Third Misconceptions Seminar Proceedings (1993)
Paper Title: C o nsistency in pupil s´ expl anatio ns abo ut co mbustio n.
Author: Pr ie to , Te r e sa; Watso n, J. Ro d & Dillo n, Justin
Abstract: This pape r r e po r ts so m e finding s o f a study o n 14-15 y e ar
o ld pupils´ ide as ab o ut co m b ustio n. Patte r ns in pupils´
e xplanatio ns acr o ss a r ang e o f q ue stio ns ar e de scr ib e d and
analy se d, in o r de r to g ain insig ht into the co nsiste ncy o r
inco nsiste ncy o f the ir e xplanatio ns. Data hav e b e e n co lle cte d
b y a q ue stio nnair e sur v e y which use s m ainly o pe n q ue stio ns,
so m e o f which ar e g e ne r al q ue stio ns ab o ut co m b ustio n and
o the r s which use spe cific e xam ple s. Re spo nse s hav e b e e n
analy se d using sy ste m ic ne two k s. C ate g o r ie s fr o m ne two r k s
hav e b e e n co m b ine d to pr o duce patte r ns o f e xplanatio ns that
co uld b e co nside r e d as the o r ie s. The g e ne r al char acte r istics o f
the se the o r ie s, the co nsiste ncy with which the y we r e use d,
and im plicatio ns fo r te aching and le ar ning ar e discusse d.
Keywords: Concept Formation,Educational
Methods,Philosophy,Constructivism,Scientific
Concepts,Misconceptions,Data Interpretation,,
General School Subject:
Specific School Subject:
Students:
Macintosh File Name: Prieto - Combustion
Release Date: 1-11-1994 D, 11-7-1994 I
Publisher: Misconceptions Trust
Publisher Location: Ithaca, NY
Volume Name: The Proceedings of the Third International Seminar on
Misconceptions and Educational Strategies in Science and Mathematics
Publication Year: 1993
Conference Date: August 1-4, 1993
Contact Information (correct as of 12-23-2010):
Web: www.mlrg.org
Email: [email protected]
A Correct Reference Format: Author, Paper Title in The Proceedings of the Third
International Seminar on Misconceptions and Educational Strategies in
Science and Mathematics, Misconceptions Trust: Ithaca, NY (1993).
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2
C o nsistency in pupil s´ expl anatio ns abo ut co mbustio n.
Te r e sa Pr i e t o. F a cul t a d de Educa t i on, U ni v e r si da d of Má l a ga .
Espa ña .
J. R od W a t son & Just i n D i l l on. Ce nt r e f or Educa t i ona l S t udi e s,
K i ng´s Col l e ge , U ni v e r si t y of London. U K .
A B STRA CT
Th i s pa pe r r e por t s some f i ndi ngs of a st udy on 14- 15 y e a r ol d pupi l s´
i de a s a bout combust i on. Pa t t e r ns i n pupi l s´ e xpl a na t i ons a cr oss a
r a nge of que st i ons a r e de scr i be d a nd a na l y se d, i n or de r t o ga i n
i nsi gh t i nt o t h e consi st e ncy or i nconsi st e ncy of t h e i r e xpl a na t i ons.
D a t a h a v e be e n col l e ct e d by a que st i onna i r e sur v e y wh i ch use s
ma i nl y ope n que st i ons, some of wh i ch a r e ge ne r a l que st i ons a bout
combust i on a nd ot h e r s wh i ch use spe ci f i c e xa mpl e s. R e sponse s h a v e
be e n a na l y se d usi ng sy st e mi c ne t wok s. Ca t e gor i e s f r om ne t wor k s
h a v e be e n combi ne d t o pr oduce pa t t e r ns of e xpl a na t i ons t h a t coul d
be consi de r e d a s t h e or i e s.
Th e ge ne r a l ch a r a ct e r i st i cs of t h e se
t h e or i e s, t h e
consi st e ncy
wi t h wh i ch t h e y we r e use d, a nd
i mpl i ca t i ons f or t e a ch i ng a nd l e a r ni ng a r e di scusse d.
I N TRODU CTI ON
Th i s pa pe r e xpl or e s t wo ge ne r a l concl usi ons t h a t a ppe a r t o be
i mpl i ci t i n much of t h e r e se a r ch l i t e r a t ur e a bout pupi l s´ a l t e r na t i v e
f r a me wor k s a nd t h e di f f i cul t i e s of pr omot i ng mor e sci e nt i f i c
e xpl a na t i ons f r om pupi l s. Th e se t wo concl usi ons a r e t h a t pupi l s t e nd
t o be i nconsi st e nt i n t h e i r e xpl a na t i ons, a nd t h e a ppa r e nt l y
conf l i ct i ng concl usi on t h a t pupi l s´ a l t e r na t i v e f r a me wor k s a r e
r obust a nd di f f i cul t t o ch a nge .
Cl ough a nd D r i v e r ( 1986) e xpl or e d t h e consi st e ncy i n t h e use of
pupi l s´ a l t e r na t i v e f r a me wor k s a cr oss di f f e r e nt a r e a s of sci e nce .
Th e y f ound t h a t pupi l s t e nde d t o use si mi l a r a l t e r na t i v e
f r a me wor k s t o one a not h e r , but t h a t i ndi v i dua l s we r e not a s
consi st e nt i n t h e i r use of a l t e r na t i v e f r a me wor k s a s t h e y we r e i n t h e
use of sci e nt i f i c e xpl a na t i ons. Pa r i s ( 1992) , i n h e r st udy of pupi l s´
unde r st a ndi ng of a ci ds a nd ba se s, a l so f ound t h a t pupi l s we r e mor e
i nconsi st e nt i n t h e use of a l t e r na t i v e f r a me wor k s t h a n sci e nt i f i c
e xpl a na t i ons. S i mi l a r l y , i n t h e f i e l d of combust i on B ouJa oude ( 1991)
cl a i ms t h a t pupi l s´ unde r st a ndi ngs a bout bur ni ng “we r e f r a gme nt e d,
i nconsi st e nt a nd a t v a r i a nce wi t h sci e nt i f i c k nowl e dge ”.
3
O n t h e ot h e r h a nd ma ny r e se a r ch e r s h a v e r e a ch e d t h e concl usi on
t h a t pupi l s´ a l t e r na t i v e conce pt i ons a r e v e r y r obust a nd r e si st a nt t o
ch a nge . Th i s a ppe a r s t o cont r a di ct t h e i nconsi st e nt use of
a l t e r na t i v e f r a me wor k s. I f pupi l s a r e wi l l i ng t o sh i f t i n t h e i r
e xpl a na t i ons f r om t h e use of one a l t e r na t i v e f r a me wor k t o a not h e r ,
wh y a r e so r e l uct a nt t o use sci e nt i f i c e xpl a na t i ons? .
I n t h i s pa pe r pupi l s´ e xpl a na t i ons of combust i on a r e e xa mi ne d t o
e xpl or e wh e t h e r t h e y use a l t e r na t i v e e xpl a na t i ons consi st e nt l y .
W h e r e t h e r e i s a ppa r e nt i nconsi st e ncy i n pupi l s´ e xpl a na t i ons,
t h r e e possi bi l i t i e s a r e e xpl or e d:
1. Th e pupi l s h a v e a n unde r l y i ng r a t i ona l e f or t h e i r
e xpl a na t i ons, wh i ch i s not i mme di a t e l y a ppa r e nt t o t h e
r e se a r ch e r . I t i s possi bl e t h a t a ppa r e nt i nconsi st e ncy i n pupi l s´
e xpl a na t i ons i s si mpl y i nconsi st e ncy wh e n v i e we d f r om a
sci e nt i f i c pe r spe ct i v a . Pupi l s´ e xpl a na t i ons ma y se e m consi st e nt
wh e n v i e we d f r om t h e pupi l s´ pe r spe ct i v e .
2. Th e v e r y na t ur e of a n a l t e r na t i v e t h e or y gi v e s r i se t o
e xpl a na t i ons wh i ch a ppe a r i nconsi st e nt f r om a sci e nt i f i c
pe r spe ct i v e . Th e pupi l s do not se e t h e ne e d f or a n e xpl a na t or y
t h e or y a s powe r f ul a s t h e sci e nt i f i c one , a nd so a r e sa t i sf i e d wi t h
l e ss powe r f ul t h e or i e s wh i ch do not t a k e i nt o a ccount some a spe ct s
of t h e ph e nome non of combust i on.
3. Th e pupi l s ma y be i n a st a t e of t r a nsi t i on f r om one t h e or y t o
a not h e r . Th e i r l e a r ni ng ma y be pr oduci ng conce pt ua l ch a nge i n
wh i ch t h e y a r e t r y i ng t o a ccommoda t e ne w i de a s.
B l a ck a nd S i mon ( 1992) t a l k a bout pupi l s´ " t h e or i e s" a nd sci e nt i st s´
t h e or i e s a s be i ng l i k e t wo i sl a nds, a nd t h a t t h e t e a ch e r ´ job i s t o
bui l d br i dge s be t we e n t h e t wo i sl a nds. F r om a r e se a r ch e r ´s
pe r spe ct i v e t h e pr obl e m of i nconsi st e ncy ma y si mpl y be t h a t we
h a v e f a i l e d t o v i si t t h e pupi l s´ i sl a nd a nd h a v e si mpl y v i e we d i t
f r om a f a r ( i t e ms 1 a nd 2 a bov e ) , or t h a t we a r e se e i ng t h e t r a f f i c
a cr oss t h e br i dge s be t we e n t h e i sl a nds ( i t e m 3) .
I n t h i s pa pe r t h e e xpl a na t i ons of 150 pupi l s a ge d 14 a nd 15 y e a r ,
a bout some a spe ct s of combust i on, a r e st udi e d usi ng a que st i onna i r e .
Th e wa y i n wh i ch t h e unde r l y i ng t h e or i e s h a v e be e n e xt r a ct e d f r om
t h e e l e me nt s of t h e i r e xpl a na t i ons i s de scr i be d, a nd t h e possi bl e
consi st e ncy or i nconsi st e ncy wi t h wh i ch t h e st ude nt s a ppl y t h e i r
i de a s i s a na l y se d. Th e r e sul t s obt a i ne d a r e di scusse d i n t e r ms of t h e
4
na t ur e of a ny i nconsi st e ncy , a nd t h e ch a nge s t h a t must be br ough t
a bout t o pr omot e mor e sci e nt i f i c e xpl a na t i ons of combust i on.
CH A RA CTERI STI CS OF TH E EX PLA N A TI ON S OF TH E STU DEN TS
DESCRI B ED I N TH E LI TERA TU RE
D r i v e r , Gue sne , a nd Ti be r gh i e n ( 1985 ( a ) ) de scr i be a numbe r of
ge ne r a l ch a r a ct e r i st i cs of t h e e xpl a na t i ons of pupi l s:
* Expl a na t i ons a r e gui de d by di r e ct l y obse r v a bl e ch a r a ct e r i st i cs
of t h e si t ua t i on a nd wh a t i s not pe r ce pt i bl e i s i gnor e d.
* Pupi l s h a v e a l i mi t e d f ocus, t h a t i s ma ni f e st e d i n:
( a ) a t e nde ncy t o i nt e r pr e t t h e ph e nome na i n r e l a t i on t o t h e
a bsol ut e pr ope r t i e s or qua l i t i e s of obje ct s i nst e a d of consi de r i ng
t h e i nt e r a ct i on be t we e n t h e e l e me nt s of a sy st e m.
( b) a t e nde ncy t o f ocus on ch a nge s a nd not on t h e st a t e of
e qui l i br i um. F or e xa mpl e , i f t h e r e i s no mov e me nt t h e r e i s no
f or ce ; or ga se s e xe r t pr e ssur e onl y wh e n t h e y mov e .
* Pupi l s use l i ne a r ca usa l r e a soni ng, a nd do not consi de r a l l t h e
r e l e v a nt v a r i a bl e s i n t h e pr obl e m a nd r e l a t i onsh i ps be t we e n
t h e m.
* Pupi l s do not di f f e r e nt i a t e cl e a r l y be t we e n di f f e r e nt conce pt s
( e . g. h e a t i ng a nd bur ni ng) . S i mi l a r l y t h e i r use of l a ngua ge i s a l so
l e ss pr e ci se t h a n t h a t of sci e nt i st s. Pupi l s of t e n use t h e sa me
wor d t o me a n ma ny t h i ngs. O n t h e ot h e r h a nd st ude nt s use ma ny
wor ds t o me a n t h e sa me t h i ng.
* Pupi l s´ e xpl a na t i ons a r e cont e xt de pe nde nt : di f f e r e nt wa y s of
e xpl a i ni ng a r e of t e n use d f or di f f e r e nt si t ua t i ons wh i ch a r e
e xa mpl e s of t h e sa me ph e nome non.
A nde r sson ( 1986( a ) )
de scr i be s t h e na t ur e of pupi l s´
ca usa l
r e a soni ng. H e cl a i ms t h e e xi st e nce of a common cor e i n st ude nt s’
e xpl a na t i ons a nd pr e di ct i ons a bout ma ny di f f e r e nt ph e nome na ,
wh i ch h e ca l l s t h e “e xpe r i e nt i a l ge st a l t of ca usa t i on”.
Th e
e xpe r i e nt i a l ge st a l t
of ca usa t i on
st a r t s t o be bui l t by
an
i ndi v i dua l a t a v e r y e a r l y a ge a nd i s
ba se d on t h e si mpl e
e xpe r i e nce of ch i l dr e n. I n e sse nce , a n a ge nt e xi st s ( t h a t ca n be a
ch i l d or a n i nst r ume nt ) wh ose di r e ct or i ndi r e ct a ct i on a f f e ct s a n
obje ct pr oduci ng a t y pe of ch a nge . Th e e sse nt i a l e l e me nt s a r e a ge nt i ns t r um e nt - o b je ct .
5
Gut i e r r e z & O gbor n ( 1992) use d t h e mode l of K l e e r a nd B r own a s a
mor e de v e l ope d ca usa l f r a me wor k f or a na l y si ng a l t e r na t i v e
conce pt i ons. Th i s de scr i pt i on
of wh a t i s i nv ol v e d i n ca usa l
r e a soni ng cont a i ns
f i v e ba si c e l e me nt s: 1) de v i ce t opol ogy : a
r e pr e se nt a t i on of t h e st r uct ur e of t h e ph y si ca l sy st e m;
2)
e nv i si oni ng: wor k i ng out f r om t h e st r uct ur e h ow t h e sy st e m coul d
wor k ;
3) ca usa l mode l : t h e r e sul t of e nv i si oni ng; 4)
r unni ng:
i nma gi ni ng wh a t t h e ca usa l mode l woul d do a nd 5) e pi sode s:
di v i si ons of t i me wi t h i n wh i ch t h e e xpl a na t i on st a y s t h e sa me .
Gut i e r r e z e t a l . sa y t h a t a n a cce pt a bl e e xpl a na t or y mode l , wh e n
r un, must sa t i sf y t h e const r a i nt s of co ns i s t e ncy , wh i ch r e qui r e s t h a t
t h e mode l doe s not suf f e r i nt e r na l cont r a di ct i ons, co r r e s p o nd e nce ,
wh i ch r e qui r e s t h a t t h e mode l pr e di ct s wh a t a ct ua l l y h a ppe n, a nd
r o b us t ne s s , wh i ch r e qui r e s t h a t t h e mode l cont i nue s t o cor r e spond t o
t h e f a ct s wh e n t h e cont e xt i s modi f i e d t o a not h e r si mi l a r one .
O gbor n a nd B l i ss ( 1990) i n t h e i r pa pe r “ A psy ch ol ogi c of mot i on”
use si mi l a r r e a soni ng t o e xpl a i n h ow pupi l s´ “common se nse i de a s” of
mot i on a r e de v e l ope d by ch i l dr e n t h r ough i nt e r a ct i on wi t h t h e i r
i mme di a t e e nv i r onme nt , t o pr oduce l ogi ca l l y consi st e nt e xpl a na t i ons
of mot i on. Th e e xpl a na t i ons t a k e t h e f or m of ca usa l sch e me s wh i ch
be come succe ssi v e l y mor e e l a bor a t e d a s a ch i l d de v e l ope s. A
concl usi on f r om a l l t h e se pa pe r s a bout t h e t y pe of r e a soni ng use d by
pupi l s i s t h a t , a l t h ough i t i s not sci e nt i f i c, i t i s i nt e r na l l y
consi st e nt wh e n v i e we d f r om t h e pe r spe ct i v e of t h e pupi l s.
A possi bl e e xpl a na t i on f or t h e pupi l s´ a l t e r na t i v e f r a me wor k s be i ng
di f f e r e nt i n na t ur e f r om sci e nt i st s´ e xpl a na t i ons, i s t h a t pupi l s a r e
l i mi t e d by t h e i r st a ge of ge ne t i c e pi st e mol ogi ca l de v e l opme nt . Pozo,
Puy a nd S a nz, ( 1992) compa r e pupi l s´ “t h e or i e s” wi t h sci e nt i f i c
t h e or i e s. S ci e nt i f i c t h e or i e s
a r e e xpl i ci t , coh e r e nt , ge ne r a l ,
de duct i v e , a r e ba se d on a compl e x mul t i pl e ca usa l i t y a nd a r e
l ook i ng f or
t h e t r ut h . Th ose of t h e pupi l s a r e : i mpl i ci t s,
i ncoh e r e nt s, spe ci f i c, i nduct i v e , a r e ba se d on t h e si mpl e l i ne a r
ca usa l i t y a nd a r e l ook i ng f or use f ul ne ss i n e v e r y da y l i f e . Th e se
a ut h or s r e l a t e some st r uct ur a l ch a r a ct e r i st i cs of st ude nt s’ i mpl i ci t
t h e or i e s, t h a t a r e di f f e r e nt f r om t h e sci e nt i f i c t h e or i e s, t o t h e l e v e l
of cogni t i v e de v e l opme nt of pupi l s, a nd i n pa r t i cul a r t o t h e l a ck of
de v e l opme nt
of
f or ma l
t h ough t
in
the
pupi l s.
Ce r t a i n
ch a r a ct e r i st i cs of pupi l s´ t h e or i e s a ct a s a ct ua l e pi st e mol ogi c
obst r uct i ons t h a t must be ov e r come : t h e y a r e one - wa y ( a ge nt - obje ct )
l i ne a r ca usa l i t y ;
wr ong st r a t e gi e s of qua nt i f i ca t i on or no
6
qua nt i f i ca t i on a t a l l ( qua l i t a t i v e de scr i pt i on) ; t r a nsf or ma t i ons
wi t h out conse r v a t i on, or f ocusi ng on wh a t i s t r a nsf or me d but not i n
wh a t i s conse r v e d.
I n a na l y se s of t h e t y pe s of e xpl a na t i ons gi v e n by pupi l s i n di f f e r e nt
a r e a s of ph y si cs, Monk ( 1990, 1991) h a s compa r e d t h e pr opor t i ons of
pupi l s´ a t di f f e r e nt a ge s gi v i ng di f f e r e nt t y pe s of a l t e r na t i v e
e xpl a na t i ons a nd sci e nt i f i c e xpl a na t i ons, wi t h t h e pr opor t i ons of
pupi l s a t t h e sa me a ge s wh o woul d be e xpe ct e d t o be a ce r t a i n l e v e l s
of ge ne t i c e pi st e mol ogi ca l de v e l opme nt . Th e si mi l a r i t y be t we e n
f i gur e s i s st r i k i ng l e ndi ng suppor t t o cl a i ms ( Monk , 1990) t h a t :
“( i ) t h e r e i s a ge ne t i c e pi st e mol ogi ca l st a ge r e l a t e d ce i l i ng t o
t h e cogni t i v e pr oce ssi ng on t h e pa r t of pupi l s;
( i i ) pupi l s ca n be ne f i t f r om t ui t i on such t h a t t h e i r pe r f or ma nce on
t e st i t e ms ca n be i ncr e a se d t o t h e l i mi t se t by t h e i r t h e n cur r e nt
st a ge of ge ne t i c e pi st e mol ogi ca l de v e l opme nt ”.
S i mi l a r l y
Eck st e i n a nd S h e me sh ( 1993) h a v e de v e l ope d a
ma t h e ma t i ca l mode l t o de scr i be t h e pa t t e r n i n pr opor t i ons of pupi l s
of di f f e r e nt a ge s gi v i ng di f f e r e nt t y pe s of a l t e r na t i v e a nd sci e nt i f i c
e xpl a na t i ons of mot i on. Th e ma t h e ma t i ca l mode l a l so a ppl i e s t o
t h e l e v e l of ge ne t i c e pi st e mol ogi ca l de v e l opme nt of pupi l s, a nd
a ga i n i mpl i e s t h a t t h e t y pe of e xpl a na t i on gi v e n by pupi l s i s
cont r ol l e d by t h e i r l e v e l of cogni t i v e de v e l opme nt .
Ch i , S l ot t a a nd Le e uw ( 1992) , a nd Ch i ( i n pr e ss) pr opose a di f f e r e nt
e xpl a na t i on of pupi l s´ a l t e r na t i v e conce pt i ons, a nd t h e di f f i cul t i e s
of ch a ngi ng pupi l s´ conce pt i ons t o mor e sci e nt i f i c one s. Th e y pr opose
t h a t k nowl e dge ca n be di v i de d i nt o v a r i ous di st i nct ont ol ogi ca l
ca t e gor i e s. Th e t h r e e ma jor ont ol ogi ca l ca t e gor i e s a r e ma t t e r ,
e v e nt s a nd a bst r a ct i ons. Ent i t i e s wh i ch a r e ca t e gor i se d i nt o one
ont ol ogi ca l ca t e gor y h a v e ce r t a i n a t t r i but e s t h a t di f f e r e nt i a t e i t
f r om ot h e r ont ol ogi ca l ca t e gor i e s. R e i ne r , Ch i a nd R e sni ck ( 1988)
gi v e ma ny e xa mpl e s f r om ph y si cs wh e r e pupi l s h a v e i ncor r e ct l y
ca t e gor i se d sci e nt i f i c pr oce sse s ( const r a i nt - ba se d e v e nt s) a s
ma t e r i a l s. Th i s l e a d t o consi de r a bl e di f f i cul t i e s f or pupi l s i n
de v e l opi ng sci e nt i f i c conce pt s. F or e xa mpl e , t h e pr oce ss of
“h e a t i ng” ma y be cl a ssi f i e d i ncor r e ct l y a s a subst a nt i a l i se d
ma t e r i a l “h e a t ”. H e a t i ng i s a pr oce ss wh i ch h a s pr ope r t i e s such a s
h a ppe ni ng dur i ng a pa r t i cul a r t i me , a nd be i ng ca use d by ce r t a i n
i nt e r a ct i ons, wh e r e a s h e a t ca n be ga i ne d or l ost , ca n t r a v e l a l ong a
me t a l ba r , or ca n be l ost dur i ng bur ni ng a nd a ccount f or t h e we i gh t
7
l oss i n ma ny bur ni ng pr oce sse s. Ch i , ( i n pr e ss) a r gue s t h a t
conce pt ua l ch a nge wi t h i n a n ont ol ogi ca l ca t e gor y ( non- r a di ca l
conce pt ua l ch a nge ) i s much e a si e r t h a n conce pt ua l ch a nge a cr oss
ont ol ogi ca l ca t e gor i e s ( r a di ca l conce pt ua l ch a nge ) , a nd t h a t i nde e d,
conce pt ua l
ch a nge a cr oss ont ol ogi ca l
ca t e gor i e s i s “ne a r l y
i mpossi bl e t o a compl i sh ”. “Th e r e a r e no concr e t e ope r a t i ons t h a t
ca n t r a nsf or m a ph y si ca l obje ct such a s a cup, i nt o a n ont ol ogi ca l
di f f e r e nt e nt i t y , such a s a dr e a m. Li k e wi se , t h e r e i s no
psy ch ol ogi ca l l e a r ni ng me ch a ni sm t h a t ca n modi f y a conce pt f r om
one ont ol ogi ca l ca t e gor y i nt o a not h e r . N o me ch a ni sm of a ddi t i on,
de l e t i on,
ge ne r a l i za t i on,
di scr i mi na t i on,
spe ci a l i za t i on,
pr oce dur a l i za t i on a nd so f or t h ca n ch a nge t h e me a ni ng of a conce pt
f r om one ont ol ogi ca l ca t e gor y t o a not h e r . . . ” . I t i s sugge st e d t h a t
t h e r a di ca l conce pt ua l ch a nge ne e de d t o de v e l op a conce pt i n a
di f f e r e nt ont ol ogi ca l ca t e gor y , ma y t a k e pl a ce by de v e l opi ng a ne w
conce pt wi t h i n t h e cor r e ct ont ol ogi ca l ca t e gor y , wh i ch ma y coe xi st
wi t h t h e ol d conce pt i n t h e i ncor r e ct ont ol ogi ca l ca t e gor y .
Th e di v i si on of conce pt ua l ch a nge i nt o t wo t y pe s h e l ps t o sol v e some
of t h e cont r a di ct i ons i n t h e l i t e r a t ur e be t we e n r e se a r ch e r s such a s
La wson ( 1988) wh o ma i nt a i ns t h a t ma ny bi ol ogi ca l conce pt s a r e
a cqui r e d t h r ough a pr oce ss of a ccr e t i on, a nd ot h e r a ut h or s wh o h a v e
f ound pupi l s´ a l t e r na t i v e conce pt i ons r obust a nd di f f i cul t t o ch a nge .
Th e f or me r i s cl a ssi f i e d a s conce pt ua l ch a nge wi t h i n a n ont ol ogi ca l
ca t e gor y ( non- r a di ca l conce pt ua l ch a nge ) a nd t h e l a t t e r a cr oss
ont ol ogi ca l ca t e gor i e s ( r a di ca l conce pt ua l ch a nge ) . I t a l so gi v e s
some i nsi gh t i nt o t h e i ssue of consi st e ncy or i nconsi st e ncy of pupi l s´
e xpl a na t i ons. Pupi l s´ e xpl a na t i ons of conce pt s or “e nt i t i e s” wi t h i n
a n ont ol ogi ca l ca t e gor y ma y we l l be consi st e nt but pupi l s ma y dr a w
on conce pt s f r om di f f e r e nt ont ol ogi ca l ca t e gor i e s ( e . g. “h e a t ” a nd
“h e a t i ng”) t o a nswe r di f f e r e nt que st i ons, wh i ch t o t h e sci e nt i st
a ppe a r t o be a bout t h e sa me conce pt . F r om t h e pupi l ´s pe r spe ct i v e
t h e a nswe r s coul d be consi st e nt , but not so f r om t h e sci e nt i st s´
pe r spe ct i v e .
MODELS OF PU PI LS´
TH E LI TERA TU RE
U N DERSTA N DI N G OF COMB U STI ON I N
A numbe r of st udi e s h a v e be e n ca r r i e d out wh i ch h a v e a t t e mpt e d t o
sy nt h e si se f i ndi ngs a bout pupi l s´ e xpl a na t i ons of combust i on by
a ppl y i ng ge ne r a l cr i t e r i a t o cl a ssi f y t h e r e sponse s t o a v a r i e t y of
que st i ons ( A nde r sson, 1986 ( b) ; A nde r sson, 1990; Me h e ut , S a l t i e l ,
8
a nd Ti be r gh i e n, 1985; Me h e ut , 1982;
a nd D i l l on, 1992) .
Pf undt , 1981; Pr i e t o, W a t son
A nde r sson ( 1990) de scr i be s a ca t e gor i sa t i on sy st e m wh i ch ca n be
a ppl i e d t o pupi l s r e sponse s t o a v a r i e t y of que st i ons conce r ni ng bot h
ch e mi ca l
a nd ph y si ca l
ch a nge .
Th e ca t e gor i e s a r e ( a )
di sa ppe a r a nce ,
( b)
di spl a ce me nt ,
( c)
modi f i ca t i on,
( d)
t r a nsmut a t i on a nd ( c) ch e mi ca l i nt e r a ct i on. Th e se a r e i l l ust r a t e d
a s f ol l ows:
( a ) D i s a p p e a r a nce
W h e n a sk e d a bout t h e we i gh t of e xh a ust ga se s pr oduce d wh e n
pe t r ol i s bur nt i n a ca r ( A nde r sson & R e nst r om, 1983) some pupi l s
a nswe r t h a t some of t h e pe t r ol i s use d up i n t h e ca r a nd di sa ppe a r s.
( b ) D i s p l a ce m e nt
A n e xa mpl e i s of pupi l s e xpl a i ni ng t h e di sa ppe a r a nce of wa t e r f r om
a puddl e on t h e f l oor , by sa y i ng t h a t t h e wa t e r h a d pe ne t r a t e d t h e
f l oor , i . e . i t h a d be e n di spl a ce d t o a di f f e r e nt pl a ce .
( c) Mo d i f i ca t i o n
Me h e ut e t a l . ( 1985) gi v e e xa mpl e s of pupi l s e xpl a i ni ng t h e bur ni ng
of a l coh ol a nd t h e boi l i ng of wa t e r i n t e r ms of modi f i ca t i on of
l i qui d a l coh ol t o a l coh ol v a pour a nd l i qui d wa t e r t o st e a m.
( d ) Tr a ns m ut a t i o n
S ome ch a nge s a r e de scr i be d i n t e r ms of t r a nsmut a t i on of subst a nce
i nt o e ne r gy , of e ne r gy i nt o subst a nce or of one subst a nce i nt o a ne w
one , f or e xa mpl e i r on wool be i ng t r a nsmut e d i nt o ca r bon dur i ng
combust i on.
( e ) C h e m i ca l ch a nge
I de a s of ch e mi ca l ch a nge a r e a ppl i e d cor r e ct l y t o e xa mpl e s such a s
pe t r ol bur ni ng, but a l so i ncor r e ct l y t o ph y si ca l ch a nge s ( O sbor ne &
Cosgr ov e , 1983) . S ome pupi l s t h i nk t h a t t h e bubbl e s of st e a m a r e
oxy ge n a nd h y dr oge n ga se s.
Me h e ut e t a l . ( 1985) de v e l ope d a wa y of ca t e gor i si ng t h e r e sponse s
of st ude nt s ( a ge d 11- 12) ba se d on t h e i r i de a s of conse r v a t i on. Th e r e
a r e some si mi l a r i t i e s wi t h A nde r sson’ s ca t e gor i sa t i on sch e me but
Me h e ut e t a l . a l so i ncor por a t e t h e na t ur e of t h e combust i bl e
ma t e r i a l i n t h e ca t e gor i sa t i on sy st e m.
Pupi l s r e sponse s ca n be
di v i de d i nt o t wo gr oups a ccor di ng t o t h e na t ur e of t h e combust i bl e
subst a nce . Th e f i r st gr oup i ncl ude s r e sponse s a bout me t a l s, wa x,
wa t e r , a nd a l coh ol , wh i ch a r e sa i d t o me l t or e v a por a t e , r a t h e r
t h a n bur n, or usi ng A nde r sson’ s t e r mi nol ogy , a r e modi f i e d.
Th e
se cond gr oup i ncl ude s r e sponse s a bout wood, ca r dboa r d, pa pe r ,
9
a l coh ol a nd a i r , wh i ch a r e se e n t o bur n a nd be ch a nge d i nt o a not h e r
subst a nce or not h i ng. U si ng A nde r sson’ s ca t e gor i e s, t h e se subst a nce s
di sa ppe a r or a r e t r a nsmut e d.
A n i mpor t a nt f e a t ur e i n t h e
ca t e gor i sa t i on of Me h e ut e t a l . i s t h a t dur i ng t r a nsmut a t i on e a ch
subst a nce i s t r a nsmut e d se pa r a t e l y . S t ude nt s of t e n f a i l t o r e a l i se
t h a t ma t t e r i s i nt e r a ct i ng.
Th e r ol e of oxy ge n a nd a i r i s not de a l t wi t h a de qua t e l y i n e i t h e r
A nde r sson’ s or Me h e ut ’ s mode l .
O ne di f f i cul t y i n i nt e r pr e t i ng
r e sponse s t o que st i ons de si gne d t o e l i ci t st ude nt s unde r st a ndi ngs of
t h e r ol e of oxy ge n a nd a i r i n combust i on i s t h a t not a l l st ude nt s
h a v e a good unde r st a ndi ng of t h e na t ur e of a i r ( R usse l e t a l . , 1991;
B r ook s & D r i v e r , 1989) . B r ook s a nd D r i v e r r e por t e d t h a t e v e n a t
a ge 16 a bout t h r e e qua r t e r s of pupi l s t h ough t t h a t a i r h a d ze r o or
ne ga t i v e we i gh t . Pupi l s ma y , t h e r e f or e , conse r v e ma t t e r i n t h e i r
e xpl a na t i ons of ch e mi ca l r e a ct i ons, but not ne ce ssa r i l y conse r v e
ma ss.
I n a n e a r l i e r pa pe r ( Pr i e t o, W a t son a nd D i l l on , 1992) , we de scr i be d
h ow t h e ca t e gor i e s of A nde r sson a nd of Me h e ut we r e de v e l ope d t o
pr oduce ope r a t i ona l de f i ni t i ons of t h r e e ca t e gor i e s of pupi l s´
e xpl a na t i ons of combust i on, t o f i t our da t a . Th e ca t e gor i e s we r e
Modi f i ca t i on,
Tr a nsmut a t i on
a nd
Ch e mi ca l
R e a ct i on.
Th e
D i sa ppe a r a nce
ca t e gor y
of
A nde r sson
is
subsume d
unde r
t r a nsmut a t i on a nd e xa mpl e s of D i spl a ce me nt we r e not f ound i n our
da t a . Th e t h r e e ca t e gor i e s a r e de f i ne d i n t a bl e 1.
______________________________________________________
__
TA B LE 1
OPERA TI ON A L DEF I N I TI ON S OF PU PI LS' EX PLA N A TI ON S
1. Rol e of oxy gen/ i nt er a ct i on
C:
C1: Pupi l s r e cogni se t h a t t h e combust i bl e subst a nce a nd oxy ge n/a i r
i nt e r a ct .
C2: Th e r e a ct i on i s i r r e v e r si bl e .
T:
T1: Th e r e i s no i nt e r a ct i on be t we e n t h e combust i bl e subst a nce a nd t h e
oxy ge n/a i r .
10
T2: O xy ge n/a i r ma y or ma y not be r e cogni se d a s ne ce ssa r y f or
combust i on t o t a k e pl a ce .
T3: B ur ni ng i s a de st r uct i v e pr oce ss.
T4: Th e de st r uct i v e pr oce ss ma y r e l e a se or l i be r a t e subst a nce s f r om
t h e combust i bl e subst a nce .
T5: B ur ni ng i s i r r e v e r si bl e .
M:
M1: O xy ge n/a i r i s not i nv ol v e d i n t h e ch a nge .
M2: Th e ch a nge i s r e v e r si bl e .
2. F l a me/ f i r e
C:
C3: Ene r gy ch a nge s ma y be obse r v e d but a r e not e xpl a i ne d.
C4: Th e f l a me /f i r e i s e v i de nce of a ch e mi ca l r e a ct i on.
C5: Th e f l a me cont a i ns bot h t h e combust i bl e subst a nce a nd oxy ge n/a i r
r e a ct i ng.
T:
T6: Th e f l a me /f i r e i s a n a ct i v e a ge nt of ch a nge .
T7: A i r /oxy ge n ma y be ne e de d t o ‘ f e e d t h e f l a me ’ or ‘ k e e p i t a l i v e ’ .
T8: A i r /oxy ge n i s t r a nsmut e d by t h e f l a me /f i r e or i s consume d by i t .
T9: Ma t t e r ma y be t r a nsmut e d i nt o h e a t .
T10: F l a me s cont a i n onl y t h e combust i bl e subst a nce or oxy ge n/a i r or
possi bl y bot h but wi t h no i nt e r a ct i on.
M:
M3:
occur .
Th e f l a me /f i r e i s a sour ce of h e a t t o ma k e t h e modi f i ca t i on
3. Pr oduct s a nd r ea ct a nt s
C:
C6: Th e pr oduct s cont a i n t h e r e a ct a nt s i n a di f f e r e nt ch e mi ca l
combi na t i on.
C7: Ma ss i s conse r v e d pr ov i de d t h a t pupi l s t h i nk t h a t ga se s we i gh
some t h i ng or ga s i s not ‘ l ost ’ t o t h e a t mosph e r e .
C8: Pr ope r t i e s a r e not conse r v e d.
T:
T11: S ubst a nce i s ch a nge d f r om one subst a nce t o a not h e r or i nt o
not h i ng dur i ng combust i on.
11
T12: O xy ge n/a i r ma y be t r a nsmut e d se pa r a t e l y i nt o a pr oduct .
T13: O xy ge n ma y be ne e de d but doe s not i nt e r a ct i n a ch e mi ca l se nse .
T14: Ma ss ma y i ncr e a se , de cr e a se or st a y t h e sa me ( be ca use t h e
t r a nsmut e d pr oduct s a r e di f f e r e nt f r om t h e r e a ct a nt s) .
T15: Pr ope r t i e s a r e not conse r v e d.
T16: Pr ope r t i e s ma y be subst a nt i a l i se d a nd t h e r e f or e be i nv ol v e d i n
t h e t r a nsmut a t i on.
M:
M4: O ne subst a nce ch a nge s t o a di f f e r e nt f or m of t h e sa me subst a nce .
M5: S ubst a nce i s conse r v e d.
M6: Ma ss ma y be conse r v e d, but t h i s de pe nds on wh e t h e r di f f e r e nt
f or ms of t h e sa me subst a nce a r e consi de r e d t o we i gh t h e sa me .
M7: S ome pr ope r t i e s a r e conse r v e d.
______________________________________________________
__
I t ca n be se e n t h a t t h e t wo a l t e r na t i v e f r a me wor k s “Tr a nsmut a t i on”
a nd “Modi f i ca t i on” sh a r e ma ny of t h e ch a r a ct e r i st i cs of pupi l s
a l t e r na t i v e e xpl a na t i ons de scr i be d i n t h e l i t e r a t ur e r e v i e we d
e a r l i e r . Th e a l t e r na t i v e f r a me wor k s f i t t h e de scr i pt i ons i n t h e
f ol l owi ng wa y s:
* Th e r e i s a h e a v y de pe nde nce on i mme di a t e l y obse r v a bl e
ch a r a ct e r i st i cs of combust i on ( D r i v e r e t a l . 1985( a ) ) . O xy ge n or
a i r , wh i ch ca nnot be se e n, pl a y no r ol e i n i nt e r a ct i ng wi t h t h e
combust i bl e subst a nce i n Tr a nsmut a t i on ( T1, T2, T7, T8, T12 a nd
T13) . a nd pl a y s no r ol e i n Modi f i ca t i on a t a l l ( M1) . Ga se ous
pr oduct s a nd we i gh t ch a nge s a r e uni mpor t a nt i n Tr a nsmut a t i on
( T14) a nd Modi f i ca t i on ( M3) e xpl a na t i ons a nd r e ce i v e l i t t l e
a t t e nt i on f r om t h e pupi l s.
* Th e l i mi t e d f ocus of t h e t wo a l t e r na t i v e e xpl a na t i ons ca n be
se e n i n t h e ma i nl y de scr i pt i v e na t ur e t h a t t h e y sh a r e ( D r i v e r e t
a l . 1985( a ) ) . Th e e xpl a na t i ons h a v e pr e di ct i v e v a l i di t y , i n t h a t
t h e y a l l ow pupi l s t o pr e di ct wh a t ch a nge s wi l l occur i n wh a t
t h e y pe r ce i v e a s si mi l a r ci r cumst a nce s, but t h e y f a i l t o go be y ond
t h e i nme di a t e l y pe r ce pt i bl e . A s pr e di ct i v e
e xpl a na t i ons
Tr a nsmut a t i on f unct i ons we l l on t h e t y pe s of e xa mpl e s of
ma t e r i a l s t h a t pupi l s nor ma l y gi v e a s e xa mpl e s of bur ni ng, i . e .
ca r bon/h y dr oge n ba se d ma t e r i a l s such a s wood, pa pe r , pl a st i c,
cl ot h a nd l i v i ng t h i ngs. Modi f i ca t i on f unct i ons we l l on e xa mpl e s
of bur ni ng t h a t pupi l s i ncor r e ct l y pe r ce i v e a s si mi l a r t o ch a nge s
of st a t e such a s a ca ndl e or a me t a l bur ni ng ( me l t i ng) a nd a l coh ol
12
bur ni ng ( e v a por a t i on) ; unde r not t oo cl ose scr ut i ny t h e or i gi na l
subst a nce r e f or ms a f t e r bur ni ng a s a sol i d pr oduct ( f r e e zi ng) or a s
a l i qui d ( dr ops sme l l i ng of a l coh ol conde nsi ng on a col d sur f a ce
f r om a n a l coh ol f r a me ) .
* Li ne a r ca usa l r e a soni ng i s use d i n bot h ca se s ( D r i v e r e t a l .
1985( a ) ; A nde r sson, 1986( a ) ) . I n Tr a nsmut a t i on t h e f l a me or f i r e
i s a n a ct i v e a ge nt of ch a nge , wh i ch a ct s on t h e combust i bl e
ma t e r i a l , a nd pe r h a ps t h e oxy ge n se pa r a t e l y , i n a de st r uct i v e
pr oce ss t o pr oduce a pr oduct wh i ch i s compl e t e l y di f f e r e nt f r om
t h e r e a ct a nt ( s) ( T3, T5, T6, T11, T12, T14, T15) . I n Modi f i ca t i on
t h e h e a t or f i r e a ct s on t h e combust i bl e subst a nce ( M4) t o ch a nge
i t i nt o a di f f e r e nt v e r si on of t h e sa me subst a nce ( M4, M5, M6,
M7) .
* B ot h Tr a nsmut a t i on a nd Modi f i ca t i on ca n be ca t e gor i se d i nt o t h e
sa me ont ol ogi ca l ca t e gor y ( Ch i , i n pr e ss) a s Ch e mi ca l r e a ct i on,
i . e , t h e “const r a i nt ba se d e v e nt s” ca t e gor y , but t h e conce pt of
h e a t /h e a t i ng wh i ch
i s use d wi t h i n t h e
Tr a nsmut a t i on
e xpl a na t i on, i s cl a ssi f i e d i ncor r e ct l y by some pupi l s. S ome pupi l s
subst a nt i a l i se h e a t ( T9) , i . e . ca t e gor i se i t a s a “ma t t e r ” i nst e a d
of a s a “const r a i nt - ba se d e v e nt ”.
* Th e i mpr e ci se use of conce pt s a nd l a ngua ge ( D r i v e r e t a l .
1985( a ) ) i s v e r y e v i de nt i n t h e pupi l s´ r e sponse s, but l e ss e v i de nt
i n t h e ope r a t i ona l de f i ni t i ons a bov e wh i ch t r y t o a v oi d
a mbi gui t y . N e v e r t h e l e ss t h e e v i de nt conf usi on be t we e n t h e
conce pt s of bur ni ng a nd h e a t i ng a r e obv i ous i n t h e Modi f i ca t i on
e xpl a na t i on.
* Th e me nt a l mode l l i ng of combust i on a s " Tr a nsmut a t i on" or a s
" Modi f i ca t i on" r e qui r e s onl y concr e t e ope r a t i ona l t h i nk i ng a s
compa r e d wi t h “Ch e mi ca l R e a ct i on” wh i ch r e qui r e s f or ma l
ope r a t i ona l t h i nk i ng ( Monk 1990, 1991) , a nd t h i s ma y e xpl a i n t h e
l ow numbe r of pupi l s wh o gi v e “Ch e mi ca l R e a t i on” e xpl a na t i ons.
Th e me nt a l mode l l i ng of combust i on a s Modi f i ca t i on i nv ol v e s t h e
r e v e r si bl e t r a nsf or ma t i on of a subst a nce wi t h ce r t a i n pr ope r t i e s
( e . g. sol i d pr ope r t i e s) i nt o t h e sa me subst a nce
wi t h some
di f f e r e nt pr ope r t i e s ( e . g. l i qui d pr ope r t i e s) a nd i s ch a r a ct e r i st i c
of
ea rl y
concr e t e
ope r a t i ona l
t h i nk i ng.
Combust i on
as
Tr a nsmut a t i on i nv ol v e s a n i ncr e a se of t h e pr oduct a t t h e e xpe nse s
of t h e combust i bl e subst a nce ; i . e . t h e sy st e m cont a i ns onl y t wo
compone nt s wh i ch a r e pol a r opposi t e s on t h e sa me sca l e : l e ss
combust i bl e subst a nce , mor e pr oduct . Th i s i s ch a r a ct e r i st i c of l a t e
concr e t e ope r a t i ona l t h i nk i ng. I n me nt a l l y mode l l i ng combust i on
a s Ch e mi ca l R e a ct i on, t h e t h i nk e r must h a v e a mode l t h a t
cont a i ns a t l e a st t h r e e compone nt s ( i . e . combust i bl e subst a nce ,
13
oxy ge n a nd pr oduct ) , a nd t h e r e l a t i v e r a t i os of t h e se co- v a r y i n a
di r e ct a nd i ndi r e ct f a sh i on. Th i s coul d be i nt e r pr e t a s r e qui r i ng
t h e compe nsa t or y t h i nk i ng t h a t i s one of t h e ch a r a ct e r i st i cs of
f or ma l ope r a t i ona l t h ough t .
RESEA RCH METH ODS
A que st i onna i r e , wh i ch cont a i ne d ni ne que st i ons, a l l of t h e m ope n
a nd one a l so cont a i ni ng a f i xe d r e sponse i t e m, wa s de v e l ope d
t h r ough a se r i e s of f our pi l ot st udi e s wh i ch i nv ol v e d a bout 150
pupi l s i n S pa i n a nd Engl a nd. Th e ma i n f oci of t h e que st i onna i r e
we r e : t h e pr oce ss; t h e pr oduct s, i ncl udi ng a spe ct s of conse r v a t i on;
a nd t h e e xa mpl e s of combust i on t h a t pupi l s gi v e . Th e que st i ons
wh i ch a r e t h e f ocus of t h i s pa pe r a r e gi v e n i n a ppe ndi x 1. Th i s
pa pe r a na l y se s da t a f r om 150 spa ni sh st ude nt s a ge d 14 a nd 15. Th i s
numbe r a l l ows pupi l s wi t h si mi l a r t y pe s of e xpl a na t i ons t o be
gr oupe d t oge t h e r . Th i s a ge wa s ch ose n a s a l l t h e pupi l s woul d h a v e
st udi e d some e l e me nt a r y ch e mi st r y i ncl udi ng combust i on. Th e pupi l s
we r e se l e ct e d f r om sch ool s t o gi v e a sa mpl e wh i ch wa s
r e pr e se nt a t i v e of t h e popul a t i on a t t h a t a ge .
Th e r e sponse s t o t h e que st i onna i r e we r e a na l y se d a s de scr i be d be l ow:
1. Th e r e sponse s we r e a na l y se d by de v e l opi ng sy st e mi c ne t wor k s
( B l i ss, Monk a nd O gbor n, 1983) t o ca pt ur e t h e me a ni ngs of t h e
r e sponse s i n a sy st e ma t i c wa y .
2. Th e ne t wor k s we r e a na l y se d t o i de nt i f y i ndi ca t or s of di f f e r e nt
ca t e gor i e s of t h i nk i ng, a nd t h e se i ndi ca t or s we r e use d t o modi f y
A nde r sson´s ( 1990) ca t e gor i e s a nd t o ge ne r a t e t h e de t a i l e d
de scr i pt i ons of di f f e r e nt ca t e gor i e s of t h i nk i ng, gi v e n i n t a bl e 1
( Pr i e t o e t a l . , 1992) .
3. Th e de t a i l e d de scr i pt i ons we r e use d t o ca t e gor i se pupi l s´
r e sponse s que st i on by que st i on.
4. Th e consi st e ncy of pupi l s´ use of di f f e r e nt e xpl a na t or y mode l s
wa s e xa mi ne d, a nd t h e pupi l s we r e di v i de d i nt o di f f e r e nt gr oups
a ccor di ng t o t h e consi st e ncy of t h e i r r e sponse s.
5. A de t a i l e d qua l i t a t i v e a na l y si s of t h e r e sponse s of pupi l s i n
t h e di f f e r e nt gr oups wa s ca r r i e d out t o e xa mi ne t h e na t ur e of
consi st e ncy /i nconsi st e ncy of e a ch gr oup.
14
RESU LTS
D e v e l o p i ng s y s t e m i c ne t w o r k s .
Th e f i r st st a ge i n t h e a na l y si s of t h e da t a wa s t o de v e l op sy st e mi c
ne t wor k s, t o ca pt ur e t h e e sse nce of t h e r e sponse s t o ope n que st i ons,
i n a wa y t h a t a l l owe d a spe ct s of t h e r e sponse s t o be qua nt i f i e d. A n
e xa mpl e of a ne t wor k i s gi v e n by t h e one f or que st i on 1( a ) a nd ( b)
sh own i n f i gur e 1. Th e e xa mpl e s of pupi l s´ r e sponse s gi v e n be l ow
sh ow h ow r e sponse s a r e e ncode d.
Pupi l 70
1a ) : “I t i s a combust i on pr oce ss t h a t h a ppe ns t o a subst a nce . I t
goe s f r om a st a t e t o a not h e r , e . g. a l e a v e i s t r a nsf or me d i nt o
a sh e s, f r om l i qui d t o ga s" . 1b) : " I t e v a por a t e s”.
Th i s a nswe r h a s be e n code d a s f ol l ow:
“I t i s a combust i on pr oce ss t h a t h a ppe ns t o a subst a nce ”: 1. 11
“I t goe s f r om a st a t e t o a not h e r , e . g. a l e a v e i s t r a nsf or me d i nt o
a sh e s”: 1. 36
“f r om l i qui d t o ga s. 1b) I t e v a por a t e s”: 1. 41
Pupi l 32
1a ) : “I t i s a ch e mi ca l r e a ct i on t h a t h a ppe ns wh e n a subst a nce
ga i ns such h i gh t e mpe r a t ur e t h a t i t ca nnot st a nd i t " . 1b) :
" Ch a nge s t o a not h e r subst a nce ”.
Th i s a nswe r h a s be e n code d a s f ol l ow:
“I t i s a ch e mi ca l r e a ct i on”: 1. 12
“t h a t h a ppe ns wh e n a subst a nce ga i ns such h i gh t e mpe r a t ur e t h a t i t
ca nnot st a nd i t ”: 2. 5
“Ch a nge s t o a not h e r subst a nce ”: 1. 32
15
Figure 1. Network for question 1 (a& b).
Combustion
Chemical Reaction
Chemical Change
Chemical
Synonimous
- Its burns
1.11
1.12
1.13
-Comp. with oxygen 1
- Another substance 15
- Gas
5
- Carbon Dioxide
1
- Smoke
2
- Ash
65
- Carbon
10
1.31
1.32
1.33
1.34
1.35
1.36
1.37
- Evaporates
5
- Melts
7
- Turns to powder
1
- Changes colour
5
- Gets hot
5
- Expands
3
- Changes form
8
- Changes state
6
- Changes appearance 1
1.41
1.42
1.43
1.44
1.45
1.46
1.47
1.48
1.49
- Is destroyed
- Is decomposed
- Loses properties
- Becomes less
- Deteriorates
3
10
2
3
3
1.51
1.52
1.53
1.54
1.55
- Is used up
- Disappears
- Disintegrates
6
14
15
1.61
1.62
1.63
- Combustible material
- Oxygen
- Air
- High temperatures
- Heat
- Fire
- Other substances
12
4
2
3
5
49
1
2.1
2.2
2.3
2.4
2.5
2.6
2.7
-Heat
-Energy
-Fire
-Combustible substance
-Smoke
-Light
10
2
17
1
5
3
3.1
3.2
3.3
3.4
3.5
3.6
Changes no
necessarily
to something
different
Disappears
Something
is liberated
11
5
1
1.20
Deteriorates
Requirements
Code
88
Changes to
something
different
Nature of
change
N
16
S ome of t h e code s a r e mor e use f ul t h a n ot h e r s i n ga i ni ng i nsi gh t i nt o
t h e pupi l ´s t h i nk i ng. Th e cl a use “I t i s a ch e mi ca l r e a ct i on” ( pupi l
32) coul d be t a k e n t o i ndi ca t e a n unde r st a ndi ng t h a t one ch e mi ca l i s
se e n t o be r e a ct i ng wi t h a not h e r . Th i s me a ni ng i s not , h owe v e r ,
cl e a r f r om t h e r e st of t h e r e sponse . S i mi l a r l y “I t a combust i on
pr oce ss” ( pupi l 70) coul d be t a k e n t o me a n t h e r e a ct i on of a
combust i bl e subst a nce wi t h oxy ge n. Th e r e st of t h e r e sponse sh ows
cl e a r l y t h a t t h i s i s not t h e ca se wi t h a ch a nge of st a t e be i ng gi v e n
a s a n e xa mpl e of combust i on.
D e v e l o p i ng o p e r a t i o na l d e f i ni t i o ns .
Th e se cond st a ge i n t h e a na l y si s di d i n f a ct r e st or e some of t h e da t a
l ost i n t h e codi ng on t h e ne t wor k s. Th e code s ge ne r a t e d i n t h e
ne t wor k s we r e use d se l e ct i v e l y t o ge ne r a t e t h e ope r a t i ona l
de f i ni t i ons of pupi l s´ e xpl a na t i ons gi v e n i n t a bl e 1. Th e pupi l s´
r e sponse s we r e t h e n r e - e xa mi ne d i n t h e l i gh t of t h e ope r a t i ona l
de f i ni t i ons t o a l l oca t e e a ch r e sponse t o a ca t e gor y of pupi l s´
e xpl a na t i ons.
O ne di f f i cul t y i n a l l oca t i ng r e sponse s t o a ca t e gor y of pupi l s´
e xpl a na t i ons wa s t h a t i t wa s of t e n di f f i cul t t o de ci de wh e t h e r a
r e sponse sh oul d be ca t e gor i se d a s Tr a nsmut a t i on ( T) or Ch e mi ca l
R e a ct i on ( CR ) . Th e r e sponse gi v e n f or pupi l 32 a bov e i s a n e xa mpl e
of t h i s. Th e use of t h e wor ds “Ch e mi ca l r e a ct i on” ma y be a n
i ndi ca t i on of CR but t h i s i s a mbi guous. Th e r e i s a me nt i on of ch a nge
t o a not h e r subst a nce but no me nt i on of oxy ge n or a i r . Th i s r e sponse
h a s, t h e r e f or e be e n ca t e gor i se d a s i nt e r me di a t e be t we e n CR a nd T a s
X . O t h e r r e sponse s a r e not a mbi guous but cont a i n a spe ct s of bot h CR
a nd T e xpl a na t i ons. Th e se h a v e be e n a l so cl a ssi f i e d a s X .
S ome t i me s pupi l s gi v e , i n di f f e r e nt pa r t s of t h e i r r e sponse s, bot h
Modi f i ca t i on e xpl a na t i ons a nd Tr a nsmut a t i on/Ch e mi ca l R e a ct i on
e xpl a na t i ons, e . g. pupi l 70 a bov e . S uch r e sponse s r e ce i v e d a doubl e
cl a ssi f i ca t i on, X a nd M i n t h e ca se of pupi l 70; T a nd M i n t h e ca se
be l ow:
Pupi l 3
1a ) : " I s wh e n a subst a nce bur ns" , 1b) : " I t be come s a sh e s or a
di f f e r e nt t h i ng h a ppe ns t o i t . F or e xa mpl e , i f i t i s wood i t t ur ns
i nt o a sh a nd i f i t i s pl a st i c i t me l t s" .
17
I n spi t e of t h e se di f f i cul t i e s i n i nt e r pr e t a t i on, t h e ope r a t i ona l
de f i ni t i ons h a v e a l l owe d a h i gh de gr e e of r e l i a bi l i t y t o be
a ch i e v e d i n a l l oca t i ng r e sponse s t o pa r t i cul a r ca t e gor i e s of
e xpl a na t i ons. A 10% sa mpl e wa s code d by t wo i nde pe nde nt code r s
a nd 94% r e l i a bi l i t y be t we e n code r s wa s a ch i e v e d.
S ome I nt e r e st i ng e xa mpl e s of r e sponse s f or e a ch of t h e ca t e gor i e s of
e xpl a na t i on a r e gi v e n be l ow:
C h e m i ca l R e a ct i o n
Th e r e a r e f e w r e sponse s wh i ch ca n be cl a ssi f i e d a s CR .
Pupi l 72
9: " c) B e ca use t h e ma gne si um wi t h t h e oxy ge n ma k e some k i nd of
mi xt ur e wh i ch we i gh s mor e " .
I nt e r m e d i a t e
Th e t wo e xa mpl e s be l ow sh ow pupi l s wh o a r e st a r t i ng t o t a k e i nt o
a ccount t h e i nt e r a ct i on be t we e n t h e combust i bl e subst a nce a nd
oxy ge n. Th e se cond st ude nt ´s use of wor ds a s “combust i on” a nd “
“r e a ct i on” i ndi ca t e s some pr ogr e ss i n t h e use of sci e nt i f i c l a ngua ge .
Pupi l 51,
1a ) : " I s t h e ch a nge t h a t h a ppe ns t o a body wh e n i t i s cont a ct wi t h
t h e oxy ge n" , 1b) : " U sua l l y gi v e of f f ume s a nd ge t s sma l l e r a nd
sma l l e r "
Pupi l 102.
1a ) : " I s a k i nd of combust i on t h a t ne e ds t h e pr e se nce of oxy ge n t o
r e a ct wi t h a nd pr oduce f i r e " , 1b) : " I t i s de compose d a nd i s
conv e r t e d i nt o a sh "
Tr a ns m ut a t i o n
Pupi l s usi ng t h i s t y pe of e xpl a na t i ons a r e usua l l y a wa r e of t h e
r e qui r e me nt of oxy ge n i n bur ni ng but do not se e i t a s i nt e r a ct i ng wi t h
t h e combust i bl e subst a nce . S ome t i me s t h e y se e i t a s ne ce ssa r y t o
f e e d t h e f i r e or t h e f l a me
Pupi l 79
6b& c) : " Th e r e i s no oxy ge n, t h e f i r e h a s a bsor be d i t . "
Pupi l 80
6b& c) : “. . . t h e ca ndl e i s a bsor bi ng t h e oxy ge n t o f e e d t h e f l a me . . . ”
18
Mo d i f i ca t i o n
Pupi l s usi ng Modi f i ca t i on e xpl a na t i ons, i n spi t e
t h e y a r e conse r v i ng t h e subst a nce ,
a ppe a r
unde r st a ndi ng of conse r v a t i on of we i gh t . W e i gh t
be i ng de pe nde nt on t h e f or m of t h e subst a nce wi t h
l i qui ds a nd ga se s h a v i ng di f f e r e nt we i gh t s.
of t h e f a ct t h a t
to h a ve l i ttl e
i s of t e n se e n a s
sol i ds, powde r s,
Pupi l 50
9: " e ) I t coul dn’ t i ncr e a se be ca use i t ch a nge d i nt o powde r a nd
powde r doe s not we i gh a ny t h i ng" .
Th e y a l so some t i me s subst a nt i a l i se h e a t or e ne r gy : a bsor bi ng h e a t
ma y ma k e a ma t e r i a l h e a v i e r :
Pupi l 35
9: " I h a v e ch ose n d) be ca use I t h i nk t h a t i n ge t t i ng h e a t t h e
ma t e r i a l ca n i n some wa y i ncr e a se i t s we i gh t " .
Pupi l 46
9: " d) H e a t of t h e f l a me ma k e s i t ge t h e a v i e r "
CLA SSI F I CA TI ON OF RESPON SES TO EA CH QU ESTI ON .
Th e a l l oca t i on of a nswe r s t o ca t e gor i e s i s sh own i n t a bl e 2.
Ta bl e 2. A l l oca t i on of a nswe r s t o ca t e gor i e s ( n = 150) .
Q 1( a & b)
Q5
Q 6a )
Q 6( b& c)
Q7
Q9
CR
2
1
1
1
6
43
X
10
2
17
24
14
3
T
106
140
20
95
73
40
T+M
13
0
2
0
0
1
M
3
0
65
10
1
21
N o code
16
5
3
11
9
28
B l a nk
0
2
42
9
47
14
Th e pa t t e r ns t h a t ca n be se e n i n t h e t a bl e a r e :
* Tr a nsmut a t i on wa s t h e most commonl y use d t y pe of e xpl a na t i on
i n que st i ons 1, 5, 6( b& c) a nd 7.
19
* Modi f i ca t i on i s onl y i mpor t a nt i n t h e ca se of t h e ca ndl e ( Q 6)
a nd t o some e xt e nd t h e ma gne si um ( Q 9) .
* Th e sci e nt i f i c t h e or y Ch e mi ca l R e a ct i on i s l i t t l e use d but some
pupi l s use some e l e me nt s of i t ( X ) .
Th e e xt e nd t o wh i ch pupi l s use d one or mor e t y pe s of e xpl a na t i ons
i s i ndi ca t e d i n t a bl e 3.
Ta bl e 3. Combi na t i ons of di f f e r e nt t y pe s of e xpl a na t i ons use d by
pupi l s ( % , n = 150) .
( M)
N o ( M)
Tot a l
( CR ) a nd/or ( X ) box 1
+ ( T)
28
box 2
22
50
( T)
box 3
34
box 4
16
50
Tot a l
62
38
100
A l l pupi l s use d a Tr a nsmut a t i on t y pe of e xpl a na t i on on a t l e a st one
occa si on, a nd 16% of pupi l s ( box 4) use onl y Tr a nsmut a t i on
e xpl a na t i ons. A bout t wo t h i r ds of t h e pupi l s ( boxe s 1 a nd 3) use
Modi f i ca t i on e xpl a na t i ons, a l t h ough most of t h e se ( 50% of t h e t ot a l
sa mpl e ) use Modi f i ca t i on e xpl a na t i ons onl y once . H a l f of t h e pupi l s
ga v e a t l e a st one r e sponse t h a t i ndi ca t e d some unde r st a ndi ng of a
ch e mi ca l r e a ct i on ( boxe s 1 a nd 2, CR or X ) , but a l l of t h e se pupi l s
a l so use d Tr a nsmut a t i on e xpl a na t i ons, a nd usua l l y t h i s k i nd of
e xpl a na t i on wa s use d mor e of t e n.
I n t h e ne xt se ct i on t h e r e sponse s of pupi l s a r e consi de r e d i n mor e
de t a i l i n or de r t o sh e d l i gh t on wh e t h e r t h e pupi l s we r e r e spondi ng
i n a consi st e nt or i nconsi st e nt wa y .
CON SI STEN CY A N D I N CON SI STEN CY I N PU PI LS´ RESPON SES.
Th e si mpl e st gr oup t o consi de r i s t h e gr oup of pupi l s i n box 4 i n t a bl e
3 ( 16% ) wh o a r e cl e a r l y consi st e nt i n t h e i r r e sponse s, usi ng onl y one
t y pe of e xpl a na t i on. A n e xa mpl e of a pupi l wh o consi st e nt l y use d
Tr a nsmut a t i on e xpl a na t i ons i s gi v e n be l ow:
Pupi l 62
1a ) : " W h a t I unde r st a nd by bur ni ng i s wh e n a ma t e r i a l i s a bl e t o
pr oduce h e a t wi t h a not h e r ma t e r i a l wh i ch h e l ps i t t o pr oduce
f l a me s" . 1b) : " I t consume d" .
20
5: " Y ou ge t a sh e s a nd r e si due " .
6a ) : " W a x h a s be e n consume d a nd t h e f l a me h a s be e n e xt i ngui sh e d
be ca use of l a ck of oxy ge n" .
6b& c) : " Th e a i r h a s be e n consume d a nd t h e r e i s no suppl y of
oxy ge n.
7:
" I t i s ma de of di f f e r e nt pa r t s of h e a t wi t h di f f e r e nt
i nt e nsi t i e s" .
9: " B e ca use a ma t e r i a l a s bur ns i t di sa ppe a r s a nd a l l t h a t i s l e f t
i s a powde r t h a t we i gh s l e ss t h a n i n i t s or i gi na l st a t e " .
U s e o r no n- us e o f Mo d i f i ca t i o n e xp l a na t i o ns .
N o pupi l s use d onl y Modi f i ca t i on t y pe s of e xpl a na t i ons.
Modi f i ca t i on i s a l wa y s use d i n combi na t i on wi t h a di f f e r e nt k i nd of
e xpl a na t i on ( boxe s 1 a nd 3, i n t a bl e 3) . F r om a sci e nt i st ´s
pe r spe ct i v e pupi l s a r e be i ng i nconsi st e nt . F r om a pupi l ´s pe r spe ct i v e
t h e y ma y i n f a ct not be so. Th e i r l a ck of pr e ci si on i n t h e use of
l a ngua ge , t h e i r l a ck of de v e l opme nt of ce r t a i n conce pt s, a nd t h e i r
l a ck of di scr i mi na t i on be t we e n conce pt s, a l l ows t h e m t o use t h e se
e xpl a na t i ons wi t h out h pr obl e ms.
S ome of t h e a ppa r e nt i nconsi st e ncy a r i se s f r om t h e l a ck of
de v e l opme nt of a ppr opi a t e sci e nt i f i c l a ngua ge i n t h e pupi l s a nd t h e
cor r e spondi ng l a ck of de v e l opme nt of ce r t a i n conce pt s. Pupi l s
some t i me s f a i l t o di st i ngui sh be t we e n h e a t i ng a nd bur ni ng:
Pupi l 11,
1a ) : " I s some t h i ng t h a t h a ppe ns wh e n t h e ma t e r i a l i s a t such a
h i gh t e mpe r a t ur e t h a t i t ca n not st a nd i t a nd a spa r k jumps out
a nd t h e n i t be gi ns t o bur n. I f we a r e t a l k i ng a bout me t a l s, t h e y do
not bur n, t h e y me l t ”.
I n t h i s r e sponse bur ni ng i s t a k e n t o me a n bot h bur ni ng a nd h e a t i ng.
Me l t i ng of me t a l s i s e l i ci t e d i n r e sponse t o a que st i on a bout bur ni ng,
not h e a t i ng, a nd t h e n ci t e d a s a n e xa mpl e of some t h i ng t h a t doe s
not bur n. Th i s l a ck of pr e ci si on i n t h e use of l a ngua ge ma y i n f a ct
r e f l e ct a n unde r l y i ng l a ck of de v e l opme nt of t h e conce pt s of bur ni ng
a nd h e a t i ng.
S i mi l a r l y bur ni ng a nd h e a t i ng a r e conf use d by some pupi l s i n
r e sponse t o que st i on 9, wh i ch i s a bout t h e bur ni ng of ma gne si um. Two
k i nds of Modi f i ca t i on e xpl a na t i on a r e gi v e n: “Ma gne si um“ wh e n
h e a t e d e xpa nde d so t h a t i t we i gh mor e ” a nd wh a t pupi l 113 sa y s:
21
Pupi l 113
9: " e ) I f y ou bur n ma gne si um i t wi l l we i gh t t h e sa me , i t i s l i k e
h e a t i ng a l i t r e of wa t e r , a t t h e e nd y ou h a v e a l i t r e of wa t e r but
v a pour ”.
Th i s conf usi on be t we e n h e a t i ng a nd bur ni ng a l l ows pupi l s t o gi v e
e xpl a na t i ons of bur ni ng, of a Modi f i ca t i on t y pe , wh e n t h e y
unde r st a nd “bur ni ng” t o me a n “h e a t i ng”. Th i s t y pe of e xpl a na t i on
ca n coe xi st wi t h e xpl a na t i ons i n wh i ch a mor e conv e nt i ona l
unde r st a ndi ng of t h e wor d bur ni ng i s use d.
A r e l a t e d pr obl e m i s t h a t pupi l s f a i l t o di st i ngui sh be t we e n
combust i on a nd ch a nge of st a t e . A n e xa mpl e i s pupi l 3 ( se e n be f or e ) :
1a ) : " I s wh e n a subst a nce bur ns" , 1b) : " I t be come s a sh e s or a
di f f e r e nt t h i ng h a pe ns t o i t . F or e xa mpl e , i f i t i s wood i t t ur ns
i nt o a sh a nd i f i t i s pl a st i c i t me l t s" .
I n ma ny wa y s pe r ce pt i ons a bout bur ni ng a l coh ol a nd boi l i ng wa t e r
ov e r a bunse n bur ne r a r e si mi l a r : a f l a me i s se e n, h e a t ca n be f e l t ,
t h e v ol ume of l i qui d ge t s l e ss a nd a v a pour i s f or me d. Th e r e a r e a l so
si mi l a r i t i e s be t we e n bur ni ng wa x i n a ca ndl e a nd me l t i ng a bl ock of
i ce . I n t h i s ca se t h e conce pt s of ch a nge of st a t e , a nd bur ni ng, a r e not
we l l de v e l ope d a nd be come conf use d, be ca use t h e pupi l s do not use
a de qua t e cr i t e r i a t o di st i ngui sh be t we e n t h e m.
A f a ct or wh i ch a ppe a r s t o cont r ol wh i ch t y pe of e xpl a na t i on i s t h e
na t ur e of t h e combust i bl e ma t e r i a l . Th e pr e se nt st udy conf i r ms t h e
r e sul t s of Me h e ut e t a l . ( 1985) i n sh owi ng a gr e a t e r t e nde ncy t o use
Modi f i ca t i on e xpl a na t i ons wi t h wa x a nd me t a l . Th e r e i s, h owe v e r ,
i nsuf f i ci e nt da t a i n t h e pr e se nt st udy t o sh ow wh e t h e r pupi l s
di scr i mi na t e be t we e n di f f e r e nt combust i bl e subst a nce s i n a consi st e nt
wa y : t h e r e a r e t oo f e w di f f e r e nt t y pe s of combust i bl e ma t e r i a l
i ncl ude d i n t h e st udy .
Th e r e a r e a numbe r of st udi e s i n t h e l i t e r a t ur e i n wh i ch
Modi f i ca t i on e xpl a na t i ons ca n be i nde nt i f i e d i n pupi l s´ r e sponse s.
Th e r e a r e i ndi ca t i ons f r om t h e l i t e r a t ur e t h a t t h i s t y pe of
e xpl a na t i ons, a s we l l a s be i ng de pe nde nt of t h e na t ur e of t h e
ma t e r i a l be i ng bur nt , i s a l so a ge de pe nde nt , wi t h i t s use de cr e a si ng
wi t h a ge . S ome r e sul t s a r e summa r i se d be l ow i n t a bl e 4. I f st ude nt s
sa y t h a t t h e subst a nce me l t s or e v a por a t e s on h e a t i ng/bur ni ng, or i f
t h e a ut h or ma i nt a i ns t h a t t h e st ude nt s consi de r t h a t t h e i nde nt i t y
22
of t h e subst a nce h a s be e n conse r v e d, t h i s h a s be e n t a k e n a s a n
i ndi ca t or of t h e Modi f i ca t i on ca t e gor y .
Ca ut i on i s ne e de d i n i nt e r pr e t i ng t h a da t a pr e se nt e d i n t a bl e 4,
be ca use t h e y a r e f e w st udi e s a nd be ca use t h e que st i ons use d t o e l i ci t
t h e r e sponse s, a nd t h e wa y t h a t t h e y h a v e be e n a sk e d v a r i e s f r om
st udy t o st udy . N e v e r t h e l e ss i t a ppe a r s t h a t t h e use of t h i s t y pe of
e xpl a na t i on doe s de cr e a se wr i t h a ge . Pr e suma bl y a s pupi l s use of
l a ngua ge de v e l ops a nd a s t h e i r unde st a ndi ng of t h e conce pt s
i nv ol v e d i n combust i on be come s mor e soph i st i ca t e d, t h e y f or m a
mor e ge ne r a l i se d v i e w of combust i on, i n wh i ch t h e y di st i ngui sh
bur ni ng f r om h e a t i ng, a nd combust i on f r om ch a nge of st a t e .
Ta bl e 4. U se of Modi f i ca t i on mode l .
S t udy
Me t a l s
Me h e ut e t a l .
( 1985) .
S a nma r t i
( 1989)
Th i s st udy
S a nma r t i
( 1989
Wax
Me h e ut e t a l .
( 1985)
B ouJa oude
( 1991)
Th i s st udy
A ge
S a mpl e si ze
S ubst a nce
% U si ng
Modi f i ca t i on
11- 12
102
i r on
82- 88
13
54
coppe r
46
14- 15
18- 19
150
59
ma gne si um
coppe r
18
12
11- 12
102
ca ndl e wa x
82- 97
12- 13
20
ca ndl e wa x
60
14- 15
150
ca ndl e wa x
43
U s e o f C h e m i ca l R e a ct i o n, I nt e r m e d i a t e a nd Tr a ns m ut a t i o n
e xp l a na t i o ns .
50% of t h e pupi l s gi v e r e sponse s wh i ch i ncl ude Tr a nsmut a t i on
e xpl a na t i ons a s we l l a s e xpl a na t i ons t h a t i ndi ca t e some a spe ct s of
Ch e mi ca l r e a ct i on or I nt e r me di a t e e xpl a na t i ons ( boxe s 1 a nd 2 i n
t a bl e 3) . Most of t h e se pupi l s se e m t o be usi ng Tr a nsmut a t i on
e xpl a na t i ons most of t h e t i me , but a t t h e sa me t i me a r e be gi nni ng t o
i ncor por a t e a spe ct s of Ch e mi ca l R e a ct i on e xpl a na t i ons i n t h e i r
r e sponse s. A n e xa mpl e i s gi v e n wi t h pupi l 64:
23
Pupi l 64:
1a ) : " S ome t h i ng bur ns wh e n i t h a s got f i r e " . 1b) : " D e pe ndi ng on
t h e subst a nce , a gr e y or bl a ck powde r e d subst a nce r e ma i ns" .
5: " Y ou de st r oy i t " .
6a ) : " I f t h e ca ndl e i s sma l l i t i s consume d. I f t h e ca ndl e i s bi g,
t h e oxy ge n i s consume d be f or e " .
6b& c) : " Th e oxy ge n i s be i ng consume d a nd t h e cont a i ne r i s f ul l of
ca r bon di oxi de " .
7: " O f gunpowde r t h a t a s i t i s bur ni ng r e l e a se s ni t r oge n" .
9: " c) " . N o e xpl a na t i on.
Th i s pupi l ch ose s t h e cor r e ct opt i on f or que st i on 9, wh i ch e xpl a i ns
a n i ncr e a se i n we i gh t of ma gne si um by i t s r e a ct i on wi t h oxy ge n. Th e
i de a of i nt e r a ct i on i s not so cl e a r i n r e sponse t o que st i on 6: t h e
ca ndl e i s consume d a nd t h e oxy ge n i s consume d a nd r e pl a ce d by
ca r bon di oxi de , but i t i s not cl e a r wh e t h e r t h e se a r e t wo
i nde pe nde nt pr oce sse s of Tr a nsmut a t i on or wh e t h e r t h e r e i s
ch e mi ca l i nt e r a ct i on be t we e n t h e t wo subst a nce s. Th e r e sponse s t o
que st i ons 1 a nd 5 a r e Tr a nsmut a t i on wi t h t h e combust i bl e subst a nce
be i ng t r a nsmut e d t o a de st r uct i on pr oduct . W h e n a sk e d a bout t h e
r ol e of oxy ge n i n combust i on t h i s pupi l , t h e r e f or e , ca n ch oose t h e
cor r e ct opt i on i n a mul t i pl e ch oi ce que st i on ( Q 9) , h a s di f f i cul t y i n
a r t i cul a t i ng t h e r ol e of t h e oxy ge n i n a n ope n f or ma t que st i on a sk i ng
a bout t h e oxy ge n ( Q 6) a nd f a i l s t o consi de r oxy ge n i n t h e ot h e r
que st i ons wh e r e h e i s not spe ci f i ca l l y a sk e d a bout i t . I t a ppe a r s
t h a t t h i s pupi l i s st r uggl i ng t o i ncor por a t e t h e r ol e of oxy ge n i nt o a
Tr a nsmut a t i on mode l , wh i ch di d not pr e v i ous t a k e oxy ge n i nt o
a ccount .
Two mor e e xa mpl e s wh i ch sh ow si mi l a r e f f or t s t o i ncor por a t e
oxy ge n i nt o a Tr a nsmut a t i on mode l a r e :
Pupi l 51
1a ) : " I t i s a ch a nge wh i ch occur s t o a body i n cont a ct wi t h
oxy ge n" . 1b) : " N or ma l l y smok e i s e v ol v e d a nd i t ge t s l e ss e v e r y
t i me " .
Pupi l 102
1a ) : " I s a f or m of combust i on wh i ch r e qui r e s t h e pr e se nce of
oxy ge n t o be a bl e t o r e a ct wi t h a nd pr oduce f i r e " . 1b) : " I t
de compose s a nd i s conv e r t e d t o a sh e s" .
24
Pupi l 138 be l ow use s i de a s of i nt e r a ct i on but
i nt e r a ct i on i s be t we e n a i r a nd t h e f l a me :
t h i s t i me
the
S t ude nt 138:
6a ) : b l a nk
6b& c) : " Th e a i r i s a bsor be d by t h e f l a me a nd wh e n t h e a i r h a s
f i ni sh e d t h e f l a me goe s out "
7: " O xy ge n a nd ma t e r i a l s f r om t h e ma t ch " .
Th e pupi l
h a s i ncor por a t e d i de a s of i nt e r a ct i on i nt o a
Tr a nsmut a t i on mode l by v i e wi ng oxy ge n/ a i r
as
ne ce ssa r y t o
i nt e r a ct wi t h t h e a ct i v e a ge nt of ch a nge , t h e f l a me , i n or de r t o
a l l ow bur ni ng t o t a k e pl a ce . A si mi l a r e xpl a na t i on of t h e r ol e of
oxy ge n i s gi v e n by pupi l 79:
Pupi l 79:
6b& c) : " Th e r e i s no oxy ge n, t h e f i r e h a s a bsor be d i t " .
I n some pupi l s t h e r e se e ms t o be some pr ogr e ssi on t owa r ds t h e
Ch e mi ca l R e a ct i on e xpl a na t i on i n t e r m of t h e l a ngua ge use d. S ome
pupi l s i ncor por a t e sci e nt i f i c l a ngua ge such a s combust i bl e , ch e mi ca l
r e a ct i on, combust i on, i nt o wh a t a r e e sse nt i a l l y Tr a nsmut a t i on
r e sponse s:
Pupi l 95
1a ) : " A ch e mi ca l r e a ct i on wh e r e t h e r e a r e a “combust i bl e " , a i r
a nd some t h i ng t h a t consume s t h e combust i bl e , f i r e i n t h i s ca se ,
a nd a sh e s i s t h e subst a nce t h a t i s l e f t f r om t h i s r e a ct i on, i t i s
wh a t r e ma i ns”. 1b) : " B e come a sh e s" .
5: " Y ou ge t a sh e s wh i ch i s t h e r e sul t of t h e ch e mi ca l r e a ct i on
f r om wood a nd f i r e " .
6a ) : b l a nk
6b& c) : " A s t h e pl a ce i s cl ose t h e r e i s a combust i on wi t h l i t t l e
a mount of combust i bl e ( a i r ) a nd a s i t i s f i ni sh e d t h e f i r e goe s
out " .
7: " F i r e " .
9: " e ) B e ca use t h e ma gne si um h a s be e n bur nt a nd t h e r e st of t h e
ga se s t h a t a r e pr oduce d by t h e f i r e a r e t a k i ng of f we i gh t " .
I t t h e r e f or e a ppe a r s t h a t t h e pupi l s i n boxe s 1 a nd 2 i n t a bl e 3 a r e
i nconsi st e nt i n t h e i r use of e xpl a na t or y mode l s. S ome of t h e
i nconsi st e ncy doe s not , h owe v e r , a r i se f r om i l l ogi ca l or a d h oc
t h i nk i ng, but f r om a st r uggl e t o come t o t e r ms wi t h t wo mut ua l l y
25
e xcl usi v e e xpl a na t or y mode l s. I t ca n be se e n t h a t some of t h e pupi l s
e xpl a na t i ons a r e a t t e mpt s t o i nt r oduce ne w i de a s f r om t h e Ch e mi ca l
R e a ct i on mode l i nt o a Tr a nsmut a t i on mode l . I t a ppe a r s t h a t f or
ot h e r pupi l s t h e k i nd of e xpl a na t or y mode l use d de pe nds on t h e
cont e xt of t h e que st i on a nd t h e wa y i t i s f or mul a t e d. Pe r h a ps some
pupi l s h a v e mor e t h a n one e xpl a na t or y mode l f or combust i on i n
t h e i r me mor i e s, a nd ca l l up f or di f f e r e nt mode l s t o use i n di f f e r e nt
ci r cumst a nce s.
DI SCU SSI ON
I n t h i s se ct i on t h e na t ur e of t h e conce pt ua l ch a nge wh i ch pupi l s
must unde r go a nd i mpl i ca t i ons f or t e a ch i ng a r e di scusse d. A n
e xa mi na t i on of pupi l s´ e xpl a na t i ons ( se e t a bl e 1) r e v e a l s t h a t
ce r t a i n a spe ct s wh i ch a r e nor ma l l y pr e se nt e d i n sci e nt i st s´
e xpl a na t i ons of ch e mi ca l ch a nge a r e compl e t e l y a bse nt :
* Pupi l s f a i l t o me nt i on i mpe r ce pt i bl e pr oduct s such a s ga se s.
Ev e n pupi l s wh o t a l k a bout t h e combust i bl e subst a nce i nt e r a ct i ng
wi t h oxy ge n, usua l l y t a l k a bout a n a sh a s t h e pr oduct a nd f a i l t o
me nt i on ga se ous
pr oduct s.
O xy ge n
is
ra rel y
me nt i one d
spont a ne ousl y : pupi l s usua l l y onl y me nt i on oxy ge n i n r e sponse t o
di r e ct que st i ons a bout i t s r ol e .
* Th e we i gh t of r e a ct a nt s a nd pr oduct s, a l t h ough pl a y i ng a n
i mpor t a nt r ol e i n sci e nt i st s´ e xpl a na t i ons, h a s a mi nor r ol e i n
pupi l s´ e xpl a na t i ons. Th i s i s not sur pr i si ng a s ma ny pupi l s of t h e
a ge of pupi l s i n t h i s st udy f a i l t o r e a l i se t h a t ga se s h a v e we i gh t ,
or e v e n t h i nk t h a t t h e y h a v e a ne ga t i v e we i gh t ( B r ook s a nd
D r i v e r , 1989; S t a v y a nd S a t ch e l , 1985) . Th i s pr e cl ude s e v e n
pupi l s wi t h a r e a sona bl e unde r st a ndi ng of ch e mi ca l r e a ct i ons
f r om dr a wi ng concl usi ons f r om me a sur e me nt s of we i gh t . F or pupi l s
usi ng Tr a nsmut a t i on e xpl a na t i ons t h e r e i s no ne ce ssi t y f or a
pr oduct t o we i gh t mor e , t h e sa me o l e ss t h a n t h e r e a ct a nt , be ca use
i t si mpl y be come s a di f f e r e nt subst a nce .
* Pupi l s ma k e no me nt i on of a t omi c or mol e cul a r pa r t i cl e s. Th i s
coul d e xpl a i n wh y a t t e mpt s t o ch a nge pupi l s conce pt i ons by
t e a ch i ng a bout pa r t i cl e s h a v e f a i l e d ( e . g. Me h e ut e t a l . 1985) .
Th e pupi l s ma y se e no r e l a t i on be t we e n t h e i r e xpl a na t i ons a nd
e xpl a na t i ons i n t e r ms or pa r t i cl e s.
A compa r i son of t h e Modi f i ca t i on e xpl a na t i on wi t h t h e Ch e mi ca l
R e a ct i on e xpl a na t i on ( t a bl e 1) r e v e a l s t h e f ol l owi ng di f f e r e nce s: I n
Modi f i ca t i on t h e r e i s no r ol e f or oxy ge n ( M1) , t h e pr oce ss i s
r e v e r si bl e ( M2) , t h e f l a me /f i r e i s t h e sour ce of h e a t t o ma k e t h e
26
modi f i ca t i on occur ( M3) a nd t h e pr oduct i s t h e sa me subst a nce a s t h e
r e a ct a nt ( M4, M5, M7) . I n ch e mi ca l r e a ct i on oxy ge n i nt e r a ct s wi t h
t h e combust i bl e subst a nce ( C1) , t h e pr oce ss i s i r r e v e r si bl e ( C2) , t h e
f l a me /f i r e i s e v i de nce of a ch e mi ca l r e a ct i on ( C4) a nd t h e pr oduct or
pr oduct s a r e a di f f e r e nt subst a nce f r om t h e r e a ct a nt s ( C6, C8) .
O f t h e pupi l s´ mode l s pr e se nt e d i n t h i s pa pe r , Modi f i ca t i on i s t h e
most pr i mi t i v e mode l :
* I t r e qui r e s t h e l owe st l e v e l of cogni t i v e pr oce ssi ng.
*
I t de pe nds on se l e ct i v e
a nd i na ccur a t e
obse r v a t i on:
Modi f i ca t i on ca n onl y be ma i nt a i ne d f or ca ndl e wa x i f t h e ca ndl e
i s obse r v e d bur ni ng f or a l i mi t e d t i me , so t h a t t h e di sa ppe a r a nce
of t h e wa x i s not a ppa r e nt .
* I t e xpl a i ns t h e most l i mi t e d r a nge of obse r v a t i ons: f or e xa mpl e
i t doe s not e xpl a i n t h e r ol e of oxy ge n, wh e r e a s Tr a nsmut a t i on ca n
e xpl a i n oxy ge n a s be i ng t r a nsmut e d se pa r a t e l y , or a s be i ng ne e de d
t o “f e e d” t h e a ct i v e a ge nt of ch a nge , t h e f l a me .
Th e f a ct , t h a t Modi f i ca t i on e xpl a na t i on coe xi st wi t h Tr a nsmut a t i on
or Ch e mi ca l R e a ct i on e xpl a na t i ons, i ndi ca t e s t h a t pupi l s a r e not
l i mi t e d t o t h i s mode l be ca use of l i mi t a t i ons i n t h e i r cogni t i v e
pr oce ssi ng powe r ( c. f . Monk 1990, 1991) . N e v e r t h e l e ss, pupi l s h a v e
t o sh i f t f r om a mode l , wh i ch i nv ol v e s l i ne a r ca usa l r e a soni ng, t o one
t h a t i nv ol v e s t h e i nt e r a ct i on of t wo ch e mi ca l s t o f or m a t l e a st one
pr oduct , of t e n mor e . Th e modi f i ca t i on e xpl a na t i on, l i k e Ch e mi ca l
R e a ct i on, f a l l s i nt o t h e ont ol ogi ca l ca t e gor y of e xpl a i ni ng a
“const r a i nt - ba se d e v e nt ” ( Ch i , i n pr e ss) .
I n or de r t o br i ng a bout t h e conce pt ua l ch a nge r e qui r e , pupi l s h a v e t o
l e a r n t o di st i ngui sh be t we e n h e a t i ng a nd bur ni ng, a nd t o di st i ngui sh
be t we e n bur ni ng a nd ch a nge of st a t e . Th e compa r i son of t h e t y pe s of
pupi l s´ e xpl a na t i ons di scusse d a bov e sugge st s t h a t pr a ct i ca l
e xe r ci se s ne e d t o be const r uct e d i n wh i ch pupi l s ca r e f ul l y compa r e
h e a t i ng, a s a pr oce ss i n wh i ch h e a t i s suppl i e d f r om a n e xt e r na l
sour ce , wi t h bur ni ng, i n wh i ch h e a t i s e v ol v e d f r om t h e r e a ct a nt s.
S i mi l a r l y ch a nge of st a t e f r om sol i d t o l i qui d, or f r om l i qui d t o ga s
must be compa r e d wi t h combust i on. Th i s compa r i son sugge st s t h a t
mor e a t e nt t i on ne e ds t o be pa i d t o compa r i ng t h e pr oduct s of t h e
r e a ct i on wi t h t h e r e a ct a nt a nd wi t h t h e pr oduct s of a ph y si ca l
ch a nge i n or de r t o pe r ce i v e t h e di f f e r e nce s. I t a ppe a r s t h a t r e l y i ng
on v i sua l l y obv i ous a t t r i but e s of r e a ct a nt a nd pr oduct s i s
i nsuf f i ci e nt f or ma ny pupi l s, f or t h e m t o r e a l i se wh e t h e r t h e pr oce ss
i s r e v e r si bl e on cool i ng.
27
A si mi l a r compa r i son of Tr a nsmut a t i on a nd Ch e mi ca l R e a ct i on
e xpl a na t i ons r e v e a l s t h a t t h e di f f e r e nce s be t we e n t h e se t wo mode l s
a r e much mor e subt l e a nd t h a t t h e conce pt ua l ch a nge s ne e de d t o
mov e f r om Tr a nsmut a t i on e xpl a na t i ons t o a Ch e mi ca l R e a ct i on
e xpl a na t i on coul d be mor e di f f i cul t t o a ch i e v e . I n t h e Tr a nsmut a t i on
mode l bur ni ng i s a de st r uct i v e pr oce ss ( T4) i n wh i ch t h e combust i bl e
subst a nce , a nd oxy ge n i f i t i s me nt i one d, a r e t r a nsmut e d se pa r a t e l y
( T1, T2) i nt o se pa r a t e pr oduct s ( T11, T12) . Th e r ol e of oxy ge n i s
uncl e a r ( T2) but i t some t i me s se e n a s i nt e r a ct i ng wi t h or f e e di ng t h e
f l a me ( T7, T8, T10) . Th e f l a me /f i r e i s t h e a ct i v e a ge nt of ch a nge
( T6) , a nd h e a t ma y be subst a nt i a l i se d so t h a t ma t t e r ca n be
t r a nsmut e d i nt o h e a t a nd v i ce - v e r sa ( T9) . Th e pr oduct of combust i on
of t h e combust i bl e subst a nce i s a di f f e r e nt subst a nce f r om t h e
r e a ct a nt a nd so h a s di f f e r e nt pr ope r t i e s ( T11) a nd i t ma y we i gh l e ss,
t h e sa me , or mor e t h a n t h e r e a ct a nt . I n t h e Ch e mi ca l R e a ct i on
mode l , oxy ge n i nt e r a ct s wi t h t h e combust i bl e subst a nce t o pr oduce
pr oduct s wh i ch cont a i n t h e combust i bl e subst a nce a nd oxy ge n i n a
di f f e r e nt ch e mi ca l combi na t i on ( C1, C6) , a nd t h e r e f or e t h e pr oduct s
we i gh mor e t h a n t h e combust i bl e subst a nce , a s l ong a s pupi l s
unde r st a nd t h a t ga se s we i gh some t h i ng a nd i ncl ude ga se s l ost t o t h e
a t mosph e r e ( C7) . Th e r ol e of t h e e ne r gy ch a nge s i s uncl e a r ( C3, C4) .
Th e pr oduct s h a v e di f f e r e nt pr ope r t i e s f r om t h e r e a ct a nt s ( C8) .
I t ca n be se e n t h a t i s qui t e di f f i cul t t o e st a bl i sh cl e a r cr i t e r i a f or
di f f e r e nci a t e be t we e n t h e t wo mode l s t h r ough e xpe r i me nt a t i on.
B ot h mode l s ca n e xpl a i n wh a t h a ppe ns t o t h e oxy ge n, a l t h ough t h e
Tr a nsmut a t i on mode l ´s e xpl a na t i on of wh y i t i s ne e de d i s we a k e r : i t
ne e de d by t h e f l a me . B ot h mode l s ca n e xpl a i n t h e r ol e of h e a t .
W e i gh t ch a nge s a r e of t e n use d t o r e i nf or ce t h e sci e nt i st s´ v i e w of
combust i on. Coppe r ca n be h e a t e d i n a t ube conne ct e d t o ga s sy r i nge s
cont a i ni ng a i r a nd t h e i ncr e a se i n ma ss of t h e coppe r e xpl a i ne d i n
t e r ms of t h e de cr e a se i n v ol ume of t h e a i r , Th i s e xpe r i me nt wh i ch
se e ms so pe r sua si v e t o a ch e mi st r y t e a ch e r ca n se e m r a t h e r st r a nge
t o a pupi l wh o be l i e v e s t h a t a i r h a s no, or ne ga t i v e we i gh t . Th e
t r a nsmut a t i on e xpl a na t i on i s qui t e si mpl e : t h e coppe r h a s be e n
t r a nsmut e d t o ca r bon, wh i ch be i ng a di f f e r e nt subst a nce h a s a
di f f e r e nt we i gh t , or possi bl y be ca use i t cont a i ns h e a t , h a s a n
i ncr e a se d we i gh t ; t h e oxi ge n h a s be e n t r a nsmut e d t o not h i ng.
Tr a nsmut a t i on mode l ca n be use d t o e xpl a i n ma ny e v e r y da y
obse r v a t i ons of combust i on. O ne r e a son f or i t s pe r si st e nce ma y be
t h a t i t i s a si mpl e mode l wh i ch r e qui r e s a l owe r l e v e l of cogni t i v e
28
pr oce ssi ng t h a n Ch e mi ca l R e a ct i on mode l . Ma ny pupi l s h a v e y e t t o
r e a ch t h e st a ge of cogni t i v e de v e l opme nt t h a t wi l l a l l ow t h e m t o
use t h e soph i st i ca t e d mode l ( Monk 1990, 1991) , a nd ch a nge f r om
usi ng l i ne a r ca usa l r e a soni ng t o usi ng a mode l t h a t i nv ol v e s t h e
i nt e r a ct i on of t wo ch e mi ca l s t o f or m a t l e a st one pr oduct , of t e n
mor e . A not h e r e xpl a na t i on of t h e pe r si st e nce of t h e Tr a nsmut a t i on
mode l coul d be t h e f a ct t h a t a l t h ough l i k e t h e Ch e mi ca l R e a ct i on
mode l i t f a l l s i nt o t h e ont ol ogi ca l ca t e gor y of e xpl a i ni ng a
“const r a i nt - ba se d e v e nt ”
ce r t a i n conce pt s, i . e . h e a t /h e a t i ng,
e mbodi e d i n t h e mode l a r e wr ongl y cl a ssi f i e d a s ma t e r i a l s i nst e a d
of const r a i nt - ba se d e v e nt s. I n or de r f or t h i s conce pt t o be pl a ce d i n
t h e cor r e ct ont ol ogi ca l ca t e gor y r a di ca l conce pt ua l ch a nge ( Ch i , i n
pr e ss) must t a k e pl a ce .
Th e e xpl a na t or y powe r of t h e Tr a nsmut a t i on mode l a nd t h e
Ch e mi ca l R e a ct i on mode l i s si mi l a r f or e xpl a i ni ng t h e ph e nome na
i ncl ude d i n t h e mode l s. I t i s onl y wh e n a spe ct s t h a t a r e not i ncl ude d
i n t h e mode l a r e e mph a si se d t h a t t h e Tr a nsmut a t i on mode l st a r t t o
f a i l , ( r ol of ga se s, qua nt i t a t i v e a spe ct s i ncl udi ng we i gh t
a nd
v ol ume ch a nge s) . Th e Tr a nsmut a t i on mode l a s a n e xpl a na t i on of a
de st r uct i v e pr oce ss wor k s we l l wi t h ca r bon/h y dr oge n ba se d
subst a nce s, but i s l e ss sa t i sf a ct or y i n e xpl a i ni ng t h e combust i on of
me t a l s a nd non- me t a l s, wh e r e t h e r e i s mor e subst a nce a f t e r bur ni ng
a nd wh e r e a gr e a t e r v a r i e t y of pr oduct s i s f or me d. I t , t h e r e f or e ,
a ppe a r s t h a t t h e pr oce ss of conce pt ua l ch a nge f r om a Tr a nsmut a t i on
mode l t o a Ch e mi ca l R e a ct i on mode l wi l l be a i de d by :
* pr ov i di ng e xpe r i e nce of a wi de r a nge of subst a nce s wh i ch pupi l s
obse r v e bur ni ng, t o i ncl ude mor e non- ca r bon/h y dr oge n ba se s
subst a nce s.
* i de nt i f y i ng t h e pr oduct s of combust i on
* e mph a si si ng t h e r ol e of ga se s of combust i on
* e mph a si si ng qua nt i t a t i v e a spe ct s of combust i on, bot h we i gh t
ch a nge s a nd v ol ume ch a nge s.
Th e Ch e mi ca l R e a ct i on e xpl a na t i on i s ca pa bl e of be i ng de v e l ope d t o
i ncl ude t h e se a spe ct s, wh e r e a s f or t h e Tr a nsmut a t i on e xpl a na t i on
t h i s i s mor e di f f i cul t . W h e t h e r such conce pt ua l ch a nge i s wi t h i n
t h e cogni t i v e ca pa bi l i t i e s of t h e pupi l s i s not cl e a r i n t h e l i gh t of
Monk ´s wor k , a nd f ur t h e r r e se a r ch i s ne e de d t o e xpl or e t h i s.
I t a ppe a r s f r om t h e cur r e nt r e se a r ch t h a t ma ny pupi l s we r e
ch a ngi ng f r om t h e Tr a nsmut a t i on mode l t o t h e Ch e mi ca l R e a ct i on
mode l by a da pt i ng t h e Tr a nsmut a t i on mode l t o i ncl ude a spe ct s of
29
t h e Ch e mi ca l R e a ct i on mode l a nd t h e e xt e nt t o wh i ch t h e y di d t h i s
v a r i e d a ccor di ng t o t h e que st i on. W h i t e a nd Gunst one ( 1992)
de scr i be t h e de v e l opme nt of conce pt s a s a cont i nuous mul t i di me nsi ona l pr oce ss, t h a t i n t h e or y ne v e r e nds. I n ch a ngi ng f r om one
mode l of ch e mi ca l t r a nsf or ma t i on t o a not h e r , pupi l s de v e l op t h e
pr e ci si on wi t h wh i ch t h e y use t h e l a ngua ge , r e pl a ce a spe ct s of t h e
ol d mode l wi t h a spe ct s of t h e ne w, i ncor por a t e ne w conce pt s, a nd
some t i me s r e t a i n a spe ct s of bot h mode l s si mul t a ne ousl y . I n v i e w of
t h e compl e xi t y of t h e ch a nge be t we e n t h e mode l s, t h e pr oce ss of
ch a nge wi l l t a k e pl a ce ov e r
a subst a nt i a l pe r i od of t i me .
I nconsi st e ncy i n t h e pupi l s´ e xpl a na t i ons ma y , t h e r e f or e , be a n
i ndi ca t or of conce pt ua l ch a nge .
A CK N OW LEDGEMEN TS
W e woul d l i k e t o t h a k D r . Ma r t i n Monk f or h i s h e l p a nd a dv i ce i n
cl a ssi f y i ng t h e ca t e gor i e s of pupi l s e xpl a na t i ons a ccor di ng t o t h e
l e v e l of cogni t i v e pr oce ssi ng r e qui r e d. W e a r e a l so gr a t e f ul f or a n
A cci one s I nt e gr a da s gr a nt wh i ch h a s f a ci l i t a t e d t h e col l a bor a t i on
be t we e n t h e F a cul t a d de Educa ci on, U ni v e r si t y of Ma l a ga a nd t h e
K i ng´s Col l e ge , U ni v e r si t y of London.
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32
A PPEN DI X : COMPRESSED V ERSI ON OF SELECTED QU ESTI ON S
F ROM TH E QU ESTI ON N A I RE.
1.- a) Please explain, in your own words, what you understand by the word
‘burning’.
b) What happens to a substance when it burns?
5.- Is anything produced when wood burns?
Yes
No
Please explain your answer.
6.
Don’t know
The candle in the gas jar goes out after a few
seconds.
(a) What do you think has happened to the wax
of the candle?
(b) What has happened to the air in the gas jar?
(c) Is anything formed that you cannot see?
Please explain your answer.
7.- When a match burns, you see a flame. What is the flame made of?
9.- A student heated 6g of magnesium ribbon in a crucible and it burnt to form a
white powder. At the end of the experiment the student weighed the burnt
magnesium and found that it now weighed 10g. Why did the weight increase?
a) The oxygen of the air mixed with the magnesium, and because of this the weight
increased.
b) When the magnesium was heated, it expanded and so its weight increased.
c) The magnesium reacted with the oxygen of the air, and because of this t h e
weight increased.
d) The magnesium gained heat from the flame, and because of this the weight
increased.
e) The result is impossible. The weight cannot have increased.
Please explain your choice:
33