Insights gained from mapping a familiar unit

1 July 2018

Author: Elisa Jimenez Grant

We are lucky enough to have a guest blog this week from Elisa Jimenez Grant (@elisachem), a Chemistry teacher, who agreed to share her thoughts on curriculum mapping, based around research she had discussed with other Science teachers.

Why map a unit?

Inspired by my son’s unexpectedly long nap and @Mr_Raichura’s invitation to think of the story-telling power of curriculum (Raichura, 2018), I decided to revisit a well-known and much-loved unit. I have lurked quietly on Twitter over the last few months, finding many thought-provoking things and I wanted to see if I could bring some of them together into a unit map. Bob Worley introduced me to Johnstone’s triangle  and other wonderful insights into teaching chemistry. Niki Kaiser got me thinking about threshold concepts (Kaiser, 2018). @throughthethresintroduced me to Tier 1, 2 and 3 vocabulary (Vincent, 2018). Rosalind Walker discussed the distinction between declarative and procedural knowledge and how to use this to decide what practice to give to students (Walker, 2018a).

Like many chemistry teachers, I like to start the course with atomic structure. I’m not saying everyone should, but it is what works for me. I like starting with the building blocks of matter, and also the sub-atomic particles that make them up. I like it because it makes sense to scrutinise what we are working with in chemistry and much of it can be seen as coming down to the adage that “protons give atoms their identity while electrons give atoms their personality”. Much of what we do after establishing atomic structure is look at the implications of those identities and personalities.

My students

In the last few years I have really tried to help students develop a solid schema for them to incorporate new knowledge into as well as being a handy way of identifying misconceptions and knowledge gaps. The links between concepts are fundamental. For example when reviewing this last round of final exams one student in particular really struggled with the connection between successive ionization energies and periodic table group, in spite of having a very strong grasp of periodic table position, electron arrangement and ionization energy. Another significant stumbling block in this unit is the hydrogen emission spectrum: how come a rectangle with four lines in it tells us so much?

My school

I work in an International Baccalaureate (IB) school. One of the programmes we offer is the IB Diploma Programme (DP), for students aged 16 to 19. In addition to their choice of academic subjects, there are additional requirements for all DP students, collectively known as the “core”, including Theory of Knowledge (TOK), a course which encourages students to delve into the nature of knowledge itself. I am very familiar with IB and DP Chemistry in particular but I always get great deal out of looking at the subject through new lenses or with novel emphases. Doing so reveals new ways to bring TOK and IB principles into my subject-specific teaching.

Making the map

This unit map-making process was by no means systematic. It very much emerged spontaneously from the intersection of a bit of time, the ideas I had read about over the last few months, and my thinking ahead to the next school year. I basically started writing ideas down on paper and saw where that took me.

1)    I established what I believe to be the two main principles of the unit. One principle is straight out of the DP chemistry guide (“The mass of an atom…”; IBO, 2014). The other what I believe is the other main idea in the unit (“Electrons are…”):

2)    While referring to the knowledge, applications and skills in the guide, I made a spider diagram, classifying the content into declarative and procedural (red and blue, respectively).

As I went, I wrote emergent links to TOK, NOS and CCL in black. Green is for practical work (including data-base investigations, a DP requirement).

3)    I hunted around for possible threshold concepts by looking out for vital linksbetween concepts that are also difficult for students. These are surrounded by dashed lines:

4)    Prior knowledge and the lead-in to the next unit went in next.

5)    Then I made a digital copy of the map and highlighted the three domains of Johnstone’s triangle (Worley, n.d) as follows:

and as I worked on that I discovered one of my possible threshold concepts, related to the hydrogen emission spectrum, was related to all three of Johnstone’s domains!!


After completing the map I scribbled down some Tier 1, 2 and 3 vocabulary (Beck, mentioned in Vincent, 2018) while the ideas were still fresh in my mind. I work with a large proportion of EAL students and need to take care when introducing and using potentially troublesome words.

Thinking back to a recent tweet by @UncleBo80053383, I included an EAL alert for Tier 2 words.

Threshold concept?

After some thought, I articulated some – possible – threshold concepts:
·     Electrons have discrete energies or “energy levels”.
·     The energy levels increase in energy further away from the nucleus.
·     Electrons can move between these levels by absorbing or releasing wavelengths of light.
·     Atomic nuclei are positively charged and very dense.

But are they indeed threshold concepts? Threshold concepts are described as being integrative, irreversible, troublesome, transformative and bounded (Meyer and Land, 2003). The ones I came up with seem to be integrative: they connect the three domains of Johnstone’s triangle, as well as linking various ideas. For example:
–      Transforming student’s prior notion of “shells” into “energy levels”,
–      Quantised nature of these energy levels,
–      Suggesting a reason whyelectrons “like” to be in the lower shells,
–      An example of how we use inference in science to tell us about things that we cannot observe directly (NOS: evidence and theories, and TOK: sensory perception and inductive reasoning).

The concepts are also troublesome, a minefield for students who find the notion of discrete energies challenging, as well as experiencing confusion over energy levels vs ionisation energy. The leap from the almost tangible idea of electron shells to electron probability “clouds” is also difficult (understandably!).

I am not sure, however, if these proposed threshold concepts are irreversible, transformative or bounded and this is something to ponder in the future. The existence of threshold concepts has been called into question previously, raising another interesting area for future discussion. Regardless, I have found it helpful to identify and articulate them as a way to hone in on crucial concepts in the unit that can further inform my planning.

Questions and next steps

Mapping this unit was very satisfying, which is all very well but the question is how does it translate into better learning for my students? For a start, this mapping exercise has already helped me to arrive at crucial (threshold?) concepts, tiered vocabulary and possible misconceptions. This is all useful fodder for hinge questions and explicit teaching of troublesome vocabulary for instance. Secondly, I plan to use this unit map to better plan my lesson sequences and better integrate TOK, NOS, CCL. In addition, my hope is that mapping the unit like this will inform the practice I give students in lessons.

The procedural/declarative distinction will be useful when planning the types of practice to give students. Rosalind Walker suggests a typology of relationships between declarative concepts and how to design suitable practice for them, depending on their type. Designing practice for procedural knowledge is slightly more straightforward: questions of increasing difficulty, answers readily available for students, worked examples for students to scrutinise, etc (Walker, 2018b).

Finally I would also like to try mapping a unit for an age group and curriculum I am not so familiar with, such as the MYP 2 unit on mixtures that I will be teaching next year after a long stretch without teaching that age group. I wonder how the experience of mapping an unfamiliar unit will be different and whether it will inform my planning in a different way? I like working on paper, but it does limit flexibility, so I might try using Cmap Tools next time.


IBO (2014) ‘Topic 2: Atomic structure’ and ‘Topic 12: Atomic structure’, Chemistry guide. [Online]. Available at 23 June 2018).

Kaiser, N. (2018) ‘Do they really get it, or are they just giving me the correct answer?’, Kaye Chem Notebook, 19 January 2018 [Blog]. Available at 24 June 2018).

Meyer, J. and Land, R. (2003) ‘Threshold concepts and troublesome knowledge: linkages to ways of thinking and practising within the disciplines’, In Improving Student Learning – Ten Years On. C. Rust (Ed), OCSLD, Oxford [Online]. Available at 24 June 2018).

Raichura, P. (2018) ‘Designing a Science Curriculum: my #rEDRugby talk’, Bunsen Blue,23 June 2018 [Blog]. Available at 23 June 2018).

@UncleBo80053383 (2018) This is from Alex Johnstone’s book…,  30 May 2018 [Twitter]. Available at 30 May 2018).

Vincent, W (2018) ‘This much I know about EAL teaching’, Through the threshold, 13 April 3018 [Blog]. Available at 53 June 2018).

Walker, R (2018a), ‘Knowledge, Philosophy and Shed Loads Of Practice: My #rEDRugby presentation’,The Fruits Are Sweet, 10June 2018 [Blog]. Available at 23 June 2018).

Walker, R (2018b) ‘My #rEDBrum talk: The Nature of School Science Knowledge’, The Fruits Are Sweet,12February 2018 [Blog]. Available at 25 June 2018).

Worley, R. (n.d.) ‘Microchemistry helping in learning’, Microchemuk [Online]. Available at 23 June 2018).



Posted on 1 July 2018
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