Practical measures for practical work

There is something about reading old educational literature that is simultaneously reaffirming and depressing. Reading a point of view from over three decades ago that confirms your current thinking belies the notion that you are jumping on “the latest fad”, while the fact that it is still an issue for discussion three decades later makes you wonder about the glacial rate of change in educational approaches.

Education in Chemistry published a series of articles on practical work by Alex Johnstone. This article from 1982 sets the scene:

It is not uncommon in undergraduate laboratories to see students working as fast as possible just to get finished, with little or no thought about what they are doing.

Students, he argues, see practical work as “an intellectual non-event”. Johnstone used this article to elaborate on his hypothesis that practical classes presented a significant challenge to students, because the idea being taught is simultaneously needed at the start of the practical to organise the information presented in the class. In the lab, they need to recall the theory of the lab, remember how to use apparatus or read new written instructions about apparatus, develop new lab skills, listen to verbal instructions, and process whatever experimental data the experiment produces. It is difficult to discern which of this information is immediately important, and which is incidental.

Information overload in a lab environment (from Education in Chemistry, 1982)
Information overload in a lab environment (from Education in Chemistry, 1982)

The result is that students will follow the laboratory procedure like a recipe, without any intellectual engagement. Or they might take unnecessary care so that they won’t regret any experimental actions later – for example using an analytical balance when only a rough estimate was needed. Or they might go all British Bake Off Technical Challenge and just look around and copy others, without knowing why they are doing what they are mimicking.

Johnstone makes an interesting point which I don’t think I have seen elsewhere. When we lecture, we start off from a single point, elaborating with examples and developing connections. However, in practical work, students are exposed to all information at once, and must navigate their own way through to find the main point, often obscured. He used the idea of a pyramid and inverted pyramid to model these approaches.

Different approaches in class work and practical work (Johnstone and Wham, from Education in Chemistry, 1982)
Different approaches in class work and practical work (Johnstone and Wham, from Education in Chemistry, 1982)

Teaching strategy

How then can this information overload be alleviated? Johnstone provides some examples, including

  • making the point of the experiment clear;
  • a consideration of the arrangement of instruction manual so that it is clear what information is preliminary, peripheral, and/or preparatory.
  • ensuring the experiment has not acquired confusing or irrelevant aspects – this resonated with me from experience: some experiments involve students making a series of dilutions and then performing experiments with this series. Students spend so much time considering the process of dilution (preparatory), this becomes the main focus, rather than the main purpose of the experiment. This involves thinking about the goals of the experiment. If it is required that students should know how to prepare a dilution series (of course it is), then that should have primary prominence elsewhere.
  • ensuring necessary skills are required before exposure to investigative experiments.

A new manual

in 1990, Michael Byrne from what was then Newcastle Polytechnic decided to put Johnstone’s ideas into practice and reported on a new first year manual with the following design considerations:

  1. Experiments included a brief introduction with key information needed to understand instruments and the principle behind the experiment.
  2. Objectives were explicitly stated, indicating exactly what the student should be able to do as a result of carrying out the experiment.
  3. The language of procedures was simplified and laid out in sequence of what he student was meant to do.
  4. Information was provided on how to present results and what the discussion should cover. Students were prompted as to how they should query their results.

These ideas aren’t exactly what we would consider radical now, but students were tested after five weeks and those using the revised manual scored significantly higher in tests about techniques and results of experiments than those who had the old manuals.

Tenacious J

In 1990s, Johnstone continued his attempts to effect change in our approach to practical teaching. In 1990, he discussed the use of student diaries to record views on their lab experiences during their second year at university. The diary consisted of short response questions that the student completed after each practical. The responses were analysed iteratively, so that the experiments could be grouped into layers of criticism. Unsurprisingly, physical chemistry experiments came out as the most unpopular. My poor subject.

Why were they unpopular? Johnstone analysed the “load” of each experiment  – the amount of information they had to process, recall, digest and interrelate in the three hour period. I’ve reproduced his table below:

Load caused by experiments, Johnstone and Letton, Education in Chemistry 1990
Load caused by experiments, Johnstone and Letton, Education in Chemistry 1990

The total load of physical chemistry experiments is much greater than the inorganic or organic labs, primarily due to theoretical aspects. Furthermore, those physical lab experiments which were subject to most criticism had a theory load of 40, compared to the average physical lab theory load of 33. The result of this was evident in the student diaries: comments such as “not learned anything” and “no satisfaction” indicates that the students had not engaged with the experiment in any way.

Practical measures for practical work

In 1991, in the final of my trio of his articles here, Johnstone reported how he addressed the issues arising from the study of load in the manuals. Five strategies were considered:

  1. Noise reduction in the lab (noise meaning extraneous information): clearly labelled solutions, provided without need for further dilution unless required as part of experiment, highlighting where a particular procedure may differ from what students have previously experienced.
  2. Noise reduction in the manual: clearer layout of manual, with consistent icons, diagrams of types of balance beside instructions, etc. (this is 1991, people…)
  3. Allowing for practice: design of the overall practical course so that required skills are progressively developed.
  4. Time for thought: requiring students to prepare some of the procedure in advance of the lab as part of their pre-practical work – e.g. amounts to be measured out, etc.
  5. Time to piece it together: arranging the lab programme so that skills are developed in one week, used in a second week, and applied in a third week in a more open-ended lab that took about half an hour of lab time.

Johnstone’s trio of papers shown here show an impressive sequence of developing a theory as to why something has gone wrong, testing that theory with some analysis, and grounding an educational approach based on these findings. It’s one of the reasons I admire his work so much.


Michael S. Byrne, More effective practical work, Education in Chemistry, 1990, 27, 12-13.

A. H. Johnstone, A. J. B. Wham, The demands of practical work, Education in Chemistry, 1982, 19, 71-73

A. H. Johnstone, K. M. Letton, Investigating undergraduate laboratory work, Education in Chemistry, 1990, 27, 9-11.

A. H. Johnstone, K. M. Letton, Practical measures for practical work, Education in Chemistry, 1991, 28, 81-83

Related Posts:

2 thoughts on “Practical measures for practical work

  1. Michael
    There are many things which are depressing when you look back at old A, O and GCE papers.
    But I look back over practical work and see the same old chestnuts time and time again. If you look at my website (, you will see a page of pictures of old labs. Look at the equipment; it is easily recognisable. You could not say the same about biology.
    We are still oxidising alcohols with dichromate; does any organic chemist use this method still? CLEAPSS received the a note only this week to say that a measuring cylinder of the mixture exploded when being used
    I can make esters using acidic ion exchange resins as catalyst not conc sulfuric acid. Why are we still adding conc sulfuric acid to solid halides and using at as a test for halides.
    Why do we use a Bunsen burner to heat tertiary butyl chloride when it boils at 51C?
    We could do most aqueous chemistry on plastic sheets with instruction on the sheet to reduce cognitive overload on the working memory.
    Why are we cracking alkanes on a large scale with suck back issues when the microscale method I use is so safe and quicker too so that all the theory is covered in the lesson as well.
    Well the question setters are one area of concern They have never been to a CLEAPSS workshop for instance. The teachers are worried that if they use a new innovation, the students will not recognise the old method when it turns up on a paper. I know a lady in a 6th college who can refute all these issues because since going microscale on a lot of her work, the results have improved. I have loads of anecdotal but no concrete evidence for these claims. If you know Chris Lloyd of SSERC, he has used many of my techniques as well.
    Love the title of the blog. I am now calling mine “Is this supposed to happen?”

  2. Lovely post, I’m very taken with Johnstone’s work as well. Tomorrow’s first year class takes a lot from his macroscopic-microscopic-symbolic work as we’ll be looking at transition metal reactions starting from dissolving the solid in water then reacting it. It feeds into a practical class nicely (which is a microscale one done on plastic sheets!) and hopefully reduces some of the cognitive load.

Leave a Reply

Your email address will not be published. Required fields are marked *