Edexcel IGCSE Chemistry Notes. Every single specification point. Got me a grade 9 in chemistry. I did very little revision but these notes were the only thing I needed
Solid- regular arrangement very close to each other, low kinetic energy and vibrates in fixed position
Liquid- randomly arranged, close still touching, medium ke and particles move around each other
Gas- randomly arrange, far apart, move around in random directions, high ke, move quickly
Condensation: gas —> liquid (less ke)
Vaporisation (evaporation and boiling): liquid—> gas (more ke)
Sublimation: solid —> gas (more ke)
Deposition: gas —> solid (less ke)
Freezing: liquid —> solid (less ke)
Melting: solid —> liquid (more ke)
Diffusion in gases:
Red brown bromine gas and air in two jars.
The bromine particles are moving randomly.
There are large gaps between the particles.
Therefore, then can easily mix together.
Diffusion in liquids:
Potassium mangante(VII) in water
Turns purple
Particles are moving randomly and particles can Slide Over each other
Particles can easily mix together.
Diffusion in liquids is lower than a gas because they are more closely packed together.
Dissolving potassium manganite in water
Colour fades but doesn’t disappear until a lot of dilution has been done.
This indicates that there are a lot of particles in a small amount of potassium manganate therefore
the particles must be very small.
Ammonia is faster than hydrochloric acid because it has a lower molecular weight so the white ring
of ammonia chloride forms closer to the HCL
Solvent: the liquid which a solute dissolve in
Solute: the substance which dissolves in a liquid to form a solution
Solution: the mixture formed when a solute is dissolved in a solvent
Saturated solution: a solution with the maximum concentration of solute dissolved in the solvent
Soluble: describes a substance that will dissolve
Insoluble: describes a substance that won’t dissolve
Solubility is the measurement of how much of a substance will dissolve in a sodium of a liquid and
can be expressed in g per 100g of solvent
,As temperature increases, solids usually become more soluble.
As pressure increases, gases become more soluble.
As temperature increases, gases become less soluble
Solubility curves are solubility in g per 100 of water against temperature.
Practice:
Prepare one hot water and one cold water beaker. Measure of put 4cm^3 of distilled water into the
boiling tube. Add ammonium chloride to boiling tube. Place in hot bath until solid dissolves. Then put
it in ice bath and stir. Note temperature where crystals first appear. Add 1cm^3 of distilled water
then warm the solution to dissolve crystals repeat cooling process. Continue the steps until 10cm^3
of water has been added
Solubility on y temp on x
Elements, compounds and mixtures
Element: a substance made up of atoms that can’t be split into anything simpler
Compound: a pure substance made up of two or more elements chemically combined together.
Mixture: a combination of two or more substances(elements or compounds) that aren’t chemically
joined together
A pure substance has a fixed boiling and melting point, but a mixture may melt or boil over a range of
temperatures.
Simple distillation: used to separate a liquid and soluble solid from a solution or a pure liquid from a
mixture of liquids. Solution is heated and pure water evaporates and goes through the lock of the
flask and into the condenser where it cools
Fractional Distillation: used to to separate two or more liquids with one another, solution is heated
and then the substance with the lowest boiling point will evaporate first and collected into a beaker.
Filtration: used to separate an undissolved solid from a mixture of solids and a liquid. Put filter paper
into a filter funnel filter paper will only allow small liquid particles to pass through as filtrate.
Crystallisation: used to separate a dissolved solid from a solution, when the solid is much more
soluble in hot solvent than in cold. Solution is heated allowing the solvent to evaporate leading a
saturated solution behind. Let it cool and the crystals will start to grow as the solids will come out
due to the decreasing solubility.
Paper chromatography: this is used to separate substances that have different solubilities in a
solvent. Draw a pencil line and spots of the sample are placed on it. Those substances with higher
solubility will travel further than others
Rf=distance travelled by substance/distance travelled by solvent
Pencil line doesn’t dissolve the solvent
Atomic structure
Atom: the smallest particles of an element that has electrons surrounding a nucleus that contains the
protons and neutrons
, Molecule: a group of two or more atoms chemically joined together
Particle Relative mass Charge
Proton 1 +1
Neutron 1 0
Electron 1/2000 -1
Atomic number: number of protons
Mass number: proton+neutron
Isotopes: Atoms of the same element containing same number of protons but different number of
neutrons
Relative atomic mass: weighted average mass of one atom of an element, taking into account the
abundance of all the isotopes of that element.
Ar = (% of isotope A * Mass of Isotope A) + (% of isotope B * Mass of Isotope B)/100
Periodic table
Horizontal: period
Vertical: group
First 20 element 2,8,8,2
Number of electrons in outer shell = group
Number of shells = period
Metals: good conductors, basic oxides, react with acids, malleable, high mp and bp
Non- metals: pool conductors, acidic oxides, don’t react with acids, flaky and brittle low mp and bp
Metals are on the left-hand side and the non-metals are on the left hand side.
Group 1 metals become more reactive as you move down.
Group 7 metals become less reactive as you move down
Elements in the same group have similar chemical properties because they have the same number of
outer electrons so they will react similarly
Noble gases are unreactive because they already have a full outer shell and to react they need to
share electrons to obtain a full outer shell
Chemical formulae, equations and calculation
Relative atomic mass (ar) = mass number
Relative Formula mass (mr)= h2So4 = 2(1) + 32 + 4(16) = 98
Mole = Avogadro’s number= 6.023x10^23
What mass of calcium oxide is obtained from 10g of calcium carbonate?
CaCO3 —> CaO + CO2
Mr=100 56
Mole ratio: 1:1
10/100=0.1
0.1* 56= 5.6
Number of moles = mass/ar or mr
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