Primary science assessment item setters’ misconceptions concerning the state changes of water

Discussion

The example assessment items discussed in this paper demonstrate some of the misconceptions perpetuated by teachers and question setters concerning basic physical science phenomena:

Confusion between the everyday use of terms such as freezing and boiling and the scientific use of these terms;
The processes of freezing, melting and boiling involve a change in temperature;
Water and ice cannot exist at the same temperature;
Water and steam cannot exist at the same temperature;
The narrow range of understandings in any given situation, for example, not recognizing that evaporation of water and melting of ice take place simultaneously at 0°C;
Evaporation of water requires the body of water or the surrounding air to be at some minimum temperature;
When salt is added to crushed ice surrounding a test tube containing a small amount of water, the resultant lower temperature in the ice-salt mixture is always low enough to cause freezing of the water in the test tube;
When salt is added to crushed ice then there is a fixed drop in temperature irrespective of the proportion of salt in the mixture.

Whilst some of the misconceptions may be due to poor item crafting - particularly the failure to see all the possible perspectives that the pupils might see, it must be assumed that many of them are deeply held and will therefore be reflected in classroom instruction. This would support the suggestion by many researchers that teachers can be the source of many of the misconceptions held by pupils.

Many in-service teachers at the primary level either do not have a science background or are only practising science teaching for a small part of their time. It is probably therefore beneficial for primary teachers to attend occasional practical science workshops where they could work through the standard experiments that demonstrate the key science concepts that are giving problems to some teachers. For example they could carry out temperature recordings through state changes and be convinced that freezing and boiling take place without change in temperature.

Poorly crafted assessment items not only invalidate the assessment process but disadvantage pupils, particularly the more creatively able, who are often able to see the correct concept or see alternate views of the problem not considered by the question setter but who have no means in an MCQ to convey their understanding. Because of the authoritative nature with which assessment items are regarded, such items may either reinforce already held misconceptions amongst pupils or, worse, introduce misconceptions where previously correct conceptions were held.

It is recommended that all test items be subject to rigorous quality review to ensure correct expression of science concepts both in the question stem and in the offered options of the MCQs. Quality review is particularly important in the case of MCQs which provide no means for the pupil to express alternate ideas to those held by the question setter and articulated in the question. In many schools, external review has been demonstrated to be highly cost effective in surfacing teacher misconceptions and improving the quality of assessment items.