ALCOHOL

Formula of alcohol :

CnH2n+1OH

Nomenclature

all alkanes begin with the prefix as mentioned below and ending with -ol

( 1 carbon atom) methan-

( 2 carbon atoms ) ethan-

( 3 carbon atoms ) propan-

( 4 carbon atoms ) butan-

( 5 carbon atoms ) pentan-

( 6 carbon atoms ) hexan-

( 7 carbon atoms ) heptan-

( 8 carbon atoms ) octan -

( 9 carbon atoms ) nonan-

(10 carbon atoms ) decan-

Properties of alkene

1) Combustion

Burns in plentify supply of air, it produces carbon dioxide and water.If INCOMPLETE COMBUSTION, it gives soot, carbon monoxide, carbon dioxide and water.

2) Oxidation

(a) ethanol oxidised to ethanoic acid by warming with acidified potassium dichromate.
(b) ethanol can be oxidised to ethanoic acid using air by the bacteria in the air.

3) Formation of esters

Alcohol reacts with carboxylic acids in the presence of a few drops of concentrated sulphuricacid as a catalyst to form esters and water.

ALKANES

Formula of Alkane :

CnH2n+2

Nomenclature ( Naming )

all alkanes begin with the prefix as mentioned below and ending with -ane

(1 carbon atom) meth-
(2 carbon atoms ) eth -
( 3 carbon atoms ) prop-
( 4 carbon atoms ) but -
( 5 carbon atoms ) pent -
( 6 carbon atoms ) hex -
( 7 carbon atoms ) hept-
( 8 carbon atoms ) oct -
( 9 carbon atoms ) non-
(10 carbon atoms ) dec-

Properties of Alkane:

1) Burns in plentify supply of air, it produces carbon dioxide and water.If INCOMPLETE COMBUSTION, it gives soot, carbon monoxide,carbon dioxide and water.

2) One reaction:Free radical Substitution
Alkane will react with Chlorine in UV light conditions ( means sunlight ) to form a variety of products:

Eg:
CH4 + Cl2 ---> CH3Cl + HCl ------ equation (1)

CH3Cl + Cl2 ---> CH2Cl2 + HCl ------ equation (2)

CH2Cl2 + Cl2 ---> CHCl3 + HCl ------- equation (3)

CHCl3 + Cl2 ---> CCl4 + HCl ----- equation (4)

Lastly, in exam, you are EXPECTED to name, form equations and draw the structure!

ALKENES

Formula of alkene :

CnH2n

Nomenclature

all alkanes begin with the prefix as mentioned below and ending with -ene

there is no methene ( 1 carbon )

(2 carbon atoms ) eth-

( 3 carbon atoms ) prop-

( 4 carbon atoms ) but-

( 5 carbon atoms ) pent-

( 6 carbon atoms ) hex-

( 7 carbon atoms ) hept-

( 8 carbon atoms ) oct-

( 9 carbon atoms ) non-

(10 carbon atoms ) dec-

Properties of alkene

1) Combustion

Burns in plentify supply of air, it produces carbon dioxide and water.

If INCOMPLETE COMBUSTION, it gives soot, carbon monoxide, carbon dioxide and water.

2) Hydrogenation

C2H4 + H2 ---> C2H6 (ethane)

3) Bromination

C2H4 + Br2 ---> C2H4Br2

** This is bromine test: used to distinguish between alkane and alkene ** ( Typical Structure Question!)

Alkene: Aqueous bromine will decolourised.
Alkane: Aqueous bromine remains unchanged.

4) Hydration

C2H4 + H2O ---> C2H5OH (ethanol)

Another method to prepare ethanol is 'fermentation'

C6H12O6 ---> 2 C2H5OH + 2 CO2

Conditions: yeast and temperature: 25'C.

5) Cracking

To break less useful linger chains into smaller useful fractions.

Conditions: 400°C - 700°C , silicon dioxide /aluminum oxide as catalyst.

OXIDATION & REDUCTION

There are basically 4 definitions of oxidation and reduction:

OXIDATION

1) Increase in oxidation states

Eg: Fe 2+ ---> Fe 3+

An increase of oxidation staes from 2+ to 3+ ( obvious, isn't it? )

2) Gain of oxygen atoms

Eg: Pb + CuO --> PbO + Cu

In this case, Lead (Pb) has gain 1 oxygen atom to form lead(II) oxide (PbO)

3) Lost of hydrogen atoms

Eg: 2 H2S (g) + SO2(g) ---> 2H2O(l) + 3S (s)

In this case, hydrogen sulphide (H2S) has lost 2 hydrogen atoms to form sulphur (S)

Note: do not be CONFUSED by the ratio: 2H2S.
We are interested in the formula, H2S instead!

4) Loss of electrons

Actually, if you look closely, the LOST of electrons is similar to the oxidation states!!!

Why Do I Say That?

Consider this example,
Fe 2+ ---> Fe 3+2+ means lost of 2 electrons and 3+ means lost of 3 electrons.In this case, we say that Fe 2+ is oxidised to Fe 3+.
Compare the oxidation states, isn't 2+ a gain of OXIDATION STATES to 3+ ??

Similarly,

REDUCTION

1) Decrease in oxidation states

Eg: Zn 2+ ---> Zn

From oxidation states of 2+ to 0 ( a decrease in oxidation states )

2) Loss of oxygen atoms

Eg: Pb + CuO ---> PbO + Cu

Copper (II) oxide has lost 1 oxygen atom to form Cu

3) Gain in hydrogen atoms

Eg: N2 + 3H2 ---> 2 NH3

Nitrogen (N2) has gain 2 hydrogen atoms to form ammonia (NH3)

4) Gain of electrons

Eg: Zn 2+ + 2 e- ---> Zn

Zinc ion has accepted 2 electrons to become Zinc ztom
or
Zinc ion has decrease in its oxidation state from 2+ to zero.

( the first rule about decrease in oxidation states )

SPEED OF REACTIONS

** IF THE QUESTION STATES THE USE OF COLLISION THEORY TO EXPLAIN THE FACTORS AFFECTING THE SPEED OF REACTION, PLEASE EXPLAIN USING THE PARTICLES!!!**

(Typical Structure Question!)

Factors affecting rate of reaction:

1) CONCENTRATION

* EXPLANATION *
The greater the number of particles, the more frequent is the collision,-----> the faster the speed of reaction.

2) EFFECTIVE SURFACE AREAS OF REACTANTS

* EXPLANATION *
The greater the effective surface area of reactants,the more frequent is the collision-----> the faster the speed of reaction.

3) TEMPERATURE

* EXPLANATION *
The higher the temperature, the greater the amount of energy the paricles have, the frequent is the collision,-----> the faster the speed of reaction.

4) CATALYST

* EXPLANATION *
The use of catalyst increases the speed of reaction.

Note: Catalyst is never used up in a reaction!!!

AIR

Composition of air

nitrogen- 78%

oxygen - 21%

other gases- 1% ---> carbon dioxide-0.03%---> noble gases - mainly argon.

NOTE: AIR DOES NOT CONTAIN HYDROGEN!!!!!!!

POLLUTANTS

For pollutants, pupils are expected to be able to least 2 pollutants: its sources, effects and solutions. (Questions on air have become very popular in examinations)

CARBON MONOXIDE

Source: incomplete combustion of fuels in vehicle engines
Solution:
1) ensure complete combustion of fuels
2) attach catalytic converter to vehicle engines.

OXIDES OF NITROGEN

Source:
1) combustion of fuel in vehicle engines at high temperature
2) lighting
Solution:
Fit catalytic converter to vehicle engines.

ACID RAIN

1) when sulphur dioxide dissolves in rain, sulphuric acid is formed.

2) when oxides of nitrogen dissolves in rain, nitric acid is formed.
(1) + (2) --- > ACID RAIN

Effects Of Acid Rain:

(1) Corrode buildings,
(2) corrode limestone structures,
(3) damage to trees and
(4) marine lives.

EXTRACTION OF METALS

Extraction of Iron

TYPICAL STRUCTURED/ ESSAY QUESTIONS

Question: Describe with the aid of equations the essential reactions in the extraction of iron.

1) Iron ore (haematite), coke and limestone are added to a blastfurnace.

2) Coke reacts with the air to form carbon dioxide.

3) Coke reacts with more carbon dioxide to form carbon monoxide.

4) Carbon monoxide reacts with iron ore to form iron and carbon dioxide gas.

5) Limestone decomposes to form calcium oxide and carbon dioxide.

6) Calcium oxide reacts with silicn dioxide to form slag.

Typical questions associating with extraction of iron:

(a) Name of the iron ore = haematite

(b) Why is limestone used in the extraction = to remove impurities ( acidic oxide, silicon dioxide )

_______________________________________________

Note:the extraction of metal depends on the reactivity of the metal.

Electrolysis of molten chlorides

Potassium, Sodium, Calcium, Magnesium, Aluminum

Heating with carbon

Zinc, Iron, Lead, Coppper

Uncombined in the ground

Silver, Gold, Platinum

ENERGY FROM CHEMICALS

EXOTHERMIC ( EXit )

Heat energy is released.

Egs: acid and metal reactions, neutralization, condensation, freezing and bond-making

Heat of Reaction (Enthalpy change) = negative

Tips for remembering: When two persons get together ( bond-making), they are in love and they will release 'sparks' of love ( 'Heat energy release') [ laugh]

ENDOTHERMIC

Heat energy is absorbed.

Eg: decomposition, melting, boiling, bond-breaking

Heat of Reaction ( Enthalpy change ) = positive

Tips for remembering: When a couple wants to break up ( bond-breaking), they need to gather all their complains and greviances to quarrel ('Heat energy gain') [laugh]

GROUP PROPERTIES

Typical Exam Questions!!!!(STR/ESSAY)

Group I ( alkali metals)

It is known as alkali metals because it reacts with water to form HYDROXIDES and hydrogen gas.

They are soft, low densities ( hence can be cut by knife ), having charges (+1) and the melting point decreases down the group. They are very reactive hence they need to be stored under oil to prevent reaction with air and water.

An Easy Way For Pupils To Remember the reactivity.......

'F' is the MOST REACTIVE !!!!!

For group I, Francium is the most reactive!!!! ( hence reactivity increases down the group )

Pupils are required to state the way the element react with water!!!!

Lithium reacts fast.
Sodium reacts quickly, catches fire sometimes explodes
Potassium reacts EXTREMELY FAST; catches fire and then EXPLODES.

As for rubidium, caesium and francium.... the reactivity will be explosion because they are more reactive than potassium.

Group VII ( halogen)

Each molecule is diatomic (F2, Cl2, Br2, I2, At2), having charges of (-1) and the boiling points increases down the group. They are very reactive and react VIGOROUSLY with metals to form ionic salts. Reactivity decreases down the group.

Remember: F is the most reactive.

Hence Fluorine is the most reactive, followered by chlorine, bromine, iodine and the least reactive is astatine.

As for the colours, it darkens down the group.

Fluorine is light yellow
Chlorine is yellow green
Bromine is brown
Iodine is dark purple ( black is acceptable)
Astatine is black

Since the boiling points increases down the group, the states are as follows:

Fluorine-(gas)
Chlorine-(gas)
Bromine-(liquid)
Iodine-(solid)
Astatine-(solid)

Since reactivity decreases down group 7, A MORE REATIVITY HALOGEN WILL BE ABLE TO DISPLACE A LESS REACTIVE HALOGEN FROM AN AQUEOUS SOLUTIONS OF ITS SALT.

This means that fluorine is able to displace (kick out) all the rest of the elements from group 7:

F2 (g) + 2 NaCl(aq) ----> 2 NaF(aq) + Cl2(aq)

However, a less reactive halogen will not be able to displace a more reactive halogen:

Cl2(g) + NaF (aq) ---> no reaction

GROUP 8 ( NOBLE GASES )

These elements are not able to combine with other atoms because of its stable electronic configuration ( octet structure can be used to replace 'stable-electronic configuration').
Hence group 8 elements are MONOATOMIC.

Pupils will need to know the uses:

Helium-hot air balloon
Neon- advertising lights
Argon / Neon - in light bulbs
Argon - manufacturing of steel ( flush air from molten steel to protect it from further reaction of the air )

PERIODIC TABLE

The elements in the periodic table are arranging according to INCREASING PROTON NUMBERS.

The vertical columns are known as Groups while the horizontal rows are known as Periods.

Elements of the same group have the same number of valence electrons ( outershell electrons)

Eg:
All ements of group 1 have 1 valence electrons;
All elements of group 2 have 2 valence electrons.

Elements of the same period have the same number of electron shells.

Eg:
All elements of period 1 ( Hydrogen and Helium ) have 1 electron shell.
All elements of period 2 (Lithium, Beryllium, Boron, Carbon, Nitrogen, Oxygen, Sulphur, Fluorine, Neon ) have 2 electron shells.

There exist a group of elements without any grouping.

These are the transition metals.

Transition metals are characterized by their variable ( more than 1 ) valencies.

Eg:
iron ion exist as iron (II) ion and iron (III) ion;
copper ion exist as copper(I) ion and copper(II) ion.

STRUCTURE OF ATOMS

(Typical MCQ Question!!)

Location of Particles

Protons, neutrons are found in nucleus
Electrons orbit in electron shells

Mass of Particles

Proton = 1
Neutron = 1
Electron = 1/1840 ~ 0

Charges of Particles

Proton = +1
Neutron = 0
Electron = -1

Isotopes (Typical Structure Question!! )

Isotopes are atoms of the same element with different nucleon numbers but same proton number.
Eg: Carbon-12, Carbon-13, Carbon-14

CHEMICAL BONDS

Ionic Compounds

Ionic compounds are formed by metal (gp 1-3) and non-metal (gp 4-7)

Properties
-High melting point and boiling point ( considered as one point in exam ).

-Soluble in water.

-Conduct electricity in molten (hot liquid ) and in aqueous states
Note: does not conduct electricity in solid states!!!

Metal conduct electricity in molten and in solid states.

Covalent Compounds

Covalent compounds are formed only by non-metal elements.

Properties
-Low melting and boiling points

-Soluble in organic solvents

-Poor conductor of electricity

EXCEPTION: HCl is a good conductor of electricity.
Reason: When HCl dissolves in water, it dissociates to produce H+ and Cl-. It is the free mobile ions that conduct electricity! (Typical MCQ Question! )

(Typical Structure Question)

Question: Both sodium chloride and chlorine gas are compounds of chlorine; sodium chloride exist as a solid while chlorine exist as a gas. Explain why.

Answer:
Sodium chloride is an ionic compound [ 1mark ]. A large amount of energy is needed to overcome the strong electrostatic forces of attraction between oppositely charged ions [ 1mark] . Hence high melting point. This is why it exist as a solid at room
temperature.

Chlorine gas is a covalent substance [ 1mark]. A small amount of energy is needed to overcome the weak intermolecular force of attraction between the molecules [ 1mark]. Hence low melting point. This is why it exist as a gas at room temperature.

Note: Although 'Hence high melting point. This is why it exist as a solid at room temperature.' has no mark allocation, this phrase has to be included for the completeness of answer!

STATES SYMBOLS

STATES SYMBOLS

(s) represents solid states
(l) represents liquid states
(g) represents gaseous states
(aq) represents aqueous states - means dissolved in water.

Question 1: 'Is water in aqueous state?'
Answer: No!! Simply because water cannot dissolve in water!!!

Question2: ' Is there any difference between gases vs gaseous?'
Answer: gases are particles that can move freely, while gaseous is to describe the state of the particles.

ELEMENTS, MIXTURES & COMPOUNDS

Element

An element is a substance that cannot be broken down into simpler substances by chemical means.
Eg: oxygen (O2), carbon (C), sulphur (S)
Note: Elements can be found in the Periodic Table.

Do not be confused:
1) An element can exist as molecules.Eg: hydrogen (H2), nitrogen (N2)
Molecule simply means more than 1 atom.
So, you can have the same type of atoms ( O2, N2, H2 , S8 ) or different types of atoms (CO2, CH4, H2O)

Compound

When it is made up by different types of atoms joined together chemically, it becomes a compound.
In this case, CO2 and CH4 are compounds.

A compound is a substance made up by more than 1 elements joined chemically together.

Eg: Calcium carbonate (CaCO3) ~contains 3 elements namely calcium(Ca), carbon (C) and oxygen (O)
Number of atoms in CaCO3 = 1+1+ 3(1) = 5 atoms

MIXTURE

Made up by at least 2 substances not joined together chemically.

Mixture can be catagorised by three types:

1) Element + Element
Eg: Iron(Fe) + Carbon(C)

2) Element + Compound
Eg: Copper (Cu)+ Water (H2O)

3) Compound + Compound
Eg: sodium chloride (NaCl) + water (H2O)

Common mistake made by students:

'A mixture can ONLY be separated by physical means'. (WRONG!!)

* EXPLANATION *
A mixture can also be separated by chemical means!!Compound is a substance that cannot be separated by physical means.

FORMULAS

All ions formed from:

group 1 ,(H+), (NH4+) have charges (+1)

group 2, Pb2+, Cu2+,Fe2+ have charges (+2)

group 3, have charges (+3)

group 6, (CO32-), (SO42- ) have charges (-2)

group 7, (OH-), (NO3-) have charges (-1)


* certain ions have various valency:
(Fe2+, Fe3+) , (Pb2+,Pb4+)

PURIFICATION

1) FILTRATION

Eg: sand from sand + water mixture



2) CRYSTALLISATION

Eg: copper(II)sulphate from impure copper(II)sulphate mixture

* Crystallisation is usually carried out with filtration.


3) DISTILLATION

Defn: to obtain pure liquid from a solution of solute
Eg: water from sea water


4) FRACTIONAL DISTILLATION

Defn: to separate liquids with different boiling points
Eg:

(i) ethanol from ethanol(78'C) + water(100'C)

(ii) crude oil into petrol, kerosene, lubicating oil etc

(iii) air into nitrogen, oxygen, carbon dioxide etc

5) CHROMATOGRAPHY

Defn: a method to separate and identify mixtures


Eg: separates dyes or colour from food/ ink/ pigments,check amounts of pesticides in vegetables, check if medicine contains banned drugs etc

(6) SUBLIMATION

Defn: a process in which substances changes from solid states to gaseous states through heating.

Eg: Ammonium chlorides ( NH4Cl ), dry ice ( solid CO2) ,naphthalene ( mothballs ), iodine



To test if a substance is pure / impure ( typical MCQ question!! )

CHECK IF IT HAS A FIXED BOILING / MELTING POINT------> IF IT IS PURE, IT WILL HAVE A FIXED MP/BP



Disclaimer: Picture are obtained from these websites-
GCSE Chemistry noteswww.wpbschoolhouse.btinternet.co.uk/page01/ElCpdMix/EleCmdMix.htm

EXPERIMENTAL DESIGN

BURETTE
- for measuring volumes of liquids up to 1 decimal place
eg: 27.5 cm3, 36.2 cm3

PIPETTE
- for measuring fixed volumes of liquids
eg: 20.0 cm3, 25.0 cm3, 50.0 cm3
Cannot measure odd volumes.
eg: 28 cm3, 38.5 cm3

MEASURING CYLINDER
-for measuring volumes of liquids to nearest 1 cm3
eg: 23 cm3, 36 cm3

BEAKER
-for boiling liquids / containing liquids
Never use it to measure volumes!

COLLECTION OF GASES

-FOR HEAVY GASES : downward delivery

-FOR LIGHT GASES : upward delivery

-FOR INSOLUBLE GASES: displacement of water