Discussions from the magazine, blog, website and social media


What’s your favourite demo?

In preparation for Demo Day (part of British Science Week), we asked teachers to tell us about their favourite chemistry demonstration.

Most popular was the screaming jelly baby. Rob Butler explained why it’s his choice:

No other practical has cruelty and sadism in large amounts!

Rajiv Manek agreed:

So many different topics can be taught with this one experiment and so much fun to pick off the jelly babies one by one.

Dan Batzel picked the nylon rope trick:

Because it’s not very often one gets to make a single molecule of such mass and it’s also the method employed to manufacture desalination (reverse osmosis) membranes.

Rhyming Chemist chose something we’ve featured in an exhibition chemistry article:

I like cannon fire. You need fresh peroxide and a range of KMnO4 grain sizes to get the best effects. It’s a nice lead in to learning about redox equations.

Explosions are certainly popular with students, but also it seems with chemistry teachers. peterdevon described his favourite demo:

Big tin can with hole in top and bottom, fill with methane, light methane escaping from top. Long delay, then BANG! Don’t try this at home.

Indeed, but here’s a version you can try in your classroom, exploding an egg and a Pringles can.

Some teachers are less concerned with experiments that go bang. Noel Dickson said:

I have many favourites, but for sheer brilliance and dynamic appeal is the giant silver mirror – love it!

Lecture capture

Katherine Haxton wrote about the value of recording lectures and a project at Keele University that publishes them on a virtual learning environment.

Rob Ackrill described his experiences:

I too have been using lecture capture for a few years now. When I have surveyed my own students about it, they say they find it particularly useful in two contexts – going back through more complex elements after a lecture and at the end of the module, as they prepare to write up and submit their final module assessment (an extended project).

I have also found, however, that even those students who really appreciate it are concerned that others are using it as an excuse not to attend. The challenge for me is always to convince students that this is a complement to attendance, not a substitute for it.

Louise Stringer likes lecture capture for the support it can offer students learning in a second language:

I think this would be especially useful for students who are not native speakers of the language the lecture is delivered in – it takes off a lot of pressure of having to ‘get it’ the first time as they know they have the opportunity to go over it again. Just having this safety net could be enough to make lectures a lot less stressful.

Professor_dave has experience introducing lecture capture at his institution:

Lecture capture was one of the single most divisive things I introduced during my time as director of teaching in the chemistry department at University of York. We started with an opt-in system for members of staff, and then transitioned to an opt-out approach. We never got to the point of making it compulsory for staff to be lecture-captured, however, over 80% of staff now routinely do it, and many previous sceptics came round to seeing its virtues.

Students do love it, however, as for them, it takes the pressure off lectures as a ‘one-off’ learning activity allowing them to revisit things, or catch up if they are ill and can’t attend in person.

As a real positive for staff, we find the ‘hot spots’ [sections in the video students view repeatedly] do indeed appear where a challenging concept was being explained – a key pointer that perhaps more time, or a different explanation may be valuable next time the lectures are given – or that a structured problem on the topic may be beneficial.

As a negative, some students do clearly passively watch the lectures in ‘box set’ mode as (relatively useless) revision in the run up to the exams, when it is absolutely clear that the best way to learn a subject is by being active, structuring your knowledge, and using your understanding to solve new problems and test yourself.

Past papers

Tom Husband’s students are obsessed with past paper questions. However, they use them to learn mark scheme answers by rote, rather than fully understanding chemistry concepts. So Tom is going to stop assigning past paper questions for homework.

A teacher from Oundle School Chemistry Department sympathised:

I find it incredibly frustrating when pupils tell me that they revise best by learning the mark schemes. I pointedly hold back on giving past papers to pupils until they can prove that they have a solid understanding of the concepts. A point of principle and honour for us in stopping the dilution of learning.

Janne Lempinen explained that this issue is not confined to the UK:

This really seems to be a universal obsession. I teach in the private sector, both Finnish and International Baccalaureate (IB) curricula. I would say that the IB students are more interested in the past papers than the ones taking the Finnish matriculation examination. Looking at the past papers I can understand it as the structure of the IB exams is quite similar year to year. The Finnish curriculum students usually start revising the past exams in their last year. I really cannot blame the students for obsessing with the past papers and wanting to do well in the exams.

Katherine Haxton described the knock-on effect to universities of a past paper mark scheme revision culture:

I’ve been asked so many times this year for mark schemes for our model exam papers and they simply don’t exist in the same sense. We provide significant numbers of questions to allow students to put their knowledge into practice but a large number of students seem to view these as being of limited use unless there is a mark scheme to go alongside them. And yes, anecdotally, when I provide a model answer (eg one possible answer, others are available and equally valid), I see very high levels of algorithmic ‘memorised the model answer’ answers to similar questions. It’s easy to spot if you give a model answer for a basic scenario (usually with quirky terminology/nomenclature) then examine the basic scenario with a twist. Many students cannot find the twist because they simply recognise that the basic scenario applies, and write that down, quirks and all.

I personally view model exam papers as a useful tool in reducing some of the cognitive loading inherent in an exam format, whether there is choice of or within questions, number of marks and providing an answer that meets the requirements of the question (‘draw structure or mechanisms’, ‘write equations’, calculate, explain). But that is all.

But some teachers on the TES forums aren’t convinced. WJClarkson said:

I think that past exam questions are an incredibly valuable resource. As we have finished the course content, I do revision for most of the lesson followed by one exam question each lesson. It helps them grasp exam technique and understand what is expected of them during the exam.

TCSC47 empathises with students and asks teachers to be sympathetic to their needs:

I think past paper questions are very important and useful. I think some (many?) teachers have forgotten what it is like to have to sit an exam and are far too close to the exam questions and formats. That is why they mistakenly think children can cope with them, when in reality they are very frightening. Don’t forget, full exam questions come right at the end of a particular topic and then the student has to whizz on to the next topic or worse still the actual exam itself. School must be quite a blur for many children. It certainly was for me.

It is not about teaching to the exam or encouraging the student to learn answers by rote. That is where the teacher and the exam question setter have to do their bit and make sure that doesn’t happen. The classroom teacher has to be sympathetic to their student’s needs and prepare them for the exam situation so that they can demonstrate their grasp of the subject to the best of their ability.

Flere-Imsahop focused on how completing past papers can help students:

I wouldn’t stop assigning them. I might ask pupils not to do them except in class. The value of past papers (beyond the one where they discover that 45 minutes isn’t very much time to write an essay and that, yes, it helps if you know the material) is in the discussion of their answers and sample answers against the mark scheme. That helps them to understand why an answer is correct and the marks awarded. Slavishly doing paper after paper without actually understanding the marks is useless.