Determination of the Turkish primary students' views about the particulate nature of matter

The results which were acquired from the test have been given in detail in Table 1.

PROPERTIES	4^th GRADE (%)			5^th GRADE (%)			6^thGRADE (%)
PROPERTIES	I	D	C	I	D	C	I	D	C
1. Size of particles when a solid is melted	43	45	12	38	40	22	36	38	25
2. Spaces between the particles when a solid is melted	56	26	16	46	41	13	58	35	6
3. Speed of the particles when a solid is melted	55	26	18	51	29	20	61	24	15
4. Number of the particles when a solid is melted	33	42	25	30	48	22	46	16	36
5. Size of particles when a liquid is freezed	54	26	19	48	24	28	32	36	32
6. Spaces between the particles when a liquid is freezed	23	59	18	33	54	13	24	64	12
6. Speed of the particles when a liquid is freezed	26	55	18	28	53	19	20	62	18
8. Number of the particles when a liquid is freezed	38	30	32	35	30	35	26	24	50
9. Size of particles when a liquid is vaporized	45	30	25	39	40	21	41	25	34
10. Spaces between the particles when a is vaporized	52	32	16	53	26	21	66	21	12
11. Speed of the particles when a liquid is vaporized	60	21	19	54	26	19	61	19	10
12. Number of the particles when a liquid is vaporized	36	35	28	25	45	30	29	30	41
13. Size of particles when a gas is condensed	38	32	30	45	25	30	36	35	29
14. Spaces between the particles when a gas is condensed	30	52	18	34	46	20	36	46	16
15. Speed of the particles when a gas is condensed	41	36	22	38	36	26	28	56	16
16. Number of the particles when a gas is condensed	35	30	35	45	23	32	36	23	40
16. Size of particles when a matter is heated	45	33	22	40	39	21	38	26	36
18. Spaces between the particles when a matter is heated	56	23	21	58	22	20	64	22	14
19. Speed of the particles when a matter is heated	40	35	25	45	35	20	58	28	14
20. Number of the particles when a matter is heated	45	30	25	32	43	25	32	30	38
21. Size of particles when a matter is cooled	40	36	24	40	38	22	33	35	32
22. Spaces between the particles when a matter is cooled	24	54	22	26	50	24	18	65	16
23. Speed of the particles when a matter is cooled	29	49	22	35	45	20	21	61	18
24. Number of the particles when a matter is cooled	36	28	35	43	32	25	34	28	38
25. Size of particles when a solid is pressed	34	42	24	40	35	25	34	30	36
26. Spaces between the particles when a solid is pressed	22	58	20	25	56	19	25	49	26
26. Speed of the particles when a solid is pressed	30	42	28	33	52	15	30	41	29
28. Number of the particles when a solid is pressed	32	30	38	25	30	45	26	24	50
29. Size of particles when a liquid is pressed	38	36	25	35	30	35	33	25	42
30. Spaces between the particles when a liquid is pressed	28	50	22	40	48	12	30	50	20
31. Speed of the particles when a liquid is pressed	35	40	25	26	48	26	30	46	24
32. Number of the particles when a liquid is pressed	31	31	38	28	30	42	25	24	51
33. Size of particles when a gas is pressed	34	36	30	40	38	22	40	25	35
34. Spaces between the particles when a gas is pressed	20	55	25	30	52	18	24	56	20
35. Speed of the particles when a gas is pressed	38	40	22	35	40	25	34	50	16
36. Number of the particles when a gas is pressed	26	36	36	35	30	35	20	25	55

I: Increase / D: Decrease / C: Constant. Students’ correct responses are written in bold.

When the results are examined, it is seen that the students in each level could not give satisfactory correct answers in desired level. The correct answers are increasing as long as the level of the students goes up. The ratios of the right answers are between 12-59% for 4^th grade, between 12-58% for 5^th grade, and between 16-61% for the 6^th grade.

The answers given to test have shown that the understanding levels of students about the microscopic properties of matter are quite low and students have several misconceptions. They had little knowledge or misconceptions about the microscopic properties of the particles such as the order of the particles, spaces between particles, the number of particles, the size of particles and the movement of the particles. And also, they have difficulties in transferring their theoretical knowledge about the particulate nature of matter to explain daily life events. It is believed that the reason they have difficulty in understanding is because the concept is abstract and the students can not make it meaningful enough in their minds.

In the test, the results show that students responses, especially related to concepts about the speed of the particles and the spaces between particles during melting, cooling and vaporizing are varying. While some students have the idea that the distance between particles would not change during these events, the others think that distances between particles will increase or decrease (Table 1). Similar results were also revealed by Osborne and Cosgrove (1983), Pereira and Pestana (1991) and Valanides (2000). While the number of the students thinking that there are no gaps between liquid and gas particles is low, most of the students have the misconceptions that there are no spaces between solid particles. Even though students could use particulate model to describe the phase changes, they still have some misconceptions. Pereira and Pestana (1991) found that many high school students have misunderstandings about the relative distance between the particles for the three states. The reason of this misconception could be that while explaining the particles structure of solids, it is explained as the space between the particles of solids is generally none instead of very little. In the literature, Boz (2006) also found that students think that particles in a solid do not have any movement at all because there is no space to go and she explains this based on the thought of particles are very close to each other and tightly packed in a solid substance. These results show that the students are insufficient in using their microscopic level ideas about the particulate nature of matters to explain the observable macroscopic properties of matters.

The other misconception getting from the test is that students think that some properties of matter such as size, spaces between particles, speed of particles and number of particles are changed with press for three states. This result is in parallel to Ben-Zvi, Eylon and Silberstein (1986), which revealed the students’ thinking about the malleability of the copper atom. This result indicates that students have a tendency to use their perceptions on macroscopic changes of a substance to infer its phase change occurring at the microscopic level.

When the test items given to define the understanding levels of students about the number and size of particles in solid, liquid and gas form were examined, it was determined that the understanding levels of students about the size and number of particles were quite low. Specially, most of the students have the misconception that the size and number of particles would change during the heating or cooling of substances. When the test results were investigated it is seen that while some of the students in three levels thought that size and number of particles change when a liquid is vaporized (Item 9 and 12 in the test). The belief that the size of a molecule depends on temperature is classified as a misconception (Griffiths and Preston, 1992; Lee et al., 1993). For example, 45% of 4^th grade students and 41% of 6^th grade students believe that the size of particles increase as stated by Pereira and Pestana (1991) and Griffiths and Preston (1992), 40% of 5^th grade students believes that the size decreases (Item 9) as stated by the studies of Pereira and Pestana (1991), Valanides (2000) and Özmen, Ayas and Coştu (2002). On the other hand, 36% of 4^th students believes that the number of particles increases, 45% of 5^th grade and 30% of 6^th grade students believe that the number of particles decrease (Item 12). These results are in parallel to Gabel, Samuel and Hunn (1987). Although there are wrong answers, 41% of 6^th grade students think that the number of particles is constant and this is true. In addition, when the test items in which the students’ ideas about the condensation concept is tried to be determined are examined (Item 13 and Item 16), same misconception about the size and number of particles during condensation is found. For example, 38% of 4^th grade students, 45% of 5^th grade students and 36% of 6^th grade students think that particle size increase during condensation. This is an interesting and original misconception and contradicts with the literature. For example, according to studies of Gabel, Samuel and Hunn (1987), Pereira and Pestana (1991), Griffiths and Preston (1992), Valanides (2000) and Özmen, Ayas and Coştu (2002), most of the students who have this misconception think that the sizes of particles decrease during cooling. In this study, if the students think that particle size would decrease, this might be explained such a student’s idea that as the temperature decreases, particles will pucker and the size will decrease. Although this is an alternative idea, it might be acceptable from the students’ point of view. But, the cause behind the idea of particle size would increase during condensation is problematic and arguable. The same interesting situation might also be said for the number of particles. As follows, students in all levels think that the number of particles would increase during condensation. Griffiths and Preston (1992) reported similar results that high school students believed that the particle size of a substance would increase as it changed from liquid state to gaseous state or when heated. And also, according to the studies of Gabel, Samuel and Hunn (1987), Pereira and Pestana (1991) and Valanides (2000), most of the students who have this misconception think that the size of particles will increase during heating and it will decrease during cooling. This is also the most common misconception meeting in the literature. For example, the research of Pereira and Pestana (1991) indicated that many high school students thought that the particle size would increase when phase change occurs from solid to liquid and gases. They thought that the size of the particles as being smallest in the solid, increasing in the liquid and gas. In another study made by Gabel Samuel and Hunn (1987), they found that many of the prospective elementary teachers did not conserve the number of the particles and also they believe that the atoms get larger as the matter changes from the liquid to the gas state. These misconceptions of students is thought to arise from the little or no information that no change will occur in the size of particles as a result of state changes, in another words, the size of particles in solid, liquid and gas form are the same.

In general, according to the results students cannot sufficiently use the idea of the particulate nature of matter in explaining the evaporation, density, and effect of temperature change on gases, mixing of liquids, diffusing of gases, and in sum application of macroscopic ideas to the particles. Similar results were obtained from the studies of Ayas and Özmen (2002), Briggs, Brook and Driver (1984) and Özmen, Ayas and Coştu (2002). And also, it is also determined that even though students have the idea of particulate nature of matter, they cannot apply their theoretical knowledge to daily life events. It is known that these abstract concepts are not explained in a concrete way, and activities as simulation and animation to help students form these changes which occur in microscopic level in their minds are not used in teaching this subjects might be thought the reason of this.