Very useful for your final exams :)

1. Chemistry Revision

2. Atoms
All chemical elements are made up of atoms
Every atom is made up of smaller particles; neutrons
and protons in the atom’s nucleus which is
surrounded by electrons
Atoms become ions when they gain/lose an electron
The atomic number is the number of protons in the
nucleus ( which is the same as the number of
electrons)
The mass number is the protons + neutrons in the
nucleus, the mass of an electron is so small it is
considered to be negligible

3. Atom Mass
A is the relative atomic mass
M is the relative molecular mass,
For example- H₂O has a relative
molecular mass of 18 [(2x1) + 16)
For ionic compounds the term relative
formula mass is used as there is no
separate molecules
r
r

4. Isotopes
Isotopes are different forms of the same
element
If an isotope has more neutrons than protons,
it can sometimes be unstable and is likely to
decay

5. Alkali Metals
Group 1 in the periodic table
More reactive as you go down the group
Low densities
Ionic compounds +1 charge
Alkaline solution
Soft shiny metals
React with the oxygen in the air and become tarnished so they
are stored in oil
React vigorously with water, they fizz and produce hydrogen gas
Identifying Alkali Metals- identified using the flame test
Lithium burns with a red colour
Sodium burns with a yellow/orange colour
Potassium burns with a lilac/purple colour

6. Halogens
Group 7 in the periodic table
More reactive as you go up the group
Reacts with alkali metals
Halogens react with iron- iron wool bursts into flames when
it reacts with fluorine gas
Halogen displacement reactions mean the more reactive
halogen displaces the less reactive halogen
Identifying Halides- identified using the precipitation test
using silver nitrate
Chlorine- white/silver
Bromine- Pale yellow/cream
Iodine- yellow

7. Metal – Physical Properties
The following properties applies to copper
High electrical conductivity
High thermal conductivity
High melting point and boiling point
Ductile
Corrosion resistant
Antibacterial
Malleable (can be hammered/squashed into different
shapes)
Easy to alloy

8. Metallic Structure
positive
The structure can
easily pass the
vibration of hot
particles along and
the free electrons
move faster which
is why metals are
such good
conductors

9. Ionic Compound- Physical Properties
The following properties applies to Sodium Chloride
High melting point- because they have strong attractive
forces ( lot of energy to separate)
Solid sodium chloride does not conduct electricity
because the lattice holds to sodium and chloride ions in
fixed positions ( Not free to move)
but it can conduct electricity does if dissolved in water
as the lattice breaks down so the ions move freely
Brittle- if a stress is applied will make the layers move
Soluble in water

10. Ionic Structure
The sodium lost an electron and
the chlorine gained an electron

11. Simple Covalent Molecule- Physical properties
Low melting point( strong bonds
but weak attractive forces)
Liquid at room temperature
Poor conductor of electricity
Water soluble

12. Simple Covalent Structure
A covalent bond
happens when
electrons are
shared between
to atoms

13. Giant Covalent Substance
Diamond
Transparent + crystalline (used for jewellery)
Extremely hard ( lot of energy needed to break
down lattice)
Electrical insulator
High melting point
Graphite
Grey/black shiny solid
Very soft- used in pencils
Conducts electricity( along the layer as
electrons are free to move but does not
conduct across the layers)
High melting point
Slippery( hexagonal layers slide across each
other
Both different forms of carbon

14. Structure of diamond and graphite
Carbon atoms each connected to
4 other atoms
3-d Lattice based on a tetrahedral
unit cell
graphite Diamond
Made up of layers
Arranged in hexagonal rings
Each carbon atom is connected
to 3 other atoms
Bonds between layers are weak
Layers can slide over each other

15. Carbon Nanotubes
One of the stiffest and strongest fibres known
High electrical conductivity
Formed when graphite layers are rolled up into
tubes
Covalently bonded hexagonal carbon sheets
make it very strong
Proposed uses for electrical connections in
smaller circuits
Used in bike components, boat hulls and
bonding of things like wind-turbines
Could be used for cancer treatment

16. Smart Materials
Smart materials are materials that change when there is a change
in their surroundings
Thermochromic Pigments
Special paints which change
colour when there is a change in
temperature
Most are base on liquid crystal
technology
Used in mugs to see hot
temperatures
Also used in T-shirts
Photochromic Pigments
Contain organic molecules which will
change colour when exposed to light,
especially ultraviolet light
Used in T-shirts and glasses

17. Smart Materials
Shape-memory
polymers
Plastics that regain their
shape when heated
Somewhere between
thermoplastics and
thermosets
Used for sealing around
window frames
Could be used for car
bodies (fix the dent)
or stitches which will adjust
to tension
Shape-memory alloys
Metal alloys that regain
their shape when heated
Used for spectacle frames,
surgical plates and wires
Hydrogels
Polymers that absorb or
expel water and swell or
shrink the size it
swells/shrinks to depends
on changes in PH or
temperature
Used in artificial muscles

18. Rates of reaction
We can measure the rate of reaction by :
-Capturing & measuring the volume of gas
produced by a reaction
- Measuring the change in mass
- Measuring the amount of light passing
through a reaction that is producing a
precipitate

19. Chemical Reactions
Chemical reactions occur when molecules/atoms/ions
collide but it only happens there is enough energy for
the bonds to break and be reformed.
Successful collisions per second = collision frequency
Factors that affect the rate of reaction
1. Temperature
2. Surface Area
3. Concentration
4. Use of a catalyst

20. Catalysts
These are
substances that
increase the rate of
reaction but remain
chemically
unchanged
It reduces the
amount of energy
needed which will
increase the
collision frequency
Used in the production of
bulk materials eg. Sulphuric
acid and food processing

21. Percentage Composition of Compounds
Calculate the % of copper in copper sulphate,
CuSO4 ◦Relative atomic masses: Cu = 64, S = 32
and O = 16
◦relative formula mass = 64 + 32 + 4x16 = 160
◦only one copper atom of relative atomic mass 64
◦% Cu = 64 x 100 / 160 = 40% copper by mass in
the compound
Example

22. Masses of reactants and products
The total mass of the reactants equals the total
mass of the products

23. The Yield of a Chemical reaction
Yield= What was obtained
What was expected
X 100 %
Example: Mass of carbon monoxide you would expect to reduce 1000g of iron oxide
Fe₂O₃ + 3CO 2Fe + 3CO₂
Fe₂O₃ CO
Mass(g) 1000 ? = 525
Mr 160 40
Mass/Mr 6.25 18.75 (3x6.25)
1 : 3

24. Combustion of methane
The breaking of the bong is endothermic (gives
out heat
The formation of the bond is exothermic (takes
in heat)

25. Oil
Crude oil is a mixture of
hydrocarbons
Fractional distillation is
how you separate
different fractions of oil
The larger the molecule
the higher the boiling
point

26. Alkanes and Alkenes
Alkanes are saturated hydrocarbons which
means they only contain single bonds
Alkenes are unsaturated hydrocarbons they
have a double bond
Alkenes can be produced from alkanes by
cracking ( heating the alkane with a catalyst)

27. Polymers
Examples: polythene , polypropene
Monomers (ie ethene) are used to form
polymers
Ethene can become polyethene by heating it
under pressure

28. Thermosets and thermoplastics
Thermosets are plastics that are resistant to
heat. Used for kettles, saucepan handles etc.
Have strong cross linkages which hold the
structure together and make them resistant to
heat make them resistant to heat
Thermoplastics are plastics that soften when
heated. Used for packaging, containers. Made
up of polymer chains not linked together so they
can slide over each other

29. Water Treatment
When the water is in
the reservoir, the large
particles will sink to
the bottom
(sedimentation), the
smaller particles will
be filtered.
The water is
chlorinated to kill the
bacteria to make it
safe to drink. Fluoride
is also added
It is then stored until it
is needed

30. Desalination
Definition: The removal of salt from sea water so it can be
used for drinking
This is usually done by reverse osmosis which goes through a
membrane that lets water molecules through but not salt
Problems
- Lots of energy required
- Produces a lot more greenhouse gases
- Expensive
- Very salty water is left when fresh water is used
- Poor countries that have droughts cannot afford this
- Some countries don’t have access to the sea

31. Extracting water
If something is dissolved in water,
you can extract it by evaporating
& condensing
To separate a liquid from water
you need to use distillation.
Different liquids have different
boiling points . If you heat an
ethanol and water mixture, the
boiling point of ethanol is 78C so
by heating the mixture at this
temperature the ethanol will
evaporate and when the ethanol
vapour reaches the condenser it
will be cooled and become a
liquid

32. Chromatography
Paper Chromatography- a drop of mixture
is placed on the Chromatography paper
and placed in a solvent used to dissolve
pigment. The solvent soaks into the paper
and moves upwards. The more soluble will
travel with the solvent and move further
up the paper.
The R value is used to measure this
(distance substance travelled/ distance solvent travelled)
f
Gas Chromatography- can be used to detect pollutants in water or
air and it is also used to test for banned substances in sports
players. The mixture must be in the form of a gas (vaporised or
naturally occurring.) The gas passes through a column and different
substances are absorbed into an inert solid or liquid. The position
the chemical moves along the column is detected electronically

33. Hard water
Hard water contains dissolved calcium and magnesium ions.
Can be temporary or permanent
Temporary hard water contains magnesium/calcium hydrogen
carbonates . When heated the hardness is removed but it forms
calcium carbonate (scale) which clogs up pipes.
Permanent hard water contains chlorides/sulphates of calcium
and magnesium which does not soften when heated
Advantages of hard water
-Some people prefer the taste
-Calcium is good for teeth and bones
-Helps reduce heart illness
- Some brewers use hard water in beer
Disadvantages of hard water
-Difficult to form lather with
soap
-Scum forms with soap
- Scale forms, clogs pipes
and kettles

34. How to soften hard water
1. Boiling- easy and cheap but doesn’t work for
permanent hardness
2. Adding Sodium Chloride- prevents calcium and
magnesium ions bonding with washing detergent.
Cheap, removes permanent hardness but deposits
are still formed
3. Ion exchange column- Column filled with resin
which has sodium ions. The calcium/magnesium
ions are swapped for the sodium ions and come out
of the tube with the water where as the calcium
ions remain in the resin. Can treat a large amount of
water but are more expensive.