Master your practical assessments with essential skills and techniques
Practical exams test your ability to carry out experiments, make accurate measurements, record data properly, analyze results, and evaluate methods. They assess hands-on scientific skills, not just theoretical knowledge.
Important: Practical exams typically count for 20-30% of your final grade, so performing well is crucial.
What it involves: You perform actual experiments in a laboratory with real equipment and materials.
Duration: Usually 1 hour 15 minutes
Skills tested:
What it involves: Written questions about practical work - no actual experiments performed.
Duration: Usually 1 hour
Skills tested:
What it involves: Questions based on practical scenarios - for students who can't access laboratory facilities.
Duration: Usually 1 hour
Skills tested: Same as Paper 3, but assessed through written responses about demonstrations or videos.
Note: You only take ONE practical paper - typically Paper 3 OR Paper 6, plus Paper 5 for some qualifications.
| Temperature / °C | Time / s | Distance / cm |
|---|---|---|
| 20 | 15.3 | 4.5 |
| 30 | 10.7 | 6.8 |
Key features:
Common Mistake: Writing units with every measurement in the table. Put units in the heading only.
Take at least 3 readings for each measurement to improve reliability
Calculate the mean (average) of your repeat readings
Identify anomalies - results that don't fit the pattern
Exclude anomalies from your mean calculation and explain why
The variable YOU change - what you're testing
Example: Temperature in an enzyme experiment
The variable you MEASURE - the result
Example: Rate of reaction
Variables you KEEP THE SAME for a fair test
Example: Volume of solution, concentration, pH
| Instrument | Used For | Typical Precision | Key Tips |
|---|---|---|---|
| Ruler | Length | ± 1 mm | Measure from 0 or subtract start position |
| Measuring Cylinder | Volume (liquids) | ± 0.5 cm³ | Read at eye level from bottom of meniscus |
| Thermometer | Temperature | ± 0.5°C | Wait for reading to stabilize |
| Stopwatch | Time | ± 0.1 s | Human reaction time adds uncertainty |
| Balance | Mass | ± 0.01 g | Zero before measuring, shield from drafts |
| Burette | Volume (titration) | ± 0.05 cm³ | Read from bottom of meniscus twice |
Most liquids (like water) form a curved surface called a meniscus. Always read from the bottom of the curve at eye level.
Correct reading: Eye level with bottom of meniscus
Incorrect reading: Looking from above or below (parallax error)
Pro Tip: When recording measurements, use the same number of decimal places throughout. If your ruler measures to 0.1 cm, record all lengths to 1 decimal place (e.g., 5.0 cm not 5 cm).
Use a ruler to draw all lines in pencil
Independent variable goes in the first column (left)
Dependent variable goes in subsequent columns
Column headings must include quantity and unit separated by / (e.g., "Time / s")
Same precision for all measurements in a column
For straight lines: Use a ruler and draw so equal numbers of points are above and below the line
For curves: Draw a smooth curve that follows the pattern - don't connect dot-to-dot
Anomalies: Circle any anomalous points and don't include them in your line
gradient = rise / run = change in y / change in x
Common Mistakes: Using awkward scales (like 1 square = 3 units), plotting points too small, forcing line through origin when data doesn't support it, connecting points dot-to-dot instead of drawing best fit line.
Following safety procedures protects you and others. Marks can be awarded for mentioning appropriate safety precautions in planning questions.
Wear when heating, using chemicals, or any risk to eyes
Use with corrosive chemicals or biological materials
Protects clothing and skin from spills
Know location of extinguisher and fire blanket
| Hazard | Precautions |
|---|---|
| Heat Sources | • Use heat-proof mat • Don't touch hot equipment • Point test tubes away from people when heating • Use tongs or holders |
| Acids/Alkalis | • Wear goggles • Use small volumes • Add acid to water, never water to acid • Wash spills immediately |
| Flames | • Tie back long hair • Keep flammable materials away • Don't leave unattended • Use correct gas:air ratio |
| Sharp Objects | • Cut away from body • Use cutting mat • Dispose in sharps container • Report breakages |
| Electrical Equipment | • Keep away from water • Check for damage first • Don't overload sockets • Turn off when not in use |
| Biological Materials | • Wash hands thoroughly • Dispose in specified waste • Don't eat or drink in lab • Cover cuts with waterproof plaster |
In Planning Questions: Always mention relevant safety precautions. Examples: "Wear goggles when using acids", "Use water bath instead of direct flame to avoid fire risk", "Keep volumes small to reduce exposure to harmful fumes".
Vernier Calipers: Can measure to 0.01 cm - read main scale first, then vernier scale
Micrometer: Measures to 0.01 mm - very precise for small objects
Ammeters: Connect in series to measure current
Voltmeters: Connect in parallel to measure voltage
Digital vs Analogue: Digital more precise, but analogue better for changing values
Physics Tip: Always repeat measurements of length at different positions along an object to account for irregularities. Take at least 3 readings and calculate mean.
Titration Technique:
Chemistry Safety: Never taste chemicals. Always add acid to water. Work in fume cupboard with toxic gases. Dispose of chemicals as instructed.
Biology Tip: When investigating enzyme activity, take measurements frequently at the start (when reaction is fastest) then less often as it slows. This gives you better data for analysis.
Systematic Errors: Errors that affect all measurements in the same way
Random Errors: Errors that vary unpredictably between measurements
| Problem | Solution | Why It Helps |
|---|---|---|
| Results vary too much | Repeat measurements and calculate mean | Reduces effect of random errors |
| Difficult to time precisely | Time over longer period or multiple cycles | Percentage error becomes smaller |
| Small change to measure | Scale up the experiment | Larger changes are easier to measure accurately |
| Reading between scale marks | Use more precise instrument or estimate carefully | Reduces measurement uncertainty |
| Heat loss affecting results | Use insulation or work more quickly | Reduces systematic error |
| Parallax error | Always read at eye level | Ensures accurate scale reading |
An anomaly is a result that doesn't fit the pattern of other results.
Review apparatus: Make sure you know how to use common equipment
Practice tables and graphs: Being quick at these saves time
Memorize key procedures: Like titration technique or microscope setup
Arrive early: You need time to read instructions calmly
Read all instructions before starting. Underline key words
Don't spend too long perfecting one measurement
Draw your results table before taking measurements
Record results immediately - don't rely on memory
Have you answered every part? Units included?
Write out calculations clearly for method marks
Golden Rule: Aim for "good enough" rather than perfect. Better to complete all tasks to a good standard than perfect one section and rush the rest.
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