Making a Soluble Salt
Prepare a pure, dry sample of a soluble salt (e.g. Copper sulfate) from an insoluble oxide or carbonate and an acid.
- Add excess insoluble base to warm acid
- Filter to remove excess solid
- Evaporate and crystallise the filtrate
- Pat dry with filter paper
Electrolysis
Investigate what happens when aqueous solutions are electrolysed using inert (carbon/graphite) electrodes.
- Set up circuit with DC power supply & inert electrodes
- Identify gases at each electrode (test with splints/litmus)
- Write half-equations for anode & cathode
- Link to reactivity series for product prediction
Temperature Changes
Investigate the variables that affect temperature changes in reacting solutions, e.g. Acid + metal or neutralisation.
- Use a polystyrene cup as insulation
- Record initial temperature of both solutions
- Mix & record maximum/minimum temperature
- Identify exothermic (temp rises) or endothermic (temp falls)
Rates of Reaction
Investigate how changes in concentration affect the rate of reaction using the disappearing cross or gas syringe methods.
- Disappearing cross: time for sulfur to obscure cross
- Gas syringe: measure volume of gas produced over time
- Control variables: temperature, volume, mass
- Plot volume vs time graph. Steeper = faster rate
Chromatography
Use paper chromatography to investigate and identify the artificial colours in food colourings or inks.
- Draw baseline in pencil (not pen. Ink dissolves)
- Solvent level must be below the baseline
- Calculate Rf = distance by substance ÷ distance by solvent
- Compare Rf values to identify unknown substances
Identifying Ions
Use flame tests, NaOH precipitates, and chemical tests to identify the ions in unknown single ionic compounds.
- Flame tests: Li (red), Na (yellow), K (lilac), Ca (crimson), Ba (green)
- NaOH precipitates: Cu²⁺ (blue), Fe²⁺ (green), Fe³⁺ (brown)
- Halides: add dilute nitric acid then silver nitrate
- Carbonates: add acid → test gas with limewater
Titration
Determine the reacting volumes of solutions of a strong acid and a strong alkali by titration.
- Pipette: measures exact volume of alkali (25.0 cm³)
- Burette: delivers the acid gradually
- Add indicator (methyl orange/phenolphthalein)
- Repeat for concordant results (within 0.10 cm³)
Water Analysis & Purification
Analysis and purification of water samples from different sources, including pH testing, dissolved solids, and distillation.
- Test pH with universal indicator or pH meter
- Evaporate sample to check for dissolved solids
- Purify by distillation (boil → condense → collect)
- Potable ≠ pure: potable is safe but contains dissolved salts