Density

AQA RP8: Investigate, using appropriate apparatus, the densities of regular and irregular solid objects and liquids, making and recording appropriate measurements.
OCR PAG1: Use of measurements to determine densities of solid and liquid objects
Edexcel 4.3: Investigate the densities of solid and liquids (such as an investigation that uses irregularly shaped objects and a density bottle)
There are lots of misconceptions here – the well known idea of comparing the weight of a kilo of feathers and a kilo of bricks shows this. We conflate density and weight in common conversation, quite apart from mass! Students have often encountered the ideas when learning about buoyancy, which is frequently taught in primary school science. You may have shown them a ball bearing floating on liquid mercury.
Predictably, there are lots of great ideas at Practical Physics; in particular I recommend reading the teaching guidance which suggests a narrative approach before introducing the maths. Considering typical misconceptions is also worthwhile. There are many practical activities which provide opportunities for various skills such as PRODME discussion, measurement and data recording. If you provide differently-sized lumps of plasticene to students and have them plot mass against volume the points should give a nice straight-line relationship – time to discuss proportionality! The same would be true of varied pieces of (the same) plywood or water balloons if you’d like more data. You might also like to discuss the difference between the name of a quantity and the unit, or the symbol and the abbreviated unit.
As a follow-up, there’s a virtual practical at PhET which could be set as homework. This, like any simulation, gives an opportunity to discuss how we collect data, which lead to models, which make predictions, which can be compared to more observations. These animations give data which are unusually neat and clear compared to the untidiness of real life. (For real data, see the A-level Nuffield data book available on the eLibrary.) The density column as described at the American TeachEngineering resource site would be a great starter in a later lesson to check understanding. And how about using the Density notes at BBC Bitesize to create a ‘mistakes’ exercise which students can correct in class?
If you want videos there are unsurprisingly many options. Bang Goes The Theory created instructions to build your own Cartesian Diver. If you’d like something more theoretical, the ever-reliable Veritasium or Sixty Symbols might be good. You may of course have access to something like BrightStorm or BrainPOP as well.
If you’ve any ideas or improvements, please add them in the comments. This is the first post of a planned series supporting teachers with the new Physics GCSE ‘required’ practicals.
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GCSE Practicals

You’ll already know that the assessment of practical work is changing. (I recommend this article by Alistair Moore and this at the RSC from @MaryUYSEG for useful perspectives.) At A-level it’s changed already, as part of many other alterations. The ISAs are gone for post-16, and it’s fair to say that most teachers aren’t going to miss them. At GCSE these changes will be part of the new specification which officially starts in September 2016, and which many schools have already started to use for their Year 9 students. Which is brave, when they’ve not been approved yet! If you’re teaching A-level Physics I’d recommend the resource created by one of my day-job colleagues at the SPN and available to all.
Different exam boards are taking different approaches, but there’s a big overlap. Each has a list of practicals which are required/recommended/suggested, and students will need to have a signed form of some kind which says they’ve done them. This means they’ll have had the opportunity to gain all the relevant skills (according to OfQual) which will be a pass/fail ‘extra’ to the grade. I predict, somewhat cynically, that the vast majority of students will have gained these skills on paper no matter how much their lab work resembles that of Beaker from the Muppets. 15% of the final exam marks will be awarded for students demonstrating in a written exam that they can think like a scientist, probably in a similar way to the ISA papers.
The list of practicals is a minimum expectation – a lower limit rather than an upper one. Most are ones we have always done, in one form or another. Students don’t have to work independently on all of them, or in exam conditions. They need not (and in my opinion should not) do them as a separate unit or topic but as part of their normal experience of science, alongside science content and social context. There is no specific way they are expected to write them up or record their results.
My plan is to create a resource list for each of the GCSE Physics practicals, drawn from AQA, Edexcel and OCR. These are my interpretation and, certainly at the moment, I’m doing them in my own time for no charge. (If anyone would like them sooner and/or to sell, contact me with a price in mind.)