In the science and engineering fields a sound understanding of both the theoretical and practical aspects of the discipline is essential. It is contended that if students better prepare for a laboratory exercise, then they should understand more fully the rationale behind the processes, both at a practical level and in terms of the chemistry involved. This would naturally lead to better manipulative skills and perhaps a greater enjoyment of laboratory classes. In an attempt to encourage students to be better prepared, pre-laboratory questions were assigned to a class of first year chemistry major students. These were completed, submitted, marked and returned prior to the laboratory session. Many of the questions which caused problems were then addressed in the pre-laboratory lecture. Students were also encouraged to summarise the laboratory procedure in a flow chart. The results of an attitudinal survey are presented. The effectiveness of using pre-laboratory exercises in chemistry classes is discussed.
The laboratory course is designed to consolidate the lecture material and develop the students' manipulative skills. The various practical exercises are programmed to be carried out at a time after the relevant theory has been taught in the lectures.
The majority of the pre-laboratory instruction in the past has been in the form of a pre-laboratory lecture by the supervisor. This system has two main disadvantages:
In recent years, a program of post-laboratory testing has been implemented in this course by Dr Mauro Mocerino. These tests consisted of five short-answer type questions directly relating to the exercise. Students completed the test before leaving the laboratory. Students were permitted to refer to their laboratory manual and notes as much as they liked to complete the test. There was also no time limit imposed on the tests.
The pre-laboratory questions set in this study replaced the post-laboratory tests. Items were included in the survey to find out which form of assessment was preferred by students. Performance on other areas of assessment (ie. laboratory reports, mid-semester tests) may provide some indication of which form of assessment was more effective in encouraging students to understand the concepts involved in laboratory exercises.
A set of model answers were made available for the students to consult after they had handed in their own answers. Answers to the questions were discussed during the pre-laboratory lecture. Any common misconceptions which became apparent from students' answers were also addressed.
For the laboratory exercises relating to 1) Alcohols and Phenols, and 2) Aldehydes and Ketones, students were required to write out their own procedure, in any form they chose, from the given instructions. Students were not permitted to take the provided instructions into the laboratory, but completed the laboratory work by referring only to their own notes. These notes were collected at the end of the laboratory class and graded by the supervisor. This idea was developed by Pickering (1987).
In the first survey students were asked to respond to a series of statements by indicating how strongly they agreed with the statement. A scale of 1 to 5 was presented for each survey item (1=strongly disagree, 5=strongly agree) for the students to indicate their response. This survey was anonymous.
In the second survey, conducted one week later, students were asked to make written responses to six questions regarding the use of pre-laboratory exercises as part of the laboratory program and assessment. This survey was also anonymous.
The most significant results of the first survey are summarised below.
|1)||Answering the pre-lab questions helped me understand what was going on during the lab.||4.24||0.56|
|2)||I understand more of what was said during the pre-lab lecture after completing the pre-lab questions.||4.21||0.68|
|3)||The instructions in the lab manual made more sense after answering the pre-lab questions.||3.92||0.82|
|6)||The pre-lab questions made me think about what I was going to be doing in the lab and why.||4.02||0.61|
|13)||I preferred completing the pre-lab questions to doing lab tests like last semester.||4.01||1.22|
|14)||On average, I spent more time answering the pre-lab questions than I did studying for the lab tests last semester.||4.16||1.00|
|15)||Having done the pre-lab questions made writing the lab report easier.||4.08||0.70|
|16)||I felt more confident of what I was doing in the lab this semester.||3.86||0.74|
|17)||I enjoyed lab classes more this semester.||3.77||0.82|
|18)||I preferred writing my own procedure for the lab to answering pre-lab questions.||2.52||1.01|
|19)||Writing my own procedure made it easier to complete the lab.||3.12||0.99|
The very positive responses to items 1), 2), 3) and 6) on the survey were particularly encouraging. It seems that the pre-laboratory questions did achieve their aim of encouraging the students to think through the laboratory procedure before coming to the laboratory.
The response to question 14) suggests that pre-laboratory assignments are time consuming. However a majority of students agreed that completing the pre-laboratory questions made writing the laboratory report easier (question 15).
The students participating in this survey clearly preferred answering pre-laboratory questions to completing post-laboratory tests (question 13).
The response to questions that delt with the students writing their own procedures (questions 18 and 19) was fairly neutral. It does not seem from the survey that students objected to the idea, but a considerable amount of nervousness was observed during the laboratory sessions.
Questions 16) and 17) suggest a positive change in the students' attitude toward laboratory work. This is perhaps the most significant result.
Student responses to the questions in the second survey are summarised below.
|1) Do you enjoy laboratory work?||Yes|
|2) On average, how much time did you spend
each week doing the pre-lab?
|Do you consider answering pre-labs time consuming?||Yes|
-Prelabs took time but were worthwhile
|3) Did answering pre-lab questions add a lot of stress to laboratory
work? If so, how could this be avoided?
- Prelabs actually made labs less stressful
|4) Would you prefer the pre-labs to be worth more marks
toward your laboratory grade? Why?
|Yes because...||No because...|
|a lot of time was spent doing prelabs||13.3%||prelabs were too difficult||8.9%|
|it tests understanding of the lab||13.3%||lab write-ups are more important||11.1%|
|it would avoid a bad lab mark if|
something went wrong in the lab
|8.9%||the lab is better understood after doing it||6.7%|
|5) Would you be happier to do pre-labs if you were not
required to submit a lab report each week?
|6) Do you consider pre-labs a better form of assessment
than lab reports or post-lab tests? Why?
|Yes because...||No because...|
|prelabs helped understanding||11.1%||only understand the lab properly afterwards||13.3%|
|prelabs helped prepare for lab||13.3%||post-lab work shows what you've learnt from labs||4.4%|
|no stress about whether or not|
the experiment will work
|13.3%||prelabs only test theory||4.4%|
The response to question 2) is of some concern. It was not intended that the pre-laboratory exercises would take an average of more than one hour for 70% of students, although a number of students indicated that this time was time well spent because it made laboratory work easier and more understandable.
The overwhelming response to question 3) was that doing pre-laboratory questions did not increase the stress associated with laboratory work. On the contrary, many students commented that having answered the pre-laboratory questions actually reduced the amount of stress in the laboratory.
The response to question 4) shows that students are very nervous about their mark in laboratory work. Students want the type of assessment at which they have the best chance of success to be worth the most marks toward their overall grade.
It was expected that the response to question 5) would be overwhelmingly in favour of abandoning laboratory reports. This was not the case. Very little explanation of this response was offered by students.
Students' response to question 6) again showed their fear of failure in the laboratory, as a major reason given for preferring pre-laboratory exercises over laboratory reports as a form of assessment was that the resulting grade was not affected by mistakes in the laboratory, and a major reason for not preferring pre-laboratory questions was that students had not yet understood the laboratory exercise (ie. would not get a good mark on the pre-laboratory exercise).
Probably the most significant result is that students' attitude towards laboratory work changed. Attitude is important in determining how much effort students put into their work and, as a result, how much learning actually takes place in the laboratory.
In order to reduce the time pressure placed on students as a result of completing pre-laboratory exercises, the assignments could be reduced to only three or four pertinent questions. The survey could be used again to try to ascertain whether or not reducing the number of pre-laboratory questions was successful in reducing the amount of work required by students.
Pickering, M. (1987). What Goes on in Students' Heads in Lab? Journal of Chemical Education, 64(6, June), 521-523.
|Please cite as: Barnes, R. and Thornton, B. (1998). Preparing for laboratory work. In Black, B. and Stanley, N. (Eds), Teaching and Learning in Changing Times, 28-32. Proceedings of the 7th Annual Teaching Learning Forum, The University of Western Australia, February 1998. Perth: UWA. http://lsn.curtin.edu.au/tlf/tlf1998/barnes.html|