questioning – Science-Education-Research

Do nerve signals travel faster than the speed of light?

Keith S. Taber

I have recently posted on the blog about having been viewing some of the court testimony being made available to the public in the State of Minnesota v. Derek Michael Chauvin court case (27-CR-20-12646: State vs. Derek Chauvin).

[Read 'Court TV: science in the media']

Prof. Martin J. Tobin, M.D., Loyola University Chicago Medical Center

I was watching the cross examination of expert witness Dr Martin J. Tobin, Professor of Pulmonary and Critical Care Medicine by defence attorney Eric Nelson, and was intrigued by the following exchange:

Now you talked quite a bit about physics in your direct testimony, agreed?

Yes

And you would agree that physics, or the application of physical forces, is a constantly changing, er, set of circumstances.

I did not catch what you said.

Sure. You would agree with me, would you not, that when you look at the concept may be considered as the sum of all its associations.<em>Read about concepts</em><br/></div>" href="https://science-education-research.com/reference/site-glossary/concepts/" target="_blank" data-mobile-support="0" data-gt-translate-attributes='[{"attribute":"data-cmtooltip", "format":"html"}]' tabindex='0' role='link'data-bgcolor="#e8e8e8"data-tcolor="#73874d">concepts of physics, these things are constantly changing, right?

Yeah, all of science is constantly changing.

Constant! I mean,

Yes.

in milliseconds and nanoseconds, right?

Yes.

And so if I put this much weight [Nelson demonstrating by shifting position] or this much weight [shifting position], all of the formulas [sic] and variations, will change from second to second, from millisecond to millisecond, nanosecond to nanosecond, agreed.

I agree.

Similarly, biology sort of works the same way. Right?

Yes.

My heart beats, my lungs breathe [sic], my brain is sending millions of signals to my body, at all times.

Correct.

Again, even, I mean, faster than the speed of light, right?

Correct.

Millions of signals every nanosecond, right?

Yes.
Day 9. 27-CR-20-12646: State vs. Derek Chauvin

Agreeing – but talking about different things?

The first thing that struck me here concerns what seems to me to be Mr Nelson and Dr Tobin talking at cross-purposes – that neither participant acknowledged (and so perhaps neither were aware of).

I think Nelson is trying to make an argument that the precise state of Mr George Floyd (who's death is at the core of the prosecution of Mr Chauvin) would have been a dynamic matter during the time he was restrained on the ground by three police officers (an argument being made in response to the expert's presentation of testimony suggesting it was possible to posit fairly precise calculations of the forces acting during the episode).

This seems fairly clear from the opening question of the exchange above:

Now you talked quite a bit about physics in your direct testimony, agreed? … And you would agree that physics, or the application of physical forces, is a constantly changing, er, set of circumstances.

However, Dr Tobin does not hear this clearly (there are plexiglass screens between them as COVID precautions, and Nelson acknowledges that he is struggling with his voice by this stage of the trial).

Nelson re-phrases, but actually says something rather different:

You would agree with me, would you not, that when you look at the concept may be considered as the sum of all its associations.<em>Read about concepts</em><br/></div>" href="https://science-education-research.com/reference/site-glossary/concepts/" target="_blank" data-mobile-support="0" data-gt-translate-attributes='[{"attribute":"data-cmtooltip", "format":"html"}]' tabindex='0' role='link'data-bgcolor="#e8e8e8"data-tcolor="#73874d">concepts of physics, these things are constantly changing, right?

['These things' presumably refers to 'the application of physical forces', but if Dr Tobin did not hear Mr Nelson's previous utterance then 'these things' would be taken to be 'the concept may be considered as the sum of all its associations.<em>Read about concepts</em><br/></div>" href="https://science-education-research.com/reference/site-glossary/concepts/" target="_blank" data-mobile-support="0" data-gt-translate-attributes='[{"attribute":"data-cmtooltip", "format":"html"}]' tabindex='0' role='link'data-bgcolor="#e8e8e8"data-tcolor="#73874d">concepts of physics'.]

So, now it is not the forces acting in a real world scenario which are posited to be constantly changing, but the concept may be considered as the sum of all its associations.<em>Read about concepts</em><br/></div>" href="https://science-education-research.com/reference/site-glossary/concepts/" target="_blank" data-mobile-support="0" data-gt-translate-attributes='[{"attribute":"data-cmtooltip", "format":"html"}]' tabindex='0' role='link'data-bgcolor="#e8e8e8"data-tcolor="#73874d">concepts of physics. Dr Tobin's response certainly seems to make most sense if the question is understood in terms of the science itself being in flux:

Yeah, all of science is constantly changing.

Given that context, the following agreement that these changes are occurring "in milliseconds and nanoseconds" seems a little surreal, as it is not quite clear in what sense science is changing on that scale (except in the sense that science is continuing constantly – certainly not in the sense that canonical accounts of concept may be considered as the sum of all its associations.<em>Read about concepts</em><br/></div>" href="https://science-education-research.com/reference/site-glossary/concepts/" target="_blank" data-mobile-support="0" data-gt-translate-attributes='[{"attribute":"data-cmtooltip", "format":"html"}]' tabindex='0' role='link'data-bgcolor="#e8e8e8"data-tcolor="#73874d">concepts shift at that pace: say, in the way Albert</div><div class=glossaryItemBody>Albert Einstein (1879 - 1955) was a theoretical physicist most famous for proposing the special theory of relativity and the general theory of relatively: theories were largely considered counter-intuitive and which contradicted ideas that had been strongly held and considered well founded for almost two centuries. The special theory suggested that light was always observed to have the same speed (invariance) in a vacuum or in a particular medium, regardless of the speed of the observer (effectively suggesting the principle of relativity of Galileo was only an approximation that work well below light speeds. The general theory suggested that what we experience as gravity can be understood as the effect of mass on the very geometry of space-time.Einstein was awarded the Novel prize for his work in the photoelectric effect which assumed that for some purposes light had to be understood as if a series of packets (quanta) rather than seen as a wave. Again, this was contrary to common scientific thinking that light was best understood as a wave.Einstein was famous for having been poor at school and not being good at maths (both vast exaggerations), for having made major contributions to science whilst working as a patent examiner having not been able to obtain a suitable academic position; for having a major role in persuading the U.S. government to develop an atomic bomb during World War 2 (fearing Germany would build its own atomic weapons) , and later working for peace. He was seen as an eccentric (not wearing socks, and having untidy hair). Although originally a German, as a Jew Einstein was subject to the anti-Semitic Nazi policies of the Third Reich and escaped to Norfolk, England, then the U.S.Einstein was not an orthodox Jew in terms of observance, and is sometimes said to be an atheist, but he seems to have held to a notion of God as an abstract guiding power behind the cosmos and did not reject all religion ("<em><strong>science without religion is lame, religion without science is blind</strong></em>"). He famously questioned the common interpretations of quantum mechanics as suggesting fundamentally the world follows statistical laws, being quoted as arguing"<em><strong>God does not play dice</strong> <strong>with the Universe</strong></em>".</div>" href="https://science-education-research.com/reference/biographical-notes/einstein-albert/" target="_blank" data-mobile-support="0" data-gt-translate-attributes='[{"attribute":"data-cmtooltip", "format":"html"}]' tabindex='0' role='link'data-bgcolor="#d9eef7"data-tcolor="#933100">Einstein's notions of physics came to replace those of Newton).

In the next exchange the original context Nelson had presented ("the application of physical forces, is … constantly changing") becomes clearer:

And so if I put this much weight [Nelson demonstrating by shifting position] or this much weight [shifting position], all of the formulas and variations, will change from second to second, from millisecond to millisecond, nanosecond to nanosecond, agreed.

I agree.

As a pedantic science teacher I would suggest that it is not the formulae of physics that change, but the values to be substituted into the system of equations derived from them to describe the particular event: but I think the intended meaning is clear. Dr Tobin is a medical expert, not a physicist nor a science teacher, and the two men appear to be agreeing that the precise configurations of forces on a person being restrained will constantly change, which seems reasonable. I guess that is what the jury would take from this.

If my interpretation of this dialogue is correct (and readers may check the footage and see how they understand the exchange) then at one point the expert witness was agreeing with the attorney, but misunderstanding what he was being asked about (how in the real world the forces acting are continuously varying, not how the concept may be considered as the sum of all its associations.<em>Read about concepts</em><br/></div>" href="https://science-education-research.com/reference/site-glossary/concepts/" target="_blank" data-mobile-support="0" data-gt-translate-attributes='[{"attribute":"data-cmtooltip", "format":"html"}]' tabindex='0' role='link'data-bgcolor="#e8e8e8"data-tcolor="#73874d">concepts of science are constantly being developed). Even if I am right, this does not seem problematic here, as the conversation shifted to the intended focus quickly (an example of Bruner's 'constant transnational calibration' perhaps?).

However, this reminds me of interview</div><div class=glossaryItemBody>Research interviewing involves a class of techniques for collecting data based upon engaging informants in conversations with various levels of structuring<em>Read more about research interviews</em><br/></div>" href="https://science-education-research.com/reference/site-glossary/interview/" target="_blank" data-mobile-support="0" data-gt-translate-attributes='[{"attribute":"data-cmtooltip", "format":"html"}]' tabindex='0' role='link'data-bgcolor="#e8e8e8"data-tcolor="#73874d">interviews with students I have carried out (and others I have listened to undertaken by colleagues), and of classroom episodes where teacher and student are agreeing – but actually are talking at cross purposes. Sometimes it becomes obvious to those involved that this is what has happened – but I wonder how often it goes undetected by either party. (And how often there are later recriminations – "but you said…"!)

Simplifying biology?

The final part of the extract above also caught my attention, as I was not sure what to make of it.

My heart beats, my lungs breathe, my brain is sending millions of signals to my body, at all times.

Correct.

Again, even, I mean, faster than the speed of light, right?

Correct.

Millions of signals every nanosecond, right?

Yes.

How frequently do our brains send out signals?

I am a chemistry and physicist, not a biologist so I was unsure what to make of the millions of signals the brain is sending out to the rest of the body every nanosecond.

I can certainly beleive that perhaps in a working human brain there will be billions of neutrons firing every nanosecond as they 'communicate' with each other. If my brain has something like 100 000 000 000 neurons then that does not seem entirely unreasonable.

But does the brain really send signals to the rest of the body (whether through nerves or by the release of hormones) at a rate of nx10⁶/10^-9 s^-1 ("millions of signals every nanosecond"), that is, multiples of 10¹⁵ signals per second, as Mr Nelson suggests and Dr Tobin agrees?

Surely not? Dr Tobin is a professor of medicine and a much published expert in his field and should know better than me. But I would need some convincing.

Biological warp-drives

I will need even more convincing that the brain sends signals to the body faster than the speed of light. Both nervous and hormonal communication are many orders of magnitude slower than light speed. The speed of light is still considered to be a practical limit on the motion of massive objects (i.e., anything with mass). Perhaps signals could be sent by quantum entanglement – but that is not how our nervous and endocrine systems function?

If Mr Nelson and Dr Tobin do have good reason to believe that communication of signals in the human body can travel faster than the speed of light then this could be a major breakthrough. Science and technology have made many advances by mimicking, or learning from, features of the structure and function of living things. Perhaps, if we can learn how the body is achieving this impossible feat, warp-drive need not remain just science fiction.

A criminal trial is a very serious matter, and I do not intend these comments to be flippant. I watched the testimony genuinely interested in what the science had to say. The real audience for this exchange was the jury and I wonder what they made of this, if anything. Perhaps it should be seen as poetic language making a general point, and not a technical account to be analysed pedantically. But I think it does raise issues about how science is communicated to non-experts in contexts such as courtrooms.

This was an expert witness for the prosecution (indeed, very much for the prosecution) who was agreeing with the defence counsel on a point strictly contrary to accepted science. If I was on a jury, and an expert made a claim that I knew was contrary to current well-established scientific thinking (whether the earth came into being 10 000 years ago, or the brain sends out signals that travel faster then the speed of light) this would rather undermine my confidence in the rest of their expert testimony.

Single bonds are different to covalent bonds

Single bonds are different to covalent bonds or ionic bonds

Keith S. Taber

Annie was a participant in the Understanding Chemical Bonding project. She was interviewed near the start of her college 'A level' course (equivalent to Y12 of the English school system). Annie was shown, and asked about, a sequence of images representing atoms, molecules and other sub-microscopic structures of the kinds commonl y used in chemistry teaching. She was shown a representation of the resonance between three canonical forms of BF3, sometimes used as away of reflection polar bonding. She had just seen another image representing resonance in the ethanoate ion, and had suggested that it contained a double bond. She had earlier in the interview referred to covalent bonding and ionic bonding, and after introducing the ideas of double bond, suggested that a double bond is different to a covalent bond.

What about diagram 14?…
Oh.
(pause, c.13s)
Seems to be different arrangements. Of the three, or two elements.
Uh hm.
(pause, c.3s)
Which are joined by single bonds.
What, where, what single, what sorry are joined by single bonds?
All the F to the B to the F. Are single bonds they are not double like before. [i.e., a figure discussed earlier in the interview]
So are they covalent bonds? Or ionic bonds, or? Or are single bonds something different again?
Single bonds are different.

This reflected her earlier comment to the effect that a double bond is different to a covalent bond, suggesting that she did not appreciate how covalent bonds are considered to be singular or multiple.

However, as I checked what she was telling me, Annie's account seemed to shift.

They're different to double bonds?
Yeah.
And are they different to covalent bonds?
No 'cause you probably get covalent bonds which are single bonds.

So single bonds, just moments before said to different to covalent bonds, were now 'probably' capable of being covalent. As she continued to answer questions, Annie decided these were 'probably' just alternative terms.

So covalent bonds and single bonds, is that another word for the same thing?
Yeah, probably. But they can probably occur in different, things like in organic you talk about single bonds more than you talk about covalent, and then like in inorganic you talk about covalent bond, more than you talk about single bonding or double bonding.
So you think that maybe inorganic things, like sort of, >> copper iodide or something like that, that would tend to be more concerned with covalent bonds?
< Yeah. < Yeah.
But if you were doing organic things like, I don't know, erm, ethane, >> that's more likely to have single bonds in.
< Yeah. < Yeah.
So single bonds are more likely to occur in carbon compounds.
Yeah.
And covalent bonds are more likely to occur in some other type of compound?
Yeah. Sort of you've got different terminology, like you could probably use single bonds to refer to something in inorganic, but when you are talking about the structures and that, it's easier to talk about single bonds and double bonds, rather than saying that's got a covalent bond or that's got an ionic bond.

Annie's explanation did not seem to be a fully thought-out position. It was not consistent with the way she had earlier reported there being five covalent bonds and one double bond in an ethanoate ion.

It seems likely that in the context of the research interview, where being asked directly about these points, Annie was forced to make explicit the reasons she tended to label particular bonds in specific ways. The interview questions may have acted like Socratic questioning, a kind of scaffolding, leading to new insights. Only in this context did she realise that the single and double bonds her organic chemistry lecturer talked about might actually be referring to the same entities as the covalent bonds her inorganic chemistry lecturer talked about.

It would probably not have occurred to Annie's lecturers (of which, I was one) that she would not realise that single and double bonds were covalent bonds. It may well have been that if she had been taught by the same lecturer in both areas, the tendency to refer to single and multiple bonds in organic compounds (where most bonds were primarily covalent) and to focus on the covalent-ionic dissension in inorganic compounds (where degree of polarity in bonds was a main theme of teaching) would still have lead to the same confusion. Later in the interview, Annie commented that:

if I use ionic or covalent I'm talking about, sort of like a general, bond, but if I use double or single bonds, that's mainly organic, because sort of it represents, sort of the sharing, 'cause like you draw all the molecules out more.

This might be considered an example of fragmentation learning impediment, where a student does not make a link that the teacher is likely to assume is obvious.

Higher resistance means less current for the same voltage – but how does that relate to the formula?

The higher resistance is when there is less current flowing around the circuit when you have the same voltage – but how does that relate to the formula?

Adrian was a participant in the Understanding Science Project. When I interviewed him in Y12 when he was studying Advanced level physics he told me that "We have looked at resistance and conductance and the formulas that go with them" and told me that "Resistance is current over, voltage, I think" although he did not think he could remember formulae. He thought that an ohm was the unit that resistance is measured in, which he suggested "comes from ohm's law which is the…formula that gives you resistance".

Two alternative conceptions

There were two apparent alternative conceptions there. One was that 'Resistance is current over voltage', but as Adrian believed that he was not good at remembering formulae, this would be a conception to which he did not have a high level of commitment. Indeed, on another occasion perhaps he would have offered a different relationship between R, I, and V. I felt that if Adrian had a decent feel for the concepts of electrical resistance, current and voltage then he should be able to appreciate that 'resistance is current over voltage' did not reflect the correct relationship. Adrian was not confident about formulae, but with some suitable leading questioning he might be able to think this through. I describe my attempts to offer this 'scaffolding' below.

The other alternative conception was to conflate two things that were conceptually different: the defining equation for resistance (that R=V/I, by definition so must be true) and Ohm's law that suggests for certain materials under certain conditions, V/I will be found to be constant (that is an empirical relationship that is only true in certain cases). (This is discussed in another post: When is V=IR the formula for Ohm’s law?)

So, I then proceeded to ask Adrian how he would explain resistance to a younger person, and he suggested that resistance is how much something is being slowed down or is stopped going round. After we had talked about that for a while, I brought the discussion back to the formula and the relationship between R, V and I.

Linking qualitative understanding of relating concepts and the mathematical formula

As Adrian considered resistance as slowing down or stopping current I thought he might be able to rationalise how a higher resistance would lead to less current for a particular potential difference ('voltage').

Okay. Let’s say we had, erm, two circuits, and they both have resistance and you wanted to get one amp of current to flow through the circuits, and you had a variable power supply.
Okay.
And the first circuit in order to get one (amp) of current to flow through the circuit.
Yes.
You have to adjust the power supply, until you had 10 volts.
Okay.
So it took 10 volts to get one amp to flow through the circuit. And the second (unclear) the circuit, when you got up to 10 volts, (there is) still a lot less than one amp flowing. You can turn it up to 25 volts, and only when it got to 25 volts did you get one amp to flow through the circuit.
Yes, okay.

In mathematical terms, the resistance of the first circuit is (R = V/I = 10/1 =) 10Ω, and the second is (25/1 =) 25Ω, so the second – the one that requires greater potential difference to drive the same current, has more resistance.

Do you think those two circuits would have resistance?
Erm, (pause, three seconds) Probably yeah.

This was not very convincing, as it should have been clear that as an infinite current was not produced there must be some resistance. However, I continued:

Same resistance?
No because they are not the same circuit, but – it would depend what components you had in your circuit, if you had different resistors in your circuit.
Yeah, I've got different resistors in these two circuits.
Then yes each would have a different resistance.
Can you tell me which one had the bigger resistance? Or can’t you tell me?
No, I can’t do that.
You can’t do it?
No I don’t think so. No.

Adrian's first response, that the circuits would 'probably' have resistance, seemed a little lacking in conviction. His subsequent responses suggested that although he knew there was a formula he did not seem to recognise that if different p.d.s were required to give the same current, this must suggest there was different resistance. Rather he argued from a common sense position that different circuits would be likely to have different components which would lead to them having different resistances. This was a weaker argument, as in principle two different circuits could have the same resistance.

We might say Adrian was applying a reasonable heuristic principle: a rule of thumb to use when definite information was not available: if two circuits have different components, then they likely they have different resistance. But this was not a definitive argument. Here, then, Adrian seemed to be applying general practical knowledge of circuits, but he was not displaying a qualitative feel for what resistance in a circuit was about in term of p.d. and current.

I shifted my approach from discussing different voltages needed to produce the same current, to asking about circuits where the same potential difference would lead to different current flowing:

Okay, let me, let me think of doing it a different way. For the same two circuits, erm, but you got one let's say for example it’s got 10 volts across it to get an amp to flow.
Yeah. So yes okay so the power supply is 10 volts.
Yeah. And the other one also set on 10 volts,
Okay.
but we don’t get an amp flow, we only get about point 4 [0.4] of an amp, something like that, to flow.
Yeah, yeah.
Any idea which has got the high resistance now?
The second would have the higher resistance.
Why do you say that?
Because less erm – There’s less current amps flowing around the circuit erm when you have the same voltage being put into each circuit.
Okay?
Yes.

This time Adrian adopted the kind of logic one would hope a physics student would apply. It was possible that this outcome was less about the different format of the two questions, and simply that Adrian had had time to adjust to thinking about how resistance might be linked to current and voltage. [It is also possible too much information was packed close together in the first attempt, challenging Adrian's working memory capacity, whereas the second attempt fed the information in a way Adrian could better manage.]

You seem pretty sure about that, does that make sense to you?
Yes, it makes sense when you put it like that.
Right, but when I had it the other way, the same current through both, and one required 10 volts and one required 25 volts to get the same current.
Yes.
You did not seem to be too convinced about that way of looking at it.
No. I suppose I have just thought about it more.

Having made progress with the fixed p.d. example, I set Adrian another with constant current:

Yes. So if I get you a different example like that then…let’s say we have two different circuits and they both had a tenth of an amp flowing,
Okay. Yes.
and one of them had 1.5 volt power supply
Okay yes.
and the other one had a two volt power supply
Yeah.
but they have both got point one [0.1] of an amp flowing. Which one has got the high resistance?
Currents the same, I would say they have got different voltages, yeah, so erm (pause, c.6s) probably the (pause, c.2s) the second one. Yeah.
Because?
Because there is more voltage being put in, if you like, to the circuit, and you are getting less current flowing in and therefore resistance must be more to stop the rest of that.
Yes?
I think so, yes.
Does that make sense to you?
Yeah.

So this time, having successfully thought through a constant p.d. example, Adrian successfully worked out that a circuit that needed more p.d. to drive a certain level of current had greater resistance (here 2.0/0.1 = 20Ω) than one that needed a smaller p.d. (i.e. 1.5/0.1 = 15Ω). However, his language revealed a lack of fluency in using the concepts of electricity. He referred to voltage being "put in" to the circuits rather than across them. Perhaps more significantly he referred to their being "less current flowing in" where there was the same current in both hypothetical circuits. It would have been more appropriate to think of there being proportionally less current. He also referred to the greater resistance stopping "the rest" of the current, which seemed to reflect his earlier suggestion that resistance is how much something is being slowed down or is stopped going round.

My purpose in offering Adrian hypothetical examples, each a little 'thought experiment', was to see if they allowed him to reconstruct the formula he could not confidently recall. As he had now established that

greater p.d. is needed when resistance is higher (for a fixed current)

and that

less current flows when resistance is higher (for a fixed p.d.)

he might (perhaps should) have been able to recognise that his suggestion that "resistance is current over, voltage" was inconsistent with these relationships.

Okay and how does that relate to the formula you were just telling me before?
Erm, No idea.
No idea?
Erm (pause, c.2s) once you know the resistance of a circuit you can work out, or once you know any of the, two of the components you can work out, the other one, so.
Yeah, providing you know the equation, when you know which way round the equation is.
Yes providing you can remember the equation.
So can you relate the equation to the explanations you have just given me about which would have the higher resistance?
So if something has got a higher resistance, so (pause, c.2s) so the current flowing round it would be – the resistance times the voltage (pause, c.2s) Is that right? No?
Erm, so the current is resistance time voltage? Are you sure?
No.

So Adrian suggested the formula was "the current flowing round it would be the resistance times the voltage", i.e., I = R × V (rather than I = V /R ), which did not reflect the qualitative relationships he had been telling me about. I had one more attempt at leading him through the logic that might have allowed him to deduce the general form of the formula.

Go back to thinking in terms of resistance.
Okay.
So you reckoned you can work out the resistance in terms of the current and the voltage?
Yes, I think.
Okay, now if we keep, if we keep the voltage the same and we get different currents,
Yes.
Which has, Which has got the higher resistance, the one with more current or the one with less current?
Erm (Pause, c.6s) So, so, if they keep the same voltage.
That’s the way we liked it the first time so.
Okay.
Let’s say we have got the same voltage across two circuits.
Yes.
Different amounts of current.
Yes.
Which one’s got the higher resistance? The one with more current or the one with less current?
The one with less current.
So less current means it must be more resistance?
Yes.
Ok, so if we had to have an equation R=.
Yes.
What’s it going to be, do you think?
Erm
(pause, c.7s)
R=
(pause, c.3s)
I don’t know. It's too hard.

Whether it really was too hard for Adrian, or simply something he lacked confidence to do, or something he found too difficult being put 'on the spot' in an interview, is difficult to say. However it seems fair to suggest that the kind of shift between qualitative relationships and algebraic representation – that is ubiquitous in studying physics at this level – did not come readily to this advanced level physics student.

I had expected my use of leading (Socratic) questioning would provide a 'scaffold' to help Adrian appreciate he had misremembered "resistance is current over, voltage, I think", and was somewhat disappointed that I had failed.

Particles in ice and water have different characteristics

Making a link between particle identity and change of state

Keith S. Taber

Bill was a participant in the Understanding Science Project. Interviews allow learners to talk about their understanding of science topics, and so to some extent allow the researcher to gauge how well integrated or fragmented a learner's ideas are.

Occasionally there is a sense of 'seeing the cogs turn', where it appears that the interview is not just an opportunity for reporting knowledge, but a genuine site for knowledge construction (on behalf of the students, as well as the researcher) as the learner's ideas seem to change and develop in the interview itself.

One example of this occurred when Bill, a Y7 student, explained what he had learnt about particles in solids, liquids and gases. Bill seemed unsure if the particles in different states of matter were different, or just had different properties. However, when asked about a change of state Bill related heating to changes in the way particles were arranged, and seemed to realise this implied the particles themselves were the same when a substance changes state. Bill seemed to be making a link between particle identity and change of state through the process of answering the researcher's questions.

Bill introduced the idea of particles when talking about what he had learn about the states of matter

Well there's three groups, solids, liquids and gases.
So how do you know if something is a solid, a liquid or a gas?
Well, solids they stay same shape and their particles only move a tiny bit.

This point was followed up later in the interview.

So, you said that solids contain particles,
Yeah.
They don't move very much?
No.
And you've told me that ice is a solid?
Yeah.
So if I put those two things together, that tells me that ice should contain particles?
Yeah.
Yeah, and you said that liquids contain particles? Did you say they move, what did you say about the particles in liquids?
Er, they're quite, they're further apart, than the ones in erm solids, so they erm, they try and take the shape, they move away, but the volume of the water doesn't change. It just moves.
Okay. So the particles in the liquid, they seem to be doing something a bit different to particles in a solid?
Yeah.
What about the particles in the gas?
The gas, they, they're really, they're far apart and they try and expand.
Does that include steam, because you said steam was a gas?
Yeah.
Yeah?
I think.
So, we've got particles in ice?
Yeah.
And they have certain characteristics?
Yeah.
And there are particles in water?
Yeah.
That have different characteristics?
Yeah.
And particles in gas, which have different characteristics again?
Yeah.
Okay. So, are they different particles, then?
N-, I'm not sure.

There are several interesting points here. Bill reports that the particles in liquids are "further apart, than the ones in … solids". This is generally true when comparing the same substance, but not always – so ice floats in water for example. Bill uses anthropomorphic language, reporting that particles try to do things.

Of particular interest here, is that at this point in the interview Bill did not seem to have a clear idea about whether particles kept their identify across changes of state. However, the next interview question seemed to trigger a response which clarified this issue for him:

So have the solid particles, sort of gone away, when we make the liquid, and we've got liquid particles instead?
No {said firmly}, when a solid goes to a liquid, the heat gives the particles energy to spread about, and then when its a liquid, it's got even more energy to spread out into a gas.
So we're talking about the same particles, but behaving differently, in a solid to a liquid to a gas?
Yeah.
That's very clear.

It appears Bill had learnt a model of what happened to the particles when a solid melted, but had not previously appreciated the consequences of this idea for the identity of particles across the different states of matter. Being cued to bring to mind his model of the effect of heating on the particles during melting seemed to make it obvious to him that there were not different particles in the different states (for the same substance), where he had seemed quite uncertain about this a few moments earlier.

Whilst this has to remain something of a speculation, the series of questions used in research interviews can be quite similar in nature to the sequences of questions used in the method of instruction known as Socratic dialogue – a method that Plato reported being used by Socrates to lead someone towards an insight.

So, a 'eureka' moment, perhaps?

Covalent bonding is sharing electrons

It's covalent bonding where the electrons are shared to create a full outer shell

Keith S. Taber

Brian was a participant in the Understanding Chemical Bonding project. He was interviewed during the first year of his college 'A level' course (equivalent to Y12 of the English school system). Brian was shown, and asked about, a sequence of images representing atoms, molecules and other sub-microscopic structures of the kinds commonly used in chemistry teaching. He was shown a simple representation of a covalent molecule:

Any idea what that's meant to be, number 2?
Hydrogen molecule.
Why, how do you recognise that as being a hydrogen molecule?
Because there's two atoms with one electron in each shell.
Uh hm. Er, what, what's going on here, in this region here, where these lines seem to meet?
Bonding.
That's bonding. So there's some sort of bonding there is there?
Yeah.
Can you tell me anything about that bonding?
It's covalent bonding.
So, so what's covalent bonding, then?
The electrons are shared to create a full outer shell.
Okay, so that's an example of covalent bonding, so can you tell me how many bonds there are there?
One.
There's one covalent bond?
Yeah.
Right, what exactly is a covalent bond?
It's where electrons are shared, almost, roughly equally, between the two atoms.
So that's what we'd call a covalent bond?
Yeah.

So according to Brian, covalent bonding is where "the electrons are shared to create a full outer shell". The idea that a covalent bond is the sharing of electrons to allow atoms to obtain full electron shells is a very common way of discussing covalent bonding, drawing upon the full shells explanatory principle, where a 'need' for completing electron shells is seen as the impetus for bonding, reactions, ion formation etc. This principle is the basis of a common alternative conceptual framework, the octet rule framework.

For some students, such ideas are the extent of their ways of discussing bonding phenomena. However, despite Brian defining the covalent bond in this way, continued questioning revealed that he was able to think about the bond in terms of physical interactions

Okay. And why do they, why do these two atoms stay stuck together like that? Why don't they just pull apart?
Because of the bond.
So how does the bond do that?
(Pause, c.13s)
Is it by electrostatic forces?
Is it – so how do you think that works then?
I'm not sure.

The long pause suggests that Brian did not have a ready formed response for such a question. It seems here that 'electrostatic forces' is little more than a guess, if perhaps an informed guess because charges and forces had features in chemistry. A pause of about 13 seconds is quite a lacuna in a conversation. In a classroom context teachers are advised to give students thinking time rather than expecting (or accepting) immediate responses. Yet, in many classrooms, 13 seconds of 'dead air' (to borrow a phrase from broadcasting) from the teacher night be taken as an invitation to retune attention to another station.

Even in an interview situation the interviewer's instinct may be to move on to a another question, but in situations where a researcher is confident that waiting is not stressful to the participant, it is sometimes productive to give thinking time.

Another issue relating to interviewing is the use of 'leading questions'. Teachers as interviewers sometimes slip between researcher and teacher roles, and may be tempted to teach rather than explore thinking.

Yet, the very act of interviewing is an intervention in the learners' thinking, in that whatever an interviewer tells us is in the context of the conversation set up by the interviewer, and the participant may have ideas they would not have done without that particular context. In any case, learning is not generally a once off event, as school learning relies on physiological process long after the initial teaching event to consolidate learning, and this is supported by 'revision'. Each time a memory is reactivated it is strengthened (and potentially changed).

So the research interview is a learning experience no matter how careful the researcher is. Therefore the idea of leading questions is much more nuanced that a binary distinction between those questions which are leading and those that are not. So rather than completely avoiding leading questions, the researcher should (a) use open-ended questions initially to best understand the ideas the learner most easily beings to mind; (b) be aware of the degree of 'scaffolding' that Socratic questioning can contribute to the construction of a learners' answer. [Read about the idea of scaffolding learning here.] The interview continued:

Can you see anything there that would give rise to electrostatic forces?
The electrons.
Right so the electrons, they're charged are they?
Yeah. Negatively.
Negatively charged – anything else?
(Pause, c.8s)
The protons in the nucleus are positively charged.
Uh hm. And so would that give rise to any electronic interactions?
Yeah.
So where would there be, sort of any kind of, any kind of force involved here is there?
By the bond.
So where would there be force, can you show me where there would be force?
By the, in the bond, down here.
So the force is localised in there, is it?
The erm, protons would be repelling each other, they'd be attracted by the electrons, so they're keep them at a set distance.

It seemed that Brian could discuss the bond as due to electrical interactions, although his initial ('instinctive') response was to explain the bond in terms of electrons shared to fill electron shells. Although the researcher channelled Brian to think about the potential source of any electrical interactions, this was only after Brian had himself conjectured the role of 'electrostatic forces.'

Often students learn to 'explain' bonds as electron sharing in school science (although arguably this is a rather limited form of explanation), and this becomes a habitual way of talking and thinking by the time they progress to college level study.