igcse chemisyrty notes -extraction of metals

Oxidation and reduction

Oxidation is a reaction where oxygen is gained.

eg iron + oxygen ---> iron oxide

Reduction is a reaction where oxygen is lost. Eg iron oxide is reduced to form iron.

Classify the following reactions as oxidation or reduction:

burning magnesium,

making aluminium from aluminium oxide,

burning carbon in air,

copper oxide + carbon --> copper + carbon dioxide

carbon monoxide forming carbon dioxide.

Electron loss and gain

Oxidation is also a loss of electrons

eg Fe --> Fe2+ + 2e-

Reduction also the gain of electrons eg (when Fe ions becomes Fe atoms

Identify all of the elements below as being oxidised or reduced in the following reactions:

Cu2+ + 2e- ---> Cu

lead ions forming lead atoms

Na ---> Na+ + e-
Ca + Cl2 --> CaCl2
Fe2+ ---> Fe3+ + e-
Reduction of metal ores
An ore is a material found in the ground which contains a metal. An ore is often a metal oxide mixed with rock . When a metal is extracted its ore is reduced. Metal loses oxygen from its oxide. Examples include: haematite which is mostly iron III oxide
bauxite which is mostly aluminium oxide Al2O3
malachite which is mostly copper carbonate CuCO3
Extraction and position in reactivity series
Uses and properties of aluminium
extraction method that uses a lot of electrical energy. Electrical energy is more expensive than energy from burning carbon
The extraction of aluminiumAluminium is found in the ground in an ore called bauxite. Bauxite is aluminium oxide (Al2O3) with iron oxide impurities.


After purification aluminium oxide is mixed with cryolite to lower the melting point from 2000º to 1000º, which saves money.
This mixture is heated and the molten liquid used as the electrolyte. Both electrodes are made of graphite (carbon). The anode (+ve) is graphite and the cathode (-ve) is a graphite lining to a steel case.
The carbon anodes react with oxygen so have to be replaced.
C + O2 --> CO2

At cathode - positive aluminium ions attracted, gain electrons and become atoms.

Al3+ + 3e- ---> Al

At anode - negative oxide ions attracted, lose electrons and become atoms.2O2- ----> O2 + 4e-
uses and properties of aluminium
overhead power cables-good electrical conductor, low density
drinks cans-Does not react with water
aircraft parts -high strength and low density
Carbon and carbon monoxide for reducing oxides
Carbon and carbon monoxide can both remove oxygen from other compounds so are good for reduction.
They are used to reduce the ores of metals below carbon in the reactivity series.
E.g. zinc, iron, tin and lead.
Iron extraction using the blast furnace Drag and drop labels test on blast furnace
A blast furnace is used in the process of extracting iron. The raw materials iron ore, coke and limestone are put in at the top. Hot air is blasted into this furnace at the bottom making the coke (carbon) burn faster and the temperature rises to about 1500º.
When the coke burns, carbon dioxide is produced. C + O2 ---> CO2 CO2 reacts with the unburnt coke to form carbon monoxide CO CO2 + C ---> 2CO Iron oxide Fe2O3 in the ore is reduced to iron by the reaction with the carbon monoxide. 3CO + Fe2O3 ---> 3CO2 + 2Fe Molten iron is a dense liquid, so runs to the bottom of the furnace and is tapped off.
Limestone CaCO3 helps remove impurities during the extraction by forming calcium oxide

CaO. CaCO3 ---> CaO + CO2



The rock impurities silicon dioxide SiO2 are then removed by the following reaction.

CaO + SiO2 ---> CaSiO3 CaSiO3
is known as slag and can be used in making cement and road building.

The purification of copperVery pure copper is needed for copper wires. Electrolysis is needed to purify copper. The anode is a mass of impure copper and the cathode is pure copper. The electrolyte is sulphuric acid. The impurities drop at the anode as sludge during electrolysis. At anode Cu ---> Cu2+ + 2e-





At cathode Cu2+ + 2e- ---> Cu

only for gcse chemistry -Chemical from calcium carbonate

Thermal decomposition of calcium carbonatecalcium carbonate ---heat---> calcium oxide + carbon dioxideCaCO3(s) ---heat---> CaO(s) +CO2(g)(limestone) (quicklime)

Water and calcium oxidecalcium oxide + water ---> calcium hydroxideCaO(s) + H2O(l) ---> Ca(OH)2(s) (slaked lime) looks flaky and gets hotWith more water the calcium hydroxide dissolves to make limewater Ca(OH)2(aq)
Neutralising soil acidityCalcium oxide and calcium hydroxide are bases. (like all metal oxides and hydroxides)acid + base ---> salt + waterso acid soil is neutralised by calcium oxide or calcium hydroxidee.g. nitric acid + calcium oxide --> calcium nitrate + water

2HNO3(aq) + CaO(s) ---> Ca(NO3)2(aq) +H2O(l)Farmers can add calcium oxide or calcium hydroxide to their acid soil to neutralise it.The neutral soil is better for growing plants.Task C3.25 Write word equations and balanced chemical equations for neutralising the following acids using calcium oxide and calcium hydroxide: nitric acid, sulphuric acid, hydrochloric acid, phosphoric acid (H3PO4)

Uses of calcium carbonateCement is made from calcium carbonate (limestone).limestone --heat--> calcium oxide + carbon dioxide


Calcium oxide + clay ----> cementGlass is made using calcium carbonate.


Calcium carbonate + sand + sodium carbonate ---heat--> glassIron is manufactured using calcium carbonate in the blast furnace.calcium carbonate --heat--> calcium oxide + carbon dioxideCalcium oxide + silicon dioxide ----> calcium silicate (mostly sand) (slag) (floats on top of molten iron)

igcse/ gcse chemistry notes- Chemicals from salt

The electrolysis of aqueous sodium chloride solutionWhen the electrolysis of aqueous sodium chloride takes place, hydrogen and chlorine are given off as gases and sodium hydroxide is left. Aqueous sodium chloride contains hydrogen ions H+ and hydroxide ions OH- (from the water) and sodium ions Na+ and chloride ions Cl-. The positive sodium and hydrogen ions go to the cathode and the negative chloride and hydroxide ions go to the anode. Hydrogen is formed at the cathode and chlorine is formed at the anode.


substance-hydrogen
test -lighted splint
result-squeaky pop

substance-chlorine
test-damp blue litmus
result-turns red then white

substance -sodium hydroxide
test-damp red litmus
result-turns blue/purple

Write a word and a balanced chemical equation for the reaction in which hydrogen burns.


Complete: Chlorine is (acidic/alkaline) because it turns litmus red. Chlorine is a (dye/bleach) because it turns litmus white. This type of reaction is (oxidation/reduction).

Uses of sodium chloride, hydrogen, chlorine and sodium hydroxide
substance


uses
sodium chloride
preserve food, flavouring, stops ice on roads because salt lowers freezing point of water to -5oC, manufacture of sodium, chlorine and sodium hydroxide


chlorine
kills bacteria in swimming pools and drinking water, bleach, making hydrochloric acid and solvents.



hydrogen
rocket fuel, making margarine, making ammonia
sodium hydroxide
detergents, bleach, paper, fibres, purifying bauxite


Match the uses above to the explanations below: compounds of carbon and chlorine are good at dissolving grease, hydrogen reacts with chlorine to form hydrogen chloride, vegetable oil reacts with hydrogen to form margarine, nitrogen and hydrogen react together in the Haber process, soap is made from vegetable oil and sodium hydroxide, the structure of wood is broken up by sodium hydroxide, salt is easily detected by the tongue, bacteria cannot survive in salty solutions, by the electrolysis of molten sodium chloride, by the electrolysis of aqueous sodium chloride.

igcse chemistry free notes -Transition metals

The colours of transition metal compoundsAll compounds of transition metals are coloured. Some examples are:copper sulphate - blue, iron III oxide - brown, cobalt chloride - pink.

Transition metals are used as catalysts
manganese (IV) oxide
decomposing hydrogen peroxide

platinum
catalytic converter in car exhaust

nickel
making margarine from vegetable oil and hydrogen

vanadium (V) oxide
making sulphuric acid

platinum with rhodium
making nitric acid


iron
making ammonia


Uses and properties of titanium, iron and copper

iron
Bridge Construction
High Strength

iron
permanent magnets
Magnetic

copper
water pipes
does not react with water

copper
Electrical wires
Good conductor of electricity

titanium
propeller shafts on ships, hip joints
does not react with water

titanium
aircraft engines
high strength, low density, high mp

igcse free chemistry notes -Halogens

Physical properties of halogens

The colour of the Halogens changes from a lighter colour to a dark colour as we go down the group and the melting and boiling points increase as you go down the group.

Fluorine at the top of the group is a yellow gas This changes to a yellow-green gas for chlorine, a red liquid for bromine and finally black solid for iodine at the bottom of the group.

Reactions of halogens with metalsMetal + Halogen --> Metal Halide

Iron reacts slowly with iodine to form iron II iodide. Iron reacts faster with bromine to form iron III bromide.

Iron reacts with chlorine reacts even faster to form iron III chloride.
Other metals like sodium also react.sodium + chlorine ---> sodium chloride

The reaction of halogens with hydrogenHydrogen reacts with halogens to form hydrogen halides. E.g.Hydrogen + chlorine ---> hydrogen chloride

H2(g) +Cl2(g) --> 2HCl(g) (a hydrogen halide)

Hydrogen halides are very soluble in water.

The gas hydrogen chloride forms hydrochloric acid when it dissolves in water. Other hydrogen halides like hydrogen bromide, HBr and hydrogen iodide, HI also dissolve to form acid solutions. An acid solution has a pH less than 7


e.g. 1. An acid turns universal indicator red.

Displacement reactions

Halogens like chlorine are very reactive and displace less reactive halogens like bromine from halides like bromides.

Potassium bromide + chlorine ---> potassium chloride + bromine

2KBr(aq) + Cl2(aq) --> 2KCl(aq) + Br2(aq)

2Br-(aq) + Cl2(aq) --> 2Cl-(aq) + Br2(aq)

Chlorine and bromine also react with potassium iodide showing that the order of reactivity is: Chlorine > bromine > iodine


Uses of halogens and halidesFluorine compounds (fluorides) are put into toothpaste and some drinking water supplies. Fluorides join with tooth enamel and make teeth resist attack by acid which prevents tooth decay. Chlorine is used to in swimming pools and drinking water to kill bacteria. Iodine is used as an antiseptic because it will kill the germs on the skin without damaging it.

IGCSE CHEMISTRY FREE NOTES Alkali metals

Properties of alkali and other metalsThe alkali metals have low melting points low densities and are soft compared to other metals.

For example lithium has a melting point of 180ºC and caesium has a melting point of just 29ºC.

These are low compared to other typical metals such as iron, melting point 1500ºC.

Sodium and potassium are soft and can be cut with a knife but iron is hard.

Alkali metals and waterWhen an alkali metal is put into water, it reacts very vigorously. It moves around the surface fizzing.

Hydrogen is produced which can be tested using a lighted splint. The metal also gets hot and potassium gets hot enough to ignite in its own heat.

The water turns into a hydroxide. Reactivity increases as you go down the group.

2Na(s) + 2H2O(l) ---- 2NaOH (aq) + H2(g

Reactivity of metal with water

lithium
fizzes gently moving slowly
reactive


sodium
fizzes vigorously, moves quickly
very reactive


potassium
violent fizzing, bursts into lilac flame
violently reactive

Properties of alkali metal compoundsAlkali metal compounds are all white solids which are soluble in water.
Alkali metal hydroxides or oxides dissolve in water and are alkalis. An alkali has a pH of over 7, e.g. 14. An alkali turns universal indicator purple. An alkali can neutralise an acid. Whenever an acid is neutralised it produces water and a salt.
sodium hydroxide + hydrochloric acid ---> sodium chloride + wateR (a salt)


NaOH(aq) + HCl(aq) ---> NaCl(aq) + H2O(l)

igcse chemistry free notes-Noble gases

Monatomic nature of noble gasesNoble gases are monatomic. This means they exist only as single atoms. Their atoms cannot combine with other atoms because in their electronic structure, the outer shell is always full and this makes noble gases unreactive


Argon
Light bulbs
Doesn’t react with the metal filament


Helium
Used with O2 for deep sea dives
Low solubility of helium in the blood.

Helium
To inflate the tyres of large aircraft
Non-flammable

Helium
To fill airships and weather balloons
Low density, does not burn
Uses and properties of noble gases


Neon
In advertising signs because it glows red when electricity passes
Conductor of electricity at high voltage

Krypton/Xenon
In lamps used in photographic flash units, in stroboscopic lamps used in lighthouses
Gives out a lot of light when electricity passes through

igcsechemistry free -notes The periodic table

Elements are placed in order of increasing atomic number so hydrogen atomic number 1 is firsthelium atomic number 2 is second etc.

Groups

A group is a column of elements with similar properties in the periodic table. See figure1. e.g all of the following are in the same group and are silver in colour, soft and good conductors of electricity.
lithium
sodium
potassium
rubidium
caesium

The position of groups in the periodic tableThe positions of the alkali metals (group 1), the halogens (group 7), the noble gases (group 0) and the transition metals are shown in figure 1 above.

Task :Label a copy of the periodic table to show a group, a period, the alkali metals, halogens, noble gases, transition metals, metals, and non-metals.

Reactions and electron arrangements

Group 1 elements all have atoms with 1 outer electron. e.g. sodium 2,8,1All of these atoms try to lose 1 electron so all react in the same way.

They all form a positive ion and form ionic compounds. E.g. sodium Na form sodium ion Na+.Group 1 elements all react with oxygen (that is burn) to form oxides. The products like sodium oxide, are all ionic.

Group 0 elements all have atoms with complete outer shells

e.g. helium 2, neon 2,8. None of these elements react with anything.

Task - Name other elements in group 1 and say how they react with oxygen giving a reason. State how argon reacts with oxygen and give a reason.

Trends in group propertiesGroup 1 elements get more reactive with water as you go down the group. e.g.Lithium (gentle fizz) is less reactive than potassium (violent lilac flame).

Group 7 elements get more reactive with iron as you go up the group.Iodine darkens iron when it is heated but chlorine makes iron burst into flames.

igcse free - chemistry notes / Metals and Non-Metal

Properties of Metals
malleable
ductile
sonorous
shiny
conduct heat
conduct electricity
hard and strong
Non Metals
brittle
dull
do not conduct electricity
do not conduct heat
not magnetic
Alkali Metals
very reaction (have to be stored under oil to prevent reaction with air)
form ions with 1+ charve.
soft and can be cut with a knife
potassium and sodium float on water
Trends down the group
atomic size increases (increased no of electrons and shells)
lose outer shell electron to form 1+ charged ions. Therefore reactivity increases as you go down the group. The electron is farther away from the nucleus.
melting points decrease
Reactions:
alkali metals with oxygen in the air
Sodium + Oxygen = Sodium Oxide
4Na + O2 -> 2NaO2
alkali metals with water
gives off hydrogen gas
resulting solution is alkali
Sodium + Water -> Sodium Hydroxide + Hydrogen
2Na + 2H20 -> 2NaOH + H2
alkali metals with halogens
they react rapidly with halogens
Sodium + Chlorine -> Sodium chloride
2Na + Cl2 -> 2NaCl
Halogens
non metals
form ions with 1- charge
very reactive
toxic
as you go down the group the colour of vapour becomes darker
fluorine - yellow
chlorine - green
bromine - red
iodine - violet
Halogens are used as bleaching agents
Trends as you go down the group
atomic size inicreases
reactivity decreases (easier to gain electrons when electron shell is closer to the nucleus)
melting and bioling point increase
Reactions
halogens with hydrogen
Chlorine + Hydrogen -> hydrogen chloride (hydrochloric acid)
Cl2 + H2 -> 2HCl
halogens with metals (forms a salt)
Magesium + Bromine -> Magnesium bromide
2Mg + Br2 -> 2MgBr
Displacement Reactions with Halogens
A more reactive halogen will displace a less reactive one.
Example: chlorine can displace bromine from potassium bromide, but cannot displace fluorine from potassium fluoride.
Cl2 + 2KBr -> 2KCl + Br2 (chlorine displaced bromine)
Br2 + 2KI -> 2KBr + I2 (bromine displaced iodine)
Br2 + 2KF -> 2KF + Br2 (bromine can't displace fluorine)
Noble Gasses
gasses at room temperature
uncreactive
density with increase in atomic size
Argon is used inside light bulbs
Helium is used in hot air ballons
boiling point increases as you go down the group
Transition Metals
hard dense metals
not very reactive
often used as catalysts
have variable valency (different charges, Fe2+ Fe3+)
Some metals form oxides in reaction to oxygen
some metals form basic oxides
some non-metals form acidic oxides
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igcse - free- chemistry notes Atoms, Bonding and the Periodic Table

The group number is related to the number of electrons in the outer shell. e.g. (Mg) Magnesium, in group 'II', has two electrons in the outer shell
electrons are arranged in shells surrounding the nucleus, with the first shell containing 2 electrons and subsequently 8.

All atoms want a full outer shell of 8 electrons (like noble gasses)


Ionic Bonding:


Ions are formed by gaining or loosing electrons
is the transfer of electrons from one atom to another, giving the atom a positive of negative charge

The two atoms together have a neutral charge
It occurs mainly when metals bond with non-metals

Examples

Magnesium + Oxygen
Electron Configuration
Mg: 2 --> transfer two electrons from Mg to give both atoms a stable


electron configuration
O: 2,6

Properties of Ionic Compounds
solids at room temperature (strong bonds, opposite charges)
high melting and boiling point (lots of energy required to overcome strong bonds)
don't conduct electrivity in the solid state, since electrons can't move (can in the molten state)
form crystaline solids because of ionic lattice
dissolve readily in water, but not in molecular solvents
Covalent Bonding
occurs when non-metals bond.
They share electrons to get a noble gas structure
Example: Hydrochloric Acid (HCl)
both H and Cl need one electron.
They form a single covalent bond to get a full outer shell
Properties of Covalent Compounds
molecules have no charge
low melting and boiling points. (little attraction between molecules,)
dont attract electricity (don't have charged particles)
liquids of gasses at room temperature
dissolve readily in molecular solvents, but not in polar solvents like water
Isotopes
are atoms of the sama element with:
same number of protons
same number of electrons
different number of neutrons
Examples
126C (6 electrons, 6 protons, 6 neutrons[12-6])
and

146C (6 electrons, 6 protons, 8 neutrons [14-6])

note: top number is the atomic mass

Relative Atomic Mass

average mass of atombased on various isotopes present

Noble Gasses

unreative (inert)because of full outer shell of electrons

igcse chemistry notes -properties of metals and non metals

metals -good conductors of heat and eletricity
non metals-poor conductors of heat and electricity
metals-shiny
non metals -dull
metals-malleable
non metals -brittle
metals -strong
nonmetals -weak
metals -react with oxygen to form basic oxides
nonmetals-react with oxygen to form acidic oxides
metals-usually high density
nonmetals-usually low density
metals -usually high melting points except alkali
nonmetals-usually low melting points except carbon
metals-many react with dilute acid to produce hydrogen
nonmetals -no reaction with dilute acid

igcse chemistry notes -compounds and mixtures

Mixture-No heat or light is given out or absorbed when mixing occurs
compound-Heat and sometimes light is usually given out or absorbed when a compound is made.
mixture-The substance in a mixture can be separated by physical means
compund -the elements in a compound cannot be separated by physical means
mixtures -the properties of a mixture are the average of the properties of thes substances in it
compounds -the properties of a compound are quite different from those of the elements in it
mixtures -the substances in a mixture can be presented in any proportions by mass
the elements in a compound are combined together in definite proportions by mass (we have not proved this yet).

igcse/gcse / o level chemistry notes -Elements and Compounds

Atoms, Elements and Compounds
The Atom
? Smallest particle that can take place in a chemical reaction
? Consists of three sub-atomic particles, electrons, protons, neutrons
Electrons
? Negatively charged, found in energy shells outside the central part of the atom
? Move at very high speeds in orbit
? Have very negligible mass
? Mass is 0.0005 of a proton
Protons
? Are positively charged and found in the nucleus of an atom
? Have a unit mass of one (ie. 1 a.m.u)
Neutrons
? Have no charge at all and are located in the nucleus
? Have a unit mass each
1 atomic mass unit (1 a.m.u) = 1.67 x 10-27 kg)
The Atomic Number is also called the proton number (distinguishes element)
The proton number equals the electron number so that charges balance
The mass number is the total mass of the atom. Calculated with proton + neutron. (Electron neglected)
Nucleon number: total number of particles inside the nucleus (ie. Protons + neutrons)
Energy Shells
? Shells increase as they become full
? The first shell only contains 2 electrons and following shells contain 8 each
Chemical Stability
? Electrons are spaced out regularly at intervals as shown below. The presence of unpaired electrons determines the chemical reactivity of the atom.
? The electrons in the outer shell of an atom are referred to as valence electrons
? If the valence electrons for the outer shell are not enough to fill the shell, then the atom is chemically reactive and unstable. (E.g. Sodium Na+)
? Atoms with fully filled outer shells such as noble gases, are chemically unreactive and stable.
Noble Gases
? Also called inert gases have fully filled outer shelled atoms (E.g. Helium, Neon, Argon, Krypton)
Electronic Configuration
? A group of numbers which show the arrangement of electrons in their various shells
? The numbers represent number of electrons in each shell starting with the innermost shell, separating each number (shell) by a comma
E.g. He: 2, Ne: 2,8, O: 2,6
Isotopes
? Atoms of the same element having different mass #s but the same atomic number (ie. Different neutrons)
? Most elements exist as a mixture of their isotopes
? Hydrogen has 3 isotopes: Protium (0n), Deuterium (1n) and Tritium (2n).
These are called H-1, H-2 and H-3
The two types of isotopes are: (i) Radioactive and (ii) Non-radioactive isotopes
? Radioactive isotopes are isotopes with an unstable nucleus (the general term for radioactive substances since they are all isotopes).
? Non-Radioactive isotopes are stable and unreactive
Medical uses:
? Isotope cobalt-60 emits gamma radiation which can be used to sterilize medical equipment
Industrial Uses:
? Uranium-238 can be used to estimate the ages of rocks
Differences between Elements, Mixtures and Compounds
? An Element is a pure and simple substance which cannot be broken down into any simpler substances other than itself by any ordinary chemical means.

? A Mixture is made up of two or more substances physically mixed together.

The components in a mixture can always be separated by physical means

A compound is a pure substance which is made up of two or more elements chemically combined.
When these combine chemically they lose their identities and the compound takes its own properties.