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Stopwatch
Measures time, commonly in seconds. Human reaction time affects very short intervals.
Learning goals
Select suitable apparatus for measuring time, temperature, mass and volume.
Compare the precision, range and practical limitations of apparatus.
Use the terms solvent, solute, solution, saturated solution, residue and filtrate correctly.
Describe an acid–base titration and identify its end-point using an indicator.
Choose the right apparatus
Good experimental design begins with the quantity being measured and the precision needed. A smaller scale division normally gives a more precise reading.
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Thermometer
Measures temperature. Read at eye level after the reading stabilises.
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Balance
Measures mass. Zero or tare the balance before adding the sample.
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Burette
Delivers accurately measured variable volumes, usually to the nearest 0.05 cm³.
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Volumetric pipette
Transfers one fixed volume very accurately using a pipette filler.
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Measuring cylinder
Measures a range of liquid volumes, but less precisely than a pipette or burette.
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Gas syringe
Collects and measures gas volume directly with little loss of gas.
Exam insight: “More accurate” is not a complete explanation. Refer to smaller scale divisions, lower uncertainty, a fixed calibrated volume or reduced loss of material.
Advantages and limitations
Repeat readings
Improve reliability and help identify anomalies, but require more time and materials.
Improve reliability and help identify anomalies, but require more time and materials.
Electronic sensors
Collect frequent readings and reduce reaction-time error, but need calibration and power.
Collect frequent readings and reduce reaction-time error, but need calibration and power.
Large sample size
Can reduce percentage uncertainty, but may increase cost, waste and safety risks.
Can reduce percentage uncertainty, but may increase cost, waste and safety risks.
Gas syringe
Direct quantitative measurement, but the plunger may stick and connections may leak.
Direct quantitative measurement, but the plunger may stick and connections may leak.
Speak the language of practical chemistry
Solvent
The substance that dissolves a solute.
The substance that dissolves a solute.
Solute
The substance dissolved in a solvent.
The substance dissolved in a solvent.
Solution
A mixture of one or more solutes dissolved in a solvent.
A mixture of one or more solutes dissolved in a solvent.
Saturated solution
Contains the maximum concentration of a solute at a specified temperature.
Contains the maximum concentration of a solute at a specified temperature.
Residue
The solid remaining after evaporation, distillation, filtration or a similar process.
The solid remaining after evaporation, distillation, filtration or a similar process.
Filtrate
The liquid or solution that has passed through a filter.
The liquid or solution that has passed through a filter.
Example: When sand is filtered from salt solution, sand is the residue and salt solution is the filtrate.
Video lesson
A precise titration, step by step
Prepare the pipette
Rinse with the solution it will contain. Use a pipette filler to transfer a fixed volume into a conical flask.
Add indicator
Add two or three drops of a suitable indicator. Too much indicator may affect the result.
Prepare the burette
Rinse with the titrant, fill it, remove the funnel, clear air bubbles from the jet and record the initial reading at eye level.
Perform a rough titration
Add titrant while swirling until the indicator changes colour permanently. Use this result to locate the approximate end-point.
Repeat accurately
Approach the end-point dropwise over a white tile. Repeat until concordant titres (typically within 0.20 cm³) are obtained.
Process the readings
Titre = final burette reading − initial burette reading. Average only concordant titres; exclude the rough result and anomalies.
End-point simulator
Move the slider to add titrant. A persistent colour change appears near the end-point.
acid + indicator
Stage: well before the end-point.
Quick check
Student details & 30-mark assessment
Answer all 15 questions in full sentences. Each question is worth 2 marks. Your work is saved automatically on this device.