GCSE Practicals: Density

Resources and ideas to support the 'required' practicals in the 2016 GCSE Physics specifications. See my GCSE Practicals post for a more detailed explanation.

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).

This collection of student videos might be worth using while planning, or to show them to students with modelled answers and explanations.

There are lots of misconceptions about density – 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. This video is a nice development of the ideas of floating and sinking.

A collection of practicals that are worth exploring with your students, whether as hands-on or for them to observe and think about. Having them commentate the results or use one of the many variations of Predict Observe Explain will help them to recognise the main concepts. I recommend checking out the teachers' notes which suggest a proportional approach before introducing the mathematical relationship.

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, this simulation will allow students to consider a range of possible materials and the consequences of placing them in liquids. Don't miss the 'For teachers' tab with explanations of the model used and submitted worksheets to accompany the 'practical'.

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.

Quality AssuredCategory:ChemistryPublisher:Longman

If you'd rather give your students real (and therefore 'messy' data why not use the genuine article?

Creating notes on density isn't difficult, but it can be useful to point students towards a (usually) reliable source. Or why not take the text from this site, add some mistakes then challenge them to correct the errors? This is a quick yet effective way to give them notes that they must still read carefully.

The accompanying notes (about groundwater pollution and immiscibility) may not be relevant, but the colourful column reinforces ideas about varying density. It also ensures students recognise that liquids also, in the right circumstances, 'float' or 'sink'.

This set of instructions for a Cartesian diver might be a fun way to introduce some of the ideas. Alternatively:

Veritasium might be a good extension for more able students.
Sixty Symbols uses examples that you're unlikely to have access to in the lab.