Using model-based scaffolds to support students solving context-based chemistry problems

Figures & data

Figure 1. Examples of open-ended context-based chemistry tasks on the topic of energy drinks in three different contextualizations.

Table 1. Overview about the operators used as specific prompts and their corresponding level of complexity.

Level	Operator	Level of complexity (MHC-C)	Example
2	Name …	Facts	‘Could you name any functional groups in the molecules?’
3	Describe …	Description of Processes	‘Can you describe how these functional groups relate to solubility?’
4	Explain …	Uni- and Multivariate Empirical and Logical Causality	‘Can you explain how solubility is related to both intra- and intermolecular bonding?’

Figure 2. An exemplary interview transcript showing the three different MHC-C-operators; name, describe, explain.

Table 2. The use of context information in students’ responses to the context-based chemistry problems (cf. Broman & Parchmann, 2014); number of responses and (in parentheses) the percentage of responses including context-related terms and examples.

Topic	Context
	Personal	Societal	Professional
Medical drugs	5 (100%)	2 (50%)	1 (0%)
Energy drinks	6 (100%)	0 (n/a)	2 (0%)
Fats	6 (83%)	1 (0%)	1 (0%)
Fuels	6 (50%)	1 (100%)	1 (0%)
Soap and detergents	7 (100%)	1 (100%)	0 (n/a)

Table 3. Distribution of student statements across the four levels of complexity before and after the interviewer provided at least one scaffold.

Level of complexity	Number of student statements prior to any hints	Number of final student statements (after all hints were provided)
5 (Multivariate Causality)	18	44
4 (Uni-variate Causality)	47	193
3 (Description of Processes)	33	107
1&2 (Facts and Everyday Experiences)	56	59

Table 4. Distribution of student complete answers across the four levels of complexity before and after the interviewer provided at least one scaffold.

Level of complexity	Number of student responses prior to any scaffolds	Number of final student responses (after all scaffolds were provided)
5 (Multivariate Causality)	9	15
4 (Uni-variate Causality)	3	16
3 (Description of Processes)	18	3
1&2 (Facts and Everyday Experiences)	10	6

Table 5. Exemplary excerpt from an interview transcript by one student labelled as independent problem-solver.

Speaker	Transcript	Classification of interviewer contributions	Classification of student answer
Interviewer	How would you start solving this energy drink task?
Student	OK, if taurine and caffeine from RedBull is going to react in the body, it has to go from the stomach to the blood from the intestines and then follow the blood to the brain. If they’re going to be solved in the blood … blood is mostly water … the molecules have to be water-soluble. So I have to define polar parts in the molecules … Let’s see … if I start with caffeine, it has methyl groups that aren’t polar, C-O-groups that might be polar I think, and then it’s the nitrogen … So caffeine is perhaps not so polar, but on the other hand, caffeine is in coffee and coffee is water-soluble, so caffeine must be polar … Then the taurine molecule, that’s tricky, is it drawn correctly?		level 4
Interviewer	Yes, why?	clarifying question
Student	The sulphur has so many bonds … But if you say it’s correct, it must be … Then, water-soluble … yes it’s water-soluble since it has an OH-group, that’s the definition: OH equals hydrogen bonding. So taurine is water-soluble. And it’s also a small molecule, easier to solve in water, since water is very small …		level 5
Interviewer	Is it only the OH that makes in water-soluble?	clarifying question
Student	Since you ask, perhaps not … I don’t know the electronegativity value for S, but perhaps the amino group … it was N, O, F connected to H that was hydrogen bonding …		level 4

Table 6. Exemplary excerpt from an interview transcript by one student labelled as insufficient problem-solver.

Speaker	Transcript	Classification of interviewer contributions	Classification of student answer
Interviewer	How would you solve the item on energy drinks?
Student	Caffeine and taurine, it’s not molecules I know so much about …		level 1&2
Interviewer	Any idea where to start?	clarifying question
Student	Caffeine has two rings, carbon and nitrogen, and also hydrogen and oxygen … Taurine has the same atoms but also S … I don’t know much more …		level 1&2
Interviewer	Can you name any important functional groups?	hint (name)
Student	OH in taurine, that one I recognise …		level 1&2
Interviewer	Anything else?	clarifying question
Student	Double bonding to O in caffeine, but I don’t know what they do …		level 1&2
Interviewer	Can you describe the molecules, what chemical properties do they have?	hint (describe)
Student	I don’t know …
Interviewer	How do you think they react in your body?	hint (describe)
Student	I don’t know … perhaps that they make you awake?		level 1&2
Interviewer	How?	clarifying question
Student	I don’t know …
Interviewer	Do you know any part in the body in charge of these reactions?	hint (name)
Student	The brain?		level 1&2
Interviewer	Yes, and can you explain how can the molecules get to the brain?	hint (explain)
Student	No, not really …

Table 7. Exemplary excerpt from an interview transcript by one student labelled as progressing problem-solver.

Speaker	Transcript	Classification of interviewer contributions	Classification of student answer
Interviewer	How would you solve the item, how can caffeine and taurine react?
Student	Well, the solvent must have the same chemical properties as the compound to solve, since it’s ‘like dissolves like’ … it’s always this like dissolves like in chemistry …		level 1&2
Interviewer	What does that mean?	clarifying question
Student	That the molecules have to be alike to solve … this is just something I know, I have read it in the chemistry textbook and my teacher uses this expression all the time, it’s something we have heard since we started reading chemistry many years ago …		level 1&2
Interviewer	Can you elaborate your ideas about like dissolves like?	clarifying question
Student	It’s just that both substances that are going to be mixed have to look the same …		level 1&2
Interviewer	What does it mean to look the same, what happens when for example taurine or caffeine mix in the blood?	hint (describe)
Student	If they look the same, I mean look the same in regard to chemistry, the blood and the energy drink with the taurine and caffeine, there is a solution, they will be solved with each other …		level 3
Interviewer	Can you try to describe this chemical process when something is solved in something else?	hint (describe)
Student	So … I check for polar and unpolar parts … caffeine has many polar groups so this might be solved into … perhaps ethyl acetate … but of course ethyl acetate is not found in the body, it’s just the solvent my teacher often mentions …		level 4
Interviewer	Where do you see polar groups in caffeine?	clarifying question
Student	It’s oxygen in C = O … perhaps also N, I don’t really know about this, but also, it doesn’t have many long C-chains … But the other one, it has … taurine has O and N, but it also has other atoms too … so … but I think it’s more polar than unpolar …		level 4
Interviewer	If you compare the two, which one do you think is more polar?	hint (explain)
Student	… oh … I would say caffeine … since it feels as if it has more polar groups … even though a bigger molecule, it has many more … these are soluble in water		level 5

Table 8. Students’ final solutions to the two problems they solved.

Problem 1	Insufficient problem-solvers	Independent problem-solvers	Progressing problem-solvers
Problem 2
Insufficient	3	0	0
Independent	0	6	0
Progressing	0	0	11

Figure 3. The categorisation of the students’ statements according to the MHC-C framework. The figure presents three interviews to exemplify each problem-solver type.

Table 9. Distribution of the categorised problem-solver types across the three contextualizations of problems

Problem-solver type	Personal context	Societal context	Professional context
Insufficient	1	2	3
Independent	10	1	1
Progressing	19	2	1
Total	30	5	5

Table

Level of complexity and indicators	Indicators	Examples
(5) Multivariate Causality   - describing and justifying arrays of causes   - taking multiple factors into consideration	Justifications beyond linear relations; handling of several variables, their interplay and interdependent cause-and-effect chains. In case of several linear chains, their interplay and interference has to be taken into consideration.	Caffeine is polar due to carbonyl groups with resonance and nitrogen in the rings, so it’s water soluble. Caffeine is also much bigger than water, I mean, the molecules. So many more water molecules probably can come closer to caffeine which probably makes it more water-soluble because of more hydrogen bond possibilities.
(4) Uni-variate Causality   - giving reasons for linear chains of causes and effects or reaction schemes   - justifying results or steps within a process   - justifying factors of influence   - deductive reasoning   - calculations with multiple steps	Registration and description of linear cause-and-effect chains. A justification of the relation is of great importance, not only the description of if-then-relations.	The molecules in RedBull must be soluble in water since we drink energy drinks. The caffeine has nitrogen atoms, and that’s one of the atoms that can participate in hydrogen bonding, you know, NOF, so caffeine can do hydrogen bonding with water … Both water and caffeine are polar molecules.
(3) Description of Processes   - describing processes or reactions   - finding or describing commonalities and differences   - drawings (unguided)	Description of processes which show a chronological or sequential progress; with or without the use of (mental) models; not only simple before-after-descriptions, but a focus on the actual process, e.g. a description of a mechanism; simple relations and dependencies without reasoning;	The taurine molecule is strange; the sulphur has six bonds … I remember sulphur as different from for example carbon which always has four bonds. It has to do with electron structure, not being as simple as we often read in books, but I don’t know how it can have six bonds.
(1 & 2) Facts and Everyday Experiences   - definitions   - stating laws, principles, terms, models, symbols   - simple calculations (routines)   - drawings (guided)   - examples   - knowledge from everyday life	Nomination of isolated terms, laws, principles without explication, argumentation or comparisons; bits of isolated factual knowledge; Pieces of knowledge that stem from students’ everyday life^a; statements without explanatory base; direct observations or sensory impressions; statements without technical terms;	The caffeine molecule has two rings, lots of nitrogen atoms in the rings and also these carbon – oxygen double bonds. The taurine molecule is trickier, the S in the middle looks strange …

^aThe reference to everyday life is not to be understood as context, e.g. when students try to connect their knowledge learned in classroom to everyday natural and societal phenomena. In this meaning, it would be possible to find aspects on each level of complexity. Rather the label stresses that knowledge on this level is seen as being predominantly isolated and unrelated to the subject structure.

Broman, K., & Parchmann, I. (2014). Students’ application of chemical concepts when solving chemistry problems in different contexts. Chemistry Education Research and Practice, 15(4), 516–529. doi: 10.1039/C4RP00051J

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