Cause and Effect – Observing

Scientific inquiry usually begins when someone notices something and asks why it happens. An observation is information gathered directly through the senses or through an instrument, such as the reading on a balance or a photograph taken through a microscope. An inference is an interpretation or explanation that goes beyond what was directly detected. Inferences are valuable because they propose possible causes, but they must be tested, because one observation can often be explained in more than one way.

Scientific ideas are tested by asking what we would expect to observe if they were true and checking that against evidence, so a careful investigator records what was seen before deciding what it means.

Qualitative observations describe properties in words: colour, smell, texture, behaviour or the shape of a pattern. Quantitative observations are numerical and carry a unit, such as 23.5 °C or a count of 14 slaters. Qualitative data is quick to collect and captures features that are hard to measure, such as the way a flame flickers, but it depends on the observer and is hard to compare.

Quantitative data supports calculation, graphing and comparison between trials and between groups, but it records only the variables the investigator chose to measure. Strong investigations usually collect both kinds, using qualitative notes to explain unexpected numbers.

In this module you conduct a practical investigation that records both kinds of data, then a second activity describing something such as cells under a microscope, rock layers, a falling object or the properties of acids and bases. These notes explain the ideas and give practice, but they cannot replace the hands-on investigations your school runs; your teacher sets the actual tasks, equipment and safety procedures.