Chemistry IGCSE Notes for paper 62 :
Describing Apparatus:
•
•
•
•
•
•
Condenser- Used for liquifying vapour in distillation and returning unreacted vapour back to the
solution.
Glass beads- Used for cooling the gases in fractional distillation by absorbing heat from them.
Fractionating column- To separate the various liquids using their boiling point.
Safety Bulb- Found in pipettes to prevent liquid from entering mouth while sucking.
Fume cupboard- to avoid toxicity.
Gas syringe – To measure volume of gas.
General Precautions:
•
•
•
•
•
•
•
For Reliability: Repeat the experiment and take average ( in case any measurements)
For Safety: Use goggles
For accuracy: Take more readings, wider range, measure carefully, avoid parallax error.
For Graphs: when drawing the best fit line in a graph, do not include points that seem to be out of the
curve, use a sharp and make the curve smooth. Label the axis.
For titration experiments: Do not round off values or moles. It will bring about a greater error in the
later parts.
For describing presence of gases after reaction: Use the words effervescence and bubbling.
Describing observations: Use the words dissolves, vigorously reacts, Colour changes / fades, precipitate
forms, beaker heats up. Do not just give a theoretical answer.
Some Precautions:
➢ Experiments involving poisonous gases like nitrogen dioxide, ammonia or bromine: Carry out the
experiment in fume cupboard or in a well ventilated room.
➢ Experiments involving heat: Use polystyrene cup for insulation and maintain the same initial
temperature.
➢ Experiments involved acids, solids or liquids: Use same concentration, volume, mass or surface area
➢ Experiments involving crystallization: Allow to cool slowly and use more water and more salt for better
results.
➢ Measuring cylinder over burette: Burette accurate. Measuring cylinder is easy to measure.
Tests:
Water:
➢ By adding anhydrous copper (II) sulphate, which will turn from white to blue.
➢ By adding anhydrous cobalt (II) chloride, which will turn from blue to pink.
Chlorine:
➢ Bleaches the damp litmus paper
➢ Damp blue litmus paper turns red and then bleaches it to white.
Oxygen:
➢ Relights the glowing splint.
Hydrogen:
➢ Ignites with a ‘pop sound’.
➢ Colourless and neutral with litmus paper.
Carbon dioxide:
➢ Turns lime water milky.
Ammonia:
➢ Turns damp red litmus paper blue.
For purity of substance:
➢ Solids – Test for melting point, if it is the correct value, it is pure. Eg. Ice at 0 degrees Celsius
➢ Liquids – Test for boiling point, Eg. Water at 100 degrees Celsius
Indicators:
➢
➢
➢
➢
Universal indicator
Phenolphthalein
Methyl Orange
Bromothymol Blue
: Acid (red- yellow), Neutral ( Green), Alkaline (Blue- violet)
: Acid (orange) , Alkaline (Pink for strong), Neutral ( Colourless)
: Acid ( Yellow), Neutral ( Colourless), Acid (Red)
: Acid (Yellow), Neutral (Dark green), Alkaline (Blue)
Common Reagents:
➢
➢
➢
➢
Concentrated sulphuric acid- Drying agent- used for drying gases except ammonia.
Anhydrous calcium chloride- Drying agent for all gases except ammonia.
Calcium oxide - Drying agent for ammonia and neutral gases.
Ninhydrin
- Locating agent for chromatography.
Collection techniques:
➢ Upward delivery – Gases less dense than air (Hydrogen and ammonia).
➢ Downward delivery—Gases denser than air (Carbon dioxide).
➢ Displacement of water method – Insoluble gases (Methane).
Compounds and colours:
➢ Group 1, 2 metals are white/silvery white. Group 3 metals are shiny grey. Their compounds are white
and their solutions are colourless.
➢ Zinc is a grey solid, its compounds are white.
➢ Lead is a shiny bluish metal.
➢ Iron is a shiny blackish solid.
➢ Iron (II) salts are green. Iron (III) salts are red-brown.
➢ Chlorine is a green gas. Silver chloride and Lead chloride are white.
➢ Bromine is a red-brown gas. Silver bromide and Lead bromide are cream coloured.
➢ Iodide is a black solid. Its vapours are purple. Silver iodide and lead iodide are yellow.
➢ Copper is a pinkish solid. Copper (II) sulphate, Copper (II) hydroxide and Copper (II) nitrate are blue.
➢ Copper (II) chloride and Copper (II) carbonate are green.
➢ Copper(II) oxide black.
➢ Nitrogen dioxide is a brown gas. Sulphur and Phosphorous are Yellow solids with different flames.
Flame Tests:
➢
➢
➢
➢
➢
Lithium
Sodium
Potassium
Iron
Magnesium
– Red
- Yellow
– Lilac
– Gold
-- Bright white ( may damage eyes, should not see directly without sun glasses).
Impurities or contaminants affect the test results. This test cannot differentiate elements or
compounds. Brightness may vary.
Important equations:
➢
➢
➢
➢
➢
➢
➢
Group 1 Elements (Metals) + H2O ---> Metal OH + Hydrogen Gas
Acid + Metal ---> Salt + Hydrogen Gas (Copper, Silver, Gold DO NOT REACT)
Acid + Bases ---> Salt + Water
Acid + Carbonate ---> Salt + Water + Carbon Dioxide
Alkalis (Metal Hydroxide) + Ammonia Salts ---> Ammonia gas + Water + Salt
Acidic Oxide + Water ---> Acid
Neutral Oxide + Air ---> Acid
➢ Basic Oxide + Acid ---> Salt + Water.
****Four tables: Solubility of Salts, Tests for Anions, Tests for Cations and Test for Gases
should be at your fingertips.
Organic Chemistry:
Important equations:
➢
➢
➢
➢
Alkene + Steam ---> Alcohol
Glucose + Yeast ---> Ethanol + CO2
Acid + Alcohol ---> Ester + Water
Alcohol (when oxidized) ---> Organic Acids + Water
Reagents:
➢
➢
➢
➢
Acidified Potassium Manganate (VII) - Oxidizing agent, colour change Purple to Colourless.
Acidified Potassium Dichromate (VI) - Oxidizing agent, colour change Orange to Green.
Aqueous Potassium Iodide - Reducing agent, colour change from colourless to Brown.
Sulphur Dioxide - Reducing agent, no colour change.
Tests:
➢ For unsaturated hydrocarbon ( Alkenes )
>Liquid : By adding Bromine water to it and shaking. (it'l go from Brown to colourless)
>Gas : By passing the compound through Bromine water. (Colour change = Brown to colourless)
➢ It will remain orange for alkanes (ethane)
Fermentation:
=> Glucose and Yeast are used! (just rememeber that Yeast contains enzymes -> Biological Catalysts)
=> Suitable Temperature 37 degrees (Optimum for Enzyme)
=> Bung is used -> To Let Carbon Dioxide out, and prevent the entry of Oxygen.
=> Why is Oxygen's entry prevented (-> because it'l oxidize the alcohol to Carboxylic Acid and also it'l affect
the anaerobic respiration)
=> Why does the reaction stop? -> Due to an excess in the conc. of alcohol, Yeast dies. Or Glucose finishes up!