Chemistry IGCSE

An atom is a collection of particles that makes a small-scale structure.

A molecule is a group of atoms joined by the forces of attraction.

Diffusion is the mixing of two substances.

• They are: 
• Elements - composed of only one type of atom
• Compounds - molecule with more than one type of atom
• Mixtures - collections of diff. molecules or atoms that are not bonded

• Filtration - separation of a liquid and a solid
• Simple distillation - separation of two liquids
• Fractional distillation - separation of three or more liquids
• Paper chromatography - separation of substances with diff. colours
• Crystallisation - separating a liquid from a solid (dilute)

• 1 heat source
• 2 Still pot
• 3 still head
• 4 thermometer 
• 5 condenser
• 6 cooling water in
• 7 cooling water out
• 8 distillate flask
• 9 vacuum/ gas inlet
• 10 still receiver
• 11 heat control
• 12 stirrer speed control
• 13 stirrer heat plate
• 14 heating (oil/sand) bath
• 15 mixture in flask
• 16 cooling bath

Through the interaction with other atoms, an ion is a non-neutrally charged atom.

• Reduction is the gain of electrons
• Oxidation is the loss of electrons

• usually a bond between a metal and a non-metal/polyatomic ion. 
• The metal donates one electron to the non-metal.

Quite strong because they are oppositely charged.

Nearly all have very high melting and boiling points

Most are soluble in water

Do not conduct electricity in the solid state but do in molten and aqueous states.

• A covalent bond is the sharing of electron pairs between atoms. 
• It normally occurs between non-metals.

Typically they are weak due to the fact that they only have a few atoms in their molecular structure.

• Tend to be gasses, liquids or soft solids. 
• Poor conductors of heat and electricity.
• Non-electrolytes.
• Molecules.

Because they aren't tightly bonded and can become delocalised by jumping from one atom to the next.

Due to its structure, electrons are attracted to the negative potential and can conduct electricity.

Metals are malleable (beaten into sheets) and ductile (pulled out into wires) because they can change form without breaking their metallic bonds.

It is the flow of electrons or ions.

Because in this case not only the nuclei of the atoms are bonded but also the electrons, stopping them from moving freely, thus conducting electricity.

In the solid state they are unable to move, whereas if they are in the liquid or aqueous states, they are free to move within that liquid.

• 1. Conductivity probe:
• The probe is lowered into the liquid and if a current is detected ...
• 2. Electrolysis: 
• 
• 3. Electrolysis of molten salts:
• 

In the periodic table of elements, there a seven vertical columns of elements aka 7 groups. The periods are horizontal.

Because they have the same number of covalent electrons.

Noble gasses are unreactive because they have a full covalent shell and so do not react with other atoms.

• B - Bi 
• At is non-metal + H.

• Alkali Metals
• Alkaline Earth Metals
• Transition Metals 
• Post Transition Metals 
• Non-metals with some metallic properties
• Other Non-Metals
• Halogens
• Noble Gasses

• By considering its conductivity and Acid/Base oxides. 
• Metals produce oxides that are bases in nature (high pH)
• Non-metals produce acidic (low pH)

• Lithium - the metal floats and fizzes
• Sodium - the metal floats and becomes sphere of molten metal
• Potassium - bursts into flames

• Fluorine yellow gas
• Chlorine green gas
• Bromine brown liquid
• Iodine purple solid

Going upwards

Going down.

By dissolving it in water. It also becomes HCL acid and is no longer a covalent compound.

• Nitrogen - 78.08 %
• Oxygen - 20.9 %
• Argon - 0.9 %
• Carbon dioxide - 0.04 %
• Neon - 0.002 %
• ...
• ...

• Burning phosphorus: P4 + 5O2 ==> P4O10
• Place a bell jar with a plate of phosphorus in a tank of water. 
• Light the phosphorus and the bell jar is sealed. 
• The water level rises by the amount of oxygen that is burned up.

Iron - Using damp iron wool in a tube in a tank and wait a week. The water level also rises because the iron rusting.

• Copper - Using two glass syringes and a silica filled with copper.
• The copper is heated and so combines with oxygen forcing the glass syringes to move.

• Hydrogen peroxide solution is dripped onto manganese (IV) oxide (catalyst).
• The H2O2 breaks up and oxygen builds up and passes through a tube into an inverted jar submerged in water.

• 2Mg(s) + O2(g) ==> 2MgO(s) 
• White coloured compound 

• C(s) + O2(g) ==> CO2(g)
• Carbon dioxide

• S(s) + O2(g) ==> SO2(g) 
• Sulphur dioxide

• Some metal oxides create small amounts of hydrogen ions (alkaline in nature)
• Non-metal oxides some create an acidic solution.

• Dilute HCL is dripped onto marble chips and the gas produced is collected in a glass jar.
• 

• When most metal carbonates are heated strongly they decompose and give off CO2. 
• 

• It dissolves in water easily 
• It is heavier than air

• By using CO2, we can change the pH of water. 
• CO2 + H2O ==> H2CO3
• H2CO3 + H2O ==> HCO3(-) + H30(+)

Hydrogen is a very flammable gas, which when burns combine with the oxygen in the air and forms water.

Even a small amount will burn with a loud pop in a test tube.

Using anhydrous copper sulphate powder, it'll turn blue from white. 

using cobalt chloride paper, it'll turn white from blue.

The sample's boiling and freezing points are tested and if they are at exactly 100 degrees C and 0 degrees C the sample is pure water.

• Potassium
• Sodium
• Lithium 
• Calcium
• Magnesium
• Aluminium
• Zinc
• Iron 
• Tin
• Lead
• Copper
• Mercury
• Silver
• Gold

Each reaction between these is somehow unique; the amount of bubbles that flow at a time is different. So you can tell which reacts stronger, placing it higher in the reactivity series.

• Magnesium - rapid flow of bubbles
• Aluminium - slower flow
• Zinc - slow
• Iron - very slow

You add a metal in powered form to a metal in a solution and if the powered metal is more reactive (i.e. higher in the reactivity series) it will replace the first metal.

Fe + H2O + O2 ==> Fe2O3

• Oxidation : Fe(s) ==> Fe2(+)(AQ) + 2e-
• Reduction: O2 + 4e- + 4H(+) ==> 2H2O

Reductant (oxidant)

Oxygen and water.

Barrier protection : this is when the metal is completely covered in a layer of a substance which stop the metal from coming into contact with water and oxygen. 

Sacrificial protection: This is when the metal is coupled to a more reactive metal, which will rust instead of the first metal.

• Anions are ions with a negative charge. 
• Cations are ions with a positive charge.

• Calcium - Red
• Lithium - Pink
• Potassium - Lilac
• Sodium - Orange

• NH4(+) is tested for by adding sodium hydroxide and heating gently. It gives off a very distinct smell. 
• It also reacts with damp litmus paper, turning it blue (showing it is an alkali metal).

• Ammonium ion - smell
• CU(2+) - pale blue that dissolves
• Fe(2+) - pale green precipitate
• Fe(3+) - red/brown precipitate

• If halogens are precent, a precipitate will form. 
• Br(-) - pale yellow precipitate that dissolves in ammonia solution

Cl(-) - thick white precipitate dissolves in ammonia solution

I(-) - pale yellow precipitate that does not dissolve in ammonia solution.

• SO4(2-) can be tested for by adding the substance to a solution of barium chloride.
• A white precipitate forms which does not dissolve in dilute hydrochloric acid.

CO3(2-) can be tested by adding the substance to dilute hydrochloric acid, carbon dioxide gas should be given off.

Bubble the gas through lime water (calcium hydroxide solution). It turns cloudy.

Put a lit splint into a sample of the gas and if it burn with a loud "pop" sound, it is hydrogen.

If you put a glowing splint into a sample of the gas and it re-lights, it is oxygen.

Expose to damp litmus paper and it'll turn blue.

Expose to damp litmus paper and it is bleached white.

CnH2n+2

• there are two possible outcomes:
• Complete and incomplete combustion. 
• When it combusts completely the alkane reacts with oxygen in the air. 
• 
• when an incomplete combustion take place the following products are created: 

• carbon (soot) (indicator)
• water
• CO

• A substitution reaction takes place resulting in hydrogen bromide and bromomethane.
• The brown (bromide) disappears. 
• 

C_nH_2N

• (Bromine solution or water)
• An addition reaction takes place. The double bond is broken and two bromine atoms are added to the molecule. 
• 
• Detect carbon double bond.
• 

• 0 - 14 
• (Strongly acidic - Neutral - Strongly Alkaline)
• Concentration of H+ ions.

• The colour the litmus paper changes to depends on the acidity of the solution. 
• 

• phenolphthalein is colourless below pH 8.0 and become deep red as of pH 10.0
• 

• It changes colour AND shows how acidic or basic a solution is. 
• 

• Acids are made of hydrogen H+ ions
• Alkalis are made of hydroxide OH- ions

This method does not work for sodium, potassium and ammonium.

With titration. You add and alkali (base) to an acid. The acid already has an indicator added to it.

• 
• Heat is taken in.         Heat is given out.

• 
• We measure the mass of the burning sample and the water. During the combustion, we measure the rise in temperature.

• In exothermic reactions bonds are made or strengthened (EMITS)
• In endothermic reactions bonds are broken (ABSORBS)

Catalysts are substances which when added to a reaction, allow the reactants to come together more easily.

Surface area, temperature, concentration and pressure.

It is the minimum energy required to start a chemical reaction.