Teaching

Teaching and learning

Teaching is what I do. Learning is what the student does. They are not the same thing, so I plan for them separately. Both of my subjects share one difficulty: a scientific explanation moves between levels of description, and experts move between those levels without noticing. Students cannot. For each subject below I set out the learning problem, then how I teach it, then how I check it is working.

Chemistry

Johnstone’s triangle

The learning problem

Chemistry is taught at three levels: what you can see in the beaker, what the particles are doing, and the symbols we write down (Johnstone, 1982, 1991). Experts move between these levels without thinking about it. Students cannot hold all three at once, so their working memory overloads (Johnstone, 1991; Sirhan, 2007).

Most lessons run mainly at the symbolic level, which is the level furthest from anything a student can see (Johnstone, 1991). Students then learn to manipulate equations without a picture of what the particles are doing. The equations look correct and the understanding is not there.

How I teach it

  • State which level we are working at.
  • Introduce a new topic at one level first, then connect it to the others.
  • Ask for a particle diagram, not only a balanced equation.
  • In practicals, separate observation from explanation.
  • Pair a diagram with the words, so the explanation does not sit in language alone.

How I check it is working

  • Diagnose errors by level. “Does not understand moles” becomes a specific gap any teacher in the department can act on.
  • A student who can balance an equation but cannot draw the particles has a conceptual gap, not a careless one.
  • Write questions that require translating between two levels, not recall at one.
  • Use mini whiteboards to see every student’s particle diagram at once, not just the three who volunteer.
experts translate freely;novices overload2SUBMICROSCOPICwhat the particles do1MACROSCOPICwhat you can see3SYMBOLICH₂O(l) → H₂O(g)what we write downONE PHENOMENON, THREE LEVELS — WATER BOILING1The liquid turns to steam.2Molecules gain energy and move further apart.3The change is written as an equation.
Figure 1. The three levels at which chemistry is explained, and the translations between them. Adapted from Johnstone (1982, 1991) and Taber (2013).
LEVELSCALEWORKED EXAMPLEzoom outzoom inEcosystem10³–10⁵ mPopulation10²–10³ mOrganism~1 mthe animal shows diseaseTissue / organ~1 cmtissue is damagedCell~10 µminfected cells dieMolecule~1 nma viral proteinCAUSE TRAVELS UPAn explanation that stops at one level is a label. One that travels is an explanation.
Figure 2. Levels of biological organisation, with the causal chain from my own virology research mapped across them. Levels after Schneewieß & Gropengießer (2022); example from Xu et al. (2014).

Biology

Reasoning across levels of organisation

The learning problem

Biology has the same difficulty. A phenomenon appears at one level, but its causes sit at another: a fever explained by a protein, a population explained by a gene (Schneeweiß & Gropengießer, 2022). Students tend to reason at one level only, so they can name a structure without explaining it.

This is not a loose analogy. Wright et al. (2017) adapted Johnstone’s triangle directly into biology as the DNA triangle, and showed that experts explain meiosis using molecular, chromosomal and informational levels together, while students stay at the chromosomal level. My own research ran down these levels, from a viral protein to a dying cell to a sick animal, so I teach the levels explicitly.

How I teach it

  • Name the level, then move up and down it with the same example.
  • Use structure, behaviour and function: what the parts are, how they interact, and what that achieves (Hmelo-Silver et al., 2007).
  • Show the mechanism with a model or drawing before the terminology arrives.
  • Give students a map of the levels they can use themselves when planning an answer (Schneewieß & Gropengießer, 2022).

How I check it is working

  • Require explanations that cross at least two levels, so “what” becomes “how”.
  • Treat purpose language as a signal. “The cell wants to” usually means the mechanism is missing.
  • Check whether a student moves down a level without being asked. That is the habit I am building.
  • Use mini whiteboards for a quick cross-level question before moving on.

Two different things

Teaching strategies and learning strategies

A teaching strategy is something I do. A learning strategy is something the student does. They are easy to confuse, and confusing them is how a lesson ends up busy but empty. The examples below are from my own action research with a Grade 9 IGCSE Chemistry class of twelve, most of them learning in English as an additional language.

Teaching strategies — what I do
  • Provide sentence stems and writing scaffolds for extended answers.
  • Match the level of support to the individual student rather than the class.
  • Withdraw support only when the evidence says the student is ready, not on a fixed schedule.
  • Judge the mark, the help the student needed, and the accuracy of the science as three separate measures.
  • Check the whole class with mini whiteboards before deciding whether to move on.
Learning strategies — what students do
  • Rehearse the explanation aloud with a partner before writing it down.
  • Sort the ideas into order on cards before turning them into sentences.
  • Use the sentence stem, then write the same answer again without it.
  • Say what help they still need, which is a skill in itself.

The distinction is not academic. When I withdrew the scaffolds too quickly, the class mean on extended writing fell to 39.6%, even though the same students had sorted the ideas correctly on cards that morning. They had the chemistry; they did not yet have a way of getting it onto paper alone. Adding paired oral rehearsal and support matched to each student lifted the mean to 62.5%, and students needed less help to get there.

A tool I use in every lesson

Mini whiteboards

Asking “any questions?” and taking three volunteers gives me evidence from a tenth of the room, and I then assume the rest followed. Mini whiteboards remove that assumption. Every student writes an answer and holds it up at the same time, so I see the whole class in one glance. Wiliam (2018) calls these all-student response systems, and Black and Wiliam (1998) found this kind of assessment to be among the strongest levers available to a teacher.

They also fit the two frameworks above exactly. The hardest thing to see in a chemistry class is whether a student can picture the particles, and the hardest thing in biology is whether they can move down a level. A whiteboard makes both visible in seconds: draw the particles, or explain this at the level below. If most of the room is wrong, I reteach there and then rather than finding out at the end of the unit.

Students holding up mini whiteboards in a science lesson

The two frameworks are the same idea, which is why I am glad to teach both subjects. A student who learns to ask “which level am I reasoning at, and what is happening one level down?” has learned something that outlasts the syllabus.

References

  1. Black, P., & Wiliam, D. (1998). Assessment and classroom learning. Assessment in Education: Principles, Policy & Practice, 5(1), 7–74. https://doi.org/10.1080/0969595980050102
  2. Hmelo-Silver, C. E., Marathe, S., & Liu, L. (2007). Fish swim, rocks sit, and lungs breathe: Expert–novice understanding of complex systems. The Journal of the Learning Sciences, 16(3), 307–331. https://doi.org/10.1080/10508400701413401
  3. Johnstone, A. H. (1982). Macro- and micro-chemistry. School Science Review, 64(227), 377–379.
  4. Johnstone, A. H. (1991). Why is science difficult to learn? Things are seldom what they seem. Journal of Computer Assisted Learning, 7(2), 75–83. https://doi.org/10.1111/j.1365-2729.1991.tb00230.x
  5. Schneeweiß, N., & Gropengießer, H. (2022). The Zoom Map: Explaining biological phenomena across the levels of organisation. Journal of Biological Education. https://doi.org/10.1080/00219266.2022.2134174
  6. Sirhan, G. (2007). Learning difficulties in chemistry: An overview. Journal of Turkish Science Education, 4(2), 2–20.
  7. Taber, K. S. (2013). Revisiting the chemistry triplet: Drawing upon the nature of chemical knowledge and the psychology of learning to inform chemistry education. Chemistry Education Research and Practice, 14(2), 156–168. https://doi.org/10.1039/C3RP00012E
  8. Wiliam, D. (2018). Embedded formative assessment (2nd ed.). Solution Tree Press.
  9. Wright, L. K., Catavero, C. M., & Newman, D. L. (2017). The DNA triangle and its application to learning meiosis. CBE—Life Sciences Education, 16(3), ar50. https://doi.org/10.1187/cbe.17-03-0046
  10. Xu, Y., Victorio, C. B. L., Ng, Q., Tan, Y. J., & Chua, K. B. (2014). Saffold virus is able to productively infect primate and rodent cell lines and induces apoptosis in these cells. Emerging Microbes & Infections, 3(2), e15. https://doi.org/10.1038/emi.2014.15