Sequencing linear and non-linear topics

I recently wrote a post about sequencing. I explained why I resequenced my specification, how I did it, as well as some advantages and disadvantages of committing to a bespoke sequence of teaching your subject.

Over a series of posts I will be exploring this idea of sequencing further, with this post specifically talking about the linearity and non-linearity of our subjects and how this can impact our approach to sequencing our topics effectively.

Linear topics

Most concepts within our subjects would naturally follow on from each other, where you can’t fully understand a concept without having the prior knowledge secure, for example:

  • Newton’s Laws follows resultant forces. You could argue that a student can recite Newton’s laws without having an understanding of resultant forces, but they will not understand what the laws mean.
  • Momentum follows velocity. Students can’t really understand momentum if they only know about speed, they must understand that velocity is a vector and that this is crucial for momentum calculations.
  • The types of nuclear radiation requires a lot of prior knowledge. Students can’t understand what alpha, beta and gamma are unless they understand the structure of the atom and have come across waves before, however they don’t need to have a secure understanding of the entirety of the waves topic.
  • The types of electromagnetic waves would naturally follow on from transverse waves, but again you could argue that students can still learn the 7 types of EM waves without knowing what a transverse wave is.

Non-linear topics

Then there are the concepts that follow on from each other, but in any order. There is no obvious linearity to the sequence, and this is where you can get a bit more creative with your sequencing. But these are the topics where it is incredibly important to keep referring back and forth between:

  • Resultant forces and velocity/acceleration. Do you teach acceleration first and then explain why objects accelerate, or do you teach resultant forces first and then describe the effects?
  • Nuclear radiation. Do you teach the findings of Rutherford’s gold foil experiment or the types of nuclear radiation first?
  • Electricity. Do you teach flowing charge or static charge first?
  • Generating electricity. Do you teach the National Grid in energy resources first, or do you teach transformers first in the Electromagnetism topic?
  • Gamma radiation. Does it first come up when talking about nuclear radiation or when talking about electromagnetic radiation?
  • Fields. Do you teach magnetic fields or electric fields first? Have you considered why? The A Level specification is good at this because it forces you to compare the two.

With these examples I believe there is no correct order, no logical sequence that seems better than the other. But what is important for these topics (and others no doubt) is that you are constantly referring to the other topic when teaching.

I would mention transformers when teaching the National Grid because it is a major feature of the system, but students do not need to know how a transformer works for them to know what it does. However this lesson on the National Grid could just as easily come up later on in the course after you have taught how transformers work.

I teach resultant forces first, but when I teach velocity, acceleration and motion graphs I would make those links back to resultant forces explicit. I saw this wonderfully effective question on Twitter recently which shows exactly what we should be doing more of within our subjects:

While this question would come after having learnt about both resultant forces and motion graphs, it explicitly shows the link between the two topics. It’s simple yet powerful.

When you start combining the linear and non-linear parts of your subject, you begin to naturally create interesting maps of concepts:

A sequence is fluid and is never set in stone. You might find that you are happy with the sequence of your subject, only to find that when you are in front of a class that you have overlooked something. In your lessons say things like “Right now that we know about Y, do you remember when we learnt about X? How do X and Y link?” And then suddenly both X and Y will make a lot more sense to them.

Create a sequence, test it, modify it, see what works and what doesn’t. But always go back and make those links with other topics.

Photo by Marco Tjokro on Unsplash

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