Designing: notes and practice questions
- This topic covers the skills required to design scientific investigations, including formulating research questions and planning experimental procedures.
- Design investigations that may involve hands-on laboratory experiments, databases, simulations, or modelling.
- Identify and justify the choice of dependent, independent, and control variables.
- Justify the range and quantity of measurements for an investigation.
- Design and explain a valid methodology, including piloting procedures.
- Appreciate when and how to calibrate measuring apparatus and maintain constant environmental conditions.
- Recognize and address relevant safety, ethical, or environmental issues in an investigation.
How it is examined
Paper 1B. The recurring shape is "explain why the student chose X". May 2025 Paper 1B TZ1 question 3(a), 2 marks, gave three coil separations and asked which to pick: the answer was r, because it gives the most uniform field between the coils, with the second mark for saying what is wrong with 2r or 0.5r. Answer plus reason, one mark each, is the standard 2-mark design question.
- Demonstrate creativity in the designing, implementation and presentation of the investigation.
- Develop investigations that involve hands-on laboratory experiments, databases, simulations and modelling.
- Identify and justify the choice of dependent, independent and control variables.
- Justify the range and quantity of measurements.
Practice questions
3 questions · 3 mediumQuestion 1
MediumPaper 2 · calculator5 marksIn a blacksmith's workshop, a 2.00 kg iron horseshoe is heated in a furnace. It is then plunged into a large, insulated barrel containing 5.00 kg of water at 15.0 °C. The system reaches a final equilibrium temperature of 100 °C, by which time 0.120 kg of the water has turned to steam.
(a) Calculate the initial temperature of the iron horseshoe.
Data:
Specific heat capacity of water = 4200 J kg⁻¹ °C⁻¹
Specific latent heat of vaporization of water = 2.26 × 10⁶ J kg⁻¹
Specific heat capacity of iron = 450 J kg⁻¹ °C⁻¹
(b) The barrel is made of wood, but in reality, it is not a perfect thermal insulator and will absorb some energy. Suggest and explain how this would affect the calculated value for the initial temperature of the horseshoe, assuming the calculation does not account for the barrel.
Apply the principle of conservation of energy. The total heat energy lost by the hot horseshoe must equal the total heat energy gained by the water. Remember that the water gains energy in two distinct ways: its temperature increases, and some of it changes state.
Consider all the places the energy from the hot horseshoe can go. In the ideal calculation, it only goes to the water. In the real experiment, where else does it go? How does this change the amount of energy that you thought the horseshoe lost, versus what it actually lost?
Question 2
MediumPaper 2 · calculator10 marksA student conducts an experiment to investigate the relationship between the period of a simple pendulum and its length . The student measures the time taken for 20 complete oscillations for various lengths of the pendulum string.
(a) State:
(i) the independent variable.
(ii) the dependent variable.
(iii) one variable that should be controlled.
(b) The student uses a digital stopwatch to measure the time. They have a consistent reaction time, starting the stopwatch 0.15 s after the pendulum bob is released from its highest point. State and explain whether this is a random or a systematic error.
(c) The student measures the time for 20 oscillations rather than for a single oscillation. Suggest why this experimental technique improves the measurement of the period .
(d) For a pendulum of length 1.00 m, the accepted value for the period is 2.01 s. The student takes three measurements of the time for 20 oscillations and calculates the period for each. The results are 2.15 s, 2.16 s, and 2.14 s. Distinguish between accuracy and precision, using the student's results as an example.
Think about what the student is deliberately changing, what they are measuring as a result, and what other factors could affect the outcome that need to be kept constant.
Does this error affect each measurement randomly, or does it introduce a consistent offset in one direction?
Consider the effect of the uncertainty in starting and stopping the timer. How does measuring a longer total time interval affect the fractional uncertainty of the final calculated period?
Accuracy relates to the 'true' value, while precision relates to the consistency of repeated measurements. How do the student's results compare to the accepted value and to each other?
Question 3
MediumPaper 1B · calculator4 marksA group of engineers is designing a new rectangular solar panel. They need to accurately determine its surface area. The dimensions of the panel are measured as length m and width m. The thickness of the panel's protective glass layer is measured as mm.
(a) Suggest an appropriate measuring instrument for determining the thickness .
(b) Calculate the percentage uncertainty in the calculated surface area of the solar panel.
Consider the precision required for the measurement of thickness. What instruments are typically used for small distances with high accuracy?
Recall how uncertainties combine when quantities are multiplied. The fractional uncertainties add.
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Where marks are lost
- Stopping one step short of the conclusion. Two numbers and no sentence is two marks out of three.
- Answering a procedure question with a platitude.
- Losing precision in Paper 1B. Uniquely to this paper, quoting the right number badly loses marks.
