No Guesswork. No Nonsense.

As a trainee, I was frequently told of the virtues of carrying out practicals in science lessons. These ‘investigations’ were touted as crucial tools for engaging pupils in science, allowing them to learn about new concepts through exploration, experimentation and enquiry. Rather than learning the underpinning knowledge first, I should create conditions for my pupils to discover scientific principles for themselves. My academic tutors and school mentors taught me that this approach was best because it simultaneously deepens pupils’ understanding and increases their engagement.

But the longer I teach, the more I realise that this approach simply does not work. Rather than deepening understanding and increasing engagement, putting experiments at the heart of the curriculum wastes time and reduces the amount of scientific knowledge they can acquire. Instead of learning about key scientific principles and learning them by heart, understanding their complexities and scope, pupils flap about with Bunsen burners and chemicals, guessing why things happen and never really getting to grips with the facts.

Without a firm understanding of important underpinning principles prior to beginning an experiment, pupils focus too heavily on the method rather than the actual science. For example, carrying out an experiment on thermal decomposition without much prior knowledge of the process would inevitably result in few tangible learning gains. Rather than observing (and crucially- understanding) the chemical changes during the complex process of thermal decomposition, pupils’ minds are more likely to be focused on whether they have pushed the rubber bung and delivery tube into the test tube properly. Whilst these things are important, and learning the method is one aspect of the process, pupils must first have a good knowledge of the chemical processes and changes happening if they are to truly appreciate what’s going on. If they are to remember these scientific concepts in the longer term, pupils first need to ensure that they know the content. Practicals provide an opportunity to see their knowledge in action, but they should not be used to learn the content in the first place.

Once pupils have learned the knowledge properly and have carried out the experiment, I then ask them to write up their findings. Below is one pupil’s report. It highlights the level of scientific knowledge they have gained throughout the process. The level of understanding is attributed to the knowledge first, experiment second model of instruction. Without a firm foundation, it is very difficult for pupils to gain a deep understanding of scientific principles.

The aim was to heat copper (II) carbonate to produce copper (II) oxide and carbon dioxide. This is known as thermal decomposition. We would first measure the copper carbonate using a special precise measuring scale. My partner and I had an initial mass of 23.3 grams for the copper carbonate. We then placed the test tube on a clamp which held it over a Bunsen burner with the collar (air hole) of the burner closed. We then held another test tube filled with three mL of limewater into the delivery tube. After a short time, we turned the collar of the Bunsen burner completely open. The limewater eventually turned cloudy. This was because the copper carbonate (CuCO3) had decomposed into copper oxide (CuO) and carbon dioxide (CO2). The carbon dioxide had moved into the limewater, causing it to become cloudy. We then measured the mass of the copper oxide. Our measurement of mass was the same as before, but that was because some of the limewater had condensed on the inside of the copper carbonate test tube, which had altered the mass of the test tube. There were also some chemical changes; the calcium carbonate had also lost two oxygen (O) atoms and one carbon (C) atom. This had formed CO2, which had transferred into the limewater. If condensation had not occurred, the mass would have decreased because CO2 molecules left the test tube by travelling through the delivery tube. The physical properties of the copper carbonate had also changed as it transferred into copper oxide; the solid had changed colour from a light green to a dark green and blackish colour. Our class knew all of this theory prior to the practical as we learned about the practical and were given a clear and detailed demonstration by Miss Dyer. We had a lot of knowledge about the practical beforehand so that pupils would be in a safe environment and able to focus on the science.

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5 thoughts on “No Guesswork. No Nonsense.

  1. Have a look at the work on ‘ getting practical’ from robin millar and the ase. All about identifying what it is you want from practical and focusing on only that e.g. developing measuring skills

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  2. Not sure this needs to be a hard and fast rule… I’m no fan of ‘discovery learning’ (which is sort of what we are getting at here), but where investigative work is carefully designed and thoughtfully located in a learning sequence (and possibly with more straightforward manipulative techniques – I’m a biologist!), I have no doubt that practical work can contribute to deep learning without having to cover all the content first. For example, teaching students about osmosis doesn’t require that they know the full detail up front: cover the principles of concentrations and standard diffusion, then investigate with potato cubes in black currant juice. Scaffolding their analysis and conclusion, supporting collaborative thinking and ultimately allowing them to arrive at their understanding in this way consistently secures an understanding that is as strong if not stronger than how I used to do it (all the theory, then the practical)

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  3. Whilst I’m certainly in agreement that flapping around with Bunsens and trying to learn scientific principles are mutually incompatible activities, I would argue that the key bit of thinking is to realise that this is a cognitive load issue. If you want children to learn how to use a Bunsen burner to heat a solid in a test tube, test for CO2 etc. then that’s a practical skill; if you want them to be able to describe the chemical process of thermal decomposition, that’s a scientific principle. If you try to teach the two things together many children won’t cope – cognitive load is too high to take it all in. You don’t have to separate them massively and the approach described in this blog is a great example of inter-weaving the teaching of the two things but I think it’s worth mentally separating the two LOs of practical skills and developing knowledge of a scientific principle. Until the former is secure, it’s not possible to think much about the latter whilst doing a whole-class practical. The other solution is to demo the practical to (a) reduce cognitive load, (b) allow you to question and focus attention on exactly what you want the children to learn. Millar & Abraham (2009) in SSR well worth reading http://www.aqa.org.uk/subjects/science/practically-speaking/are-practicals-effective

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