during
incomplete combustion.
Consequences:
 global dimming
 respiratory problems
Reduced by:
 Well serviced engines
Respiratory
problems
Global
Dimming
Destroys
forests
Carbon
particulates
Pollution from
crude oil
Ice caps
melt
Severe
weather
CO2
Global
Warming
Acid
Rain
SO2
Kills
aquatic life
Alternative
Fuels
Hydrogen
 Can be extracted from water
 Very clean (only water & oxygen produced)
 Electric cars aren’t noisy
 Photocells are
expensive
 Photocells need
sunlight to work
Biodiesel
 Made from crops (carbon
neutral and renewable)
 Can be used in regular
diesel engines
 Less polluting gases
 Engines last longer
 Safe to handle/transport
 Land could be used to
grow food crops
Ethanol
 Made from sugar cane & other
crops (carbon neutral and
renewable)
 No pollution caused
 Waste products are useful
 Keeps engine very clean
 Very flammable – can be
dangerous to store and handle
 Land could be used to grow
food crops
Carbon Neutral
Plants absorb CO2 from
the atmosphere as they
grow (photosynthesis)
CO2 released back
into atmosphere when
bio-fuel is burnt
CO2 in = CO2 out
Cracking
Short vs Long Hydrocarbons
Short hydrocarbons are more useful than
long ones because they can be used for fuels.
We can break long hydrocarbons down into shorter ones
by a thermal decomposition reaction called cracking.
Heat and a catalyst (e.g. porcelain) are required:
C10H22

C5H12 + C3H6 + C2H4
alkenes produced
Cracking Process
Alkenes
The general formula
for alkenes is CnH2n
Alkenes are
unsaturated because
they contain double
bonds.
Alkenes can be used to
make polymers
(plastics and fabrics)
Formula
Name
C2H4
Ethene
C3H6
Propene
C4H8
Butene
Alkenes
Name
Formula
Ethene
C2H4
Propene
C3H6
Butene
C4H8
Structure
Alkenes turn bromine water from orange to
colourless because the double bond can be broken.
Bromine
(Br2)
H H
+
C=C
H H
Br Br
H
C-C
H H
H
Making
Polymers
Monomers are short alkenes that can be used to
make plastics called polymers.
Polymers are long molecules that are formed when
lots of monomers are joined together.
= =
= =
Monomers
-
-
- -
Polymer
This is called addition polymerisation because
only one product is formed.
Showing Polymerisation
H H
H H
n C=C
C-C
H H
H H
n shows
number of
monomers
n
Brackets show this
is repeated to make
a long polymer
Naming Polymers
Ethene
Styrene
Poly(ethene)
Poly(styrene)
Useful
Polymers
Polymers are used for different jobs
depending on their properties:
Waterproof
Windproof
Strong
Flexible
Light
Smart Polymers
Smart polymers can change their
properties when their surrounding
conditions change
Hydrogels are used in contact
lenses because they trap water
Light sensitive polymers are used
to make painless plasters
Shape memory polymers are
sensitive to temperature. They
are used in stitches that tighten
due to body heat.
Plastic
Waste
Most polymers are nonbiodegradable.
This means that they cannot
be broken down easily by
microbes.
Huge landfill sites are taken
up by this plastic waste.
Biodegradable plastics are
now also being made
e.g. poly(lactic acid) can
be made from cornstarch.
Recycling helps to conserve natural resources and
reduce the need for landfills, but....
 Plastics must be sorted into correct groups
 Heat & electrical energy is required for recycling
Making
Ethanol
Ethanol (C2H5OH) is used in solvents and bio fuels
and can be made using two processes:
1. Fermentation – Enzymes in yeast break sugar
down into ethanol and carbon dioxide.
sugar
yeast
ethanol + carbon dioxide
2. Hydration – Ethene reacts with steam at high
temperatures to form ethanol
ethene + steam
catalyst
ethanol
C2H4 + H2O

C2H5OH
Pros and Cons of Both Methods
Fermentation
Hydration
 Cheap, renewable
resources used
(plants)
 High purity of ethanol
produced
 Non-continuous
process (must wait
for plants to grow)
 Non-renewable
resource used (ethene
from crude oil)
 Continuous process
 Ethanol must be
(can produce large
purified by distillation
quantities)
Plant Oils
What are Plant Oils?
Plant oils (vegetable oils) contain
a large amount of energy.
Uses
Bio-fuels: these are both
renewable and carbon neutral.
Food: plant oils contain fats that
are essential to our health and
also a large number of calories
(energy)
Structure of Plant Oils
Vegetable oils are usually unsaturated (contain C=C
double bonds) and so will decolourise bromine water
Vegetable oils can be extracted by pressing
the seeds from a plant…
...or by distillation:
1. Plant is mixed with
water and heated
2. The mixture boils and
rises up distillation
column
3. The mixture condenses
and is collected
4. Plant oil is separated
from the water
Cooking with
Plant Oils
Boiling in Water vs Frying in Oil
Water
Oil
Boiling
point
100oC
~250oC
Speed of
cooking
Slow
Fast
Taste
Bland
Yummy
Vegetable oils have
very high boiling
points
This means that foods
can be cooked much
faster in oil than in
boiling water
Animal Fats vs Plant Oils
Saturated fat
Unsaturated fat
Unhealthy
Healthy
Saturated animal fats
can lead to high
cholesterol, blocked
arteries and heart disease.
Vegetable oils contain
double bonds which makes
them unsaturated.
Unsaturated vegetable oils
can actually lower
cholesterol.
Hardening Vegetable Oils
We can increase the melting point of vegetable
oils by hydrogenation (adding hydrogen).
This hardens the oil to make it spreadable.
H H
C=C
Hydrogen (H2)
Nickel catalyst
Heat to 60oC
H H
C-C
H H
Emulsions
Emulsions are smooth,
thick mixtures of oil and
water. E.g. mayonnaise, ice
cream, cosmetics
However oil and water are
immiscible (do not mix).
Emulsifiers can be used to
get oil and water to mix
together to produce an
emulsion.
Oil
Water
How Emulsifiers Work
+
Hydrophilic head Hydrophobic
(loves water)
tail (loves oil)
Oil
+
Oil
Water
Charged oil droplets
repel each other
Layers of
the Earth
Crust
Mantle
Outer
& Inner
Core
Crust – Very thin solid layer that contains all of the
minerals that we can use. Mainly made of granite and basalt.
Mantle – Much thicker layer than the crust, made from a
semi-solid material that can flow very slowly
Core – A mixture of radioactive nickel and iron. It consists
of a liquid outer core and solid inner core
Earthquakes
and Volcanoes
The crust of the
Earth is cracked into
large pieces called
the tectonic plates.
Radioactive decay in
the core produces lots
of heat energy.
This produces
convection currents in
the mantle which cause
the plates to move.
These movements cause
earthquakes, volcanoes
and mountain formations
at plate boundaries.
Because the plates are
constantly moving it is
difficult to predict when
there will be a sudden
and significant
movement which leads to
a disaster.
Continental
Drift
Alfred Wegener’s Theory
Wegner believed that the
world once consisted of a
single super continent called
Pangaea.
Slowly, over millions of
years Pangaea drifted apart
to give the world that we
know today.
He called this theory
continental drift.
The Evidence:
Continents seemed
to fit like a jigsaw
Identical fossils
and rocks were
found in different
continents
Tropical plant
fossils were found
in the arctic
Many didn’t agree with Wegner They suggested that
because he couldn’t explain how land bridges sunk
into the seas.
the continents moved.
Land Bridge
Old Theory of Mountain Formation
Scientists also suggested that mountains
were formed by the crust shrinking as the
Earth cooled down (a bit like an old apple).
The
Atmosphere
History of the Earth’s Atmosphere
1. Volcanoes released
CO2, H20 & N2. Traces
of CH4 & NH3 also made
the first atmosphere.
4. Increased oxygen
 animals evolved &
protective ozone
layer formed
2. Earth started
to cool  water
vapour condensed
 oceans formed.
3. Plants evolved 
oxygen released by
photosynthesis  CH4
and NH3 removed.
CH4 + 2O2  CO2 + 2H2O
4NH3 + 3O2  2N2 + 6H2O
Separating Air
Air can be separated by
fractional distillation:
1. Air is condensed by cooling
to -2000C
2. Solid H2O and CO2 are
removed
3. Remaining liquid air is
allowed to warm
4. N2 has a lower boiling point
than O2 so boil’s first
Earth’s Atmosphere Today
0.04% CO2
0.96% Argon
21%
Oxygen
Nitrogen 78%
Oxygen 21%
Noble gases 1%
78%
Nitrogen
Carbon dioxide 0.04%
Carbon
Cycle
Oceans
dissolving
Atmosphere
respiration
Fossil
Fuels
Animals
death
Dead
organisms
feeding
Plants
The early atmosphere contained high levels of CO2
But the atmosphere now only contains 0.04% of CO2...
Plants took in CO2 through photosynthesis
CO2 became “locked away” in rocks & fossil fuels
CO2 also dissolved in the oceans (CO2 sinks)
The level of CO2 is now
increasing rapidly due
to deforestation and
burning fossil fuels.
Origins
of Life
At some point, the gases in the early atmosphere
combined to give the complex organic molecules
needed for life to begin on Earth:
CO2
N2
CH4
H2
H2O
NH3
Simple molecules
found in early
atmosphere
Complex organic
molecules needed
for life
There are 2 main theories of how this happened...
Primordial Soup Theory
Urey-Miller Theory
 Meteors crashed to earth Lightening caused
containing organic molecules the gases in the
atmosphere to react
 The molecules formed a
‘primordial soup’
This formed the
amino acids needed
 The molecules reacted
to make DNA and new
with each other to make new
life
life