Thinking and Working Scientifically: Carrying out scientific enquiry

Carrying out any scientific enquiry begins with safety. Before you start an experiment, you must assess the risks involved. This means identifying potential hazards and taking specific precautions to prevent harm to yourself and others. Common laboratory rules include wearing eye protection, tying back long hair, clearing your workspace, and never eating or drinking. It's also vital to understand hazard symbols, which are visual warnings about the dangers of certain chemicals. For example, a substance might be corrosive (damages skin/eyes), flammable (catches fire easily), or toxic (poisonous if ingested, inhaled, or absorbed).

To get reliable results, you must select the right tool for the job. The piece of equipment you choose depends on the quantity you are measuring and the precision required. For measuring the volume of a liquid, a 25 cm³ pipette is very precise for delivering a fixed volume, a burette is very precise for delivering variable volumes, while a 100 cm³ measuring cylinder is less precise but suitable for larger, approximate volumes. For measuring time, a digital stopwatch is usually sufficient, but for very fast events, light gates connected to a timer provide much greater precision. Always consider the resolution of the instrument – the smallest change it can detect.

Accuracy is about how close your measurement is to the true value. To ensure accuracy when carrying out an experiment, you need to minimise errors. One common source of error is parallax error, which occurs when you read a scale from an angle instead of directly at eye level. Always position your eye level with the marking on the scale, for example, the bottom of the meniscus in a measuring cylinder. Another issue can be zero error, where an instrument doesn't start from exactly zero. Always check your balance or stopwatch before use. The best way to increase the reliability of your data is to take repeat readings. This allows you to spot any anomalous results (readings that don't fit the pattern) and calculate a mean (average), which is likely to be more accurate than any single measurement.

As you carry out your experiment, you must record your findings systematically. This includes both qualitative observations (descriptions) and quantitative measurements (numbers). For quantitative data, a well-structured table is essential. A good table has clear column headings stating the quantity being measured and its units (e.g., 'Temperature / °C'). The independent variable (what you change) goes in the first column, and the dependent variable (what you measure) goes in the following columns. Use a ruler to draw neat lines. If you take repeat readings, include separate columns for each repeat and a final column for the calculated mean. Qualitative observations, such as colour changes or fizzing, should be written down as clear, concise notes using precise scientific language (e.g., 'effervescence observed' instead of 'it bubbled').