Every required practical activity for AQA GCSE Biology (8461), Chemistry (8462) and Physics (8463), written as revision notes: the aim, a method you can actually remember, the variables, what the results show, the calculations and the evaluation points that earn marks.
Practical questions reward understanding the science of the investigation, not memorising instructions. Work out why each variable is controlled and what the data means, then test yourself rather than re-reading.
AQA GCSE Biology lists ten required practical activities. Seven are shared with GCSE Combined Science, and practicals 2, 8 and 10 are on the separate Biology specification only. Written papers can ask about the methods, the variables, the data and how you would improve the investigation, so revise the thinking behind each practical rather than the instructions alone.
Using a light microscope to observe, draw and label plant and animal cells, including a magnification scale on the drawing.
Aim
Observe cell structures that are too small to see unaided and record them as accurate, scaled biological drawings.
Method
Prepare a slide: place the specimen on the slide, add a drop of stain such as iodine, then lower a coverslip at an angle to avoid air bubbles.
Clip the slide onto the stage and select the lowest power objective lens.
Use the coarse focus to bring the stage and objective close, then focus by moving them apart while looking through the eyepiece.
Sharpen the image with the fine focus, then switch to a higher power objective and refocus with the fine focus only.
Draw what you actually see with a sharp pencil, using clear unbroken lines, no shading, and label lines that do not cross.
Record the total magnification and add a magnification scale to the drawing.
Variables
Dependent
The structures observed and their measured or estimated size
Control
Same specimen preparation and stain
Same lighting
Refocus with the fine focus only at high power
Equipment
Light microscope, Slides and coverslips, Iodine or methylene blue stain, Mounted needle, Pencil and ruler.
Results and observations
Plant cells show a cell wall, large permanent vacuole and often chloroplasts; animal cells show a membrane, cytoplasm and nucleus but no wall or chloroplasts.
Calculations
Total magnification = eyepiece magnification × objective magnification
Magnification = size of image ÷ size of real object (rearrange to find real size)
Convert carefully: 1 mm = 1000 µm
Graphs and data
No graph is needed, but you must be able to use a scale bar and convert between millimetres and micrometres.
Evaluation
Air bubbles under the coverslip can be mistaken for cells, so lower the coverslip slowly at an angle.
Too much stain darkens the field and hides detail.
Estimating size from a drawing is less reliable than using a stage micrometer or an eyepiece graticule.
Common mistakes
Focusing downwards at high power and cracking the slide.
Drawing what a textbook shows rather than what is on the slide.
Forgetting units or the magnification scale on the drawing.
Quick self-test
An image is 50 mm across and the magnification is ×100. What is the real width in micrometres?+
50 mm ÷ 100 = 0.5 mm, which is 500 µm.
Why is a stain used when preparing a slide?+
It increases contrast so that structures such as the nucleus become visible against the cytoplasm.
Give two structures visible in a plant cell but not in an animal cell.+
Cell wall and chloroplasts (a large permanent vacuole is also acceptable).
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Required practical 2 · separate biology only
Microbiology: antiseptics and antibiotics
Investigating the effect of antiseptics or antibiotics on bacterial growth using agar plates and measuring zones of inhibition.
Aim
Compare how effectively different antimicrobial substances (or different concentrations) inhibit bacterial growth.
Method
Work using aseptic technique: sterilise equipment, flame the neck of the culture bottle and lift the lid of the Petri dish at an angle only.
Spread a uniform lawn of bacteria over sterile nutrient agar with a sterile spreader.
Soak filter paper discs in each antiseptic or antibiotic, plus one in sterile water as a control, and blot off the excess.
Place the discs evenly spaced on the agar and secure the lid with tape (do not seal it completely).
Incubate inverted at no more than 25 °C in a school laboratory for around 48 hours.
Measure the diameter of each clear zone of inhibition and calculate its area.
Variables
Independent
The antiseptic or antibiotic used, or its concentration
Dependent
The size of the zone of inhibition (diameter, then area)
Control
Same bacterial species and lawn density
Same incubation temperature and time
Same disc size and volume of solution
Same agar type and depth
Equipment
Sterile agar plates, Bacterial culture and sterile spreader, Sterile filter paper discs, Forceps, Ruler, Incubator.
Results and observations
A clear zone around a disc shows bacteria have been killed or prevented from growing; a larger zone indicates a more effective substance.
Calculations
Area of a zone of inhibition = πr², where r is half the measured diameter
Calculate a mean area from repeats for each substance
Graphs and data
Plot mean zone area as a bar chart for different substances, or as a line graph against concentration.
Evaluation
The sterile water control shows any zone is caused by the substance and not the disc itself.
Measure the diameter in two directions and take a mean because zones are rarely perfect circles.
Repeats and a consistent lawn density improve reliability; contamination is the main source of anomalies.
Incubating at 25 °C reduces the risk of growing pathogens that thrive at human body temperature.
Common mistakes
Comparing diameters when the question asks for area.
Leaving the Petri dish lid fully open, allowing airborne contamination.
Forgetting to state a control disc soaked in sterile water.
Quick self-test
Why is a disc soaked in sterile water used?+
It is a control: it shows that any clear zone is caused by the antiseptic or antibiotic and not by the paper disc itself.
A zone of inhibition has a diameter of 18 mm. Calculate its area.+
r = 9 mm, so area = pi x 9^2 = 254 mm^2 (3 s.f.).
Give one reason plates are incubated at 25 degrees C in school.+
Lower temperatures reduce the risk of growing microorganisms that are pathogenic to humans.
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Required practical 3
Osmosis
Investigating the effect of a range of concentrations of salt or sugar solutions on the mass of plant tissue.
Aim
Find how the concentration of a surrounding solution affects net water movement into or out of plant cells.
Method
Cut cylinders of potato with a cork borer and trim them to the same length.
Blot each cylinder dry and record its initial mass.
Place one cylinder in each of a range of sugar concentrations (for example 0.0 to 1.0 mol/dm³), fully submerged.
Leave for a set time, for example 30 minutes or overnight.
Remove, blot gently to remove surface liquid and record the final mass.
Repeat at each concentration and calculate percentage change in mass.
Variables
Independent
Concentration of the sugar or salt solution
Dependent
Percentage change in mass of the plant tissue
Control
Same tissue type, length and surface area
Same volume of solution
Same time in solution
Same temperature
Same blotting method
Equipment
Potato and cork borer, Scalpel and tile, Balance, Boiling tubes or beakers, Sugar solutions of known concentration, Paper towels.
Results and observations
Cylinders gain mass in dilute solutions (water enters by osmosis), lose mass in concentrated solutions, and show no net change where the solution concentration matches the cell contents.
Calculations
Percentage change in mass = (final mass − initial mass) ÷ initial mass × 100
Read the concentration where the line crosses 0% change to estimate the internal concentration of the tissue
Graphs and data
Plot percentage change in mass (y) against concentration (x) and draw a line of best fit; the x-intercept is the isotonic point.
Evaluation
Percentage change is used rather than raw change so cylinders of slightly different starting mass can be compared fairly.
Inconsistent blotting is the biggest source of error, as surface water adds mass.
Repeats at each concentration allow a mean and make anomalies visible.
Common mistakes
Reporting change in mass instead of percentage change.
Saying sugar molecules move into the cell rather than water moving out.
Leaving cylinders in solution for different lengths of time.
Quick self-test
Why is percentage change in mass used rather than change in mass?+
The cylinders do not all start with exactly the same mass, so percentage change allows a fair comparison between them.
A cylinder shows no change in mass. What does this tell you?+
The concentration of the solution is the same as the concentration inside the cells, so there is no net movement of water.
Suggest one improvement to reduce error in this practical.+
Blot every cylinder for the same time in the same way, since surface water added or left behind changes the recorded mass.
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Required practical 4
Food tests
Using qualitative reagents to test for carbohydrates, lipids and proteins: Benedict's test for sugars, iodine for starch and Biuret reagent for protein.
Aim
Identify the biological molecules present in a food sample using colour-change reagents.
Method
Grind the food sample and mix with distilled water to make a solution, then filter it.
Starch: add a few drops of iodine solution to a sample.
Sugars: add Benedict's solution to a sample and heat in a water bath at about 75 °C for a few minutes.
Protein: add Biuret reagent to a sample and mix.
Lipids: mix the sample with ethanol, then pour into water (the emulsion test).
Record the colour of each test alongside a negative control of distilled water.
Variables
Independent
The food sample tested
Dependent
The colour observed in each test
Control
Same volume of sample and reagent
Same water bath temperature and heating time
Distilled water negative control
Equipment
Pestle and mortar, Test tubes and rack, Water bath, Iodine solution, Benedict's solution, Biuret reagent, Ethanol.
Results and observations
Starch: orange-brown to blue-black. Reducing sugars: blue to green, yellow, orange or brick red depending on amount. Protein: blue to purple. Lipids: clear to a milky white emulsion.
Calculations
No calculation is required, though Benedict's colour can be used to rank samples semi-quantitatively.
Graphs and data
Record results in a table of food sample against test result rather than a graph.
Evaluation
The tests are qualitative, so they show presence rather than exact amount.
Benedict's does not detect non-reducing sugars such as sucrose without further treatment.
A negative control confirms the colour change comes from the food, not the reagent.
Common mistakes
Describing the Benedict's result as simply 'red' without stating the starting blue colour.
Not heating the Benedict's test, which gives a false negative.
Confusing the iodine and Biuret colour changes.
Quick self-test
A student adds Benedict's solution and sees no change. Suggest two possible reasons.+
There is no reducing sugar present, or the mixture was not heated in a hot water bath so the reaction did not occur.
State the colour change for a positive protein test.+
Biuret reagent changes from blue to purple.
Why are these tests described as qualitative?+
They show whether a substance is present but do not measure how much of it there is.
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Required practical 5
Effect of pH on amylase
Investigating the effect of pH on the rate of reaction of amylase using continuous sampling, testing for starch with iodine every 30 seconds.
Aim
Find how pH affects how quickly amylase breaks down starch.
Method
Place drops of iodine solution in the wells of a spotting tile.
Mix starch solution and a buffer of known pH in a test tube and place in a water bath at a fixed temperature.
Add amylase, mix and start the stopwatch.
Every 30 seconds transfer a drop of the mixture to a fresh well of iodine.
Record the time when the iodine first stays orange-brown, showing all the starch has been digested.
Repeat with buffers at different pH values.
Variables
Independent
pH of the buffer solution
Dependent
Time taken for the starch to be fully digested
Control
Temperature (water bath)
Concentration and volume of amylase and starch
Sampling interval of 30 seconds
Same iodine concentration
Equipment
Amylase and starch solutions, pH buffers, Spotting tile and iodine, Water bath, Stopwatch, Pipettes.
Results and observations
Digestion is fastest at the optimum pH (shortest time). Times get longer either side, and at extreme pH the starch may never be fully digested because the enzyme is denatured.
Calculations
Rate of reaction = 1 ÷ time taken (units s⁻¹)
Calculate a mean time from repeats before finding the rate
Graphs and data
Plot rate (1/time) against pH; the peak of the curve identifies the optimum pH.
Evaluation
Sampling every 30 seconds means the true end point lies somewhere in that interval, which limits resolution.
Judging the colour change is subjective, so a colorimeter would be more objective.
A water bath keeps temperature constant, otherwise temperature would be a confounding variable.
Common mistakes
Plotting time instead of rate and then describing the curve backwards.
Saying the enzyme is 'killed' rather than denatured.
Forgetting that no colour change at extreme pH means no reaction, not a missing result.
Quick self-test
Why must the temperature be kept constant in this investigation?+
Temperature also affects enzyme activity, so if it varied you could not tell whether the change in rate was caused by pH.
Starch is digested in 60 s. Calculate the rate.+
Rate = 1 / 60 = 0.017 s^-1.
At pH 2 the iodine still turns blue-black after 10 minutes. Explain why.+
The enzyme has been denatured at this pH, so its active site no longer fits the starch and little or no digestion occurs.
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Required practical 7
Reaction time
Planning and carrying out an investigation into the effect of a factor on human reaction time.
Aim
Measure how a chosen factor, such as caffeine, background noise or the hand used, affects reaction time.
Method
The subject sits with their forearm over the edge of a table and thumb and forefinger open.
A partner holds a ruler vertically with the zero mark between the subject's fingers.
Drop the ruler without warning; the subject catches it as quickly as possible.
Record the distance fallen in centimetres at the top of the thumb.
Repeat several times and discard obvious anomalies, then calculate a mean.
Change the chosen factor and repeat the whole procedure.
Variables
Independent
The chosen factor, for example caffeine intake, dominant versus non-dominant hand or background noise
Dependent
Distance the ruler falls, converted to reaction time
Control
Same subject
Same hand and starting finger position
Same ruler and drop height
No countdown or warning
Same time of day where possible
Equipment
30 cm or metre ruler, Chair and table, Optional: computer reaction-timer program.
Results and observations
A shorter drop distance means a faster reaction. Results usually improve slightly with practice, so early trials can be higher than later ones.
Calculations
Convert distance to time using t = √(2s ÷ g), with s in metres and g = 9.8 m/s²
Calculate a mean distance or time from the repeats
Graphs and data
Use a bar chart to compare conditions, or a scatter graph if the factor is continuous.
Evaluation
Anticipation is a major source of error, so avoid patterns or countdowns.
Human variation means comparing conditions on the same person is more valid than comparing people.
A computer-based test removes the partner's inconsistent release and measures time directly.
Common mistakes
Treating distance as if it were time without converting.
Averaging in obvious anomalies caused by a missed catch.
Changing more than one factor between conditions.
Quick self-test
Why should the ruler be dropped without warning?+
A warning lets the subject anticipate the drop, so the measurement no longer reflects their true reaction time.
Give one reason for testing the same person under both conditions.+
It controls for natural variation between people, making the comparison of the factor more valid.
The ruler falls 0.20 m. Calculate the reaction time using t = sqrt(2s/g).+
t = sqrt(2 x 0.20 / 9.8) = 0.20 s (2 s.f.).
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Required practical 8 · separate biology only
Plant responses
Investigating the effect of light or gravity on the growth of newly germinated seedlings, recording results as measurements and labelled biological drawings.
Aim
Show how seedlings respond to a directional stimulus through phototropism or gravitropism.
Method
Germinate seedlings on damp cotton wool or filter paper in identical dishes.
For light: place groups in full light, unidirectional light through a slit, and darkness.
For gravity: keep some dishes upright and turn others through 90 degrees, using a klinostat as a control if available.
Leave for several days, keeping water supply the same.
Measure the length of shoots and roots and record the direction of growth.
Make accurate labelled drawings showing the direction of bending.
Variables
Independent
Direction or presence of light, or the orientation relative to gravity
Dependent
Length of shoot or root and the direction of growth
Control
Same species and number of seedlings
Same water supply
Same temperature
Same growth time
Equipment
Cress or similar seedlings, Petri dishes, Cotton wool or filter paper, Light source and card with a slit, Ruler, Klinostat (optional).
Results and observations
Shoots grow towards unidirectional light (positive phototropism) and away from gravity; roots grow towards gravity. Seedlings in darkness are typically longer, thin and pale.
Calculations
Calculate mean shoot or root length for each condition
Measure the angle of bending if comparing responses
Graphs and data
Bar chart of mean length by condition, supported by labelled drawings of the direction of growth.
Evaluation
Seedlings vary naturally, so use several per condition and take a mean.
A klinostat controls for the effect of rotation itself when testing gravity.
Measuring a curved shoot with a straight ruler underestimates its true length.
Common mistakes
Saying plants 'want' to grow towards light rather than describing unequal auxin distribution.
Using only one seedling per condition.
Not keeping the seedlings equally watered.
Quick self-test
Explain why several seedlings are used in each condition.+
Individual seedlings vary, so a mean from several reduces the effect of that natural variation.
Predict what happens to shoots given light from one side only.+
They grow towards the light because auxin accumulates on the shaded side and causes greater elongation there.
Why are seedlings grown in the dark taller and paler?+
They elongate rapidly searching for light and cannot make chlorophyll without it.
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Required practical 9
Field investigations
Measuring the population size of a common species in a habitat and using sampling techniques to investigate the effect of a factor on its distribution.
Aim
Estimate population size and show how an abiotic factor affects where a species is found.
Method
For population size, place quadrats at random using coordinates from a random number generator over a gridded area.
Count the number of individuals, or estimate percentage cover, in each quadrat.
Repeat for a suitable number of quadrats and calculate a mean per quadrat.
For distribution, lay a transect line from one habitat condition to another, for example from open ground into shade.
Place quadrats at regular intervals along the transect and record abundance plus the abiotic factor, such as light intensity or soil moisture.
Record all data in a results table as you go.
Variables
Independent
Distance along the transect, or the abiotic factor being investigated
Dependent
Number of individuals or percentage cover of the species
Control
Same quadrat size
Same sampling method and counting rules
Same time of day and weather conditions
Equipment
Quadrats, Tape measure or transect line, Random number generator, Light meter or soil moisture meter, Identification key.
Results and observations
Abundance usually changes systematically along the transect as the abiotic factor changes; random quadrats give a mean used to estimate the total population.
Calculations
Mean number per quadrat = total counted ÷ number of quadrats
Estimated population = mean per quadrat × (total area ÷ area of one quadrat)
Graphs and data
Plot abundance against distance along the transect as a line graph, or use a kite diagram to show distribution.
Evaluation
Sampling must be random for population estimates, otherwise the result is biased.
More quadrats reduce the effect of chance and make the estimate more reliable.
Percentage cover is subjective; counting individuals is more precise where the species is countable.
Common mistakes
Placing quadrats where the species looks abundant instead of randomly.
Forgetting to scale the mean up by total area when estimating the population.
Using a transect for a population estimate, which is intended for distribution.
Quick self-test
Why must quadrat positions be chosen randomly?+
Choosing where to place quadrats introduces bias, which would make the population estimate unrepresentative.
Mean count is 6 per 0.25 m^2 quadrat over a 200 m^2 field. Estimate the population.+
200 / 0.25 = 800 quadrat areas, so 800 x 6 = 4800 individuals.
When is a transect used rather than random quadrats?+
When investigating how distribution changes across a gradient, such as from shade into open ground.
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Required practical 10 · separate biology only
Rate of decay
Investigating the effect of temperature on the rate of decay of fresh milk by measuring pH change.
Aim
Show how temperature affects the activity of decay microorganisms, measured through the acid they produce.
Method
Measure a fixed volume of fresh milk into a boiling tube and add a fixed volume of lipase and sodium carbonate solution with cresol red indicator.
Place the tube in a water bath at a set temperature and allow it to reach that temperature.
Start the stopwatch and record the time taken for the indicator to change from purple to yellow, showing the pH has fallen.
Alternatively, record pH with a pH meter at fixed time intervals.
Repeat at a range of temperatures.
Repeat each temperature and take a mean.
Variables
Independent
Temperature
Dependent
Time taken for the pH to fall to the end point, or pH after a fixed time
Control
Volume and concentration of milk, lipase and indicator
Same starting pH
Same end-point colour judgement
Same tube and mixing
Equipment
Fresh milk, Lipase solution, Sodium carbonate solution, Cresol red indicator or pH meter, Water baths, Stopwatch, Thermometer.
Results and observations
The pH falls as fatty acids are produced. The change is fastest at the optimum temperature and slower at low temperatures; at high temperatures enzymes denature and the reaction slows or stops.
Calculations
Rate = 1 ÷ time to reach the end point
Mean time from repeats before calculating rate
Graphs and data
Plot rate against temperature; expect a peak at the optimum temperature.
Evaluation
Judging a colour end point by eye is subjective; a pH meter or colorimeter is more objective.
Water baths must be checked with a thermometer because they drift.
The tube needs time to reach the water bath temperature before timing starts.
Common mistakes
Saying the pH rises rather than falls as acid is produced.
Not allowing the mixture to reach the set temperature before starting.
Reporting time as though it were the rate.
Quick self-test
Explain why the pH of the milk falls.+
Microorganisms and lipase break down fats to produce fatty acids, which lower the pH.
Why is a water bath used rather than heating directly?+
It holds the mixture at a steady, known temperature, which is the variable being investigated.
Suggest why the rate falls at very high temperatures.+
The enzymes are denatured, so their active sites no longer fit their substrates.
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Practical names follow the required practical activities listed in the official AQA GCSE Biology 8461 specification. Always check the current specification for the authoritative list.
AQA GCSE Chemistry Required Practicals
AQA GCSE Chemistry lists eight required practical activities, with titration, identifying ions and water purification on the separate Chemistry specification only. Many Chemistry practical questions combine technique with calculation, so practise the maths as well as the method.
Preparing a pure, dry sample of a soluble salt from an insoluble oxide or carbonate, heating dilute acid with a Bunsen burner and evaporating with a water bath or electric heater.
Aim
Produce a pure, dry sample of a soluble salt by neutralising an acid with an excess of an insoluble base.
Method
Warm about 25 cm³ of dilute acid in a beaker using a Bunsen burner, then stop heating.
Add the insoluble oxide or carbonate a spatula at a time, stirring, until no more reacts and solid remains in excess.
Filter the mixture to remove the unreacted solid, keeping the filtrate.
Pour the filtrate into an evaporating basin and heat gently with a water bath or electric heater until crystals start to form.
Leave the solution to cool so crystals form slowly.
Pat the crystals dry between filter paper.
Variables
Independent
The acid and base combination chosen, which determines the salt made
Dependent
Mass and purity of the dry crystals produced
Control
Volume and concentration of acid
Excess of base added
Same drying method
Equipment
Dilute acid, Insoluble metal oxide or carbonate, Beaker and stirring rod, Filter funnel and paper, Evaporating basin, Bunsen burner or electric heater.
Results and observations
The reaction mixture fizzes with a carbonate as carbon dioxide is released. Once the reaction is complete, solid remains undissolved and the filtrate is a clear salt solution that yields crystals on evaporation.
Calculations
Percentage yield = (mass of salt actually made ÷ maximum theoretical mass) × 100
Theoretical mass comes from a balanced equation and relative formula masses
Graphs and data
No graph is needed; results are recorded as observations and masses.
Evaluation
Adding the base in excess ensures all the acid reacts, so the final solution is not acidic.
Filtering removes the excess solid, which is essential for purity.
Evaporating to dryness over a flame can decompose the salt or cause spitting; slow crystallisation gives better crystals.
Yield is usually below 100% because some solution is lost in filtering and transferring.
Common mistakes
Adding just enough base rather than an excess.
Boiling the solution dry instead of leaving it to crystallise.
Forgetting that the excess solid must be filtered off before evaporation.
Quick self-test
Why is the insoluble base added in excess?+
To make sure all of the acid reacts, so no acid remains in the final solution.
How do you know the reaction is complete?+
Solid stops dissolving and remains at the bottom of the beaker, and with a carbonate the fizzing stops.
Why is the solution left to crystallise rather than evaporated to dryness?+
Slow crystallisation gives larger, purer crystals and avoids decomposing the salt or losing it through spitting.
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Required practical 2 · separate chemistry only
Titration
Determining the reacting volumes of a strong acid and a strong alkali by titration, and (Higher Tier) calculating the concentration of one solution in mol/dm³ and g/dm³.
Aim
Find accurately what volume of acid reacts with a known volume of alkali, and use that to find an unknown concentration.
Method
Rinse the pipette with the alkali and use it to transfer a fixed volume, typically 25.0 cm³, into a conical flask.
Add a few drops of indicator such as phenolphthalein or methyl orange.
Rinse the burette with the acid, fill it and record the initial reading to the nearest 0.05 cm³.
Run acid in quickly to get a rough titre, noting the approximate end point.
Repeat, adding dropwise near the end point, and record the volume at the first permanent colour change.
Repeat until you have concordant titres within 0.10 cm³ and calculate a mean of those.
Variables
Independent
Volume of acid added
Dependent
Volume of acid required to neutralise the alkali (the titre)
Control
Same volume and concentration of alkali
Same indicator and number of drops
Same end-point judgement
Equipment
Burette and stand, Pipette and filler, Conical flask, White tile, Indicator, Acid and alkali solutions.
Results and observations
Phenolphthalein turns from pink to colourless when titrating acid into alkali; methyl orange turns from yellow to red. The titre is the volume at the first permanent colour change.
Calculations
Mean titre uses concordant results only
moles = concentration (mol/dm³) × volume (dm³), where volume in dm³ = cm³ ÷ 1000
Use the balanced equation's ratio to find moles of the unknown, then concentration = moles ÷ volume
Concentration in g/dm³ = concentration in mol/dm³ × relative formula mass
Graphs and data
No graph is required; results go in a titration table showing initial, final and titre values to two decimal places.
Evaluation
Only concordant titres are averaged because the rough titre overshoots the end point.
Rinsing apparatus with the solution it will hold prevents dilution errors.
A white tile makes the colour change easier to see, reducing end-point error.
Overshooting even one drop can change the titre measurably.
Common mistakes
Including the rough titre in the mean.
Recording burette readings to the nearest whole cm³ instead of 0.05 cm³.
Forgetting to convert cm³ to dm³ in the moles calculation.
Quick self-test
Why is the pipette rinsed with the alkali before use?+
Any water left inside would dilute the alkali and change the number of moles transferred.
25.0 cm^3 of alkali needs 20.0 cm^3 of 0.100 mol/dm^3 acid in a 1:1 reaction. Calculate the alkali concentration.+
Moles of acid = 0.100 x 0.0200 = 0.00200 mol, so the alkali is 0.00200 / 0.0250 = 0.0800 mol/dm^3.
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Required practical 3
Electrolysis
Investigating what happens when aqueous solutions are electrolysed using inert electrodes, developing and testing a hypothesis.
Aim
Predict and identify the products formed at each electrode when different aqueous solutions are electrolysed.
Method
Half fill an electrolysis cell or beaker with the solution to be tested.
Place two inert graphite electrodes in the solution, not touching, and connect to a d.c. power supply.
Position an inverted test tube over each electrode to collect any gas.
Switch on and observe both electrodes, recording bubbling, colour changes or deposits.
Test the gases collected: a lit splint pops for hydrogen; a glowing splint relights in oxygen; damp litmus paper is bleached by chlorine.
Repeat with the other solutions and compare with your predictions.
Variables
Independent
The aqueous solution being electrolysed
Dependent
The products formed at the cathode and the anode
Control
Same voltage and time
Same inert electrodes
Same volume and concentration of solution
Equipment
d.c. power supply, Graphite (inert) electrodes, Electrolysis cell or beaker, Test tubes, Solutions such as copper chloride, sodium chloride and sodium sulfate, Splints and litmus paper.
Results and observations
At the cathode, hydrogen is produced unless the metal is less reactive than hydrogen, in which case the metal is deposited. At the anode, a halogen is produced if a halide is present; otherwise oxygen is produced from hydroxide ions.
Calculations
No routine calculation, though relative volumes of gas can be compared
Half equations describe what happens at each electrode
Graphs and data
Results are recorded as a table of solution against products at each electrode.
Evaluation
Inert electrodes are used so that the electrodes themselves do not react and change the products.
Small gas volumes can make tests unreliable, so allow enough time to collect gas.
Chlorine is toxic and dissolves in water, so yields appear lower than expected.
Common mistakes
Mixing up the electrodes: reduction happens at the cathode (negative), oxidation at the anode (positive).
Forgetting that water provides H⁺ and OH⁻ ions in aqueous solutions.
Writing half equations that do not balance for charge.
Quick self-test
Why are inert electrodes used?+
So the electrodes do not take part in the reaction and change the products formed.
Predict the products of electrolysing aqueous sodium chloride.+
Hydrogen at the cathode, because sodium is more reactive than hydrogen, and chlorine at the anode because a halide is present.
Describe the test for the gas produced at the cathode in that reaction.+
Hold a lit splint at the mouth of the tube; hydrogen burns with a squeaky pop.
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Required practical 4
Temperature changes
Investigating the variables that affect temperature changes in reacting solutions, such as acid plus metals, acid plus carbonates, neutralisation and displacement.
Aim
Measure the temperature change of a reaction and find how a chosen variable affects it.
Method
Place a polystyrene cup inside a beaker for support and add a fixed volume of the first solution.
Record the starting temperature with a thermometer.
Add a measured volume or mass of the second reactant, stir and put a lid on to reduce heat loss.
Record the highest (or lowest) temperature reached.
Repeat with different volumes or concentrations of the reactant being varied.
Repeat each combination and calculate mean temperature changes.
Variables
Independent
The variable investigated, for example volume or concentration of one reactant
Dependent
Temperature change of the mixture
Control
Total volume of solution
Starting temperature
Same insulation and lid
Same stirring
Equipment
Polystyrene cup with lid, Beaker, Thermometer, Measuring cylinders, Acid and alkali (or metal/carbonate), Stirrer.
Results and observations
Exothermic reactions show a temperature rise; endothermic reactions show a fall. In a neutralisation, the temperature rise peaks when the acid and alkali react in exactly the right proportions and falls again as excess reactant cools the mixture.
Calculations
Temperature change = highest temperature − starting temperature
Mean temperature change from repeats
Graphs and data
Plot temperature change against volume of reactant added; two straight lines that intersect identify the point of maximum change.
Evaluation
A polystyrene cup and lid reduce heat loss to the surroundings, the main source of error.
The thermometer resolution (often 1 °C) limits precision; a digital probe is better.
Repeats identify anomalies caused by inconsistent stirring or delayed reading.
Common mistakes
Recording the final temperature after the mixture has started cooling rather than the maximum.
Changing the total volume between runs, which changes the mass being heated.
Describing a temperature rise as endothermic.
Quick self-test
Why is a polystyrene cup used instead of a glass beaker?+
Polystyrene is a good insulator, so less energy is transferred to the surroundings and the temperature change measured is closer to the true value.
The temperature falls from 21 to 15 degrees C. What type of reaction is this?+
Endothermic, because energy is taken in from the surroundings.
Why should the total volume be kept the same in every run?+
A different total volume would change the mass being heated, so the temperature change would not be comparable.
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Required practical 5
Rates of reaction
Investigating how changes in concentration affect rates of reaction using two methods: measuring the volume of gas produced, and observing a change in colour or turbidity.
Aim
Show how concentration affects reaction rate, measured both by gas production and by a change in cloudiness.
Method
Gas method: add a measured volume of hydrochloric acid to marble chips or magnesium in a conical flask fitted with a bung and gas syringe.
Record the volume of gas collected at regular intervals, for example every 10 seconds.
Repeat with different acid concentrations, keeping everything else the same.
Turbidity method: mix sodium thiosulfate solution with hydrochloric acid in a flask placed over a printed cross.
Time how long the cross takes to disappear as sulfur forms.
Repeat at different thiosulfate concentrations and calculate a mean time for each.
Variables
Independent
Concentration of the reactant solution
Dependent
Volume of gas produced in a set time, or time for the cross to disappear
Control
Temperature
Volume of solutions
Surface area and mass of solid
Same observer and same cross for turbidity
Equipment
Conical flask and bung, Gas syringe, Measuring cylinders, Stopwatch, Sodium thiosulfate and hydrochloric acid, Printed cross card.
Results and observations
Higher concentration gives more gas in the same time and a shorter time for the cross to disappear. Gas volume curves are steepest at the start and flatten when a reactant runs out.
Calculations
Mean rate = quantity of product formed ÷ time taken (for example cm³/s)
Rate from the turbidity method = 1 ÷ time (s⁻¹)
Rate at a given moment = gradient of the tangent to the curve (Higher Tier)
Graphs and data
Plot volume of gas against time for each concentration; a steeper initial gradient means a faster rate. For turbidity, plot 1/time against concentration.
Evaluation
Gas can escape while the bung is being fitted, lowering early readings.
Judging when the cross disappears is subjective, so the same observer should judge every run.
Temperature must be controlled because it strongly affects rate.
Repeats allow a mean and expose anomalies.
Common mistakes
Plotting time on the y-axis when the question asks for volume against time.
Reading the gradient at the plateau instead of at the start when asked for initial rate.
Forgetting that surface area, not just mass, affects the rate with solids.
Quick self-test
Why does the gas volume curve flatten out?+
One of the reactants has been used up, so no more product is formed.
Explain why higher concentration increases rate.+
There are more reactant particles in the same volume, so collisions are more frequent.
The cross disappears in 25 s. Calculate the rate.+
Rate = 1 / 25 = 0.04 s^-1.
Why should the same person judge every cross?+
Judging when the cross disappears is subjective, so using one observer keeps the end point consistent.
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Required practical 6
Chromatography
Investigating how paper chromatography separates and distinguishes between coloured substances, including calculating Rf values.
Aim
Separate the components of a coloured mixture and identify them using Rf values.
Method
Draw a pencil start line about 1 cm from the bottom of the chromatography paper.
Spot small samples of each ink or dye on the line and let them dry, repeating to concentrate the spot.
Pour solvent into a beaker so the level is below the pencil line.
Hang the paper so the bottom edge dips into the solvent without submerging the spots.
Cover the beaker and let the solvent rise until it is near the top.
Remove the paper, immediately mark the solvent front in pencil and let it dry.
Variables
Independent
The substance or mixture spotted onto the paper
Dependent
Distance travelled by each spot, and the Rf value calculated from it
Control
Same solvent and depth
Same paper type and size
Same start line position
Same run time or solvent front distance
Equipment
Chromatography paper, Beaker and lid or watch glass, Solvent (water or ethanol), Pencil and ruler, Capillary tubes or dropper.
Results and observations
A pure substance produces one spot; a mixture separates into several. Substances more attracted to the solvent than to the paper travel further.
Calculations
Rf = distance travelled by the spot ÷ distance travelled by the solvent front
Both distances are measured from the pencil start line to the centre of the spot
Rf values are always between 0 and 1 and have no units
Graphs and data
No graph; results are recorded as measured distances and calculated Rf values in a table.
Evaluation
The start line must be pencil because ink would dissolve and run.
If the solvent level is above the start line the spots dissolve into the solvent instead of moving up the paper.
Covering the beaker prevents solvent evaporation, which would change how far the front travels.
Rf values are only comparable when the same solvent and paper are used.
Common mistakes
Measuring to the edge of a spot instead of its centre.
Forgetting to mark the solvent front before it evaporates.
Quoting Rf with units or as a value greater than 1.
Quick self-test
Why must the start line be drawn in pencil?+
Pencil is insoluble, whereas ink would dissolve in the solvent and travel up the paper.
A spot moves 4.5 cm and the solvent front moves 9.0 cm. Calculate Rf.+
Rf = 4.5 / 9.0 = 0.50.
How can you tell a substance is pure from a chromatogram?+
A pure substance produces a single spot in every solvent.
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Required practical 7 · separate chemistry only
Identifying ions
Using chemical tests to identify the ions in unknown single ionic compounds, covering flame tests through to sulfates.
Aim
Identify the positive and negative ion in an unknown ionic compound using qualitative tests.
Method
Flame test: dip a clean nichrome wire loop in acid, then in the solid, and hold it in a blue Bunsen flame; record the flame colour.
Metal hydroxide test: add sodium hydroxide solution dropwise to a solution of the compound and record any precipitate colour, including whether it dissolves in excess.
Carbonates: add dilute acid and bubble any gas through limewater.
Halides: acidify with dilute nitric acid, then add silver nitrate solution and record the precipitate colour.
Sulfates: acidify with dilute hydrochloric acid, then add barium chloride solution.
Combine the positive and negative ion results to name the compound.
Variables
Independent
The unknown compound being tested
Dependent
The observations: flame colour, precipitate colour and gas test results
Control
Clean apparatus between tests
Same volumes of reagents
Known samples tested alongside for comparison
Equipment
Nichrome wire loop, Bunsen burner, Sodium hydroxide solution, Dilute nitric and hydrochloric acid, Silver nitrate and barium chloride solutions, Limewater, Test tubes.
Results and observations
Flame colours indicate the metal ion. Sodium hydroxide gives coloured precipitates for transition metal ions and a white precipitate for several others. Effervescence with acid that turns limewater cloudy indicates a carbonate. Silver nitrate gives white, cream or yellow precipitates for chloride, bromide and iodide. Barium chloride gives a white precipitate with sulfates.
Calculations
No calculation; the practical is qualitative
Write balanced ionic equations for the precipitation reactions
Graphs and data
Record all observations in a systematic results table linking test, observation and conclusion.
Evaluation
The wire loop must be cleaned between flame tests or a previous ion's colour carries over.
Sodium contamination easily masks other flame colours because its yellow flame is intense.
Acidifying before the silver nitrate or barium chloride test removes carbonate ions that would otherwise give a false positive.
Flame colours can be hard to distinguish by eye; flame emission spectroscopy is more reliable.
Common mistakes
Skipping the acidification step before the halide or sulfate test.
Describing a precipitate without naming the colour.
Reporting a colour change rather than a precipitate for the sodium hydroxide test.
Quick self-test
Why is the sample acidified before adding silver nitrate?+
To remove carbonate ions, which would otherwise form a white precipitate and give a false positive.
A white precipitate forms with barium chloride. What ion is present?+
Sulfate ions.
Why must the flame test wire be cleaned between samples?+
Residue from the previous sample would produce its own flame colour and mask the result.
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Required practical 8 · separate chemistry only
Water purification
Analysing and purifying water samples from different sources, including pH, dissolved solids and distillation.
Aim
Test water samples for pH and dissolved solids, then purify a sample by distillation and check the result.
Method
Test the pH of each water sample with universal indicator paper or a pH probe.
Weigh a clean, dry evaporating basin.
Add a measured volume of the sample, evaporate the water and reweigh to find the mass of dissolved solids.
Set up a distillation apparatus with a condenser and collect the distillate from a fresh sample of the same water.
Test the pH of the distillate and repeat the evaporation test on it.
Compare the results before and after distillation.
Variables
Independent
The source of the water sample, and whether it has been distilled
Dependent
pH and mass of dissolved solids per unit volume
Control
Same volume of each sample
Same evaporation method and drying time
Same pH measurement method
Equipment
Water samples, Universal indicator paper or pH probe, Evaporating basin and balance, Bunsen burner and tripod, Distillation apparatus with condenser, Thermometer.
Results and observations
Untreated samples leave a solid residue after evaporation and may not be neutral. The distillate leaves little or no residue and has a pH close to 7, showing dissolved solids have been removed.
Calculations
Mass of dissolved solids = mass of basin plus residue − mass of empty basin
Concentration of dissolved solids in g/dm³ = mass of solids ÷ volume of sample in dm³
Graphs and data
Compare samples with a bar chart of dissolved solids per dm³ alongside a table of pH values.
Evaluation
The basin must be completely dry before both weighings or the residue mass is overestimated.
Distillation removes dissolved solids but does not remove substances with a similar boiling point to water.
Universal indicator gives pH to the nearest whole number; a pH probe is more precise.
Distillation uses a lot of energy, which is why it is not the usual method for large-scale drinking water.
Common mistakes
Assuming a clear sample is pure because dissolved solids are invisible.
Weighing the basin while it is still warm or damp.
Confusing distillation with filtration, which does not remove dissolved substances.
Quick self-test
Why does a clear water sample still leave a residue after evaporation?+
Dissolved solids are invisible in solution but remain behind when the water evaporates.
A 50 cm^3 sample leaves 0.20 g of residue. Calculate the concentration in g/dm^3.+
0.20 / 0.050 = 4.0 g/dm^3.
Give one limitation of distillation for producing drinking water.+
It requires a large amount of energy, which makes it expensive on a large scale.
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Practical names follow the required practical activities listed in the official AQA GCSE Chemistry 8462 specification. Always check the current specification for the authoritative list.
AQA GCSE Physics Required Practicals
AQA GCSE Physics lists ten required practical activities, with thermal insulation and light on the separate Physics specification only. Physics practical questions usually involve an equation, a graph or an uncertainty, so make sure you can handle the data as confidently as the apparatus.
Determining the specific heat capacity of one or more materials by linking the energy transferred to the rise in temperature and the thermal energy stored.
Aim
Measure how much energy is needed to raise the temperature of 1 kg of a material by 1 °C.
Method
Measure the mass of the block with a balance.
Insulate the block and place a heater in the larger hole and a thermometer in the smaller hole, using a little oil or water for good thermal contact.
Connect the heater to a power supply through an ammeter, with a voltmeter across the heater, and record the starting temperature.
Switch on and start the stopwatch, recording current and potential difference.
Record the temperature at regular intervals, for example every minute, for around 10 minutes.
Calculate the energy supplied and plot temperature against energy.
Variables
Independent
Energy transferred to the block (or time)
Dependent
Temperature of the block
Control
Same mass of material
Same insulation
Same heater and power supply setting
Equipment
Metal block with holes, Immersion heater, Thermometer, Power supply, Ammeter and voltmeter, Balance, Stopwatch, Insulation.
Results and observations
Temperature rises steadily as energy is supplied. Different materials of the same mass reach different temperatures for the same energy input.
Calculations
E = P × t, and P = V × I, so energy supplied E = V × I × t
ΔE = m × c × Δθ, so c = ΔE ÷ (m × Δθ)
Mass must be in kilograms and temperature change in °C
Graphs and data
Plot temperature (y) against energy supplied (x); the specific heat capacity is 1 ÷ (gradient × mass).
Evaluation
Energy lost to the surroundings makes the measured specific heat capacity higher than the true value, so insulation is important.
The thermometer measures the block near the surface, which may lag behind the average temperature.
Oil in the thermometer hole improves thermal contact and reduces the lag.
Not all electrical energy heats the block; some warms the heater and the surroundings.
Common mistakes
Using mass in grams instead of kilograms.
Using the final temperature instead of the temperature change.
Forgetting that the heater needs time before the temperature responds.
Quick self-test
Why is the block insulated?+
To reduce energy transfer to the surroundings, which would otherwise make the calculated specific heat capacity too high.
A heater runs at 12 V and 4.0 A for 300 s. Calculate the energy supplied.+
E = V x I x t = 12 x 4.0 x 300 = 14 400 J.
Why is a little oil put in the thermometer hole?+
It improves thermal contact between the block and the thermometer so the reading responds more quickly.
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Required practical 2 · separate physics only
Thermal insulation
Investigating the effectiveness of different materials as thermal insulators and the factors affecting their insulating properties.
Aim
Compare how well different materials, or different thicknesses of a material, reduce the rate of cooling.
Method
Wrap an identical beaker in each insulating material, keeping the number of layers consistent within a run.
Pour the same volume of hot water at the same starting temperature into each beaker.
Fit a lid with a thermometer through it to reduce evaporation.
Record the temperature every minute for around 10 minutes.
Repeat with the other materials, and with different thicknesses of one material.
Compare temperature drops over the same time interval.
Variables
Independent
Type of insulating material, or number of layers
Dependent
Temperature after a fixed time, or the temperature drop
Control
Volume and starting temperature of water
Same beakers and lids
Same room temperature
Same time interval
Equipment
Identical beakers, Insulating materials, Thermometer or temperature probe, Lids, Measuring cylinder, Stopwatch, Kettle.
Results and observations
Better insulators show a smaller temperature drop over the same time. Adding layers reduces the drop further, with diminishing returns.
Calculations
Temperature drop = starting temperature − final temperature
Mean rate of cooling = temperature drop ÷ time (°C per minute)
Graphs and data
Plot temperature against time for each material on the same axes; the shallowest curve is the best insulator.
Evaluation
Using the same volume and starting temperature makes the comparison fair, since more water cools more slowly.
Lids are needed because evaporation causes cooling independently of the insulation.
Room temperature drifting between runs affects the rate of cooling.
Repeats give a mean and reduce the effect of random variation.
Common mistakes
Comparing final temperatures when the starting temperatures were different.
Varying the thickness and material at the same time.
Leaving beakers uncovered so evaporation dominates.
Quick self-test
Why is a lid used on each beaker?+
To reduce cooling by evaporation so that the insulation is the variable being tested.
Water cools from 80 to 62 degrees C in 10 minutes. Calculate the mean rate of cooling.+
18 / 10 = 1.8 degrees C per minute.
Explain why the same volume of water must be used each time.+
A larger volume stores more energy and cools more slowly, which would make the comparison unfair.
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Required practical 3
Resistance
Using circuit diagrams to set up and check circuits investigating the factors affecting resistance, including the length of a wire at constant temperature and combinations of resistors in series and parallel.
Aim
Find how the length of a wire affects its resistance, and how resistance changes for resistors in series and parallel.
Method
Set up a circuit with a power supply, ammeter in series and a voltmeter in parallel across the test wire.
Attach crocodile clips to the wire so that a measured length is in the circuit.
Close the switch briefly, record current and potential difference, then open it again to avoid heating the wire.
Repeat for a range of lengths, for example 10 cm to 100 cm.
For the resistor part, measure current and potential difference for one resistor, then for two in series, then two in parallel.
Calculate resistance for each arrangement using R = V ÷ I.
Variables
Independent
Length of wire (or the resistor arrangement)
Dependent
Resistance, calculated from measured current and potential difference
Control
Same wire material and thickness
Same supply voltage
Wire kept at constant temperature by switching off between readings
Equipment
Power supply, Ammeter and voltmeter, Resistance wire on a metre rule, Crocodile clips, Switch, Fixed resistors, Leads.
Results and observations
Resistance is directly proportional to length for a wire at constant temperature. Resistors in series give a total resistance equal to the sum; resistors in parallel give a total less than the smallest individual resistance.
Calculations
R = V ÷ I
Series: R_total = R₁ + R₂
Parallel: the total resistance is smaller than either individual resistance
Graphs and data
Plot resistance (y) against length (x); a straight line through the origin shows direct proportionality.
Evaluation
Current heats the wire, which raises its resistance, so the switch is kept closed only briefly.
Crocodile clip position must be read carefully against the ruler; parallax causes systematic error.
Contact resistance at the clips adds a small constant error.
Repeats at each length allow a mean resistance.
Common mistakes
Leaving the circuit switched on so the wire heats up and results drift.
Connecting the voltmeter in series rather than in parallel.
Assuming parallel resistance is the sum, rather than less than the smallest resistor.
Quick self-test
Why is the switch only closed briefly for each reading?+
Current heats the wire, and a hotter wire has a higher resistance, which would change the results.
V = 3.0 V and I = 0.25 A. Calculate the resistance.+
R = V / I = 3.0 / 0.25 = 12 ohms.
Two 10 ohm resistors are connected in parallel. What can you say about the total resistance?+
It is less than 10 ohms, because there are more paths for the current to flow through.
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Required practical 4
I–V characteristics
Constructing circuits to investigate the current–potential difference characteristics of a filament lamp, a diode and a resistor at constant temperature.
Aim
Show how current varies with potential difference for different circuit components.
Method
Build a series circuit with the component, an ammeter and a variable resistor, with a voltmeter across the component.
Adjust the variable resistor to change the potential difference in steps.
Record current and potential difference at each step.
Reverse the connections to the power supply and repeat to get negative values.
Repeat for the resistor, the filament lamp and the diode.
For the diode, add a protective resistor in series to limit the current.
Variables
Independent
Potential difference across the component
Dependent
Current through the component
Control
Same component in each run
Temperature kept constant for the resistor by taking readings quickly
Same circuit layout
Equipment
Power supply, Ammeter and voltmeter, Variable resistor, Fixed resistor, filament lamp and diode, Protective resistor, Leads and switch.
Results and observations
A resistor at constant temperature gives a straight line through the origin. A filament lamp gives an S-shaped curve that flattens as it heats up. A diode conducts in one direction only, with almost no current in reverse.
Calculations
R = V ÷ I at any point on the graph
For the ohmic resistor, resistance is the reciprocal of the gradient of I against V
Graphs and data
Plot current (y) against potential difference (x), including negative values, so the shape either side of the origin is visible.
Evaluation
The filament lamp's resistance rises because the metal filament gets hotter, so the graph curves.
Taking readings quickly keeps the resistor near constant temperature so its line stays straight.
A protective resistor prevents a large current damaging the diode when forward biased.
Repeats and reversed readings check for symmetry and expose anomalies.
Common mistakes
Plotting potential difference on the y-axis when the question specifies I–V.
Saying the lamp is ohmic because part of the graph looks straight.
Omitting the protective resistor with the diode.
Quick self-test
Explain the shape of the filament lamp graph.+
As current increases the filament gets hotter, so its resistance rises and the graph curves away from a straight line.
How would you show a component is ohmic?+
Its current-potential difference graph is a straight line through the origin at constant temperature.
Why is a protective resistor used with the diode?+
It limits the current when the diode is forward biased, preventing damage to the diode.
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Required practical 5
Density
Making and recording the measurements needed to determine the densities of regular and irregular solid objects and of liquids, using dimensions for regular shapes and displacement for irregular ones.
Aim
Determine density from measurements of mass and volume for solids and liquids.
Method
Regular solid: measure mass on a balance, then measure the dimensions with a ruler or vernier callipers and calculate the volume.
Irregular solid: measure the mass, then lower the object into a eureka can filled to the spout and collect the displaced water in a measuring cylinder.
The volume of displaced water equals the volume of the object.
Liquid: measure the mass of an empty measuring cylinder, add a known volume of liquid, then reweigh.
Subtract to find the mass of the liquid.
Calculate density in each case and repeat measurements to find means.
Variables
Independent
The object or liquid whose density is being found
Dependent
Density, calculated from mass and volume
Control
Same balance and its zero setting
Same temperature
Consistent reading of the measuring cylinder at eye level
Equipment
Balance, Ruler or vernier callipers, Eureka (displacement) can, Measuring cylinder, Beaker, Objects and liquids to test.
Results and observations
Density values allow materials to be identified and compared; objects less dense than water float, which affects how they must be submerged.
Calculations
ρ = m ÷ V, with mass in kg and volume in m³ for kg/m³, or g and cm³ for g/cm³
Volume of a cuboid = length × width × height
1 cm³ of displaced water = 1 cm³ of object volume
Graphs and data
For a liquid, plot mass against volume; the gradient is the density.
Evaluation
A floating object must be pushed fully under with a thin rod, or the volume is underestimated.
Water left clinging to the object or lost as splashes gives a systematic error in the displaced volume.
A measuring cylinder has lower resolution than a burette, and the meniscus must be read at eye level.
Vernier callipers give a more precise dimension measurement than a ruler.
Common mistakes
Mixing units, for example mass in grams with volume in m³.
Reading the measuring cylinder from above, causing parallax error.
Forgetting to subtract the mass of the empty container when finding a liquid's mass.
Quick self-test
Why must a floating object be pushed fully under the water?+
Otherwise it displaces less water than its own volume, so the measured volume is too small.
An object has mass 240 g and volume 30 cm^3. Calculate its density.+
240 / 30 = 8.0 g/cm^3.
Give one reason a measuring cylinder should be read at eye level.+
Reading from above or below causes a parallax error in the volume measurement.
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Required practical 6
Force and extension
Investigating the relationship between force and extension for a spring.
Aim
Show how the extension of a spring changes with the force applied, and find its spring constant.
Method
Clamp the spring securely to a stand with a ruler fixed vertically alongside it.
Record the unstretched length of the spring.
Add a known mass to the hanger and record the new length once it is still.
Repeat, adding masses one at a time and recording the length each time.
Remove the masses one at a time, checking the spring returns to its original length.
Calculate the extension for each force and plot a graph.
Variables
Independent
Force applied to the spring (weight of the masses)
Dependent
Extension of the spring
Control
Same spring throughout
Same starting position and ruler
Masses added gently without bouncing
Equipment
Spring, Clamp stand, boss and clamp, Ruler and set square, Slotted masses and hanger, Safety goggles and floor mat.
Results and observations
Extension is directly proportional to force up to the limit of proportionality. Beyond that the line curves and the spring may not return to its original length.
Calculations
Weight: W = m × g, with g = 9.8 N/kg
Extension = stretched length − original length
F = k × e, so the spring constant k = force ÷ extension (N/m)
Graphs and data
Plot force (y) against extension (x); the straight section passes through the origin and its gradient is the spring constant.
Evaluation
Reading the ruler at eye level with a set square reduces parallax error.
Exceeding the limit of proportionality permanently deforms the spring and invalidates later readings.
Checking that the spring returns to its original length confirms the deformation was elastic.
Repeats at each mass reduce random error in the length readings.
Common mistakes
Plotting length instead of extension.
Using mass in kilograms directly as the force in newtons.
Ignoring the curve at high forces and forcing a straight line through all points.
Quick self-test
What does a straight line through the origin on a force-extension graph show?+
Extension is directly proportional to the force applied.
A spring extends 0.080 m under a force of 4.0 N. Calculate the spring constant.+
k = F / e = 4.0 / 0.080 = 50 N/m.
How can you check the spring has not been permanently deformed?+
Remove the masses and check that the spring returns to its original unstretched length.
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Required practical 8
Waves
Identifying suitable apparatus to measure the frequency, wavelength and speed of waves in a ripple tank and waves in a solid, and taking the measurements.
Aim
Measure wave speed for water waves and for waves on a stretched string.
Method
Ripple tank: set up the tank with a vibrating dipper and a lamp above so waves cast shadows on paper below.
Measure the length of, say, ten wave shadows and divide by ten to find the wavelength.
Find the frequency from the dipper setting, or by counting waves passing a point over a timed interval.
Stretched string: attach a string to a vibration generator with a mass hanging over a pulley to keep it taut.
Adjust the frequency until a clear standing wave pattern forms and measure the length of a whole number of half-wavelengths.
Calculate the wavelength and use the generator frequency to find the wave speed.
Variables
Independent
Frequency of the wave source
Dependent
Wavelength measured, and the wave speed calculated from it
Control
Same water depth in the ripple tank
Same string, tension and length
Same measuring method
Equipment
Ripple tank with dipper and motor, Lamp and white paper, Signal generator and vibration generator, String, pulley and masses, Metre rule, Stopwatch.
Results and observations
Higher frequency gives a shorter wavelength for the same wave speed. Water waves slow down in shallower water.
Calculations
v = f × λ
Wavelength on a string = 2 × length of one loop (half-wavelength)
Frequency by counting: f = number of waves ÷ time
Graphs and data
Plot wavelength against 1/frequency; a straight line through the origin has a gradient equal to the wave speed.
Evaluation
Measuring across ten wavelengths and dividing reduces the percentage uncertainty in the wavelength.
Ripple tank waves are hard to see clearly; a strobe or the shadow method makes them easier to measure.
Water depth must be constant because it changes wave speed.
The standing wave pattern must be stable before measuring, otherwise the wavelength reading is unreliable.
Common mistakes
Measuring one loop of a standing wave and calling it the wavelength.
Mixing units, for example wavelength in centimetres with speed in m/s.
Counting waves for one second only, which gives a large percentage uncertainty.
Quick self-test
Why measure ten wavelengths and divide by ten?+
It reduces the percentage uncertainty compared with measuring a single wavelength.
A wave has frequency 12 Hz and wavelength 0.025 m. Calculate its speed.+
v = f x lambda = 12 x 0.025 = 0.30 m/s.
On a stretched string, one loop measures 0.40 m. What is the wavelength?+
0.80 m, because one loop is half a wavelength.
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Required practical 9 · separate physics only
Light: reflection and refraction
Investigating the reflection of light by different types of surface and the refraction of light by different substances.
Aim
Compare how different surfaces reflect light and measure how light refracts when entering different materials.
Method
Place the object (mirror, or a glass or perspex block) on plain paper and draw around it.
Direct a ray of light from a ray box at the surface and mark the incident and emerging rays with crosses.
Remove the object and join the crosses with a ruler to draw the ray paths.
Draw the normal at 90 degrees to the surface at the point where the ray hits.
Measure the angles of incidence, reflection and refraction from the normal with a protractor.
Repeat for different angles of incidence and different materials or surfaces.
Variables
Independent
Angle of incidence, and the surface or material used
Dependent
Angle of reflection or refraction, and the nature of the reflected light
Control
Same ray box and slit width
Same block position outline
Angles always measured from the normal
Equipment
Ray box with single slit, Glass and perspex blocks, Plane mirror and rough surfaces, Protractor and ruler, Plain paper and sharp pencil.
Results and observations
For reflection, the angle of reflection equals the angle of incidence. A smooth surface gives specular reflection; a rough surface scatters light (diffuse reflection). Light entering a denser material bends towards the normal and bends away on leaving.
Calculations
No calculation is required at GCSE beyond comparing measured angles
Compare the angle of refraction between materials at the same angle of incidence
Graphs and data
Plot angle of refraction against angle of incidence for each material and compare the curves.
Evaluation
A sharp pencil and thin ray line reduce the uncertainty in the marked ray positions.
The normal must be drawn at exactly 90 degrees or every angle is systematically wrong.
Measuring angles from the surface instead of the normal is a systematic error.
Repeating at several angles of incidence shows whether the pattern is consistent.
Common mistakes
Measuring angles from the surface rather than the normal.
Moving the block after drawing round it.
Saying a rough surface does not reflect light, rather than that it scatters it.
Quick self-test
Why must angles be measured from the normal?+
The normal is the agreed reference line at 90 degrees to the surface; measuring from the surface gives values that are systematically wrong.
Describe what happens to a ray entering a glass block at an angle.+
It slows down and refracts towards the normal, then bends away from the normal as it leaves the block.
Explain the difference between specular and diffuse reflection.+
A smooth surface reflects rays in one direction (specular), whereas a rough surface scatters them in many directions (diffuse).
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Required practical 10
Infrared radiation
Investigating how the amount of infrared radiation absorbed or radiated by a surface depends on the nature of that surface.
Aim
Compare how different surfaces emit or absorb infrared radiation.
Method
Fill a Leslie cube with hot water; its faces are matt black, shiny black, matt white and shiny metal.
Hold an infrared detector or thermometer a fixed distance from one face and record the reading after a set time.
Repeat for each face at the same distance and time.
For absorption, place identical sheets or flasks with different surfaces the same distance from a radiant heater.
Record the starting temperature and the temperature after a set time.
Compare the temperature rises for the different surfaces.
Variables
Independent
The type of surface
Dependent
Infrared detector reading, or temperature rise in a fixed time
Control
Distance from the surface to the detector
Water temperature in the cube
Time interval
Same detector and room temperature
Equipment
Leslie cube, Infrared detector or thermometer, Ruler, Kettle, Radiant heater, Stopwatch, Test surfaces.
Results and observations
Matt black surfaces emit and absorb infrared radiation best; shiny, light-coloured surfaces are the poorest emitters and absorbers and the best reflectors.
Calculations
Temperature rise = final temperature − starting temperature
Mean readings from repeats for each surface
Graphs and data
Bar chart of detector reading or temperature rise for each surface makes the comparison clear.
Evaluation
Distance must be identical for every face, because intensity falls rapidly with distance.
The water cools during the experiment, so work quickly or refill between faces.
The detector picks up background infrared from the room, so keep conditions constant.
Repeats and a mean reduce random error in the detector readings.
Common mistakes
Changing the distance between measurements.
Assuming colour alone matters and ignoring whether the surface is matt or shiny.
Comparing readings taken after different times.
Quick self-test
Which face of a Leslie cube emits the most infrared radiation?+
The matt black face.
Why must the detector stay the same distance from each face?+
Detected intensity falls quickly with distance, so a different distance would make the comparison unfair.
Suggest why readings drift lower during the experiment.+
The water inside the cube cools as time passes, so all faces radiate less.
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Practical names follow the required practical activities listed in the official AQA GCSE Physics 8463 specification. Always check the current specification for the authoritative list.
How to answer GCSE required practical questions
Practical questions rarely ask you to recite a method. They usually give data, a diagram or an unfamiliar setup and test whether you can think like an experimenter. The exact skills depend on the practical and on the specification you are sitting, so use this as a checklist rather than a prediction.
Identifying variablesPick out what was changed, what was measured and what had to stay the same.
Choosing control variablesName the specific variables that would otherwise affect the dependent variable.
Describing a valid methodWrite steps in order, with quantities and a clear measurement, so someone else could repeat it.
Selecting measurementsChoose apparatus with a sensible resolution and range for what you are measuring.
Recording resultsUse a table with headings, units and a consistent number of decimal places.
Calculating valuesMeans, percentage change, rate, gradient, density and other calculations set by the practical.
Plotting and reading graphsSensible scales, labelled axes with units, plotted points and a line of best fit.
Identifying anomaliesSpot results that do not fit the pattern, exclude them from means and suggest a cause.
Evaluating reliabilityExplain how repeats, means and controlled variables strengthen a conclusion.
Sources of errorSeparate random error from systematic error and say which affects your data.
Suggesting improvementsChange one specific thing and say what it would improve, rather than 'be more careful'.
Drawing conclusionsState the relationship the data supports and refer back to the values you collected.
Applying to new contextsUse the same reasoning on an unfamiliar experiment you have never carried out.
GCSE Required Practical Exam Questions
These are original practice questions written for this page, not past-paper questions. They cover the skills practical questions tend to test: variables, calculations, anomalies, graphs and improvements.
BiologyA student investigates the effect of sugar concentration on the mass of potato cylinders. Identify the independent variable and one control variable.+
Independent variable: the concentration of the sugar solution. A control variable could be the length or surface area of the potato cylinders, the volume of solution, the temperature or the time left in solution.
BiologyIn an osmosis investigation, a cylinder starts at 4.0 g and ends at 3.4 g. Calculate the percentage change in mass.+
(3.4 − 4.0) ÷ 4.0 × 100 = −15%. The negative sign shows the cylinder lost mass, so water moved out of the cells.
BiologyExplain why a student repeats each light intensity three times in the photosynthesis practical.+
Repeats allow a mean to be calculated, which reduces the effect of random error, and they make anomalous results easier to spot so they can be excluded.
ChemistryA student's rough titre is 25.90 cm³ and their next three titres are 24.85, 24.90 and 25.40 cm³. Which values should they average, and why?+
Average 24.85 and 24.90 cm³ because these are concordant, within 0.10 cm³ of each other. The rough titre and the 25.40 cm³ result are excluded as they are less accurate.
ChemistryIn a rates investigation, 48 cm³ of gas is produced in 40 seconds. Calculate the mean rate of reaction.+
48 ÷ 40 = 1.2 cm³/s.
ChemistryA spot travels 3.6 cm while the solvent front travels 8.0 cm. Calculate the Rf value.+
Rf = 3.6 ÷ 8.0 = 0.45. Rf has no units and is always between 0 and 1.
ChemistrySuggest why the temperature rise measured in a polystyrene cup is smaller than the true value.+
Some energy is transferred to the surroundings, to the cup and to the thermometer, so less energy warms the solution than the reaction actually releases.
PhysicsA student plots force against extension for a spring. The graph is straight up to 6.0 N and then curves. Explain what the curve shows.+
The straight section shows extension is directly proportional to force. The curve begins beyond the limit of proportionality, where the spring extends more per newton and may be permanently deformed.
PhysicsA resistance value at 80 cm is well above the line of best fit. Suggest one reason for this anomaly.+
The wire may have heated up because the circuit was left switched on, raising its resistance; alternatively the crocodile clip was misread or contact at the clip was poor.
PhysicsA 0.50 kg block is heated with 12 000 J and rises by 48 °C. Calculate the specific heat capacity.+
PhysicsSuggest one improvement to the acceleration practical that would reduce random error.+
Use light gates and a data logger instead of a stopwatch, which removes human reaction time from the timing, and repeat each force to calculate a mean acceleration.
BiologyA results table shows the cross disappeared in 42 s, 44 s and 78 s at the same concentration. Explain what the student should do.+
Treat 78 s as an anomaly, exclude it from the mean and, if possible, repeat that run. The anomaly may be caused by a misjudged end point, a wrong volume or a different observer.
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AQA GCSE Required Practicals FAQs
What are GCSE required practicals?+
They are the practical activities AQA states every student must carry out during the course. There is no separate practical exam at GCSE: instead, the written papers include questions that draw on the knowledge, skills and understanding you gained from doing them.
How many AQA GCSE Biology required practicals are there?+
The AQA GCSE Biology (8461) specification lists ten required practical activities. Seven of them are shared with GCSE Combined Science, while practicals 2, 8 and 10 are on the separate Biology specification only.
How many AQA GCSE Chemistry required practicals are there?+
The AQA GCSE Chemistry (8462) specification lists eight required practical activities. Titration, identifying ions and water purification appear on the separate Chemistry specification rather than Combined Science.
How many AQA GCSE Physics required practicals are there?+
The AQA GCSE Physics (8463) specification lists ten required practical activities, of which thermal insulation and the light practical are on the separate Physics specification only.
Do required practicals appear in GCSE exams?+
AQA states that written papers include questions requiring knowledge gained from carrying out the specified practicals. The exact questions vary from paper to paper, so no one can tell you which practical will come up or how many marks it will carry.
How should I revise required practicals?+
For each practical, be able to state the aim, outline the method in order, identify the independent, dependent and control variables, describe what the results show, do any calculation involved and suggest one improvement. Then self-test rather than re-reading, which is where flashcards and exam-style questions help.
Are required practicals the same for every exam board?+
No. Every board has to cover the same underlying apparatus and techniques requirements, but the named practical activities and their wording differ between AQA, Edexcel and OCR. Use the list that matches the specification you are entered for.
Where can I check the official list?+
AQA publishes the required practical activities in the practical assessment section of each specification, and provides a required practical handbook with suggested methods. Always treat AQA as the authoritative source for the current list.