Tag: materials and substances

Scientific errors in the English National Curriculum

Keith S. Taber

I am writing this open letter to the Institute of Physics and the Royal Society of Chemistry to request that as Learned Societies with some influence with government (perhaps limited, but certainly vastly more than an academic) the Societies might ask the Department for Education to correct two basic errors of science in the National Curriculum for England which is set out as the basis for teaching school age learerns and for developing public examinations specifications and papers.
The two errors relate to (a) the misuse of scientific terminology (the word substance) and (b) a failure of logic (in a reference to conservation of energy). As you will no doubt be aware, the original published version of this iteration of the programmes of study for science in the English National Curriculum included some basic errors (incorrect physics formulae) that received wide publicity and which were quickly amended. Despite some other issues also getting early attention, these other problems have never been addressed. One more complex issue that I strongly feel deserves addressing, but which would would require considerable redrafting, is the confused and incoherent treatment of the nature of chemical reactions across the secondary phase (Key Stages 3 and 4). I have raised these issues at various times, and have published a scholarly analysis of these problems .Whilst I obviously did not expect an article in an academic journal to directly impact policy, I thought this could be a 'springboard' to then approach government. I have contacted the relevant ministers (the Rt Hon Gavin Williamson CBE MP, Secretary of State for Education and the Rt Hon Nick Gibb MP, Minister of State for School Standards), and in response to instructions to refer this issue to the Department for Education website, I did so. My comments have been noted, but I was informed
"there are no current plans to review the curriculum".
Whilst I accept that any detailed re-working of the curriculum is not imminent, I do think the Department could still instigate minor corrections to errors which are published on the government's website, and then consequently repeated by the examination authorities, the examination boards and even individual school websites. Correcting these (surely, embarrassing) errors would require very little effort. The first error I refer to is the incorrect use of the term 'substance'. In science, the term substance has a fairly specific meaning. Although, as with many science concepts, there may be some discussion over precise definitions and demarcations, there is general agreement at the level at which the term would be used in introductory science at school level. In the primary stages of the English National Curriculum for Science we read that Y5 learners should be
"taught to…explain that some changes result in the formation of new materials [sic], and that this kind of change is not usually reversible, including changes associated with burning and the action of acid on bicarbonate of soda".
A better term here would be 'substances', not 'materials' (although this is more a mater of the wording being imprecise than incorrect). However in relation to Y4 learners there is a reference to
"exploring the effect of temperature on substances [sic] such as chocolate, butter, cream"
none of which are substances as the word is used in science.This is a misuse of the term 'substance'. So whereas in secondary school, learners are taught to distinguish the meanings of 'material' and the more specific 'substance', it seems these terms are being used interchangeably in the National Curriculum specification itself. The other issue relates to the statement (in the Key Stage 4 specification) that
"energy is conserved in chemical reactions so can therefore be neither created nor destroyed".
To my reading this suggests a blatant error of logic, which I can only assume does not reflect scientific ignorance by the person drafting the document – but more likely is a typographic error that has never been corrected. Conservation of energy is a general (universal) principle, and its more specific application to chemical reactions as one class of changes is then subsumed under that principle. I have long assumed that what had been intended (but mistyped) was either "energy is conserved in chemical reactions BECAUSE it can be neither created nor destroyed" or "energy CAN be neither created nor destroyed SO THEREFORE is conserved in chemical reactions" – that is, the logic has been completely reversed in the curriculum document. I have recently realised that there is a third possibility: that this statement is not meant as an explanation (of energy conservation in reactions under a more general principle) but as a definition, along the lines "energy is conserved in chemical reactions WHICH MEANS THAT IT CAN be neither created nor destroyed". Whatever was meant, the current wording implies a logical non sequitur, and should, surely, be corrected. I would hope you might agree that these kinds of errors should not be included in what teachers are asked to teach, students to learn, and examining boards to assess; and that when a suitable opportunity arrises you might make appropriate representations regarding the desirability of corrections being made. Your sincerely, Dr Keith S.Taber Emeritus Professor of Science Education (I have had constructive replies from both the RSC and IoP)

A wooden table is solid…or is it?

Keith S. Taber

Wood (cork coaster captured with Veho Discovery USB microscope)

Bill was a participant in the Understanding Science Project. Bill (Y7) was explaining that he had been learning about the states of matter, and introduced the notion of there being particles:

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

So what are these particles then?

Erm, they're the bits that make it what it is, I think.

Ah. So are there any solids round here?:

Yeah, this table. [The wooden table Bill was sitting at.]

That's a solid, is it?:

Yeah

Technically the terms solid, liquid and gas refer to samples of substances and not objects. From a chemical perspective a table is not solid. A wooden table (such as those in the school laboratory where I talked to Bill) is made of a complex composite material that includes various different substances such as a lignin and cellulose in its structure.

Wood contains some water, and has air pockets, so technically wood is not a solid to a chemist. However, in everyday life we do thing of objects such as tables as being solid.

Yet if wood is heated, water can be driven off. Timber can be mostly water by weight, and is 'seasoned' to remove much of the water content before being used as a construction material. Under the microscope the complex structure of woods can be seen, including spaces containing air.

Bill also suggested that a living plant should be considered a solid.

I think teaching may be a problem here, as when the states of matter are taught it is often not made clear these distinctions only apply clearly to fairly pure samples of substances. In effect the teaching model is that materials occur as solids, liquids and gases – when a good many materials (emulsions, gels, aerosols, etc.) do not fit this model at all well.

Iron turning into a gas sounds weird

Keith S. Taber

Amy was a participant in the Understanding Science Project. She was interviewed when she had just started her 'A level' (i.e. college) chemistry, and one of the topics that the course had started with was mass spectrometry – (see A dusty analogy – a visual demonstration of ionisation in a mass spectrometer). Amy seemed to be unconvinced, or at least surprised by a number of aspects of the material she had learnt about the mass spectrometer.

So, for example, she found it strange that iron could be vaporised:

So which bits of that are you not convinced about then?

(Pause, c.3 seconds)

It just all … I don't, it's not that I'm not convinced about it, it's just sound strange, because it's like…

(Pause, c.2s)

… erm, well this sounds like ridiculous but, like but before today like none of the people in out class had thought about iron being turned into a gas, and it's little things like that which sound weird.

Okay, erm so if you said to people, can you turn water into a gas, most people would say.

Yeah.

Yeah, do it in the kettle all the time, sort of thing.

Yeah.

But if you said to people can you turn iron into a gas? – do people find that a strange idea?

Yeah.

Yeah?

Well we did. (She laughs)

Although Amy and her classmates had studied the states of matter years earlier at the start of secondary school, and would have learnt that substances can commonly be converted between solid, liquid and gaseous phases, their life-world (everyday) experience of iron – the metallic material – made the idea of iron vapour seem 'weird'.

Given the prevalence of grounded learning impediments where prior learning interferes with new learning, this did not seem as "ridiculous" to the interviewer as Amy suspected it may appear.

As science teachers we have spent many years thinking in terms of substances, and the common pattern that a substance can exist as a solid, liquid or gas – yet most people (even when they refer to 'substances') usually think in terms of materials, not substances. Iron, as a material, is a strong solid material suitable for use in building structures – thinking of iron the familiar material as becoming a gas requires a lot of imagination for someone who not habitually think in terms of scientific models.

Although Amy thought her classmates had found the idea of iron as gas as weird, they had not rejected it. Yet, if it is such a counter-intuitive idea, it may not be later readily brought to mind when it might be relevant, unless it is consolidated into memory by reinforcement through being revisited and reiterated. (Indeed the research interview provides one opportunity for rehearsing the idea: research suggests that whenever a memory is activated this strengthens it.)

[Another student I interviewed told me that Iron is too heavy to completely evaporate.]