Planet Earth
Examples of resources in the Earth: coal, natural gas, metals, NaCl and limestone…
Matters are something that has mass.
Matter Pure substances Elements Can’t be broken into anything simpler by
chemical methods.
Compound Composed of 2+ elements joined
chemically together.
Mixtures – 2+ pure substances which haven’t joint chemically
Some examples of compounds and their uses:
Ammonia ( NH 3 ) – glass cleanser, fertilizer
Calcium carbonate ( CaCO3 ) – calcium supplement tablets
Sodium hydroxide ( NaOH ) : drain cleanser
Mixture Compound
Mixed together in any proportion. In a fixed ratio.
No chemical change when it’s formed Energy is usually released when forming the
compound (chemical change occurred)
Similar properties with the original Can have very different chemical properties then
substances that made up the mixture the elements that it contains
Don’t have a sharp BP/MP (it varies) Have a definite/sharp/unique MP/BP
Can be separated by physical method Have to be separated through chemical method.
(e.g. electrolysis)
Method of separation
1) Decantation
Let the residue sinks in the bottom of the beak and pour the decant away through the glass rod.
It’s suitable for separating insoluble liquid from a liquid.
2) Filtration
Pour the mixture into a filter funnel with filter paper through the glass rod. Residue is in the
beaker underneath and the filtrate left in the filter paper. It’s suitable for separating insoluble
liquid from a liquid. (e.g. separate sand from sea water)
3) Evaporation.
Heat the mixture in a evaporating dish by Bunsen flame. When solution is evaporated, solid
remains. It’s used to separate dissolved solid from a solution. (e.g. NaCl from Sea Water)
4) Crystallization
Method I: Heat the mixture, some solvent boils away, but hot solution can hold more solute.
Cool it down and the solution can’t hold such solute, crystal formed.
Method II: Pour the mixture in a beaker with cover, let the solvent evaporate under room
temperature, it will over-saturated and from crystals.
It’s used to separate dissolved solid from a solution. (e.g. CuSO4 from Water)
5) Distillation (evaporation + crystallization)
Evaporate the solution in a distillation flask, a tube with condenser receives the solution vapour
and turn it into liquid, and collected by the conical flask. It’s suitable to separate dissolved solid
from a solution.
6) Fractional distillation
Remove impurities such as dust, water vapour and CO2 ; compress the air in a high pressure
(by the Ideal Gas Law it’ll get hotter), then it’s cooled in a cool chamber (by water), it’s
expanded (by IGL it’s cooler). Repeated this step until the air is liquefied. Pump the air into the
fractioning column, the temperature is slowly increased. The B.P. of N 2 , Ar and O2 are
196C , 186C and 183C respectively, therefore N 2 is collected in the bottom of the
tower, followed Ar and O 2 .
It’s suitable to separate two miscible liquids.
7) Sublimation
Put the mixture in a beaker covered by a evaporating dish. Heat the beaker until it sublimes.
Those sublimed gas will become solid again in the bottom of the dish.
It’s suitable to separate mixture of two solids which one of them can sublime.
Physical properties are something that can be measured without changing the chemical
composition of the substance.
No new substances are formed during physical change.
Chemical properties describe the ability of a substance to form new substances.
One or more new substances is formed in chemical change. In another way, energy is
absorbed or released.
Test for O 2 : (glowing splint test) Oxygen relights glowing splint.
Test for H 2 : (burning splint test) Hydrogen gives a “pop” sound when burning.
Test for H 2 O : Water turns dry cobalt(II) chloride paper from blue to pink.
Test for some metals (flame test): If it’s not clean, dip it into conc.
HCl solution, heat it until
no characteristic flame is shown. Dip the clean Pt wire into (fresh) conc. HCl solution (or
dip it into conc. HCl solution, heat it until no characteristic flame is shown.), then dip it into
the solid sample power and heat it.
1) Na gives golden yellow flame.
2
2) Ca gives brick-red flame.
3) K gives lilac flame.
2
4) Cu gives bluish green flame.
Test for chloride: add (dilute) nitric acid followed by silver nitrate solution, Cl gives white
ppt (participate).
Four layers of Earth’s atmosphere: troposphere, stratosphere, mesosphere and ionosphere.
Composition of atmosphere – 78% of N 2 , 21% of O 2 , 0.9% of noble gases, 0.03% of
CO2 , variant amount of H 2 O and some other gases.
Sea covers over 70% surface area of the Earth. It dissolved different salts. Most salts are
brought by rivers. Composition of sea salt (3.5% of the sea water): about 68% of NaCl ,
15% of MgCl 2 , 11% of Na 2 SO4 , 3% of CaCl 2 and some other salt.
A solution forms when a substance (solute) dissolves in another (solvent). Dilute solution
contains a very small amount of solute in given amount of solution. When solute increase, it
becomes concentrated, and finally saturated. Saturated solution means it can’t dissolve
anymore solute in a given temperature.
Electrolysis of water
electricity r
e l e c ty i c i t
2 H 2 O 2 H 2 O2 H 2 ( g ) Cl 2 ( g ) N a O Hl )
s e aw a t e r (
Manufacture of ammonia ( NH 3 )
Hydrogen As rocket fuel ( 2 H 2 O2 H 2 O )
Manufacture of hydrochloric acid ( HCl )
Sterilizing drinking water
Chloride Sterilizing swimming pool water
Manufacture of PVC (polyvinyl chloride) and organic solvents
Manufacture of bleach
Sodium Hydroxide
Manufacture of soaps and detergents
Particle theory of matter – all substances are made up by very small particles.
Limestone – calcium carbonate ( CaCO3 )
1) Heat and limewater(calcium hydroxide)
Heating calcium carbonate gives calcium oxide (quick lime) and carbon dioxide:
CaCO3 CaO(s) CO2 ( g )
Adding water to calcium oxide gives lime water (slaked lime in solution):
CaO H 2 O Ca(OH ) 2 (aq)
Test for CO2 : turns lime water from colourless to milky:
Ca (OH ) 2 CO2 CaCO3 H 2 O
Excess carbon dioxide makes it becomes colourless again:
Ca (OH ) 2 2CO2 CaCO3 H 2 O CO2 Ca ( HCO 3 ) 2
2) Acid
Adding (dilute) hydrochloric acid gives calcium chloride, water and carbon dioxide:
CaCO3 2 HCl CaCl 2 H 2 O CO2
CaCl2 is soluble in water so that CaCO3 is soluble in hydrochloric acid.
CaCO3 is insoluble in water.
Use of limestone
1) Crushed limestone (CaCO3) – extraction of iron; construction material for road and
buildings.
2) Powered limestone (CaCO3, grinded) – neutralize acidity of soil and sulphur dioxide in
flue gas of power stations; making glass.
3) Quicklime (CaO) – making steel with Fe, neutralize acidity in soil; drying agent in industry.
4) Slaked lime (Ca(OH)2) – neutralize acidity in soil and lake affected by acid rain.
5) Cement (limestone heating with shale) – ingredients of concrete.
Formation of limestone cave
Solid rock broke down and changed into other materials by weathering, its surface is wearied
away while the movement of products of weathering that changed their location is called
erosion. Rainfalls becomes carbonic acid with carbon dioxide in air (H2O+CO2→H2CO3)
(Note that the reaction can occur the inverse direction here) while carbonic acid dissolves the
underground limestone deposits to form calcium hydrogencarbonate:
CaCO3+H2CO3→Ca(HCO3)2
(Ca(HCO3)2 is the main cause of hard water.)
The underground limestone is dissolved in this way over millions of years to form underground
holes called limestone caves.
Formation of limestone
CaCO3 exists naturally in 3 forms: chalk, limestone and marble, depends on their hardness.
When sea animals die, their skeletons and shells (mainly contains CaCO 3) sink into the mud at
the bottom of the oceans. After many years layers built up and pressure from top layers
changes the bottom layers to chalk. Earth movements such as earthquake may lift the layer to
Earth’s surface. They changes to limestone and marble under. higher pressure and heat