12.1 Experimental design
- Syllabus
- 0620–2026–2027
- Topic
- 12.1
- Level
- —
Learning objectives
12.1.1Appropriate apparatus for the• Name appropriate apparatus for the measurement of time, temperature, mass and volume, (a) stop-watches (b) thermometers (c) balances (d) burettes (e) volumetric pipettes (f) measuring cylinders (g) gas syringes12.1.2Suggest advantages and disadvantages• Suggest advantages and disadvantages of experimental methods and apparatus12.1.3Solvent dissolves a solute• Define: solvent dissolves a solute; solute is dissolved; solution is solute(s) in solvent; saturated solution has maximum solute at a specified temperature; residue remains after separation; filtrate passes through a filter
Choose apparatus for each measurement
Choose apparatus by identifying the quantity to measure, then matching the required type and range of measurement.
| Quantity | Appropriate apparatus | What it measures |
|---|---|---|
| time | stop-watch / stop-clock | time interval |
| temperature | thermometer | temperature |
| mass | balance | mass |
| one fixed liquid volume | volumetric pipette | one stated volume |
| variable liquid volume delivered | burette | a chosen delivered volume |
| variable liquid volume | measuring cylinder | a range of liquid volumes |
| gas volume | gas syringe | volume of gas produced or used |
To measure the time for 2.0 g of magnesium to react with 50 cm³ of acid, use a stop-clock for time, a balance for mass and a measuring cylinder for the liquid volume.
Beakers and conical flasks are useful containers, but they are not the appropriate apparatus when the task requires a measured mass, time, temperature or volume.
Compare experimental methods and apparatus
An advantage or disadvantage must link a feature of the method or apparatus to its effect on the measurement or the experiment.
| Feature being compared | Possible advantage | Possible disadvantage |
|---|---|---|
| smaller scale divisions | allows a more precise reading | may take longer or require more careful reading |
| fixed-volume apparatus | delivers one volume consistently | cannot measure a different chosen volume |
| variable-volume apparatus | can measure a range of volumes | suitability depends on its scale and capacity |
| enclosed gas collection | reduces loss of gas to the surroundings | unsuitable if the gas volume exceeds the apparatus capacity |
| repeated measurements | reveal consistency and support a mean | require more time and materials |
For exactly 25.0 cm³, a volumetric pipette is advantageous because it delivers that fixed volume consistently; a measuring cylinder is more flexible but gives a less precise reading.
State the feature, name its consequence and relate that consequence to the aim. For example: 'The gas syringe is enclosed, so less product gas escapes and the measured volume is more reliable.'
Do not write 'more accurate' or 'better' without explaining which design feature causes the improvement and which measurement it affects.
Distinguish solution and separation terms
| Term | Meaning |
|---|---|
| solvent | substance that dissolves a solute |
| solute | substance dissolved in a solvent |
| solution | mixture of one or more solutes dissolved in a solvent |
| saturated solution | solution containing the maximum concentration of a solute in that solvent at a specified temperature |
| residue | substance that remains after evaporation, distillation, filtration or a similar separation process |
| filtrate | liquid or solution that has passed through a filter |
When rock salt is stirred with water, salt is the solute and water is the solvent. After filtration, insoluble sand is the residue and salt solution is the filtrate.
A solution is saturated only under stated conditions: at the specified temperature, no more of that solute can dissolve in that amount of solvent.
Residue is what remains after a separation process; filtrate specifically means the liquid that passes through a filter. A filtrate can still contain dissolved solute.