Skip to 0 minutes and 7 secondsSPEAKER: When planning practical work in the classroom, it is important to ensure that each student in the class is directly involved. A common issue with this arises when we look at the amount of equipment or reagents involved in a full class practical, often resulting in a small number of very large groups. In large groups, a small number of students are directly involved in the practical, while others tend to sit around watching or chatting and are not focused or involved in the manipulation of the apparatus or the practise of the techniques. One way to resolve this would be to consider conducting the experiments on the microscale, often using drops of reagents as opposed to the tens of centimetres cubed.
Skip to 0 minutes and 46 secondsThere may be other reasons you wish to conduct your practical work this way. It could be to minimise risk. This may include the use of such practicals with harder to manage classes, groups where you'd rather not use the traditional macroscale quantities. So in this microscale electrolysis set up, we have a simple set up comprising of a Petri dish with some pieces of carbon rod through the side that's been sealed on both sides. This is the type of carbon rod that you can find in kites. And you can buy it in the hobby stores and places like that. Just make sure you sand off the ends to remove any lacquer so that you get a good connection with your crocodile clips.
Skip to 1 minute and 24 secondsThen take a couple of drops of copper chloride and place that into the space between the two electrodes.
Skip to 1 minute and 36 secondsAnd then we connect the power. We can pop a lid over the top. And we can observe our electrolysis taking place. During this process, the copper 2 ions will move towards the negative electrode, where they'll gain two electrons to form copper atoms. And those will then be deposited onto the surface of the electrode. This can be observed on the electrode itself. At the positive electrode, chloride ions lose one electron and bond together to form chlorine gas. And those chlorine gas molecules are involved. And we can test for those using a piece of moistened litmus paper.
Skip to 2 minutes and 27 secondsAnd if we observe the piece of litmus paper over time, we should see that that will bleach and turn white in the presence of chlorine gas. This is another positive of the use of mircoscale experiment, because the chlorine is produced in such small volumes and is contained within the Petri dish, so there is no need to consider the use of a fume cupboard. One consideration on the use of a microscalar electrolysis experiment is that students do need to be familiar with the traditional larger scale setup of electrolysis for the purposes of examination.
Microscale practical work
Microscale practical work offers a way of increasing hands-on engagement for all students. There are times when it may not be appropriate to undertake the traditional set ups of an experiment. For example, you may have a particularly large class, be short on a certain piece of equipment, have a class whose behaviour may not be up to expectation, or simply because it is not environmentally friendly to use large quantities of reagents.
In these cases it may be possible to consider a microscale alternative to the traditional experiment. CLEAPSS have a number of alternative methods which you can find on their website, as do SSERC. During this video we will discuss a couple of examples of microscale set ups, including advantages and disadvantages of these alternative methods.
If you use microscale equivalents of required practicals (those set by examining bodies), students will still need to be familiar with the traditional set ups for examinations.
Take a look at the STEM Learning online resource library. Find a microscale experiment that’s relevant to your scheme of work and consider how you might use this approach with your students. If you found any microscale experiments that are particularly valuable, do share a link in the comments below.
© National STEM Learning Centre