Measurements and recording

Choose apparatus for the needed measurement: a volumetric pipette delivers a fixed accurate volume, a burette delivers a variable accurately measured volume, a measuring cylinder is suitable for less exact volume work, and a balance measures mass. Read the scale at eye level to avoid parallax; use the bottom of the meniscus for a clear aqueous solution unless the instructions specify otherwise.

For Secondary Chemistry, the syllabus normally expects burette readings to the nearest 0.05 cm³, and sufficient titrations to obtain, for a good end-point, two titres within 0.20 cm³. Record both readings and the difference. Follow the question if it gives a particular agreement criterion; do not include the rough titre in a precise mean.

Separate raw observations from interpretation. "A white precipitate forms after three drops and dissolves in excess" preserves information that "positive test" loses. Record colour, physical state, changes on standing or warming, and any confirmed gas test. Put units in table headings; do not attach a unit to a pure ratio.

For a temperature-change experiment, measure a stable starting temperature, combine the stated quantities, stir consistently and follow temperature with time. Use a suitable thermometer or probe, keeping it immersed appropriately without resting on the vessel. A lid and insulation reduce exchange with the surroundings. Do not treat a single late reading as the maximum change if the mixture has already cooled.

A temperature rise indicates energy transferred to the measured surroundings in an exothermic process; a fall indicates an endothermic process under comparable conditions. To compare reactions fairly, account for the amounts reacting and the mass being warmed, rather than ranking enthalpy changes by temperature rise alone.