IGCSE Chemistry: Tips for Paper 6 (Alternative to Practical)

Apparatus: Names and Drawing

• Filtration for separating insoluble solute (e.g., sand) from solvent (e.g., water): Beaker, funnel, filter paper. Residue (sand) and filtrate (water).
• Crystallization: Heat proof mat, Bunsen burner, tripod, gauze, evaporating basin.
• Simple Distillation: Bunsen burner, gauze, round bottom flask, condenser.
• Measuring Liquids: Measuring cylinder (inaccurate), pipette, burette (accurate).

Titration

• Indicator choice critical: Methyl orange or phenolphthalein. Avoid universal indicator due to a wide range of colors.

Reactions

• Endothermic: Energy absorbed, surroundings feel colder.
• Exothermic: Energy released, surroundings get hotter.

Safety

• Alcohols are flammable; use a water bath for safe heating.
• Gases: Beware of dangerous gases like chlorine and hydrogen chloride gas.

Rates of Reaction

• Measured by the amount of reactants used or products formed over time.

Chromatography

• Steps: Crush sample, dissolve in solvent, set up chromatogram with reference line on pencil, use solvent like water or ethanol.

Calculating RF Values

• Distance traveled by substance divided by distance traveled by solvent.

Percentage Mass in a Substance

• Example: Determining zinc content in brass (alloy of zinc and copper).
• Use excess sulfuric acid to react with zinc, remove mass from brass, wash and dry remaining copper, find mass of copper, and calculate percentage mass of zinc.

Key Takeaways

• Be familiar with apparatus names and drawings, understand reaction types (endothermic vs. exothermic), prioritize safety, efficiently calculate rates of reactions and RF values, and accurately determine percentage mass in substances.