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IGCSE
Complete
Chemistry
Notes

By: Abdulla Al Zaabi
Refined and cleared by KmQ! :D

Unit 1: States of matter
Everything is made of particles
...
Liquids
and gases can
...
This is called random motion
...

This mixing process is called diffusion
...

The smallest particle that cannot be broken down by chemical means is called an atom
...
For example the gas argon, found
in air, is made up of single argon atoms
...
These are called
molecules
...

These particles are called ions
...

• High Density
• Not compressible
Model:
• Occur in clusters with molecules slightly further apart compared to solids
• Free to move about within a confined vessel

Gas Properties:
• No Fixed volume and no fixed shape
• Low density
• Compressible
Model:
• Very far apart
• Travel at high speed
• Independent and random motions
• Negligible forces of attraction between them

Diffusion in Gases
Gases diffuse in different rates
...
Mass of the particles
The lower the mass of its particles the faster a gas will diffuse
...
the faster it will travel (obviously
...
The temperature
The higher the temperature, the faster a gas will diffuse
...
They are just mixed together and not
chemically combined
...

Solution: It is when a solute and a solvent mix
...

Example: sugar (solute) dissolves in water (solvent) making a solution of sugar
and water
...

To help a solute dissolve you could:
• Stir it
• Rise the temperature
If you add excess amount of sugar in a small amount of water
...
The solution becomes saturated
...

An unwanted substance, mixed with a wanted substance, is called an impurity
...

A pure substance has a definite, sharp, melting point
...
So the more impurity present, the wider and
bigger the change in melting and boiling point
...
Filtering
Example:
A mixture of chalk and water
...
A filter paper is placed in a funnel, the funnel placed on a flask
...
The mixture is poured on the filter paper
...

2
...
Inside a centrifuge
(it’s a machine), test tubes are spun very fast so the solid gets flung to the bottom
...
Evaporation
This method is used to separate a solution in which the solid is dissolved in the liquid
...
The solution is heated so that the liquid evaporates and the solid remains in the
bottom of the evaporating dish
...
Crystallization
This method is similar to evaporation but here the solid forms crystals then the crystals
are left to dry
...
This can be done by dissolving one in an appropriate solvent
...
Then filtering one and extracting the other from the solution by evaporation
...
Simple distillation
1
...

3
...


The impure liquid is heated
...

The impurities are left behind
...


6
...
The mixture is heated
...
The wanted substance boils and evaporates
(some of the unwanted liquid will evaporate
too) and rises up the column
...
The substance will condense on the beads
in the column causing them to heat
...
When the beads reach a certain temperature
when the wanted liquid wont condense
anymore (That’s the boiling point) it will rise
while the unwanted liquid will condense and
drop
...


7
...
For example you can use it to
find how many coloured substances there are in black ink
...
Drop the black ink on to the center of a filter paper and allow it to dry
...
Drop water on to the ink spot, one drop at a time
...
Suppose there are three rings: yellow, red and blue
...

The substances travel across the paper at different rates
...
The filter paper showing the separate substances is called a chromatogram
...


Uses of chromatography:
•
•
•

Separate mixtures of substances
Purify a substance by separating the impurities from it
Identify a substance

Unit 2: The Atom
Atoms are the smallest particles
...

An element is a substance that contains only one kind of atom
...
g
...
The group of elements that have similar properties are
put in a numbered column
...

The rows are called periods
...
So most elements are metals
...
For example carbon dioxide is a compound of carbon and oxygen
(1 carbon and 2 oxygen molecules)
...
So the formula
for carbon dioxide is CO2
...
For example, only sodium atoms
have 11 protons
...

Some isotopes are radioactive
...

Like carbon-14, a number of other elements have radioisotopes that occur naturally and
eventually decays
...

You can know when radioisotopes decay by looking at there half life
...


Uses of radiation:
1
...
At a leak, the radiation is
detected using an instrument
...

2
...
Using radiotherapy the
radioisotope will decay and give out rays that can kill cancer cells
...

3
...
When living thing dies it no
longer takes in new carbon atoms
...


How electrons are arranged
The electrons in an atom circle fast around the nucleus, at different levels from it
...
The further the shell is from the nucleus, the
higher the energy level
...

First shell can hold up to 2 electrons
Second shell can hold up to 8 electrons
The third shell can also hold up to 8 electrons
Electronic configuration means the arrangement of electrons in an atom
...
These are called Valency electrons
...


•

If an element posses a full outer shell, the element become unreactive

Unit 3: Atoms combining
Most elements form compounds because they want a full outer shell and to achieve that
they must react with other atoms
...
It can obtain a full outer shell by losing this electron to anther atoms and by that it
becomes a sodium ion
...
it now has 10 electrons
but 11 protons
...

An ion is a charged particle
...


The ionic bond
Example:
Sodium and chlorine react together; sodium gives its electron to chlorine
...
Now they are ions
...

Chlorine now has 18 electrons but 17 protons so it has a negative charge
...
The force of attraction
between them is strong
...

When sodium reacts with chlorine, billions and billions of sodium and chlorine ions form
and they attract each other
...
They cluster together so that
each ion is surrounded by 6 ions of opposite charges
...
The overall charge of the structure is 0 since 1 positive
charge and 1 negative charge neutralize each other
...

Important notes:
•
•
•
•
•
•

Hydrogen and the metals form positive ions
Non-metals form negative ions, and their names end in -ide
Group 4 and 5 do not usually form ions because they would have to lose or gain
several electrons and that takes too much energy
Group 0 elements do not form ions; they already have full outer shells
Some of the transition metals form more than one ion
...
These are called
compound ions
...
Ionic compounds have high melting and boiling points
...

2
...

The water molecules can attract the ions away from the lattice
...

3
...

When melted the lattice breaks up and the ions are free to move
...
The solutions of ionic compounds
conduct electricity too because they are also free to move
...


Covalent bonding is for non-metals only since only non-metals need to
gain electrons
...

When a pair of electrons is shared, it is called a single covalent bond, or just single
bond
...

When 3 pairs of electrons are shared, it is called a triple covalent bond, or just triple
bond
...

The molecules in a covalent compound isn’t flat because each electron repel each other
and try to get as far apart from each other
...
Molecular solids
are held in a lattice but the forces between the molecules are weak
...
The molecules are held in regular pattern in a lattice
...

When you cool down a molecular liquid or gas the molecules lose energy so they start
moving slowly and at the freezing point, they form a lattice (a good example would be
ice)

Properties of covalent bonding
1
...

2
...


Diamond – a giant covalent structure
Diamond is made of carbon atoms held in a strong lattice
...
Eventually billions of carbon atoms bond together to form a
crystal of diamond
...
It is very hard because each atom is held by four strong bonds
...
It has a very high melting point because of the strong bonds
...
It can’t conduct electricity because there are no free electrons to carry the
charge
...


Graphite – a very different giant structure
Like diamond graphite is made only of carbon atoms
...

In graphite, each carbon atom forms a covalent bond to three others
...

Graphite properties:
1
...
Is a good conductor of electricity because each carbon atom has four outer
electron and graphite bonds 3 only so the fourth electron is free to move carrying
a charge
...


Properties of Diamond:
•
•
•

Hard substance
High MP / BP
Cant conduct electricity

Properties of Graphite:
•
•

Soft and slippery
Good Conductor

Properties of Silica:
•
•

High BP / MP
Hard

Comparing Bonds
Differences in STRUCTURE
Covalent

Ionic

Molecular

ionic

Shares electrons

Exchange electrons

Simple molecules

Giant lattices

Non metal only

Metals and non metals

Differences in PROPERTIES
Dissolves in organic liquid (not water)

Dissolves in water

Low Boiling and melting point

High boiling and melting point

Does no conduct electricity

Conducts electricity

Metallic bonding
Metals form giant structures in which electrons in the outer shells of the metal atoms are
free to move
...
Metallic bonds are strong, so metals can maintain a regular structure
and usually have high melting and boiling points
...
Metals have high melting points
This is because it takes a lot of heat energy to break up the lattice
...
Metals are malleable and ductile
...

Ductile: They can be drawn out into wires
...

3
...

4
...


Unit 4: The Periodic Table
The periodic table is a list of all the elements, in order of increasing atomic number
...

The rows are called periods
...

The outer-shell electrons are also called valency electrons and their number
shows how the elements behave
...

Group 0 elements have a full outer shell
...

Some of the groups have special names:

Group 1 – The alkali metals
Group 2 – The alkaline earth metals
Group 7 – The halogens
Group 0 – The noble gases

Periods
The period number gives information about the number of electron shells that are
available in that period
...


Trends in the periodic table
The elements in each numbered group shows trends in their properties
...


Group 1: The alkali metals
Their physical properties:
1
...

2
...

3
...

Their chemical properties:
1
...
The hydroxides give alkaline solutions
...
They react with non-metals
...

They form ionic compounds in which the metal ion has a charge of 1+
...


The trend in physical properties
Lithium
Sodium

Softness

Density

Potassium

Increases

Increases

Melting
points
decrease

Boiling
points
decreases

Rubidium
Caesium

Why they have similar properties?
Because atoms with the same number of valency electrons react in a similar way
...

Why?
Because the atoms get larger down the group because they add electron shells
...

•
•
•
•

Form colored gases
...

Form diatomic molecules (means they exist as 2 atoms)

Trends in their physical properties
Fluorine
Chlorine
Bromine

Size and
mass of
atom
increases

Density
increases

Melting and
boiling
points
increase

iodine

Trends in their chemical properties
Reactivity increases as you go up group 7
...

Why are they so reactive?
Because their atoms are only one electron short of a full shell
...

Trends in their physical properties

Helium
Neon
Argon
Krypton

Size and
mass of
atom
increases

Density of
gas
increases

boiling
points
increase

Xenon

Uses of noble gases
Noble gases are unreactive, making them safe to use
...

Gas
Helium

Neon

Argon

Krypton
Xenon

Use
-Used to fill balloons and airships, because
it is much lighter than air and will not catch
fire
-Used in advertising signs
...

-Used as a filler in ordinary tungsten light
bulbs
...
It won’t react with the hot metals
(unlike oxygen)
-Used in lasers
...


The transition elements
The transition elements are the block of 30 elements in the middle of the periodic table
...


Their physical properties
•
•
•
•
•

Hard, tough and strong
High melting points (mercury is an exception)
Malleable and ductile
Good conductors of heat and electricity
High density

Their chemical properties
1
...

3
...

5
...


They are much less reactive than the metals of group 1
...

Most transition metals form colored compounds
Most can form ions with different charges (they have variable valency)
They can form more than one compound with another element
Most transition metals can form complex ions

Uses of transition metals
•
•
•
•

The hard strong transition metals are used in structure such as bridges,
buildings, cars etc
...

Transition metals are used as conductors of heat and electricity
...
The change that takes place will be either chemical change or a
physical change
...


The difference between a mixture and a compound
Mixture: 2 substances are mixed together but not chemically bonded
...
You can tell when a chemical
reaction has taken place by these signs:
1
...

2
...

A change that gives out heat energy is called exothermic
A change that takes in heat energy is called endothermic
3
...

This means it will be hard to get back the raw materials of the reaction
...


Equations for chemical reactions
The reaction between carbon and oxygen
...
Carbon and oxygen are the reactants
...


C

+

1 atom of
carbon

O

O

O



1 molecule of
oxygen

C

O

1 molecule of
carbon dioxide

Or in a shorter way, using symbols and numbers like this:

C

+



O²

CO²

This short way to describe the reaction is called a chemical equation
...

Litmus is a purple dye
...

Acids turn litmus red
Alkalis
You can tell if something is alkali, by its effect on litmus
...

Neutral substances
Many substances are not acids or alkalis
...
Example is pure water
...
The numbers go from 0 to 14:

On this scale:
An acidic solution has a pH number less than 7
An alkaline solution has a pH number greater than 7
A neutral solution has a pH number of exactly 7
Acids produce hydrogen ions
Acidic solutions contain hydrogen ions, this what makes them ‘acidic’

The difference between strong and weak acids
In solution of strong acids, all molecules become ions
...

The higher the concentration of hydrogen ions, the lower the pH, the stronger the acid
...

The difference between a strong alkali and weak alkali
In solution of strong alkali, it contains more hydroxide ions
...

The higher the concentration of hydroxide ions, the higher the pH
...
You can also measure there conductivity
...
A weak acid does not conduct well,
and has a higher pH
...
A weak acid will
show low conductivity and low pH
...
It’s a
redox reaction
...
Bases include alkalis, and insoluble metal oxides, hydroxides and
carbonates
...
With alkalis
Acid + alkali  salt + water
2
...
With carbonates
Acid + metal carbonate  salt + water + carbon dioxide

Reactions of bases
1
...
With carbonates carbon dioxide is
produce too
...
All the alkalis (except ammonia) will react with ammonium compounds, giving
ammonia out
...
It leaves out
the rest
...
First write down all the ions present in the equation
2
...
What’s left is the ionic equation for the reaction
Proton donors and acceptors
Acids donate its protons to bases and bases accept them
...
The acid donates its H+ protons and the oxygen
from magnesium oxide react with it to make water molecules
...
If soil is too acidic or too alkaline,
crops grow badly or not at all
...
Why? Because of a lot of vegetation rotting in it or
because too much fertilizer was used in the past
...

Acid rain
Acid rain is caused by factories, power stations, homes who burn fossil fuels to make
electricity
...
They go into the air and react with air and water to produce sulphuric acid
and nitric acid which are strong acids
...

With metals:
Example:
1
...
Stops when all the acid is
used up
...
Excess zinc is removed by filtering
...


3
...
Then it is left to cool and
crystals of zinc sulphate start to form
...
So you
must start with a metal oxide
...
Put the alkali into a flask and add some drops of indicator
2
...
Swirl the flask to help the acid
and alkali mix
...
When the indicator turns green stop adding acid
...
Calculate how much acid was used
...
Carry out the experiment again without the indicator and add same amount of
acid that was used before
...

6
...


Making insoluble salts by precipitation
Not all salts are soluble
...


Insoluble salts can be made by precipitation

Preparing barium sulphate
Barium sulphate is a insoluble salt
...

1
...

3
...

5
...

Mix them
...

Filter the mixture
...

Rinse the precipitate by running distilled water through it
...


Unit 10: How fast reactions are?
Rates of reaction
Some reaction are fast and some are slow
...

Rate is a measure of the change that happens in a single unit of time
...
To
measure the rate of this reaction this method is set up:

Stop clock

Using this you can measure the amount of hydrogen produced in a period of time
...
But collisions with
too little energy do not produce a reaction
...

The rate of reaction depends on the rate of successful collisions between reactant
particles
...

Changing the temperature
If the temperature is increased:
•
•
•
•

the reactant particles move more quickly
they have more energy
the particles collide more often, and more of the collisions result in a reaction
the rate of reaction increases
Changing the concentration or pressure

If the concentration of a dissolved reactant is increased, or the pressure of a reacting
gas is increased:
•
•
•

the reactant particles become more crowded
there is a greater chance of the particles colliding
the rate of reaction increases
Changing the surface area

If a solid reactant is broken into small pieces or ground into a powder:
•
•
•
•

its surface area increases
more particles are exposed to the other reactant
there are more collisions
the rate of reaction increases
The effect of light

Some chemical reactions obtain the energy from light
...
For example:
1
...
Plants use carbon dioxide from the air to make sugar called glucose, in a
reaction called photosynthesis
...
The green
substance – chlorophyll – in leaves speeds up the reaction:
6CO² + 6H²O  C6 H12 O6 + 6O²
Light
chlorophyll

Carbon dioxide + water  glucose + oxygen
In both these reaction, the stronger the light, the more energy it provides so the faster
the reaction goes
...
The catalyst itself
remains unchanged at the end of the reaction it catalyses
...

A catalyst works by lowering the activation energy for the reaction
...
So they are often called biological
catalysts
...
The reactant molecule
has to be the right shape
...

Important notes:
•
•
•
•

An enzyme works best in conditions that match those in the living cells it came
from
...

An enzyme also works best in a particular pH range
...
In making ethanol
2
...
In biological detergents

Unit 12: The behavior of metals
Most elements are metals
...

2
...

4
...

6
...


They are strong
...
They have high density (they are heavy)
9
...
When they react, metals form positive ions
...


Metals reactivity
A reactive element has a strong drive to become a compound
...

If a metal is more reactive than another metal, then it displaces it and takes it place
...

The reaction always gives out heat – it is exothermic
...
)
A metal will always displace a less reactive metal from solutions of its compounds
...


Aluminum, Al
Carbon
Zinc, Zn
Iron, Fe

Increasing
Reactivity

Metals above the red line: They displace
hydrogen from acids, and hydrogen
can’t reduce their oxides
...

The more reactive the metal, the more easily it gives up electrons to form positive
ions
...

The more reactive the metal, the more stable its compounds are
...

The less reactive the metal, the less it likes to form compound
...
In other words, they undergo thermal
decomposition
...
Carbonates
Most decompose to oxide and carbon dioxide, on heating
...

Strong heating is needed to break down calcium carbonate and the reaction is
reversible
...

For example Copper(II) carbonate breaks down very easily, like this:

CuCO³ (s)  CuO (s) + CO² (g)
2
...

The further down the series, the more easily the others break down
...
Nitrates
All decompose on heating – but not all the same products
...
So
no chemical
reaction is
needed
...
First it is roasted in air, giving zinc oxide:
Zinc sulphide

+

2ZnS (s)



Oxygen
3O²

Zinc oxide

+

Sulphur dioxide

2ZnO (s)

2SO²

Then the oxide is reduced in one of the two ways below:
1
...
This is carried in a furnace:
Zinc oxide

+

Carbon monoxide

ZnO (s)

CO (g)



Zinc
Zn (s)

+

Carbon dioxide
CO² (g)

The final mixture contains zinc and a slag of impurities
...
(It boils at 907ºC)
2
...
It reacts with the oxygen in the air, giving
carbon dioxide:
Carbon

+

C (s)

Oxygen



Carbon dioxide

O² (g)

CO²

Explanation: It’s a combustion reaction which means it’s a redox reaction
...
The blast of air provides the oxygen for the reaction
...

Stage 2: Carbon monoxide is made
The carbon dioxide reacts with more coke, giving carbon monoxide:
Carbon

+

C (s)

Carbon dioxide



Carbon monoxide

CO² (g)

2CO (g)

Explanation: In this redox reaction, the carbon dioxide loses oxygen
...

The reaction is endothermic – it takes in heat from the furnace
...

Stage 3: The iron(III) oxide is reduced
This is where the actual extraction occurs
...

Explanation: In this redox reaction, carbon monoxide acts as the reducing agent
...

At the same time the carbon monoxide is oxidized to carbon dioxide
...

Limestone
CaCO³ (s)

+ Silica
SiO² (s)



Calcium silicate

+

Carbon dioxide

CaSiO³ (s)

CO² (g)

The slag runs down the furnace and floats on the iron
...

Silica is an acidic oxide
...

The waste gases
These are carbon dioxide and nitrogen
...

Explanation: The carbon dioxide is from the reduction reaction in stage 3
...
It has not taken part in the reactions so has not been changed
...
It is impure with carbon as the main impurity
...
This is hard but brittle
...


Uses of some metals

Steel and other alloys
An alloy is a mixture of metals that changes there properties or increase them
...

Pure iron is too soft and stretches easily and rusts
...
5%) is mixed with it, the result is mild steel
...

Uses of mild steel (MUST KNOW): buildings, ships, car bodies and machinery
When nickel and chromium are mixed with iron, the result is stainless steel
...

Uses of stainless steel (MUST KNOW): car parts, kitchen sinks and cutlery
...
First, unwanted impurities are removed from the iron
...
Calcium oxide
is added, and a jet of oxygen is turned on
...
The oxygen reacts with the others burning
them away
...
Then other elements may be added
This is measured out carefully, to give steels with the required properties
...

The more reactive a metal is, the more readily it corrodes
...
Coat the metal with something to keep out air and moisture
...
For example:

Zinc: by dipping iron into molten zinc
...

Tin: deposited on the steel by electrolysis, in a process called tin plating
...
The chromium is deposited by electrolysis
...
Use sacrificial protection
This is when a more reactive metal is attached to the metal and it corrodes instead of the
steel
...


Does aluminum corrode?
No, because a coat of aluminum oxide forms on the aluminum which acts as a seal
preventing corrosion
...


These can be separated by fraction distillation
...


Uses of oxygen
1
...

2
...


Air pollutants

Ways to reduce pollution
•
•
•

Use less fossil fuels
Switch to clean sources of power
Try to find ways to store CO² and not let it escape to the atmosphere

Catalytic converters
A exhaust pipe is a pipe where waste gases are disposed off
...

On farms it is needed as a drink for animals, and to water crops
...

Power stations use it to make steam
...


Purifying water

Chemical tests for water
1
...

2
...


Unit 17: Organic chemistry
Organic chemistry is a branch of chemistry connected with
compounds of hydrogen and carbon (hydrocarbons)
...
They can form very long chains, and can form chains
linked by one double bond or triple bond

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