Chemistry practical: planning and precautions

Planning is its own assessed skill in G3 Chemistry (about 15% of the practical paper). A strong plan controls the right variables, sets out a method someone else could follow, says what to measure and how, and names sensible precautions.

Identify the variables

Start by naming the independent variable (what you change), the dependent variable (what you measure), and the controlled variables (what you keep the same to make it a fair test). Getting these right is the backbone of a planning answer — most marks hinge on a genuinely fair comparison.

Write a method someone could follow

Set out clear, ordered steps: what apparatus, what quantities, what to do, and in what order. Choose apparatus that fits the precision you need — a burette or pipette for accurate volumes, a balance reading to 0.01 g for mass. State how many readings and that you'll repeat for reliability.

Say what to measure and how

Be specific about the measurement: the quantity, the instrument, the units, and the precision (for example, burette readings to the nearest 0.05 cm³). Mention how you'll process the data — a table, a graph, an average of concordant results — so the plan leads to a conclusion, not just raw numbers.

Precautions and safety

Name precautions that improve accuracy (avoid parallax error, rinse the pipette, allow apparatus to reach room temperature) and safety measures suited to the chemicals (eye protection, handling acids and alkalis with care, working in a fume cupboard for harmful gases). Precautions should be relevant to this experiment, not a generic list.