Skip to 0 minutes and 2 seconds MARK LANGLEY: Hello and welcome to the question and answer session for teaching practical science chemistry. Thank you very much for the contributions you’ve made over the last few weeks. We’ve valued what you’ve said, and we hope you’ve learned quite a lot from that and taken away some new ideas to try it in the classroom. Myself and Tim Bradbury now are going to go through some of the questions that have been posted, and give you a little bit of update on some other things that you might be able to do.
Skip to 0 minutes and 26 seconds TIM BRADBURY: So our first question comes from Katie who asks, do you have any guides for the apparatus used in the microscale practicals. For example, the plastic boxes for the thiosulphate rate of reaction. I would have used takeaway boxes, but to get several class sets, they should all be the same size. So would you just use Amazon? To answer that question, Katie, there are a number of different sources and procedures for microscale experiments available. We have lots of them on these STEM learning website. If you pop onto our resources section and into the search bar just search microscale, you will get a plethora of different experiments, which you can set up and– technician requirements, et cetera.
Skip to 1 minute and 13 seconds With regards to the finding of plastic boxes, you are right. We do use take away– the little plastic take away tubs. And you can order those en mass from such as Amazon or a number of– just sort of home stores as well sell those plastic boxes in large volumes that you can purchase. You can then search other places such as CLEAPSS, the IOP, the Royal Society of Chemistry, the Institute of Biology. And again, just simply search their websites for microscale, and you will pull up lots of procedures that you can follow. Next up, we have a question from Hussein who asks, Hello, Mark. You said in the video that we add copper oxide to sulfuric acid until no more effervescence.
Skip to 2 minutes and 3 seconds Acid plus carbonates will produce carbon dioxide gas while acid plus oxygen will produce salt and water. So here it is supposed to be no gas produced while practically, we have seen effervescence when you’ve added copper oxide to sulfuric acid. Have you used copper carbonate? This is a really good question. This gets pointed out on a number of different occasions where we use this video. And the most plausible explanation for what’s happening is that this is actually the nucleation of trapped gases from the sulfuric acid and from the copper oxide coming out of solution when you add the copper oxide into the sulfuric acid. You’re quite right.
Skip to 2 minutes and 42 seconds When you look at the equation for the reaction, there is no gaseous product as this is the only possible explanation for those gases. For our next question, we are looking at using iron nails rather than carbon electrodes in the YouTube showing the electroplating. From the comments, I was a little bit unsure what this meant. But I’m going to assume that it’s a suggestion to use iron nails rather than carbon electrodes. This should be absolutely fine in this demonstration.
Skip to 3 minutes and 11 seconds But what I would do is to clean the iron nails with fine sand paper and acetone or similar just to wipe them down and remove any possible evidence of iron oxide on those nails as students could confuse iron oxide, which is on the nails already, with the formation of copper metal on both electrodes. Rebecca’s question now, moving on. Rebecca would like to ask a question regarding the Petri dish electrolysis. For the Petri dish with the built in rods, could you do that same experiment with pencils instead? And also given the propelling pencil leads are very expensive, could you use regular carbon rods with the wider diameter in the homemade U-tubes?
Skip to 3 minutes and 56 seconds I know they might not fit, but there are other reasons– any other reasons why that wouldn’t work? The reason that we’ve actually used the carbon rods we have and I think this is an easy mistake to make simply from the video. These aren’t the propelling winding pencil leads that we’ve actually used in those Petri dishes. This is carbon fibre rod that you can get from hobby stores and things like that, which is used for making kites and things like that at home. So it’s not just a very thin graphite rod.
Skip to 4 minutes and 27 seconds The reason that we use that is because once you’ve sanded the ends off and removed any lacquer or anything like that glue from the ends, then they are very strong and durable and they will last a very long time. The problem with using a traditional carbon rod or graphite rod or pencil lead with the wood stripped off is that they are very, very fragile and brittle, and they will break very easily. So you would be constantly having to replace the rod within those Petri dishes.
Skip to 4 minutes and 58 seconds In saying that, you could use a traditional piece of carbon rod or graphite rod, but one of the problems might be being able to get a hold in the side of the Petri dish is large enough to accommodate the carbon rod, and leaves enough plastic surrounding that hole to actually make a strong seal. I would be a little bit wary knowing that the diameter of the traditional carbon rod. You can, indeed, use pencils. That’s a great way to demonstrate electrolysis. Sharpened pencils of both that ends. So you’ve got the lead exposed at both ends. And then, attach the crocodile clips as you would for any other electrolysis experiment. It’s a really good demonstration.
Skip to 5 minutes and 37 seconds It’s one of the conductive properties of graphite.
Skip to 5 minutes and 41 seconds MARK LANGLEY: Right, Juliet asks about– in specifically the Edexcel GCSE course. It states that students must know the products generated in electrolysis of sodium sulphate solution, water is acidified with sulfuric acid, and molten lead bromide, the latter one is a demo. And do we have any tips about this? Well actually, the electrolysis of sodium sulphate, which yields oxygen and hydrogen is a great one to do on a small scale. Then, the resulting mixture is bubbled into washing up liquid and ignited with a very loud pop. As well as being interesting, and a so small scale the students can ignite it, it demonstrates exothermic reaction as well.
Skip to 6 minutes and 18 seconds And it leads to discussions about energy needed to split the water into hydrogen oxygen, and the energy released when they recombine. And also why we’re actually having to put in an electrolyte to make the water conduct in the first place. This is much the same for water acidified with sulfuric acid. This is traditionally demonstrated in Hoffman voltameter. And although the big glass ones are expensive, you can make, actually, much smaller versions. And there’s guidance for this on microscale chemistry. An advantage of this is you can see the resultant amounts of hydrogen and oxygen produced in a 2 to 1 ratio as well.
Skip to 6 minutes and 53 seconds Molten lead bromide is a challenge to actually do as a demonstration, and it must be done in a fume cupboard. When you heat up the lead bromide, it will actually start to decompose as it reaches its melting point, which defeats the process of actually showing the electrolysis. It can be very fiddly to set up. Much better is to use either zinc chloride or lead chloride, which give you the ability to reclaim the metal products at the end of the reaction as well because the remaining products are soluble in water and it’s much safer. You can actually do it in open lab.
Skip to 7 minutes and 30 seconds And if you’re a CLEAPSS member, then if you have a look at guide L195, safe for chemicals, safe for reactions, there’s a great way of explaining how to do this on a microscale, where you’re not going to generate large quantities of halogens released into the labs. Along the electrolysis theme, Severine has a question about how we demonstrate or discuss the production of aluminium using cryolite and aluminium oxide. And this is actually one of those good practicals where it’s really useful to use a video of the industrial process, and then actually pick apart from the diagrams what’s going on.
Skip to 8 minutes and 3 seconds This is often best done by choosing good videos from the Royal Society of Chemistry, et cetera, which actually do come from worksheets. So I strongly suggest you have a look at their industrial chemistry videos. Katie asks two questions. The first one is, are there any resources to help improve teacher’s knowledge of the theory behind experiments? If you’re using practicals from the Royal Society of Chemistry or from CLEAPSS or SERC, they usually come with information that explains the science behind them, which also will help you with your risk assessment as well. And sometimes we find that schemes of work don’t contain enough details.
Skip to 8 minutes and 37 seconds So it may be worth, then, going and finding these materials on CLEAPSS, SERC, or the Royal Society of Chemistry so that you can actually expand your own knowledge. Second question is about week two from the iodine clock. And Katie asks, is solution B in the iodine clock experiment made up with water? The iodine clock is actually quite a challenge for students to understand. And up to the age of 16, they’re not going to need to know the mechanism behind it. All the solutions are aqueous, and there are a number of recipes around. But I’m going to give you the recipe that we use. Firstly, you need to make up a solution a 5% soluble starch in distilled water.
Skip to 9 minutes and 13 seconds And that’ll need to be made to be hot distilled water to get it to dissolve. Then, you need to make up solutions A and B. Solution A is 2 grammes of potassium iodate added to 12.5 centimetres cubed of 0.5 molar sulfuric acid made up to 1 litre with distilled water. Solution B is 2 grammes of sodium metabisulfate made up to 1 litre with distilled water. The solutions are used in equal volumes, but the concentrations of each solution can be varied by the students. The last question from Denise asking for any suggestion that for science club experiments that are fast and easy to do, and can be done within the hour.
Skip to 9 minutes and 56 seconds And we actually have a whole page dedicated to science and STEM clubs with lots of activities that are easy to use, and that are not just chemistry but go across all of the sciences and into DT and computing as well. And the link below will take you to that page.
Skip to 10 minutes and 14 seconds Once again, thank you very much for the time and effort you’ve put into the course. We hope you find this all useful. And from Tim, myself, and Louise, we thank you for the time and effort.
Q&A with Course Educators
The Q&A sessions on courses from the National STEM Learning Centre provide you with the opportunity to ask more about the course content and issues from your own classroom practice.
Video table of contents (time and question)
0:28 Guides to apparatus in microscale practicals.
1:51 Using CuCO3.
3:34 Petri dish replacing built in rods with pencils.
5:40 Tips for Edexcel GCSE products of chemical reaction.
7:43 Industrial process of electrolysis.
8:12 Improving knowledge of theory.
8:45 What is Solution B from iodine clock week 2?
9:50 Quick science club experiments.
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