Journal of Science Education and Technology

, Volume 16, Issue 3, pp 257–270

Investigating the Effectiveness of a Constructivist-based Teaching Model on Student Understanding of the Dissolution of Gases in Liquids

Authors

    • Department of Science EducationGiresun University
  • Alipaşa Ayas
    • Department of Secondary Science and Mathematics EducationKaradeniz Technical University
  • Richard K. Coll
    • Centre for Science & Technology Education ResearchUniversity of Waikato
  • Suat Ünal
    • Department of Secondary Science and Mathematics EducationKaradeniz Technical University
  • Bayram Coştu
    • Department of Secondary Science and Mathematics EducationKaradeniz Technical University
Article

DOI: 10.1007/s10956-006-9040-4

Cite this article as:
Çalık, M., Ayas, A., Coll, R.K. et al. J Sci Educ Technol (2007) 16: 257. doi:10.1007/s10956-006-9040-4

The research presented in this paper consisted of an investigation of the effectiveness of a four-step constructivist-based teaching activity on student understanding of how pressure and temperature influence the dissolution of a gas in a liquid. Some 44 Grade 9 students (18 boys and 26 girls) selected purposively from two school classes in the city of Trabzon, Turkey participated in the study. Students’ understanding were evaluated from examination of two items from a purpose-designed solution concept test, face-to-face semi-structured interviews and examination of students’ self-assessment exercises. Statistical analysis using two-way ANOVA of student test scores point to statistically-significant differences in test and total scores (p < 0.05) suggesting that the teaching activities employed help students achieve better conceptual understanding. Further, no statistically significant differences were seen between post-test and delayed test scores, suggesting that teaching the activities enable students to retain their new conceptions in their long-term memory. However, in a few instances the activities resulted in the development of new alternative conceptions, suggesting teachers need to be conscious of the positive and negative effects of any teaching intervention.

Keywords

four-step constructivist teaching activitysolution chemistryeffects of temperature and pressure to dissolution of gas in a liquidconceptual change

In the early 1990s, Fensham asserted that ‘The most conspicuous psychological influence on curriculum thinking in science since 1980 has been the constructivist view of learning’ (Fensham, 1992, p. 801). Constructivism as Fensham sees it, requires teachers to deconstruct traditional objectivist conceptions of the nature of science and knowledge acquisition, and to evaluate their personal epistemologies, teaching practices that result from these epistemologies, and seek to develop appropriate educative relationships with their students. Despite some reservations of constructivism, and its many variants (see, e.g., (Matthews, 2002), this learning theory has exerted considerable influence on thinking on educational research and thinking about teaching and learning. The basic premise of constructivism is that each individual mentally constructs understanding, rather than acts as a passive receiver of knowledge. This construction is mediated by the individual’s prior knowledge of actual and related concepts, and is influenced by a variety of socio-cultural factors (leading to ‘variants’ of constructivism such as social and contextual constructivism, Good et al., 1993).

However, as Matthews (2002) and others point out, there is not necessarily any simple, coherent link between theories of learning like constructivism and appropriate pedagogies. Furthermore, even if one ‘buys in’ to new learning theories, changing teaching practice is difficult for teachers for a variety of philosophical and logistical reasons (e.g., constructivist-based teaching usually requires more classroom time). This point is emphasized by Widodo et al. (2002) who comment that there is a considerable gap between what is known about effective teaching and learning based on constructivist learning theory, and the actual practice in the classroom. There are a number of potential reasons for this. First, although constructivism is a popular learning theory (at least in the education research community), teachers may be unfamiliar with actual constructivist-based teaching approaches, or think they are too problematic to introduce. One might then argue that science educators can play a key role in facilitating the application of constructivist-based strategies. Clearly to do this, researchers first need to convince teachers that new approaches are effective, and second that they are worth the trouble. One way this can be approached is to deal with concepts teachers and researchers agree are problematic in terms of teaching and learning, and for which more modest changes to pedagogy are not likely to be effective. Generally, we are talking about bringing about conceptual change in our students, and in this there is a nice overlap between constructivism and many conceptual change approaches; both suggest we need to pay attention to students’ prior conceptions (e.g., Duit and Treagust, 1998; Tytler, 2002; Widodo et al., 2002).

Hence, in summary, because teachers typically are busy people, if we wish to convince teachers to take on board innovative new teaching activities incorporating students’ prior conceptions, we need not only to provide details of such activities, but also describe how to implement them in the classroom. Çalık et al. (2006a) present details of a fairly straightforward four-step constructivist-based teaching strategy, which they report helped students understand the dissolution of a gas into a liquid. This approach drew upon students’ prior conceptions as recommended by adherents of constructivism. Interestingly, there are no reports in the science education literature of research on a related topic; how physical properties such as temperature and pressure affect the dissolution of a gas in a liquid (but see Çalık et al., 2005). The ubiquitous nature of liquid-gas solutions (e.g., popular ‘fizzy’ drinks) provides a useful context for teaching students about science concepts in a way that helps them see how science relates to their everyday life (see, Pilot and Bulte, 2006).

The research in this work describes the use of a four-step constructivist-based teaching activity on the teaching of the effect temperature and pressure on the dissolution of gases in liquids. Evidence for students’ conceptual change when using the teaching activity, is a key focus of the work. The specific research questions for this work are:
  1. 1.

    Does a four-step constructivist-based teaching activity help students to change their alternative conceptions towards more scientific ones?

     
  2. 2.

    Does a four-step constructivist-based teaching activity used here enable students to store their new conceptions in long-term memory?

     
  3. 3.

    What influence, if any does gender exert on students’ conceptual change when exposed to a four-step constructivist-based teaching activity?

     

Methodology

Sample

The sample comprises of 44 Grade 9 students (18 boys and 26 girls) chosen purposively from two different classes (22 each) in the city of Trabzon, Turkey. The school’s elementary school achievement levels, ranged in GPA from 3.36 to 4.85, with a maximum possible score of 5.00. Students from one school are boarders, and as a consequence come from different cities, across Turkey: Giresun (7 students), Erzurum (3 students), Rize (2 students), Samsun (1 student), Artvin (1 student), Ordu (1 student), Bingöl (1 student) and İstanbul (1 student). Participants at the other school came from Trabzon (27 students) where the study was conducted.

In Turkey, topics such as the properties of matter, naming compounds, mole concept, solubility, variables affecting solubility, separation of mixtures and compound, periodic table and its properties, atoms and molecules, chemical bonding and intermolecular forces, all are taught at Grade 9. The students in this investigation all had been taught the topics from properties of matter, separation of mixtures and compound, mole concept, naming compounds before the intervention.

Data Collection

The research here was conducted within an interpretive paradigm, and drew on constructivist epistemologies. Consistent with the recommendations of Guba and Lincoln (1989) multiple methods of data collection were employed; items from a solution concept test, semi-structured face-to-face interviews, and examination of students’ self-assessment tasks. This approach also provided for data triangulation as recommended by Harrison and Treagust (2001). The solution concept test used here drew upon work by Çalık (2003), who developed a 17 item chemistry concept test; in the present work two items from this test were employed as they directly addressed the concepts investigated in this study. These items are shown below. Consistent with the views of Harrison and Treagust (2001), the test items required students to select a response and then to justify their selection.
  • Item 1

  • The dissolution of a gas into a liquid ............... with pressure.

  • (a) increases (b) decreases (c) no change

  • Because ...........................................................................

  • Item 2

  • The dissolution of a gas into a liquid ............... with temperature.

  • (a) increases (b) decreases (c) no change

  • Because ..........................................................................................

The items were administered one month before the intervention as a form of pre-test. After completing 10 teaching activities (across 8 class periods) the test was employed as a post-test. Finally, the test was re-administered as a delayed test 10 weeks after intervention.

Semi-structured interviews were conducted with six students; two each of average (S6 & S9), below average (S8 & S25) and above average (S16 & S42) who were selected based on their scores in pre-test, post-test and delayed tests. That is, above average students showed the most conceptual change, whilst below average ones revealed the least conceptual change. In the interviews, students were initially asked to make a prediction about the effect of pressure and temperature on the dissolution of a gas into a liquid. Then, they were asked to conduct the first activity that is the similar to the one used for intervention whose details are reported in Çalık et al. (2006a), but in brief the students were shown a diagram in which the pressure was increased on a gas-liquid solution by means of a simple injector-plunger. The activity was repeated by students and a series of questions were asked (e.g., ‘when pulling the pump of the injector from 10 to 40 mL, ‘please explain what you observed’, ‘Locate the pump of the injector towards its initial position, please explain what happened’). Depending on the students’ responses to principal questions, follow-up questions were then asked because some students tended to answer the questions briefly as a result of their schooling experience (e.g., ‘what do you think the bubbles are’, ‘what do you mean by an increase in the amount of matter’). The interviews covered a number of concepts from solution chemistry, but here we report discourse associated with the influence of pressure and temperature on the dissolution of a gas into a liquid. The interviews were of 35–40 min in duration.

A student self-assessment exercise was employed after each activity. Each of the 44 participants were asked to complete a form in which they shared their learning experiences—the form was that used by Çalık et al. (2006a) (Figure 1).
https://static-content.springer.com/image/art%3A10.1007%2Fs10956-006-9040-4/MediaObjects/10956_2006_9040_Fig1_HTML.gif
Fig. 1.

Student self-assessment form used in the study.

Data Analysis Procedures

In analyzing the test items, firstly students’ responses were examined thematically and the following criteria were used to classify the responses: Correct Choice with Sound Understanding (CCSU) (10 point), Correct Choice with Partial Understanding (CCPU) (9 point), No Choice with Sound Understanding (NCSU) (8 point), Incorrect Choice with Sound Understanding (ICSU) (7 point), No Choice with Partial Understanding (NCPU) (6 point), Correct Choice with Specific Alternative Conception (CCSAC) (5 point), Correct Choice (CC) (4 point), Incorrect Choice with Specific Alternative Conception (ICSAC) (3 point), No Choice with Specific Alternative Conception (NCSAC) (2 point), Incorrect Choice (IC) (1 point) and No response or Irrelevant Responses (0 point). These are the same criteria were used by Çalık et al. (2006b) to grade two-tier questions of this type. The purpose of this analysis procedure was to allow statistical comparisons, and the total number of points for each student was computed and inputted into SPSS 10.0™. This was followed by statistical analyses using two-way ANOVA. Interview data along with student’s self-assessment exercises were analyzed qualitatively, in which we analyzed student responses thematically seeking to identify similarities and differences as suggested by Yin (1994) and Merriam (1988).

Teaching Intervention

The first teaching activity used as part of the intervention consisted of the teaching of the injector activity; this was as noted based on a four-step constructivist teaching strategy, nowadays termed 4E by Bodzin et al. (2003) and Bodzin et al. (2003). The second was likewise based on the four-step constructivist teaching strategy (4E model) and is now described.

Second Activity

The first activity used in the present study is that used by Çalık et al. (2006a). The second activity used in the present work consisted of the following instructional steps. Meanwhile, these activities were also used for data collection procedure during interview sessions.
  1. 1.

    In your small group of 4 students, take two beakers and then fill 20 mL of carbonate drink into each beaker

     
  2. 2.

    Heat one of the beakers and observe the bubbles given off, and

     
  3. 3.

    Repeat these steps at least twice.

     

Eliciting Students’ Pre-existing Ideas

The first step for the four-step constructivist model (4E) involves elicitation of students’ prior ideas. Before the activity, all students are divided into groups of four. The teacher then asks students about their pre-existing ideas using prompt questions such as: ‘How does the dissolution of gas change with temperature? Please explain your reasons’.

Focusing

In the next step, the activity is presented to each student so that the students can gain experience in following the directions. The teacher observes students’ activities and fosters discussion of the topics within the groups. Also, the teacher tries to clarify any points, but refrains from giving away clues to the correct answers. After the activity, the teacher asks the students to respond to questions presented in the activity paper, and explain their answers within their groups. The questions used in this activity are as follows: ‘Please explain the observation of the presence of the bubbles in the heated beaker with that of the unheated one. Explain your given reasons; and, using your understanding and the experiences you acquired as a consequence of this activity, please discuss the effect of temperature on the dissolution of a gas into water.

Challenging

In this step, any students possessing a higher scientific process skill can already comprehend the target concept easily. However, if some students exhibit a lower scientific knowledge, the teachers should confirm the knowledge domain for those students. In this case, for the concept under investigation, using Figure 2, the teacher emphasizes that there is an inverse relationship between dissolution of the gas into liquid with temperature; that is, as temperature increases, the dissolution of a gas into water also decreases. This is based on kinetic theory which posits that because a particle’s kinetic energy increases and it then moves faster, the interaction between gas and solvent particles decreases and gas particles can escape more easily; if temperature decreases, dissolution will increase because the particle’s kinetic energy decreases, and they move more slowly; hence the interaction between gas and solvent particles increases, and gas particles find it more difficult to escape. Additionally, using Table I, the teacher asks students to interpret this idea based on their experiences, and to compare how temperature affects the dissolution of a gas or a solid in a liquid.
https://static-content.springer.com/image/art%3A10.1007%2Fs10956-006-9040-4/MediaObjects/10956_2006_9040_Fig2_HTML.gif
Fig. 2.

Transparency used to explain the effect of temperature to the dissolution of a gas into a liquid.

Table I

Transparency used to Explain the Effect of Temperature to the Dissolution of a Gas or a Solid into a Liquid

Matter

0 °C

20 °C

40 °C

60 °C

80 °C

100 °C

KCl

28

34.2

40.1

45.8

51.3

56.3

NaCl

35.7

35.9

36.4

37.1

38

39.2

Sugar

179

204

238

287

362

487

Ca(OH)2

0.19

0.17

0.14

0.12

0.09

0.07

KNO3

13.9

31.6

61.3

106

167

245

Li2CO3

1.54

1.33

1.17

1.01

0.85

0.72

CO2*

0.34

0.17

0.10

0.06

O2*

0.007

0.005

0.003

0.002

0.001

0

Applying (Fruitfulness)

In this step, it is intended that the students attempt to apply their experience learned in the activity to another, different situation, in order to reinforce their newly structured knowledge. Likewise, they also may be able to make relationships between these rather contrived examples and their daily life. In case of the above concept, students are asked to respond the following questions: ‘The number of fish living in the cold water is more than that in hot water. Please explain this situation based on your acquired experiences’, and ‘When you forget and leave a bottle of cola outside of refrigerator, what happens?’.

Research Findings

We first present student response to the questions, and this is followed by a summary of the interview data and self-assessment exercises.

Findings from the Solution Concept Test for Items 1 and 2

As can be seen from Table II, most of the students’ responses for Item 1 and Item 2 fell into Correct Choice with Partial Understanding (CCPU) categories for both the post-test and delayed test, about half of the responses in the pre-test for those items were categorized as ‘No Understanding’. Additionally, the proportion of students who marked the correct choice but did not explain their reasons changed from 13,6%, 15,9% and 6,8% for Item 1 for pre- post- and delayed tests scores respectively. For Item 2 a similar result was seen with 6,8%, 6,8% and 13,6% for pre- post- and delayed tests scores, respectively. Moreover, the proportion of students’ responses in the ‘Incorrect Choice with Specific Alternative Conception’ category for Item 1 changed from 18,2%, 13,6% and 36,4% for pre- post- and delayed tests scores, respectively, and for Item 2 are 18,2%, 18,2% and 34,1% for pre- post- and delayed tests scores, respectively.
Table II

Frequency and Proportion of Students’ Responses for Items 1 and 2 for Categories of Understanding

Category

Item 1

Item 2

Pre-test

Post-test

Delayed test

Pre-test

Post-test

Delayed test

N

%

N

%

N

%

N

%

N

%

N

%

CCPU

2

4.5

27

61.4

22

50

26

59.1

19

43.2

CCSAC

1

2.3

1

2.3

1

2.3

CC

6

13.6

7

15.9

3

6.8

3

6.8

3

6.8

6

13.6

ICSAC

8

18.2

6

13.6

16

36.4

8

18.2

8

18.2

15

34.1

IC

8

18.2

1

2.3

12

27.3

2

4.5

1

2.3

NR

17

38.6

1

2.3

18

40.9

3

6.8

1

2.3

MD

2

4.5

2

4.5

2

4.5

2

4.5

2

4.5

2

4.5

CCPU: Correct Choice with Partial Understanding, CCSAC: Correct Choice with Specific Alternative Conception, CC: Correct Choice, ICSAC: Incorrect Choice with Specific Alternative Conception, IC: Incorrect Choice, NR: No Response, MD: Missing data incorporates student who did not participate the test.

These differences were examined for statistical significance, and as can be seen from Table III, there are statistically significant differences between the test scores (p < 0.05). There are no statistically significant differences based on gender. However, from Table IV, it can be seen that multiple comparisons (based on the Tukey post-hoc test) suggest that whilst there is a statistically significant difference between pre-test and post-test scores, and between pre-test and delayed test scores (p < 0.05), no statistically significant differences are seen between post-test and delayed test scores (p > 0.05).
Table III

Tests of Between-subjects Effects (Dependent Variable: Total Score)

Source

Type III Sum of Squares

df

Mean Square

F

Sig.

Gender

33.810

1

33.810

1.382

0.242

Test

2176.585

2

1088.292

44.473

0.000

Gender * Test

61.076

2

30.538

1.248

0.291

Table IV

Multiple Comparisons of Test Scores (Tukey Post-hoc Test)

Tukey HSD

Mean Difference (IJ)

Std. Error

Sig.

(I) TEST

(J) TEST

Pre-test

Post-test

−10.61*

1.13

0.000

Delayed-test

−9.13*

1.13

0.000

Post-test

Pre-test

10.61*

1.13

0.000

Delayed-test

1.47

1.13

0.399

Delayed-test

Pre-test

9.13*

1.13

0.000

Post-test

−1.47

1.13

0.399

* The mean difference is significant at the 0.05 level.

As noted above, we were interested in student responses to test items, and the reasoning behind these responses. Hence here we present a detailed analysis of student responses for their alternative conceptions for item 1 in Table V; a similar analysis for Item 2 is shown in Table VI.
Table V

In Depth Analysis of Student Responses Including Alternative Conceptions for Item 1 with Respect to Level of Understanding (S means Student)

Category

Student’s response

Pre-test

%

Post-test

%

Delayed test

%

CCSAC

The gap amongst gas particles engenders an increase of the dissolution

S15

2.3

If pressure is applied, the bubbles involving in gas particles given off rapidly

S5*

2.3

ICSAC

Pressing gas particles liquefies them. Therefore, their dissolution gets difficult.

S5, S26

4.5

If gas particles are squeezed, new particles among them appear

S13

2.3

S13

2.3

In pressing gas particles, the gap among them decreases so that the dissolution increases

S17

2.3

S17

2.3

Gas particles cannot be squeezed thereby, their solubility is unchangeable

S20, S38

4.5

Gas particles take the shape of beaker where they exist. For this reason, when pressing them, their solubility entails

S24

2.3

In squeezing gas particles, different gas particles arise, thus, their solubility decreases

S37

2.3

There is an inverse relationship between solubility of a gas in a liquid and pressure

S1, S3, S30, S37, S41

11.4

S4, S14, S17, S24, S30, S32, S33, S37, S38, S39, S44

25

If pressure occurs, volume boost, as well. Therefore, gas particles dissolve into a liquid

S11

2.3

Since there is a gap amongst gas particles, their solubility is unchangeable

S2*

2.3

Since the dissolved particles with pressure are even squeezed, their solubility is unchangeable and stable

S18

2.3

While there is no relationship between solubility of a gas into a liquid and pressure, it is related to temperature

S19

2.3

IC

B choice

S9, S25, S32, S35

9.1

S25

2.3

C choice

S1, S4, S23, S34

9.1

*These students did not take part in the related activities.

Table VI

In Depth Analysis of Student Responses Including Alternative Conceptions for Item 2 with Respect to Level of Understanding (S means Student)

Category

Student’s response

Pre-test

%

Post-test

%

Delayed test

%

CCSAC

Temperature liquefies gas particles, hence, its solubility decreases

S30

2.3

ICSAC

The more temperature increases, the more density of gas does too

S2

2.3

The more temperature boosts, the more the solubility of a gas into a liquid takes place easily

S9

2.3

The solubility of a gas into a liquid increases because of the gap amongst gas particles

S15

2.3

Temperature liquefies gas particles

S16

2.3

If temperature increases, gas particles expand more, so that they dissolve easily

S17

2.3

Temperature does not affect the dissolution of a gas into a liquid, that is, this ratio is stable for gases

S23, S38

4.5

The dissolved gas particles impact the temperature so that both temperature and solubility boost

S37

2.3

Gas particles existing at a more temperature dissolve rapidly and easier

S1

2.3

There is a linear relationship between temperature and the solubility of a gas into a liquid

S4, S13, S30, S33, S35, S37, S43

15.9

S4, S11, S13, S14, S17, S24, S30, S32, S33, S37, S38, S39, S44

29.5

The dissolved particles dissolves easier with increasing temperature

S18, S19

4.5

IC

A choice

S1, S5, S20, S25, S26, S32, S34, S40

18.2

S5*, S25

4.5

C choice

S4, S11, S12, S18

9.1

S40

2.3

*This student did not take part in the related activities.

Findings from the Student Interviews

Before commencing the first activity, students were asked to make a prediction as to how pressure affects the dissolution of a gas into a liquid. As can be seen from Table VII, whilst three students (students S6, S16 and S42) pointed out that the dissolution of a gas into a liquid increases with temperature, two students (students S9 and S25) said that there is an inverse relationship between pressure and the dissolution of a gas into a liquid; in other words, increasing pressure aids the dissolution of a gas into a liquid. Student S8 declared that dispersion takes place and the dissolution of a gas into a liquid enhances this. Latter, the students were asked to conduct the first activity and their responses to initial probe questions are outlined in Table VII.
Table VII

Students’ Responses to Principal Questions for Interviews

Principal questions

Students’ responses

Students

Could you make a prediction how pressure affects the dissolution of a gas into a liquid?

The dissolution of a gas into a liquid increases with temperature

S6, S16, S42

There is an inverse relationship between pressure and the dissolution of a gas into a liquid or increasing pressure entails the dissolution of gas into a liquid

S9, S25

The dispersion takes place and the dissolution of a gas into a liquid enhances

S8

Suck up 10 mL of a carbonate drink like cola using an injector since ensuring that there is no air space between the cola and injector, and when pulling the pump of the injector from 10 to 40 mL, please explain what you observed

The liquid stays as it is but bubbles gave off

S6

Bubbles given off

S8, S16

Since pressure occurs, bubbles given off and there is an inverse proportion between pressure and solubility of a gas into a liquid

S9

In a decrease of pressure, bubbles move upwards and there is an inverse relationship between pressure and solubility of a gas into a liquid

S25

If pressure reduces, volume increases and bubbles give off

S42

Locate the pump of the injector towards its initial position, please explain what happened

Escape of bubbles occurs

S6, S8, S9, S16, S25, S42

Please explain your reason based on particulate nature of matter

If pressure increases, interaction between gas particles and water does, as well. Therefore, amount of the dissolved gas particles boosts

S8, S9. S16, S25, S42

Since pressure increases, the volume where gas particles move ceaselessly reduces so that they can interact with water particles easily

S6

Would you mind predicting how temperature influences the dissolution of a gas into a liquid

There is an inverse ratio between temperature and the dissolution of a gas into a liquid

S6, S9, S42

There is a linear relationship between temperature and the dissolution of a gas into a liquid

S16

An increase of temperature boosts the solubility of a gas into a liquid

S25

Increasing temperature increases the solubility of a gas into a liquid

S8

After taking two beakers and then fill 20 mL carbonate drink into each beaker and heating one of the beakers, could you explain what you observed in both beakers

Bubbles gave off

S6

Increasing temperature cause an increase of amount of bubbles

S8, S9, S16, S25

In increasing temperature, gas particles escape from solution environment, hence, amount of the dissolved gas particles decreases

S42

Please explain your reason based on particulate nature of matter

In an increase with temperature, the interaction between gas and water particles reduces, thereon, gas particles escape

S8, S9, S16

Because gas particles move faster than the first position where the temperature is lower, bubbles give off rapidly

S25

Interaction between gas and water particles changes in an inverse ratio and bubbles give off

S6

Since gas particles move faster as a consequence of an increase in temperature, the interaction between gas and water particles reduces

S42

To follow-up student S8’s response, the question ‘what do you think the bubbles are?’ was asked; he firstly stated that these were air, and then later suggested that these were in fact dissolved gas particles. The question ‘when pressure decreases, could you explain what happens?’ was asked to the same student, he said that there was an increase in the amount of matter present. When asked the follow-up question ‘what do you mean by an increase in the amount of matter?’, he suggested that the amount of gas particles given off increases, but the amount of gas particles remaining at the solution decreases at the same time. Likewise, when student S8 was asked to re-state the relationship between pressure and the solubility of a gas into a liquid, he asserted that as the pressure increases, the solubility of a gas into a liquid does too; that is, he seems to think there is a linear relationship between pressure and dissolution.

To probe S9 and S25’s responses, the question ‘could you explain your response that there is an inverse proportion between pressure and solubility of a gas into a liquid?’ was asked. Here student S9 said that if pressure decreases, the amount of bubbles is enhanced, and the amount of the dissolved gas reduces. Similarly, student S25 stated that there is an increase in the amount of bubbles given off, but there is a decrease in the amount of the dissolved gas. To follow-up these responses, the question ‘what kind of relationship is available between pressure and the solubility of a gas into a liquid?’ was asked. Student S9 then changed her initial notion, and said that there is a linear relationship between them. As in case of student S9’s response, student S25 also said that there is a linear relationship between them, he had thus modified his initial response. To illustrate the process of the interviews, the following quotation which is representative is presented (S: Student, R: Researcher).
  • R: Could you make a prediction how pressure affects the dissolution of a gas into a liquid?

  • S9: There is an inverse relationship between pressure and the dissolution of a gas into a liquid

  • R: Suck up 10 mL of a carbonate drink like ‘cola’ using an injector since ensuring that there is no air space between the cola and injector, and when pulling the pump of the injector from 10 to 40 mL, please explain what you observed

  • S9: Since pressure occurs, bubbles are given off and there is an inverse relationship between pressure and solubility of a gas into a liquid

  • R: Could you explain your response that there is an inverse relationship between pressure and solubility of a gas into a liquid?

  • S9: If pressure decreases, the amount of bubbles is enhanced, and the amount of the dissolved gas reduces

  • R: What kind of relationship is there between pressure and the solubility of a gas into a liquid?

  • S9: When pressure reduces more bubbles are given off... but the amount of the dissolved gas decreases... certainly there is a linear relationship between them

  • R: Locate the pump of the injector towards its initial position, please explain what happened?

  • S9: Escape of bubbles occurs

  • R: Please explain your reasoning based on the particulate nature of matter

  • S9: If pressure increases... Interaction between gas particles and water increases too.... Therefore, amount of the dissolved gas particles boosts. As mentioned earlier, there is a linear connection between them

Similarly, before starting the second activity, the students were asked to predict how temperature influences the dissolution of a gas into a liquid. Three students (students S6, S9 and S42) said that there is an inverse relationship between temperature and the dissolution of a gas into a liquid. S16 in contrast stated that there is a linear relationship between temperature and the dissolution of a gas into a liquid, but as in case of S16’s, student S8 implied that increasing temperature increases the solubility of a gas into a liquid. Student S25 also predicted that an increase of temperature boosts the solubility of a gas into a liquid. However, after the students had carried out the second activity, their views changed and these are presented in Table VII. Again to track students’ responses to probe questions, some follow-up questions were also used. For example, when the question ‘in case of increasing temperature, what type of energy increases?’ was asked, all interviewees answered that kinetic energy increases. Similarly, when the question ‘if kinetic energy increases, how do particles move?’ was asked, all interviewees declared that since kinetic energy increases, the particles move faster. Next, when the question ‘what kind of relationship exists between temperature and solubility of a gas into a liquid’ was asked, students S6, S8, S9 and S42 said that there is an inverse relationship between them. Student S16 stated that if temperature boosts, solubility of a gas into a liquid occurs, and student S25 said that there is a linear relationship in terms of the amount of gas given off, but there is an inverse relationship in terms of the amount of the dissolved gas. Student S8 also said that the more the temperature increases, the more bubbles escape and the amount of the dissolved gas decreases. When asked the question ‘could you give more information on your response?’ was asked to S6, she focused on the amount of gas given off as was seen in the case of students S8 and S25 responses. When the question ‘why did you change your initial idea?’ was asked of S16, she confessed that when she thinks of the solubility of a gas into a liquid, she firstly thinks of the solubility of a solid into a liquid meaning that she responds to the gas solubility questions based on her ideas about the solubility of a solid in a liquid. When she was asked to explain her reasoning, she stressed that she frequently encounters examples related to the solubility of a solid into a liquid, rather than the solubility of a gas into a liquid. An excerpt for these interviews is presented below:
  • R: Would you mind predicting how temperature influences the dissolution of a gas into a liquid?

  • S16: There is a linear relationship between temperature and the dissolution of a gas into a liquid

  • R: After taking two beakers and then fill 20 mL of carbonate drink into each beaker and heating one of the beakers, could you explain what you observed in both beakers?

  • S16: Increasing temperature cause an increase of amount of bubbles

  • R: How does the amount of the dissolved gas particles change?

  • S16: The dissolved gas particles will be more... escape of bubbles... escape of bubbles means that the dissolved gas particles gave off

  • R: Could you give me more information about this?

  • S16: Some of gas particles escape and the rest of them remain there... in regard to its initial position, the amount of the dissolved gas particles occurs

  • R: In case of increasing temperature, what type of energy increases?

  • S16: Kinetic energy increases

  • R: If kinetic energy increases, how do particles move?

  • S16: Since kinetic energy increases, particles move faster... both water and gas particles move faster

  • R: What kind of relationship exists between temperature and solubility of a gas into a liquid?

  • S16: If temperature boosts, the solubility of a gas into a liquid occurs

  • R: Please explain your reason based on particulate nature of matter?

  • S16: In an increase with temperature, the interaction between gas and water particles reduces, thereon, gas particles escape

  • R: Why did you change your initial idea?

  • S16: While I am considering the solubility of a gas into a liquid, I firstly remember and retrieve the solubility of a solid into a liquid so that I respond gas solubility as the solubility of a solid into a liquid

  • R: Do you have any idea why you preferred such a tendency?

  • S16: Ooh... yes... because I frequently encounter many examples related to the solubility of a solid into a liquid rather than the solubility of a gas into a liquid

Findings from Student’s Self-Assessment Exercise

As can be seen from Table VIII, whilst about three-fifth of the students said that from the intervention they learned how pressure affects the solubility of a gas into a liquid and the amount of bubbles giving off, similar proportion (59%) reported that they learned how temperature impacts on the amount of bubbles given off, and the inverse relationship between temperature and the solubility of a gas into a liquid. Additionally, whereas about one-fifth of the students said that they learned how temperature and pressure affect the solubility of a gas into a liquid, five referred to the probes about why the number of fish living in cold water is more than that in hot water, and why a kind of paralysis occurs in divers. Moreover, while four said that since the amount of bubbles giving off is lower in cold water, they said this contains much more oxygen, or that the number of gas particles given off in cold water is lower than in hot water. Two students said that there is a linear relationship between the amount of bubbles giving off and pressure, and two further expressed that increasing temperature boosts the amount of bubbles given off, only one student said that there is an inverse relationship between volume and pressure. Finally, only one student declared that she did not learn why a kind of paralysis occurs in a diver body.
Table VIII

The Results of Student’s Self-assessment After Two Activities

Category

f

%

Students

The concepts I have learned

Increasing pressure enhances the solubility of a gas into a liquid and entails escape of gas particles and an increase in volume decreases the solubility of a gas into a liquid

29

65.9

S4, S6, S7, S9, S10, S12–S15, S17–S20, S23–S28, S30, S31, S33, S34, S36, S37, S39, S41, S42, S44

Increasing temperature boosts the amount of bubbles giving off and there is an inverse relationship between temperature and the solubility of a gas into a liquid or the solubility of a gas into a liquid decreases

26

59.1

S3, S4, S6, S7, S9, S10, S12, S14–S20, S22–S26, S31, S32, S34, S36, S39, S42, S44

Temperature and pressure affect the solubility of a gas into a liquid

8

18.2

S11, S21, S28, S29, S30, S35, S40, S43

The reasons why the number of fish living in cold water is more than that in hot water and why a kind of paralysis appears in a diver body

5

11.4

S1, S9, S22, S28, S35

Since the amount of bubbles giving off is lower in cold water, it includes much more oxygen or the number of gas particles giving off in cold water is lower than that in hot water

4

9.1

S3, S25, S27, S37

There is a linear relationship between the amount of bubbles giving off and pressure

2

4.5

S16, S38

Increasing temperature boosts the amount of bubbles giving off

2

4.5

S37, S38

There is an inverse proportion between volume and pressure

1

2.3

S13

The concepts I have not learned

The reason why a kind of paralysis occurs in a diver body

1

2.3

S20

Discussion

As noted in Table III, there are some statistically significant differences between pre- post- and delayed test scores (p < 0.05). This suggests that the activities employed, as an intervention here not only helped these students to understand the specific science activities, but also to achieve conceptual understanding. Also, since there are no statistically significant differences between post-test and delayed test scores (Table IV), this suggests that the activities helped the students to retain their conceptions in their long-term memory (Glynn and Takahashi, 1998; Hynd, Alvermann and Qian, 1997; Palmer, 2003; Tsai, 1999). Moreover, the findings form the two-way ANOVA suggests that in this case gender did not influence students’ conceptual understanding, and that these activities are thus equally suitable for boys and girls.

As seen from Tables V and VI, for pre-test some of the students held an alternative conception about how the pressure or temperature affects the solubility of a gas in a liquid. This may result from misinterpretation of the theory of the particulate nature of matter. For example, many science textbooks provide illustrations that show that in the solid phase the distance between particles is short, but that in the case of the gas phase it is very large. An alternative conception that seems to be retained by one students is that ‘Gas particles take the shape of beaker where they exist. For this reason, in pressing them, solubility occurs’ (S24) (Table V). Even though this student may have thought that gas particles fill the beaker, that is, the volume of gas particles is equal to that of the beaker, it seems he has used this idea in a situation to which it is not relevant. Similarly, as can be seen from Table VI, students S23 and S38 stated that temperature does not affect the dissolution of a gas into a liquid, and that is, this is stable for gases. Such a view may come from misinterpretation of the idea gas particles at the same temperature expand equally. Such a suggestion is consistent with that expressed by Ebenezer and Gaskell (1995) and Prieto et al. (1989). Moreover, some of the students here seemed to focus on liquefaction of gas particles rather than solubility of them in a liquid. This may stem from a daily life experience; for example students would likely be aware of the fact that cooking gases such as LPG, lighter gases and so on are produced by pressurization of gases. One interesting alternative conception about the effect of pressure is ‘If gas particles are squeezed, new particles among them appear’ (S13). Two possible reasons are possible for this view. Firstly, this may come from misinterpretation of the particulate nature of matter and its representation. In case of squeezing the particles, these would mean the particles get closer together. If no specific attention is paid of the total number of particles, this may engender such an alternative conception. Secondly, this student may think gas particles or gases as having gaps within the molecule and so squeezing them may engender new substances.

After the intervention, over half of the students seemed to have improved their conceptual understanding, at least to some extent. This suggests that the intervention activities are effective in enhancing students’ conceptual understanding, and reducing their alternative conceptions. However, as noted the researchers also sought to further explain the interaction between solute and solvent particles, using an overhead transparency (Figure 2). Interestingly, the students tended not to refer to this transparency, and instead they preferred stating their conclusion based on the activities. This may be because the activities were more visually dramatic and thus more easily remembered. Additionally, it may stem from the educational system in which the study was conducted, in which students are accustomed to short-answer or multiple-choice questions. As a matter of fact, during the interview sessions, when the students were asked to use the particulate nature of matter concept, the students did indeed attempt to use this and explain the given situation scientifically especially when prompted with the follow-up questions.

The intervention activities used in this work seem in some cases to result in the development of new alternative conceptions as reported by Coştu (2006), Ebenezer and Gaskell (1995), Ebenezer (2001) and Hynd et al. (1997). For example, some of the students said that there is an inverse relationship between the solubility of a gas in a liquid and pressure, or there is a linear relationship between the solubility of a gas in a liquid and temperature. This may possibility result from the students’ observations of the activities. For example, the students may focus on the escape of bubbles, rather than on the dissolution of the gas into a liquid which is more difficult to see. This seemed to be the case for the interviews with students S8, S9 and S25’s responses (for pressure) and S6, S8 and S25’s responses (for temperature). In support of this, as can be seen in Table VIII, many of the students referred to the escape of bubbles. Further, with respect to the effect of temperature on the dissolution of a gas in a liquid, a large proportion of the students said that there is a linear relationship between temperature and the solubility of the gas. This may result from confusion about how temperature affects the dissolution of a gas or a solid into a liquid. For example, student S16 said that when she thinks of the solubility of a gas in a liquid, she firstly remembers and retrieves the idea of solubility of solids in a liquid. This may mean she sees gas solubility in the same way she sees the solubility of a solid in a liquid. This suggests that this student at least draws upon her own related experiences from examples she encountered in daily life. In support of this latter notion, one of the more notable student responses seen in the delayed test was ‘If pressure increases, volume boosts, as well. Therefore, gas particles dissolve into a liquid’. Here such a view may come from the notion that a gap is necessary for dissolution to occur. As seen from Table V, even though student S13 changed her view as a result of the intervention, she turned back to her first notion over time. This suggests that the activity in this case only temporarily helped this student to change her view, but since her alternative conception is based on personal experiences, it may dominate and outweigh the effect of the intervention (Stavy, 1990). This finding that this student returned to her initial conception is consistent with work by Taber (2001) and Teichert and Stacy (2002). However, in other cases as can be seen from Table V, students such as S17’s pre-test and post-test responses point to an increase in understanding on the course of time (Coştu, 2006). Finally, Pınarbaşı and Canpolat (2003) and Pınarbaşı et al. (2005) report an alternative conception, that ‘The amount of gas dissolved in a solvent is proportional to total pressure of gases above the solution’. However, this did not surface in the current work, neither in the elicitation phase; nor was it engendered as a result of the intervention. It is of course possible that the students never thought of this, and they may still hold such an alternative conception, but this was simply not revealed by the probes used here.

In light of the current study, some suggestions are made here for other researchers and teachers and some suggestions for future studies are presented. This study suggests students have difficulty in connecting their ideas with particulate nature of matter, especially when it comes to the interaction between solute and solvent particles. It also seems they find it hard to decide how temperature influences the dissolution of a solid or a gas into a liquid. This may mean we need different materials or strategies in order to make clear the scientific view of microscopic phenomena. Our work suggest a simple overhead transparency and argument will not suffice. Next, although other constructivist-based strategies such as 5E and 7E are quite popular nowadays, this work suggest the simpler four-step constructivist teaching strategy (4E) is quite effective and simple to implement. Even experienced teachers may lose track of complicated sequences if the teaching strategy has many steps (Treagust et al., 1998). More research could focus on the nature of the strategy to test this proposition strategy. Future research also could start by an examination of student’s Piagatian stage of development, using say the Logical Thinking Ability Test (LTAT) (Tobin and Capie, 1981) or Reasoning Ability Test. Such data may be show how student’s conceptual understanding may help in the interpretation of students’ responses based on their level; early concrete operational, late concrete operational, early formal operational, late formal operational.

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© Springer Science+Business Media, LLC 2006