Use of measuring instruments
It is important from the outset to ensure that students are familiar with and correctly use basic apparatus when, for example,
- reading volume,
- measuring length,
- mass, etc.
- They should be encouraged to take accurate readings, and to record all measurements, using appropriate units
It is by means of observation that we gain much information about the world around us. The skill of observation needs to be developed if students are to study natural phenomena and form opinions or make judgements about naturally occurring objects and events. Students should be encouraged to
(a) use all of their senses, each where appropriate
(b) assess quantitatively – size, weight, etc.
(c) note changes, patterns or trends
(d) observe only what is there and avoid making inappropriate inferences.
Classification can be used to show relationships between things or for identification purposes.
It is usually based on the fact that objects / substances / organisms / reactions share common characteristics or properties.
Students can classify by
• careful observation of objects or events
• identification of similar or dissimilar characteristics or properties
• grouping of objects or events on the basis of their observations of chosen characteristics or properties.
Examples might include
- classification of plants and animals,
- acids and bases,
- insulators and conductors.
Students should develop the ability to convey information accurately. Communication skills can be
(a) oral/aural: through discussion and verbal reporting of observations, facts and conclusions
(b) graphical: by use of diagrams, graphs, tables, etc.
(c) written: by recording observations, describing procedures (for example, steps taken in an experiment), recording results and conclusions.
For effective communication, information must be accurate and clearly presented, using the language
of science as appropriate. Students should be encouraged to develop their understanding and use
of correct scientific terms.
Planning and designing investigations
Designing investigations involves the application of a scientific method, which will in practice incorporate many, if not all, of the skills and processes of science. Initially, the teacher will have a central role to play in leading students, through guided discovery, to develop their own skills of planning and designing investigations.
An investigation involves a step-by-step procedure:
(i) defining the problem and forming a prediction or hypothesis
(ii) planning the investigation and controlling variables where appropriate
(iii) testing/carrying out the investigation and observing/recording
(iv) interpreting the results and drawing conclusions.
(i) Defining the problem/forming a hypothesis
The problem may arise from a number of sources, for example, observation, class discussion, previous
work, reading or from an everyday situation.
The student is required to think about or pose questions such as: ‘What might happen if ... ?’. For
example, if a student has been studying evaporation he/she may ask why some clothes dry more quickly
than others. This leads to other questions: is it the type of material?… is it the weather?, and so on.
From these questions it may become clear that there are a number of factors (variables) involved.
The student cannot test all of these together, so a hypothesis may be stated; for example, the type of
material affects the evaporation rate.
(ii) Planning the investigation/identifying and controlling variables
The student must now decide how the hypothesis will be tested or investigated, and select the appropriate apparatus and procedures. Thus, continuing with the ‘clothes’ example above, to measure the rate implies timing how long it takes for the materials to dry.
It is important for the student to understand the concept of a fair test. Suppose the student hung a nylon sheet outdoors and a matching cotton sheet indoors and, having observed both over a period of time, found that the nylon sheet dried first. What conclusions can the student draw? Why did the
nylon sheet dry first – was it the nature of the material as was first suggested or had the temperature, sunlight or wind any influence?
These questions cannot be answered, since there are too many variables; that is, it was not a fair test. The relevant variables must be noted and controlled. In this investigation the student should have placed
both materials in identical conditions of sunlight, temperature, breeze, etc. Any difference in drying
time, and thus evaporation rate, can then be attributed to the nature of the material, which is the
only other variable.
It should be noted that the question of multiple variables may not always arise.
(iii) Testing/carrying out the investigation/ recording data
This involves carrying out the required practical procedures using suitable apparatus correctly and with due regard to safety. Appropriate measurements and/or observations must be made and recorded accurately. Results need to be organised and presented clearly so that their meaning can be evaluated. Use of tables, trend graphs and bar charts may help in the recording of the data or observations.
(iv) Interpreting results and drawing conclusions
To interpret or explain the results the student should
(a) look for common patterns or trends, or relationships between factors or variables
(b) relate results or patterns to prior knowledge
(c) relate results to the original hypothesis
(d) generalise where necessary.
The student should then be able to reach a conclusion.
In some cases the results may be inconclusive, so it may be necessary to re-examine the methods used or carry out further investigations