Last week saw the ASE conference taking place at the University of Reading and some of the School Teacher Fellows decided to get together for a “Teacher Fellow Tag Team” demo event to kick off the International Year of Chemistry for the RSC. As we would be mostly talking to teachers, we wanted to use the opportunity to inspire and empower them with demonstrations they may not have seen or tried themselves before to take back to their schools.

Penny Bagshaw (Reading), Tim Harrison (Bristol) and I rocked up to make a mess of Chemistry LT2.

From left to Right, Tim Harrison, Declan Fleming, Penny Bagshaw. Photos kindly taken by Amanda Middleton from the RSCIt looks like someone shrunk my head in the wash!

I decided to use my segment to explore some slightly unusual displacement demos. Metal displacements are the bread and butter of a Chemistry teacher’s repertoire and alongside the alkali metal demos, tend to be the reactions that stick in students’ memories for a long time. The classic class experiment is to take a variety of metal strips and place them in a collection of aqueous metal salts to build up a reactivity series. This is usually backed up by a magnesium / copper oxide displacement or maybe a zinc / copper oxide one which may be tamer but is rather pretty! The thermite reaction is often requested by students and is performed in so many different ways across the country that we could even adapt the Creme Egg slogan to “how do you ignite yours?”(Thermite image courtesy amazingrust.com)There are some more unusual displacements that get less attention which I also use to support lessons from year 9 (age 13-14) right through to year 12 (age 16-17).

We had 20 minutes each (although I’m told I may have gone over just a little bit!) so I decided to do 3 demos which would leave me time to explain the context to non-chemistry teachers in the audience.

I started off by pointing teachers in the direction of the excellent free resources at Freezeray and of course the ASE’s “Chemwars”. Unfortunately the mouse decided to pack it in meaning I couldn’t show them off in their full glory.

Silver Nitrate + Magnesium (info and RA)
The first demo is from the additional demonstrations that were released to the web to accompany the “Classic Chemistry Demonstrations” book which was sent free to school in the UK. This worked a treat with my ice-cube initiator although in the interests of showmanship I ought not to have walked in front of it just before it went off!

My own experiences and thoughts shared*.

  • The advised burette technique makes me very nervous and can needlessly wreck a perfectly good burette – or at the very least add unnecessary washing up. Some teachers go for the water pistol approach – I’m not such a fan as it can spread the chemicals over a wider area with unpredictable results and potential damage to surfaces. When using an ice-cube initiator I use a gauntlet glove and tongs and ensure the ice cube is completely dry (I collect one from the freezer just as I do the demo – I acknowledge this may not be possible in all schools).
  • The reaction can generate small, red-hot molten balls which will happily roll off a desk onto any flammable materials nearby. I usually give some thought as to how I can contain these and always make sure that anything that could be scorched is well out of the way.
  • Really take the time to read through some of the reported accidents. If you underestimate the risks incurred by performing this demonstration, you could pay a heavy price.

Magnesium + Silicon Dioxide
I really like this demo. It’s quick (assuming you remembered to dry your reagents), simple to perform and reliable. It also offers a magic combination of wonder, the production of unusual chemicals from commonly found ones and it can assist in the teaching of many different topics. Personally, I use it in the context of covalent bonding at KS4 (14-16). I’ll perform the displacement first – students don’t always make the connection from sand to silicon dioxide to displacement reactions. I’ve usually covered ionic bonding beforehand so the unusual example of magnesium silicide gives my students something to think about whilst the reaction cools ready for the finale. Having explained that silanes will be produced as a side-product, I ask them to discuss in small groups the similarities and differences they would expect in the bonding and properties of methane and monosilane (as well as what its formula might be). There is usually one group who asks if the size of the central atom will have any effect on the way the compound behaves. This ties together so many areas of chemistry and shows where the story is goign to lead in terms of periodicity and bonding at the next level. It’s a demo that just keeps on giving! For many students, this is also the first and last time they will get to experience a pyrophoric compound.


Using a cheap webcam to try to reveal the lovely glow from the displacement to a big room

My own experiences and thoughts shared*

  • Even if you think the tube and reagents are thoroughly dry, it can still produce a hydrogen pop exactly as you would expect to find from the magnesium + steam experiment. It’s nothing too dramatic and is also mentioned in the notes but it really can make you jump if you’re not ready for it!
  • Following from above – the reaction can produce a build-up of gas so I always ensure my reaction mixture has “room to breathe” all the way up the tube. I always go with a boiling tube – and am never tempted to use a thinner test-tube.
  • Even a good quality tube will be heavily damaged by the heat of this reaction. The directions recommend scraping out the contents but I rarely manage to do so without the tube breaking. I usually gently cradle the tube in an old rag so if the end falls off it won’t break any further, I won’t be injured by any broken glass and I won’t lose any of the product.
  • I’ve never had the time to filter the product and given that most students don’t have much of an idea of what silicon looks like anyway which is ironic given how much we as a society are now dependent on it! I usually have a sample handy to show them – It’s a stunning element.
This reaction was the subject of a previous Exhibition Chemistry by Adrian Guy

Magnesium and Carbon Dioxide
This is a strikingly beautiful demo although it can be hard to get going as the audience on Saturday found out! The familiarity students have with carbon makes the change from a metal to a non-metal quite dramatic. Other displacements require some work-up to produce a “clean” product that students can examine and instantly recognise. I would use it after discussing the use of carbon to extract metals from their ores in order to show that for more reactive metals the opposite can happen and as such we need to use other techniques. There are no instructions or a model risk assessment supplied for this demo.


Honest Guv, it’s carbon!

My own thoughts and experiences shared*

  • I cut the dry ice to size with a regular wood saw. The very last part of the cut took a long time to complete and I found myself entering the cutting surface on both sides before the end was released so make sure you have an appropriate work bench. The block is very brittle so I avoid the temptation to coax it off before it’s ready to come. If the liberated end falls more than a few centimetres onto a surface it is likely to break!
  • I carved out a well with a chisel. Patience was key here, taking a little at a time to avoid breaking the block. If you attempt to do this on a smooth worksurface be prepared to get frustrated! The gas evolved will make it move around as if on an Air Hockey table! Once I had a small well, I used a small amount of magnesium to deepen it for me.
  • I never fill the reaction cavity too full. The reaction wants to vent from the centre and burning turnings can be ejected when you place the lid on if there isn’t a good lip on the cavity.

Penny Bagshaw kicked off the show on an oxygen theme with “the blue bottle”, “screaming jelly babies” and “elephant’s toothpaste”. Tim Harrison finished the show with a selection of quick dry ice and liquid nitrogen demos from A Pollutant’s Tale. I’m grateful to both for their support as well as the technical staff at Reading (particularly John) and to the RSC for footing the bill to turn off the fire alarm!


Tim Harrison  and Penny Bagshaw say “Test Tube, Not Youtube!”

Out and about in the rest of the conference…
Although I wasn’t able to attend on Thursday (in order to make sure my dry ice didn’t disappear!) and setting up and clearning away wiped out Friday and Saturday mornings, I was able to have a peek around on the Friday and Saturday afternoons and the experience was both useful and enjoyable. Things I’ll take away with me include …

  • An instant and highly accurate eye exam by laser speckle (for once I felt like being a long-sighted astigmatic glasses wearer was an advantage!)
  • Watching a green laser pop a black balloon but not a green one (I trust them that the other variables were kept constant!)
  • Holding a massive molymod carbon nanotorus although I’m not impressed that others were given free molymod kits and I wasn’t!
  • Getting a much needed upgrade to my blowtorch “Betsy”, her big brother “Brian” who comes with inbuilt piezo-igniter. Betsy will always be useful for launching methane rockets (no moving parts to destroy) but Brian is just so convenient!
  • Seeing a proper spud cannon in person courtesy of keystagesolutions who were sadly left high and dry by the multiple science show plus attenborough clash slot
  • An excellent session jam packed with ideas to get me thinking from the IOP Talk Physics’ “What Happens Next?” – including if I want to avoid hassling my old school to borrow their bell jar and vacuum pump – this could make a  servicable emergency substitute
  • www.chemistryteachers.org (and the forthcoming but not yet titled e-learning project). So many of the teachers I spoke to at ASE did not have access to even the most commonly available of the excellent RSC resources that have been sent out to schools. The move to make as much as possible available online looks really exciting and will have a massively positive impact on teachers and through them the subject.
  • There is a reason we wear safety specs at all times. I must have been splashed with silver nitrate during the clean up – the taps in the lecture theatre were pretty spicy. If I hadn’t have been wearing safety specs for the wash up, even with glasses on, there would have been a very real risk of getting that splash in my eye which would have been game over.

Boys and their toys
To finish the weekend, I had a fair amount of dry ice still going spare so spent yesterday afternoon on the streets of north Bristol showing friends and passers by some of the cool chemistry (and physics) you can do with it.

* This information in no way endorsed by any professional safety body and neither I nor the RSC can be held responsible for any accidents that result from using it. You should always consult your own workplace’s risk assessments to decide whether a special risk assessment is necessary.