Paper 3 is two practical questions: an investigation to carry out, record and evaluate, and a microscope or photomicrograph question with a drawing and a calculation. Each paper below is rephrased from a real past paper, with realistic readings to process: answer it part by part, then compare with a worked full-mark answer and the examiner's comments.
The independent and dependent variables as they apply here, the standardised variables with how each is controlled, a control, and steps someone else could follow.
A table with headings and units, raw readings to a consistent precision, processed values such as rates or percentage changes, means of replicates.
Axes with labels and units, points plotted accurately, a line or curve that fits the data, and a conclusion that quotes the data.
Clear, sharp, unshaded drawings in proportion with ruled label lines; sources of error and improvements that fit this investigation; a risk assessment.
The questions on this page are rephrased from a Cambridge International past paper for teaching. The readings, figures, wording of the workout and the worked answers are our own; the marking follows the published mark scheme. The original question paper is available from Cambridge.