Skip to 0 minutes and 0 secondsMark Langley: Hello and welcome to the last video session of this course. Thank you very much for engaging and it's been wonderful reading the comments that you've made on the different sections of the course as we've gone through. Today, we've got quite a number of questions that people have asked online and we're going to try and provide some comments and some answers to those questions. Emma has asked what are the top five skills for students progressing on to 16 to 18 science and chemistry? And one of the first ones of those, I would say, is actually being able to handle equipment and glassware safely.
Skip to 0 minutes and 35 secondsStudents are expecting an awful lot of practical in post 16 education and particularly within chemistry where there's an awful lot of material to handle. And the more opportunities they have to do practical work where they're handling a variety of equipment means they're going to be more likely to succeed without having to be taught the basics over again. It's also really important as well that students have an opportunity to carry out titrations and actually learn not just how to do it but how to understand the process because they'll be expected to do. more quantitative analysis at post 16 than they have done before. It's also really important that skills...
Skip to 1 minute and 14 secondsThat the basic ones such as chromatography can be done accurately and students know how to handle small quantities of materials as well as the more larger scale reactions. And students need to have good practical skills in how they record and observe and that's something that again, students need practice all the way through their school career. And lastly, one of the classic ways of doing distillation using quick fit apparatus is something that's often demonstrated before the age of 16. But when students progress on further, they're expected to be able to handle the glassware themselves.
Skip to 1 minute and 46 secondsSo if you can give students who are looking to progress beyond 16in chemistry and other science subjects, the more opportunities to work with practical glassware such as quick fit apparatus, then that can help them immensely. Several people have asked about more micro scale chemistry experiments and how you might use these to persuade schools to engage where although you have the equipment for larger scale reactions, teachers want to do it for smaller scale, better quality. And there are a number of ways that you can do micro scale experiments that don't break the bank. Some of these include doing titrations on a small scale, but also doing general reactions.
Skip to 2 minutes and 27 secondsReactions can often be done on drop scale, where they can be done on much smaller quantities where you don't actually even have to think about the waste disposal route. We're going to have a look at a classic reaction where we react lead nitrate and potassium iodide, which is a way of showing the diffusion of irons. If you do it on large scale, then you have the issues of waste disposal but here we can do it on a much smaller scale where students can work on their own.
Skip to 2 minutes and 49 secondsWe’ve got a series of circles on a plastic sheet and we've made that by laminating a sheet of A4 paper which we've just printed with circles on and we can use as our reaction circles much as you might use a dimple tray. What we’re going to do is take a small amount of our crystals and place them just outside one of the circles. And we've made the spatulas here out of splints, where we’ve cut the end, and that way there's no need to worry about cleaning them up, they can just be thrown away. So I've got my two substances either side, and I'm going to fill the space in between with a drop of water..
Skip to 3 minutes and 36 secondsWith the edge of my spatulas, I'm now going to push my crystals into.. and Very quickly, we can see a precipitate forming. Students can then observe how that happens and you can try with other substances that might give a precipitate or might not. And once you've finished with the activity then all you need to do is wipe up the solution with a paper towel and dispose of it in the bin. There's no need to collect the residue. This is one big advantage of working at micro scale. We’re now going to have a quick look at another micro scale activity which comes from our colleagues at CLEAPSS this is a way of doing ammonia chemistry on a small scale.
Skip to 4 minutes and 18 secondsIf done on a larger, test tube scale, far too much ammonia is released into the atmosphere and that can cause difficulties with breathing. Here, we're actually containing the ammonia in a much smaller container and it's much easier for students to actually see the results of the experiment. We've got a petri dish which is on a laminated sheet, much as we did with the other practical, and we're going to add a strip of universal indicator paper which we're going to wet.
Skip to 4 minutes and 43 secondsWe're going to add some hydrochloric acid with a drop of universal indicator, we're going to add some copper sulfate solution, some iron II sulfate solution, some iron III, some zinc sulfate solution, and then in the centre, in a small reaction vessel which we’ve taken from a tablet packet, we're going to add some ammonia solution and a couple of granules of calcium chloride, which will generate heat to release the ammonia. We're going to put drops of the chemicals around the outside as well, so students can easily see what goes on inside the reaction.
Skip to 5 minutes and 29 secondsSo the reaction is halfway through at the moment, you can see that our universal indicator paper has reacted with the ammonia and it's showing that it's an alkali, and the same with the hydrochloric acid, which is neutralized and it actually become alkaline as it's absorbed some of the ammonia gas. We've got a precipitate of copper complex here, which is very similar to the metal test using sodium hydroxide for ions, and we're starting to get precipitates in our two iron compounds. One will be green, the other will be red. Then you can see we have a white precipitate forming of a zinc complex in our zinc sulfate solution.
Skip to 6 minutes and 7 secondsAnother question from Maureen is about making links across sciences as well as with mathematics. And I believe it's exceptionally important that students do make these links. For example, the topic of energy has links across biology, chemistry, and physics, and students need to be able to apply their knowledge across the disciplines. It's also very important that when activities are carried out where there's the opportunity to do calculations, then students take the opportunity to apply their mathematics. And especially for students who are going to study chemistry or other sciences post16, the more opportunities they have to apply their mathematical skills within science are very important.
Skip to 6 minutes and 46 secondsIt's actually quite important for discussions to be had between science departments and maths departments so that they can actually have a common way of approaching topics and the language used as well so students don't get disadvantaged or put off by some of the different terminology we might use in the different subject areas. Also some practical skills can be done in different ways across the different subject areas. So for example, chromatography in chemistry is often done by using coloured inks. However if students only come across chromatography in the form of separating out different coloured inks, then they may be challenged if they come across a different example in an assessment paper, for example.
Skip to 7 minutes and 26 secondsTo help students get over this, you might, in biology for example, do chromatography of plant pigments. So you look at, for example, are there differences between red plants and green plants and the pigments they carry or do they have some common pigments as well? This would involve using different solvents and possibly a slightly different technique, maybe using thin layer chromatography. This however give students the opportunities to practice the skills they've learnt in chemistry but apply to the different context. Another question asked is about contextualizing chemistry, and it's very important that we start to make links between the chemistry we’re teaching and the everyday lives of our young people. However those links are not always obvious.
Skip to 8 minutes and 8 secondsTo start out, it's very important that you really understand your own students and you have a good idea of their background lives, what their interests or hobbies are, and also what they're being exposed to in the media around them. Then you can start, where possible, to contextualize the content of the material so that you're making things relevant to them. This can be a challenge for some topic areas, but with practice and the better you know your students, the more likely you are to be able to succeed. A question from Susanne is how can you demonstrate the extraction of aluminium from its ore, bauxite, in the lab? And unfortunately, the short answer is you can't.
Skip to 8 minutes and 48 secondsIt's a very difficult practical to do because it requires large amounts of energy and high temperatures to achieve this. However, we can show the fact that aluminium is actually very reactive metal, hence why we need electricity to be able to extract it from its ore. Most students think that aluminium is quite an unreactive metal and in everyday life, it is because it's protected by a thick layer of its own oxide, aluminium oxide. Unlike iron oxide, rust, which swells up and falls off the surface, exposing more of the iron to rust underneath, aluminium oxide is impervious to water and oxygen and it prevents further oxidation of the surface.
Skip to 9 minutes and 28 secondsAluminium oxide is very tough, in fact, it's used in abrasive papers and sand papers. So what we can do is we can show what happens when we remove the oxide layer from the aluminium. And this is something that we used to be able to do with mercury chloride, but for obvious reasons we try to avoid the use of mercury in the classroom. So what we're going to do now is remove the oxide layer and also explain why you can't use salt to deice a runway. Okay, students will have understood that if you have a more reactive metal, it would displace a less reactive metal from its solutions. This is something that's done quite early on in secondary education.
Skip to 10 minutes and 8 secondsWe're going to use some copper sulfate and students will be familiar with that, and obviously we've used this in earlier experiments. Here we're going to take a quite concentrated solution, which is about 0.5 to 1 molar solution. To one of these, we're going to add some aluminium foil, which we're just going to pop in. And if aluminium was reactive, then it would start to react. But students would be expecting to see some reddish brown material in there, nothing's happening. It's doing absolutely nothing. So into another one, we're going to add some more aluminium foil and I'll push that down with my spatula, into the solution. And again, nothing happening inside of there.
Skip to 10 minutes and 57 secondsBut what we're going to do is we're going to add a little bit of ordinary sodium chloride to that and we're also going to add some sodium chloride just to just some copper sulfate, to look at what happens. If we look in there, nothing is happening apart from it's still blue and a little bit of green at the bottom where the sodium chloride's absorbing some of the colour. But in the one where we've added the salt, we're starting to get a bit of bubbling and fizzing going on, which is hydrogen gas being produced. And this reaction is actually getting quite exothermic, this tube is starting to get quite hot.
Skip to 11 minutes and 32 secondsIf students try this experiment, it needs to be with a much more dilute solution such as 0.1, but it's getting very hot and we can start to see copper forming in there and the aluminium is dissolving. And that is getting almost to boiling point. The sodium chloride reacts with the surface of the aluminium oxide and etches its way through, exposing the aluminium underneath which then reacts with the solution, so we end up with aluminium sulfate in solution and solid copper metal being produced. This is one reason why salt is not spread on runways.
Skip to 12 minutes and 10 secondsIf salt comes into the contact with airplanes, which are mainly made of aluminium, then if it finds its way through the paint layer, it will then attack the oxide layer underneath and can cause severe damage to the airplane's infrastructure. We’ve had a question about carrying out micro scale titrations and there are a number of ways of doing this. The simplest one is just clamping a 5 or 10 millilitre syringe and actually pushing down the plunger gently. This can be very useful for small scale titration, particularly if you use small containers such as bijou bottles, such as the ones we were using earlier for the ammonia experiment to contain the reagents.
Skip to 12 minutes and 47 secondsThere are some other ways that we can do this as well, there are some commercial made kits which use very small burettes or pipettes, which can be filled with syringes and are tipped with very fine nozzles to give very small droplet sizes. This is a commercial size where we have a very fine dropping nozzle at the end and a syringe at the top which we can use to draw liquid up and also then to give us controlled droplets into a reaction vessel. This type of kit is quite expensive to buy but it's very easy to control. Students can squeeze down and add very small amounts and can measure very precisely the level that they're adding to.
Skip to 13 minutes and 35 secondsA slightly simpler version which students can use is just clamping an ordinary disposal pipette with a fine nozzle at the end and clamping it in an ordinary boss clamp and stand and just by tightening the clamp, you can dispense very small amounts of liquid. And students could do this by dropwise otherwise it's possible to contain nozzles at the end which are calibrated so that you can actually measure the volume that’s being dispensed. For those who are interested in taking their chemistry further, we have a residential course at the National STEM Learning Centre coming up in April which may be of interest.
Skip to 14 minutes and 15 secondsThe New to Teaching A Level Chemistry course looks at the basics of teaching chemistry and the fundamentals of effective pedagogy and practical skills at post 16. The course starts on the26th of April and for those schools who are state funded in the UK an ENTHUSE bursary may be available. The course code is NY251 and that can be available on our website www.stem.org.uk. Thank you very much for looking at this video and especially big thank you for taking part in the course. We've really enjoyed and valued the comments and contributions you've made and we look forward to welcoming you online again or face to face in our centres.
Q&A with Mark
Thank you to those who posted questions about practical chemistry below and throughout the course.
Mark Langley responded to a selection and provided some extra video demonstrations just for you. We uploaded the video on 6 December 2017. Captions and transcript were available from 8 December 2017.
0:23. Practical skills for progression for 16-18 year old students - Emma.
2:01. Microscale experiments without new equipment - Emma.
4:10. More microscale experiments - Faith.
6:08. Linking chemistry to other subjects - Maureen.
7:05. Contextualising chemistry - Maureen.
8:40. Aluminium from bauxite - Susanne.
12:23. Microscale titrations - Sandhya.
- Reactivity of aluminium from RSC.
- Ammonia microscale from SSERC.
- New to teaching A level chemistry course at the National STEM Learning Centre in York, UK.
Joined us after 6 December?
If you’ve joined the course after our supported period, you can still ask questions by:
- Posting questions to steps in the course and asking other learners for their suggestions.
- Joining the STEM Group for Secondary Science and asking the wider teaching community.
- Register and take part in the next run of Teaching Practical Science: Chemistry starting in February 2018 where Mark Langley will be running another question and answer session.
© STEM Learning