In their characterisation of talk in science lessons, Mortimer and Scott* suggest that the communication approach can take four main forms as shown in the quartet below:
In this blog, I look at what these forms of communication might look like, and suggest when each of them can be helpful to build students understanding in Chemistry.
The term 'interactive' shows that there is back and forth discussion with the students. 'Authoritative' demonstrates that the teacher occupies and promotes only the perspective that they want students to learn in the lesson. In my experience as an observer, this form of communication makes up the majority of all classroom discussion.
In this dialogue, the student and the teacher are interacting, but the teacher is steering the student towards the correct explanation for the difference in melting point between diamond and oxygen:
Teacher: Explain to me then, in two sentences, what’s going on.
Student: I can’t do it in two sentences. The carbon, when it’s joined together, there aren’t any left-over electrons. They form bonds that are…
Teacher: So you have those spare electrons...
Student: You have those spare electrons and the covalent bonds are stronger than the intermolecular forces.
Teacher: So that’s the key point. Don’t worry too much about the unpaired electrons. They’re important for how chemicals react…
Teacher: … having those unpaired electrons, but in terms of melting point we don’t need to be thinking about that so much.
Student: So it takes more energy to split up the carbon atoms than to split up the oxygen. Teacher: Very good.
The teacher disregards the spare (or unpaired) electrons for the student, sticking to the accepted response, and then the student goes back to the distinction between covalent bonds and intermolecular forces for her explanation.
When should this be used?
When discussing abstract or unfamiliar concepts. In these cases adopting lots of unorthodox perspectives can be conceptually confusing for the students as their grasp of the ideas is still very tenuous.
When consolidating and reviewing new ideas in classroom discussion. This then reinforces the accepted 'school science' explanation with the students.
In contrast, 'dialogic' means that the teacher takes on different perspectives as part of the interaction: they don't always stick to the accepted 'school science' perspective for the discussion. This usually happens when teachers are gathering students' ideas about a new observation, and they allow students to work out for themselves which ideas are likely to be valuable.
Teacher: Why do you think this one took more time than the last one?
Student: I don't know. I used more acid, so it should have been faster. [student thinking] Maybe when I washed up the flask it got colder and so it slowed the reaction down?
Teacher: That's a good idea. How could you test whether that's the right explanation?
Student: I could do the first one again after washing the flask and see if it makes a difference to the time.
Teacher: You could. Could you use a thermometer to work out if there's a difference in temperature?
Student: Yeah... I could measure the temperature at the start of both experiments and see if it's the same.
Teacher: So what if they come out the same? Is there anything else which might explain why the second reaction happened slower?
In this dialogue, the teacher knows that the reactions are likely to be at the same temperature, but instead of immediately telling the student this and asking for another idea, they listen to the student's perspective and operate within it to get the student thinking about how they can work out if this is the right error.
When should this be used?
During demonstrations. Asking students about all of their observations and guiding them to which are relevant and which are not, and what each particular observation is telling them on a more abstract level, by letting them reason for themselves.
During practicals to discuss sources of error, such as in the example above.
To identify and challenge misconceptions by taking them to their logical conclusions (this can be supported really well using concept cartoons).
The lecture. There is no interaction between the student and the teacher, and there only story is the accepted scientific one. An expert, who could be the teacher, or could be a student, presents an idea without any discussion.
In Chemistry lessons this is most commonly observed during the introduction of a new concept. The teacher talks for a minute or so, before opening up the floor to interaction. However, I have also seen it when students have been asked to do some research and are presenting their findings to the class: they adopt the scientific story and explain it to their peers.
To do this well, there needs to be a good interplay between visual and aural stimuli for the listeners, and the content needs to be pitched at the right level: if it is too easy the students will switch off, bored; and if it's too hard, they will struggle for a minute, and then switch off, disenchanted.
When should this be used?
When explaining a new idea to a class. Particularly if it is completely new, so the students cannot be easily involved in co-construction using their prior knowledge. But, keep the timing of the monologue down and move on to interactive authoritative discussion as soon as possible.
When students are presenting their learning, either from an independent research project, or their learning during the lesson.
When giving assemblies which are well supported by visuals, and pitched at the right level, using anecdotes to bring students back in if they have become lost, and big questions to get them thinking and prevent boredom.
Mortimer and Scott suggest that non-interactive dialogic communication sounds incoherent. How is it possible for the teacher to listen and accept multiple perspectives without the students interacting? But there are actually lots of ways.
The example they give is that the teacher might adopt the students' previous explanation. Here is an example from a Year 12 Chemistry lesson:
Teacher: So you can see that the ionisation energies increase across the period and then decrease dramatically at the start of the next period. We can explain this overall trend using your knowledge from GCSE. The number of protons in the nucleus increases across the period, and the distance of the outer shell stays the same, so the force of attraction between the outer electron and the nucleus increases, so the ionisation energy increases. This is the overall trend that we see here. Then as we move to the next period, there is a new shell, which is further away from the nucleus. This means the force of attraction is much weaker, even though there are more protons in the nucleus, so the ionisation energy decreases a lot. But, now at A-level we need to explain these irregularities in the trend, here, between magnesium and boron, and nitrogen and oxygen, which we cannot explain with the old model. So we need a new model for electronic structure which can explain this, and this looks like....
When should this be used?
To highlight the move from students' previous ideas to new ideas about Chemistry that they are learning.
To highlight different ethical or religious perspectives on an aspect of what the students are studying, such as animal testing in drug design.
To teach students the ideas of different scientists or thinkers about particular experiments or observations, such as Priestley and Lavoisier's different ideas about phlogiston, or the strengths and weaknesses of the different models of the atom.
It could even be used to highlight some philosophical perspectives in Chemistry, such as the reductionist debate (can all Chemistry be reduced to Physics?), or the realism vs. anti-realism debate (full blog post on this coming soon).
So, challenge yourself to use all four forms of classroom interaction in a single lesson. See how focusing on this can:
help you plan varied and interesting learning,
improve lesson pace,
and force you out of your comfort zone (which is interactive authoritative for most of us).
*Mortimer and Scott (2003) Meaning Making in Secondary Science Classrooms. Maidenhead: Open University Press.