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Research In Science Education, 1988, 18, 220-226.

BEING COOL IN THE COOL UNIT

OR

EVALUATING THE LEARNING OF REFRIGERATION FROM SCRATCH

Barry Newman, Mark Cosgrove and Mike Forret

Learning to design your own refrigerator, trying to understand how and why one

works and finding that your teacher won't tell you, could be a little disconcerting. Not

being all that interested in the topic to start with, feeling that as a female it was beyond

you, reeognising that you'd been quite suceessful learning physics by the old method or not

being all that good at physics anyway, wouldn't seem to help either. What's it really like?

INTRODUCTION

A unit on ref r igera t ion was designed for the teaching of New Zealand sixth form

physics students. The approaeh adopted by the unit is charac te r i sed par t ly by the

in terae t ive teaching model developed by Bicldulph and Osborne (1984), a model based upon

a generat ive learning theory (Osborne and Wittroek, 1985) and par t ly by an assumption of

the usefulness of teaehing seience through technology. A deseript ion of the unit is to be

found in Working Paper No. 211 (Cosgrove and Mueggenburg, 1986), S.E.R.U., University of

Waikato - Hamilton Teaehers College. Working Paper No. 212 (Newman, 1986) of the

same es tabl ishment is a repor t on i ts evaluation. A paper detai l ing the underlying

assumptions of the unit and outlining some of the findings from the evaluat ion was

presented a t an internat ional symposium on science and teehnology educat ion (Cogrove,

Newman and Forre t , 1987). What is repor ted below is a more deta i led deser ipt ion of the

evaluat ion proeess and findings together with some reference to a repl ica t ing study

carr ied out one year a f te r the original.

TEACHING THE UNIT

The unit as taught had a number of stages. Students viewed a video on the use of

ref r igerat ion, raised some questions about ref r igerat ion, made "before statements" on how

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they thought a refrigerator worked, interacted with some practical activities, discussed

the subject with their peers and teacher, interviewed an "expert", experienced a slide/tape

presentation on the subject, design a refrigerator and made "after statements" on how

they now thought a refrigerator worked.

While the slide/tape segment dealt with heat and its connection with refrigeration

neither the "expert" nor the teacher involved indicated how refrigerators worked. The

unit was characterised by students having to create their own understanding with little

feedback given by "expert" or teacher.

The unit was taught over 9 periods to 53 students (36 males, 17 females) in 3 classes,

two teachers participating. The replicating study involved 35 students (23 males, 12

females) in 2 classes, one teacher being involved.

EVALUATING THE UNIT

There were three major components to the evaluation. During the unit informal

observations were made of teacher and student activity and informal interviews were

carried out with students. At the end of the unit a questionnaire was given to 45 students

(28 male, 17 female). Thirdly, statements made by students at the beginning of the unit

(43) and 4 weeks after the unit (47) on how a refrigerator works, were analysed. No notice

was given in either case of such a statement being required.

The replicating study involved a different evaluator and brief reference only, will be

made below, to some of its findings.

RESULTS

Some gender differences on a number of measures were observed and these are

reported in Table 1.

Observations and Interviews

I. Students' Misconceptions

Observations and interviews revealed a number of "misconceptions" which students

brought to their understanding of the practical activities of the unit or which arose during

the activities. Some of these beliefs carried over into their understanding of how a

refrigerator works and some persisted throughout the unit. For example, at least one

student thought that in order for acetone to evaporate air was necessary. Another student

believed that freon in a can was cold because it had been liquified and liquified freon was

very cold. Some thought that where there were temperature changes perhaps endo-and

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exo-thermic react ions were involved. Friction was appealed to by a number of s tudents to

explain why a gas became hot under compression. At least one s tudent believed that

because the act iv i t ies with thermostats only involved heating, deformation by cooling

would be difficult.

2. Appraisal of Pract ical Activit ies

A crit ical appraisal of the practical act ivi t ies could be made on the basis of an

examination of their nature together with what students had to say of them and the way

they interacted with them. For example, a wet and dry bulb thermometer activity,

designed to i l lustrate that as water evaporates the temperature drops, was confusing

because of its association with the measure of humidity. Dismantling a refr igerator was

helpful to some of those actively engaged in the dismantling but not for those who were

not. An act ivi ty of examining a working refrigerator was engaged in by only few students,

perhaps because of its inconvenient location and because of its familiari ty. In a bicycle

pump act ivi ty the ouly measure of an increase in temperature of compressed air was the

temperature of the pump barrel itself; it was then questionable whether this was due to

any increase in the temperature of the air. There was no act ivi ty where a gas was

compressed to a liquid, with a consequent rise in temperatures; understandably, that

aspect of refr igerat ion was generally omit ted in s ta tements on how a refr igerator works.

3. Students I Views on the Unit

During the unit students were encouraged to indicate what their views were on what

they were doing. During the act ivi t ies section, one student stated: "ItTs a good way of

helping us to understand the very technical" while another exclaimed: "You wouldn't want

to be a person who gave up easily in this exercise". During the design stage, one male

indicated that the unit neither a t t rac ted nor bothered him, while another felt it could get

a bit boring. One group of females upon being asked ,Is this too tough?" replied "Yes, it

sure is!". One female, experiencing difficulty in gett ing started, believed that maybe she

didnlt think logically enough.

THE QUESTIONNAIRE

1. The Praetical Activit ies

Two questions dealt with how the students perceived each of the pract ical ac t iv i t ies

- their interest in them and the help they thought they reeeived from them. An act ivi ty

with thermostats, another involving the dismantling of a refrigerator and a third involving

the use of freon gas were regarded as being among the most interesting. The freon

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activity was also the one that most students thought was the most helpful

There were some gender differences relating to the perceived helpfulness of two of

t h e act ivi t ies - see Table 1.

A similar profile of, interest in and perceived help from, the various activities, was

obtained in the second study.

TABLE 1 Some Gender Comparisons from Study 1

A. QUESTIONNAIRE ANALYSIS

Mentioning dismantling a refr igerator as an act ivi ty that helped understanding ...

Mentioning using freon as an act ivi ty that helped understanding ...

Claiming interest in how a refrigerator works before the s tar t of unit ...

Claiming to have ideas on the operation of a refrigerator before the s tar t of the unit ...

Claiming to have ideas on the operation of a refrigerator during the audiovisual segment ...

B. AFTER STATEMENT ANALYSIS Making satisfactory after s ta tements . . . Of those making satisfactory af ter s ta tements

those using one or more diagrams... Of those making satisfactory af ter s ta tements

the average number of words used ...

C. END-OF-YEAR PHYSICS EXAMINATION Mean % performanee on the examination for all

students involved in the study ... M e a n % p e r f o r m a n c e on the examination for those

making af ter s ta tements ... Mean % performance on the examination for those

making satisfactory after s ta tements . . .

NS

% % Male Female

43 6*

46 82*

36 0*

57 18"

25 65*

33 70*

80 17"*

77 127"**

58.3 55.3 NS

59.2 56.6 NS

62.9 59.6 NS

stat is t ical ly significant at the 5% level using a 2 test with a Yates correction. s tat is t ical ly significant at the 2% level using a 2 test with a Yates correction. s tat is t ical ly significant at the 2% level using a Coehran and Cox t test. not stat is t ical ly signifieant at the 20 % level using a Cochran and Cox t test.

2. The Stages of the Unit

Three questions dealt with interest and ideas before working on the unit and then at

the various stages of the unit. No female and only 36% of males claimed interest in the

subject before the unit started. A majority of students indieated that it was while they

were working with the praetieal act ivi t ies and designing their own system that they were

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interested in how a refrigerator works. These aspects of the unit together with that of

working with the expert and interaet ing with the class as a whole were also mentioned by

a majority as those when they had some ideas on how a refrigerator works. In addition to

these elements, a fifth - in teract ing with oneVs peers, was cited by a majority as being

those when they put some of those ideas together.

Some gender differenees relating to two of the questions are referred to in Table 1.

The overall profiles obtained in both studies for these three questions were, again

with few exeeptions, found to be very similar.

3. Student Atti tudes, Confidence and Perceived Understanding

Two questions were directed at the students ' a t t i tudes towards the unit as a whole.

61% elaimed they liked the unit ei ther a reasonable amount or a lot, while a further 20%

claimed they liked it a l i t t le. When asked to compare the approach of the unit in teaching

physics with "the usual way physics is taught" 51% claimed they liked the approaeh of the

unit better, with 13% claiming the reverse.

One question dealt with how eonfident they felt while working through the unit.

Only 7% reported that they did not feel all that confident, while 44% claimed to feel

reasonably confident. The remainder claimed that they felt O.K.

As regards their understanding on how a refrigerator works, 93% claimed, at the end

of the unit, that they thought they had a reasonable understanding or greater.

4. Students ~ Free Response Corn ments

Most students made comments in a free response section of the questionnaire. A

number of students referred favourably to the methodology of the unit with s ta tements

such as: "This unit helped you to develop ideas in your own words without somebody telling

you (and this) gave you a greater understanding" and "I really enjoyed trying to find out for

myself how a fridge works; now I will remember it much clearer than other things I have

been taught". A few students, all who liked the usual approach to teaching physics better,

made negative remarks about the methodology. For example: "The questions we formed

during the unit were usually not answered and that left us nowhere. It kept us off balance

and most of the t ime we worked out wrong solutions" and "I thought that it took too long

to find out the answers about fridges".

BEFORE AND AFTER STATEMENTS

When asked to make a s ta tement at the beginning of the unit on how a refrigerator

worked, 23% claimed they didntt know and made no further s ta tement . In general, "before

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statements" were sketchy comments involving some mention of heat and various

refrigerator components. "After statements", with far more detail, had descriptions that

incorporated closed eyelieal systems involving liquid to gas to liquid changes with

references to transfer of heat between various entities, transfer of heat from inside the

refrigerator to outside, and notions of expansion and compression.

"After statements" were credited as being "satisfactory" provided they were not

deficient in more than a few significant features of a "good" explanation. On this basis

47 % of the statements were designated "satisfactory". It should be borne in mind that the

task of providing these statements was given four weeks after the completion of the unit

and without notice. Those statements regarded as satisfactory were analysed for gender

differences - see Table I. A higher percentage of females than males made satisfactory

statements and the females making such statements used more words than males. More

males than females used diagrams. These gender differences were not confirmed in the

second study. Part of the explanation for this discrepancy could be due to the use of two

different evaluators. Furthermore some changes had been made to the unit on the second

occasion as a result of the findings gathered on the first.

The students' performance on an end-of-year physics examination was also analysed

for gender differences for all students involved in the study, for all those making after

statements and for all those making satisfactory after statements. No significant

differences up to the 20% level were found. Details are to be found in Table I. Using a

Cochran and Cox t test no significant difference up to the 20% level on examination

performance was found between all females making after statements and all females

making satisfactory after statements. The same was true for males.

DISC USSIO N

The evaluation would appear to be valuable in terms of giving suggestions on how the

unit could be improved. For one thing, it highlights the plausible. Activities that don't

clearly relate to refrigeration are likely to result in confusion and the absence of

activities related to principles of refrigeration is likely to result in those principles not

being understood. It also enables the teacher to see what facets of the unit students

perceive to be helpful and interesting.

Hawthorn effects were almost certainly operating during the unit. This aside

however, the unit with its interactive teaching components, its generative learning theory

underpinnings and its science in technology perspective could not be judged to be a

failure. In terms of students' perceptions of their understanding at the end of the unit,

their view of the methodology of the unit and the statements they made on how a

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refrigerator works, four weeks after the unit, the unit was more like a success than a

failure.

Of some interest is the finding that, based on the performance in the end--of-year

physics examination, the females who were able to make adequate statements on the

working of a refrigerator were approximately representative of all females making such

statements, adequate or otherwise, the same being true for males, Does the methodology

of the unit favour reasonably equally the seholarly and the less scholarly?

Perhaps of most interest are the gender differences. That females performed better

than males in a senior physics unit, in the first study (and no worse in the second) is worthy

of note. Did the females "work harder", because they were less interested before the unit

began? Were the females choosing physics more mature than their female peers? Did

they act more responsibly and with less warranted confidence than the males? Did the

autonomy given to students in the unit favour the females rather than the males?

Whether females or males however, students, need to be considered as individuals. It

is one thing to assert that a majority of students liked the unit and that most thought they

had a reasonable understanding of how a refrigerator works at the end of the unit. It is

another to realise that some individuals had no confidence that they had worked out the

principles of refrigeration or preferred by far, the usual method of teaching physics, What

is suitable for Jack and Jill is not so for Jean and John.

REFERENCES

BIDOULPH, F. & OSBORNE, R. (eds.) (1984) Making sense of our world: An interactive teaching approach , S.E.R.U., University of Waikato-Hamilton Teachers College, Hamilton, New Zealand.

COSGROVE, M. & MUEGGENBURG, G. (1988) Refrigeration: A teaching unit for form 6 physics, Working Paper No. 211 S.E.R.U., University of Waikato--Hamilton Teachers College, Hamilton, New Zealand.

COSGROVE, M., NEWMAN, B. & FORRET, M. (1987) "Teaching t e c h n o l o g y - refrigeration, an example from New Zealand's economic history". In K. RIQUARTS (ed.): Science and technology education and the quality of life, 2, IPN, Kiel. Proceedings of the 4th International Symposium on World Trends in Science and Technology Education, 467- 472.

NEWMAN, B. (1986) Evaluation of refrigeration: A teaching unit for form 6 physics. Working Paper No. 212. S.E.R.U., University of Waikato-Hamilton Teachers College, Hamilton, New Zealand.

OSBORNE, B.J. & WITTROCK, M.C. (1985) The generative teaching model and its implications for science education, Studies in Science Education, 12, 59-87.