Required practicals are tested on every AQA GCSE Physics paper. For Paper 1, there are four practicals you need to know: specific heat capacity, resistance of a wire, I-V characteristics and density. At least one of these will come up as a 4 to 6 mark question, and it will almost never be asked as straightforward recall. The examiner will present the practical in an unfamiliar context and ask you to evaluate the method, identify variables, suggest improvements or interpret results.
This applies to both Triple Science (8463) and Combined Science (8464). The practicals and the exam technique required are the same for both.
The marks go to students who understand why each step is done, what the variables are, and how to identify and fix problems with the method. Read the question carefully, identify the command word, and structure your answer around what is actually being asked rather than writing out the full method from memory.
Practical 1: Specific heat capacity
Aim
To determine the specific heat capacity of a material, typically a metal block.
Equipment
- Metal block
- Electric heater
- Thermometer or temperature probe
- Insulation (to wrap the block)
- Stopwatch
- Balance
- Ammeter (in series)
- Voltmeter (in parallel)
- Power supply
Method
- Measure the mass of the metal block using a balance.
- Insert the heater and thermometer into the holes in the block.
- Wrap the block in insulation to reduce heat loss to the surroundings.
- Set up the circuit with the ammeter in series and the voltmeter in parallel across the heater.
- Record the starting temperature.
- Turn on the power supply and start the stopwatch simultaneously.
- Heat the block for a measured time, typically around 10 minutes.
- Record the voltage, current, final temperature and time taken.
- Calculate the energy transferred using E = IVt.
- Calculate specific heat capacity using c = E divided by (m multiplied by the temperature change).
Variables
- Independent variable: time or energy supplied
- Dependent variable: temperature increase
- Control variables: mass of block, insulation used, starting temperature
Why is the block wrapped in insulation? To reduce heat loss to the surroundings, which would make the calculated specific heat capacity too high. Why is the ammeter placed in series? Because the ammeter must measure the current through the heater. Why is the voltmeter placed in parallel? Because it measures the potential difference across the heater only.
Practical 2: Resistance of a wire
Aim
To investigate how the length of a wire affects its resistance.
Equipment
- Resistance wire (nichrome or constantan)
- Power supply
- Ammeter
- Voltmeter
- Metre ruler
- Crocodile clips
Method
- Set up the circuit with the ammeter in series and the voltmeter across the wire being tested.
- Attach one crocodile clip at 0 cm.
- Place the second crocodile clip at 10 cm.
- Turn on the power supply briefly and record the current and voltage.
- Calculate resistance using R = V divided by I.
- Move the second crocodile clip to 20 cm, 30 cm, 40 cm and so on.
- Repeat the readings at each length and calculate an average.
Variables
- Independent variable: length of wire
- Dependent variable: resistance
- Control variables: wire material, thickness and temperature
Expected result: resistance increases as wire length increases because electrons collide more often in a longer wire.
Why should the power supply be turned off between readings? To prevent the wire overheating, which would increase resistance and make the results unreliable. Why is temperature a control variable? Because resistance increases with temperature, so if the wire heats up during the experiment the results would not be valid.
Practical 3: I-V characteristics
Aim
To investigate the relationship between current and voltage for different electrical components.
Equipment
- Power supply
- Ammeter
- Voltmeter
- Variable resistor
- Resistor, filament lamp and diode (tested separately)
Method
- Build the circuit with the component being tested, the ammeter in series and the voltmeter in parallel across the component.
- Use the variable resistor to adjust the voltage across the component.
- Record the current and voltage at several different settings.
- Plot current on the y-axis against voltage on the x-axis.
- Repeat the experiment for each component.
Expected results
- Resistor: straight line through the origin, showing current is directly proportional to voltage and resistance is constant
- Filament lamp: curved line, because resistance increases as the filament heats up
- Diode: current only flows in one direction, above a threshold voltage
Variables
- Independent variable: voltage (adjusted using the variable resistor)
- Dependent variable: current
Why does the filament lamp graph curve? Because as the filament heats up, resistance increases, so the current does not increase proportionally with voltage. Why is a variable resistor used? To change the voltage across the component and collect a range of current-voltage readings. What does a straight line through the origin tell you? That the component is ohmic and resistance is constant.
Practical 4: Density
Aim
To determine the density of regular and irregular solid objects.
Equation
Density = mass divided by volume.
Part A: Regular object
- Measure the mass of the object using a balance.
- Measure the dimensions using a ruler or calipers.
- Calculate volume using length multiplied by width multiplied by height.
- Calculate density using the equation.
Part B: Irregular object (Eureka can method)
- Measure the mass of the object using a digital balance. Zero the balance before placing the object on it.
- Fill the displacement can (Eureka can) with water until water drips out of the spout. Wait for the dripping to stop completely before proceeding.
- Place an empty measuring cylinder under the spout to collect the displaced water.
- Tie a thread around the object and carefully lower it into the Eureka can until it is fully submerged.
- The water displaced into the measuring cylinder is equal to the volume of the object. Record this volume.
- Calculate density using density = mass divided by volume.
An irregular object cannot have its volume calculated from measurements alone because it has no simple geometric shape. The Eureka can uses water displacement to find the volume directly. The key is waiting for the initial dripping to stop before placing the object in, otherwise the volume reading will be inaccurate. The thread ensures the object is fully submerged and can be removed cleanly without splashing water out of the can.
Variables
- Independent variable: the object being tested
- Dependent variable: density calculated
Why must the irregular object be fully submerged? Because if it is only partially submerged the volume of water displaced will not equal the full volume of the object. Why use a displacement method rather than measuring dimensions? Because the object is irregular and cannot be measured directly with a ruler to calculate volume.
Exam technique for practical questions
Required practical questions follow predictable patterns. The examiner is not just checking that you know what you did in the lab. They are checking whether you understand why the method works, what could go wrong, and how to improve it. The answers below come up repeatedly across every series.
Why is insulation used in the specific heat capacity practical? To reduce heat loss to the surroundings, which would make the results less accurate.
Why should readings be repeated? To improve reliability, identify anomalous results and calculate a mean.
Why must control variables be kept constant? To make the experiment a fair test and to ensure any change in the dependent variable is caused only by the independent variable.
How could the accuracy of this experiment be improved? Use more precise equipment, reduce human error, or use digital sensors instead of manual readings.
Accuracy, repeatability, reproducibility and validity
These four terms appear regularly on practical questions, often in a "suggest improvement" or "evaluate the method" context. Getting them right and using them correctly in answers is one of the most reliable ways to pick up marks on practical questions.
Accuracy
Accuracy describes how close a result is to the true or accepted value. A result is accurate if it agrees with the known value for that measurement.
- Water boils at 100 degrees Celsius. A measured result of 99.8 is accurate.
- Using a digital balance gives more accurate mass readings than an analogue one.
In exam answers: "The results are accurate because they are close to the accepted value." Or: "Using more precise equipment improves accuracy."
To improve accuracy: use more precise equipment, reduce human error, use digital sensors instead of manual readings. Examples of more accurate equipment include a burette instead of a measuring cylinder, a light gate instead of a stopwatch, and a digital thermometer instead of a standard one.
Repeatability
Repeatability means the same person, using the same equipment and the same method, gets similar results each time they repeat the experiment.
- A student repeats an experiment three times and gets 42 s, 43 s, 42 s. These results are repeatable.
In exam answers: "The experiment was repeated to check repeatability." Or: "Results are repeatable because similar values were obtained each time."
To improve repeatability: repeat the measurements, calculate a mean, identify and ignore anomalies.
Reproducibility
Reproducibility means different people, using different equipment, still obtain similar results when they carry out the same experiment independently.
- Different groups in different schools carry out the same experiment and get similar results. This shows the experiment is reproducible.
In exam answers: "The experiment is reproducible because different groups obtained consistent results." Or: "Independent repeats produced similar values."
To improve reproducibility: allow other groups to repeat the experiment using different equipment and labs.
Validity
Validity means the experiment is a fair test and actually measures what it is supposed to measure. A valid experiment changes only the independent variable while keeping all other variables constant.
- Testing the effect of wire length on resistance: if only the length changes and all other factors such as material, thickness and temperature are kept the same, the experiment is valid.
- If temperature also changes during the experiment, the test is less valid because it is not clear whether the change in resistance is caused by length or temperature.
In exam answers: "The experiment is valid because only the independent variable was changed." Or: "Control variables were kept constant throughout."
To improve validity: control all variables except the one being investigated, keep conditions constant, and use the same method each time.
Results can be repeatable but still inaccurate. If a ruler is broken and always measures 2 cm too long, the results will be consistent every time, making them repeatable. But they will not match the true value, so they are not accurate. Examiners use this kind of example specifically to check whether students understand the difference between the two terms.
Quick reference: improvement answers by term
When a question asks how to improve an experiment, the answer depends on which quality is being asked about:
- To improve accuracy: use more precise equipment, reduce human error, use digital sensors
- To improve repeatability: repeat the experiment, calculate a mean, identify and exclude anomalies
- To improve reproducibility: allow different groups to repeat the experiment independently with different equipment
- To improve validity: control all variables except the independent variable, keep all conditions constant, only change one variable at a time
For the Physics Paper 1 practicals, the specific heat capacity practical is the one most commonly examined in depth because it involves the most variables, the most potential sources of error and the most opportunities to ask about circuit setup. Make sure you can explain the purpose of every piece of equipment in that experiment and the effect of any source of error on the final calculated value.
