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This content is taken from the National STEM Learning Centre's online course, Managing the Practical Classroom in Secondary School Science. Join the course to learn more.

Skip to 0 minutes and 7 seconds SPEAKER 1: In this demonstration of the fractional distillation of crude oil, we shall discuss two video clips. In the first, the teacher is conducting the demonstration alone, managing all roles in the classroom. The second shows the technician undertaking the practical procedure, while the teacher stands to one side and discusses the science behind the demo and manages the behaviour of the group.

Skip to 0 minutes and 31 seconds SPEAKER 2: So here we have the standard set for the fractional distillation demonstration. And what we’re going to do is we’re going to run through this in two slightly different ways. The first way is using the teacher to conduct the demonstration and the second is to use another adult. And we’ll discuss reasons why shortly. So what we’ve got is the standard round bottom flask, thermometer, condenser, and then some fraction tubes. And we are going to start by gently heating our synthetic crude oil in the round bottom flask.

Skip to 1 minute and 7 seconds And all the time that we’re heating that, we’re keeping an eye on the thermometer, making sure that we’re just bringing that synthetic crude oil up to temperature to separate off the first fraction– so gently heating. And then once we’re there getting ready to collect that first fraction into our first tube. And what we can see here is that all the time I’m conducting this demonstration, because I’m trying to keep my eye on what’s going on in the round bottom flask to make sure I don’t overheat it, I’m trying to keep my eye on the thermometer to check that I’m only getting one fraction coming off, and I’m trying to collect the fraction at the same time.

Skip to 2 minutes and 1 second At no point was I actually looking up to pay attention to what was going on in the classroom. I didn’t know what the students were doing, making sure they were all focused and engaged with the demonstration. And because of the amount of concentration I had, I wasn’t actually able to ask questions of the students to make sure that they were understanding the processes that were going on. So in this version of the demonstration, I’ve asked one of our lab technicians to undertake the practical side of the experiment for me. So Helen’s going to start off the fractional distillation.

Skip to 2 minutes and 32 seconds What this means is that I can spend all of my time with my face forwards, making sure that I can see what the students are doing, checking their understanding. I’m able to ask them questions about the apparatus and techniques that we’re using and make sure they’re understanding the purpose of the demonstration and the science behind what’s going on.

Demonstrations with others

In the video above we clearly show the difference between undertaking a demonstration on your own and a demonstration involving others. Tim mentions the multiple tasks that a teacher would need to undertake in a demonstration, and how the support from a technician can better allow learning to be managed by the teacher during the demonstration.

Involving students

It is important to note that if you are demonstrating because of hazards associated with the demonstration, it is not appropriate to ask the student to undertake the experiment in place of another member of staff. You should consult your health and safety guidance as appropriate.


Discuss with a colleague how you might plan to deliver a demonstration together. Think about how this frees up your time to ask students questions, highlight key points from the demonstration and the key skills being shown. Share below your ideas for a demonstration with two people, and what this would allow you to focus on as the teacher.

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This video is from the free online course:

Managing the Practical Classroom in Secondary School Science

National STEM Learning Centre