So till now I’ve been talking about in a very general, philosophical sense about practicals. I’ve just started at a new school where there are only two A-Level chemistry teachers; myself and the head of department (who is also new). I’ve been given a good amount of freedom to chart a path through the A-Level chem course and especially to experiment with how to make the required practicals meaningful.
The practical I want to discuss here is:
Distillation of a product from a reaction: To prepare cyclohexene by the dehydration of cyclohexanol and to distil the cyclohexene from the reaction mixture (from the AQA Chemistry Practical Handbook)
My goals are:
- To assess students against the 5 AQA CPAC statements
- For students to practice the use of distillation and separation apparatus
- Consolidate knowledge of the dehydration of alcohols
As mentioned in my last post, my first rule is to respect the students’ working memories. To this end, my plan is to split the practical into three phases. The basic structure here is similar to how I conducted undergraduate lab work when I was a student at UCL.
Much of the below goes beyond the strict requirement from the exam board.
Phase 1: The Pre-Lab
First and foremost, students will have learned all the relevant theory with me beforehand and will have achieved a high level of knowledge (hopefully) with respect to the scientific content.
In preparation for the practical, students will complete a Pre-Lab. This is basically a small amount of work which tells me that they are ready to do the practical and gives me an indication that they have enough knowledge of the relevant science to be able to carry out the practical and think about the content at the same time.
Students will log into our course’s Moodle page. There they will be told to answer the questions below in their lab books (lab books are not required by the exam board but we are using them anyway):
- Draw out a reaction mechanism showing the dehydration of cyclohexanol to form cyclohexene
- State the conditions under which the above reaction occurs
- Use the Sigma Aldrich website to locate the Safety Data Sheets of cyclohexanol and cyclohexene (students will have been shown how to do this)
- State the major hazards associated with using these chemicals
- State their boiling points
- Use your answers to point 3 to explain why distillation is a good method for separating cyclohexanol and cyclohexene
- The method states to distil off any liquid which boils below 100°C. This is much lower than the boiling point of cyclohexanol. Explain this requirement from the method.
Students will be provided with links to help them where necessary.
Students have also seen me demonstrate the use of a separating funnel + still and they have also done a full practical where they have practised using the equipment in an environment where I was not assessing them. To additionally prepare for that they had also watched the excellent RSC Lab Primers on the topic.
This way, I know that students are well prepared not just for the science content, but for the use of equipment as well. This should reduce the burden on their working memories.
Once I have checked student responses to the Pre-Lab, they can start the work. I will not be giving feedback during the practical (except for safety purposes). I will print off a table with all the students’ names and five additional columns for each CPAC statement as below. During the practical I will give them a 0, 1 or 2 for each statement. 0 for not met, 1 for partially met and 2 for fully met. This will then be transferred onto our central tracking sheet (designed by AQA) (1). In this, I take a Direct Assessment of Practical Skills approach; I want to see with my own eyes that they can act and think in a specific way.
1. Follows written instructions
To assess this I will, at arbitrary stages, speak to individual students about the practical. I will ask them which stage they are up to, what they have just done and what they are about to do.
2. Applies investigative approaches and methods when using instruments and equipment
I think the terminology of “investigative approaches” here is a little objectionable. I take this statement (as per the Handbook’s description of it) as boiling down to “can they use equipment?” For this practical, I will ask every student to ask me to look at their distillation apparatus once it is set up. I will check that everything is connected correctly and assess accordingly. I will also ask them to show me their use of the separating funnel and assess accordingly.
3. Safely uses a range of practical equipment and materials
My requirement here is always the same: “anything stupid?” If a student is without goggles, they score 0. If a student is not using a fume cupboard when the method says to use one, they score zero. If they set their distillation apparatus on fire (only happened once I promise) they score zero. But it could be anything, from messing around to dumping their bag in the middle of the classroom where it could block other students’ safe passage.
4. Makes and records observations
Before students leave the lab they need to show me their notes on the measurements they have taken (in this case masses + results from test). I will not expect a full table but I do expect it to be neat, clear and with units.
5. Researches, references and reports
This is a bit of a funny one. AQA say students can actually satisfy this by using a calculator (which they will do when calculating the yield). Generally I will ask students a question and expect them to write a brief answer. It could be further research (e.g. what is cyclohexanol used for industrially) or it could be something more procedural (e.g. watch the RSC Lab Primer video on x and write an evaluation of your method accordingly). If so, students will need to reference properly (2) (3).
Students will be told in advance what I will be looking at.
Phase 3: After the practical
This is the point at which we verbally go over the practical, check yield calculations, discuss reasons for low yield, and I will deliver general feedback to the class about things they did well and things which need improvement. If I feel that a particular student needs individualised feedback they will receive it. All students are welcome to come and find me in their own time to ask for specific feedback if they want it.
And that’s pretty much it.
I think this route not only respects the students’ working memories but is also a meaningful way to carry out the practical. It isn’t hugely labour intensive from my standpoint, and things like setting up the Moodle is a good investment – I will be able to use it many times. I think it also encourages a certain independence on the part of the students which is a disposition we are trying to instil in them after a relatively spoon-feedy GCSE experience.
I would love to hear what other schools are doing or if anyone has any general or specific constructive feedback on my route here.
(1) The exam board are clear that you don’t need to assess every CPAC statement every practical but I will discuss this here anyway.
(2) This doesn’t mean using any specific notation e.g. Harvard. The specification states that as long as they would be able to find it again based on their reference that would be sufficient. I think that is a reasonable enough level at KS5. EDIT: According to Joe on Twitter AQA do actually prefer Harvard and have said so in training which is really annoying.
(3) I know that there are sub-categories I haven’t addressed here. One at a time…