Learning in the laboratory

In the science and engineering fields a good understanding of the practical aspects of the discipline is essential. It is contended that if students are stimulated to critically evaluate the processes/techniques employed in a laboratory exercise, then they will understand more fully the rationale behind these processes. This should also lead to better practical skills and a better understanding of the concepts involved in the exercise. Short laboratory test were introduced in an attempt to stimulate students to critically evaluate the experimental processes and concepts involved in each laboratory exercise. The effectiveness of the practice of using laboratory tests will be discussed.

Introduction

Laboratory tests

A well constructed laboratory test can require observations, details of technique, explanations, inferences, generalisations, predictions, calculations and anything else that is pertinent. The questions in the test should require the student to demonstrate an understanding of the experiment. For example, consider an experiment in which students were asked to add five millilitres of dilute sulfuric acid to a reaction flask. To encourage the students to think about the function of the acid, one could ask a question relating to the degree of accuracy required in measuring the volume of acid, or whether another acid could be used instead. If the questions are trivial, then there is no stimulus for the student to perform at a higher level. Students are still required to prepare and submit laboratory reports but they are not examined in detail. Instead an aspect of the report is examined and the results of the experiment are usually included as part of the laboratory test assessment.

The intended outcomes of using laboratory tests included:

• students would work harder during the experiment in an effort to gain as much information as possible to answer potential test questions.

• Students would gain a better understanding of the chemistry involved in the experiments.

• Students would learn to link laboratory practices to theory.

• The tests would provide a focus of the main points of the experiment.

• The tests would be a useful form of rapid feedback for both the student and the instructor.

• Tests would be a fairer form of assessment. Laboratory marks would be based on the students' understanding of the laboratory, not on their ability to produce write-ups.

• Laboratory work would be easier to mark.

Evaluation

The response to question two was of serious concern. The low score was probably due to the added stress caused by having the tests at the end of the laboratory class (see also question ten). Many students indicated (in Part B) that they had to rush the experiment and had no time to digest the information gained during the experiment. Many of these students also indicated that they would have preferred to do the test in the following laboratory class. The level of discussion relating to the experiment in the classes with laboratory tests seemed to be higher than in those without the tests. Furthermore, students in classes which had weekly laboratory tests asked more questions of the laboratory supervisor and a greater proportion were directed towards an understanding of the concepts involved. These observations are in agreement with the student responses to questions 5-7.

The open ended questions in Part B gave a clearer indication of some of the opinions/concerns of the students. Approximately 60% of the survey forms have been analysed to date and some of the more common responses are listed in Table 2 (the number of responses is given in brackets). The number of responses may exceed the number of survey forms as many students gave more than one point in response to some questions. It should also be noted that a response of 'no' to questions 13-15 is not necessarily a negative result as many of these students already perform at a high level (the students involved in this trial are among our top students).

In the main the comments were very favourable, with the most obvious criticism relating to the added stress caused by the tests. It is believed that by doing the tests in the following laboratory class, prior to commencing the new experiment, much of this stress will be relieved. Students will then have the week to go through their results and properly digest their data. Some students who severely criticised the laboratory tests indicated in an interview that they would be happy with the tests if they were administered the following week. Another criticism stems from the apparent lack of understanding by the students of the objectives of the laboratory tests. Many saw them as assessment tools for theory which was covered in lectures and did not recognise that the questions were directly related to the laboratory. This inability to associate laboratory experience with theory has also been observed by others (Stensvold and Wilson, 1992; Nakhleh, 1994). Some thought that the laboratory work carried out was not adequately rewarded, especially given their perception that the test were theory based. A pleasing aspect of the comments was the large number of times students indicated that the tests stimulated them to modify their behaviour for the better. These improvements included better preparation, more concentration, better attitude, deeper thought and understanding.

Conclusion

Acknowledgments

References

Simpson, P. (1993). A new approach to teaching and assessing practical work in upper school chemistry. Perth: Science Teachers' Association of Western Australia.

Stensvold, M. and Wilson, J. T. (1992). Using concept maps as a tool to apply chemistry concepts to laboratory activities. Journal of Chemical Education, 69, 230-232.