Asia-Pacific Forum on Science Learning and Teaching, Volume 12, Issue 2, Article 4 (Dec., 2011)
Asiana BANDA, Frackson MUMBA, Vivien M. CHABALENGULA & Simeon MBEWE
Teachers’ understanding of the particulate nature of matter: The case of Zambian pre-service science teachers

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Results

Effect of Phase Change on Size, Speed, Number and Spaces between Particles

Solid melting: Table 1 below shows that most pre-service teachers correctly believed that spaces between particles (83.3%) and speed of the particles (93.1%) increase when a solid is melted. They also correctly viewed that the number of particles remain constant when a solid is melted (62.1%). In contrast, 89.7% of the pre-service teachers exhibited poor understanding of the effect of melting on size of particles. For example, 48.3% of the teachers erroneously subscribed to the idea that the size of particles increase when a solid is melted while 41% said the size of particles decrease when a solid is melted. Only 10.3% said the size of particles remain constant when a solid is melted.

Table 1: Percentage of Responses on Effect of Phase Change

Physical Change

Items

I

D

C

Melting

1
2
3
4

Size of particles when a solid is melted
Spaces between the particles when a solid is melted
Speed of the particles when a solid is melted
Number of particles when a solid is melted

48.3
83.3*
93.1*
10.3

41.4
10.0
00.0
27.6

10.3*
6.7
6.9
62.1*

Freezing

5
6
7
8

Size of particles when a liquid freezes
Spaces between the particles when a liquid freezes
Speed of the particles when a liquid freezes
Number of particles when a liquid freezes

26.6
13.8
3.6
20.7

46.7
86.2*
82.1*
17.2

26.7*
0
14.3
62.1*

Vaporizing

9
10
11
12

Size of particles when a liquid is vaporized
Spaces between the particles when a liquid is vaporized
Speed of the particles when a liquid is vaporized
Number of particles when a liquid is vaporized

34.5
80.0*
89.3*
6.9

48.3
13.3
3.6
37.9

17.2*
6.7
7.1
55.2*

Condensing

13
14
15
16

Size of particles when a gas is condensed
Spaces between the particles when a gas is condensed
Speed of the particles when a gas is condensed
Number of particles when a gas is condensed

25.0
13.8
17.2
10.3

39.3
82.8*
75.9*
24.2

35.7*
3.4
6.9
65.5*

*% of correct responses; I=increase; D= decrease; C= constant

Liquid freezing: As shown in Table 1 above, most pre-service teachers correctly agreed that the spaces between particles (86.2%) and the speed of the particles (82.1%) decrease when a liquid is frozen. However, this is not always true for water at below 4°C where ice start expanding resulting into increased spaces between its molecules. Most pre-service teachers (62.1%) also held a scientifically correct idea that the number of particles remain constant when a solid is frozen. However, almost half of the participants (46.7%) erroneously believed that the size of particles decrease when a liquid is frozen, and only about a quarter of them (27%) correctly indicated that the size of particles remain constant when a liquid is frozen.

Liquid vaporizing: Table 1 shows that most pre-service teachers had a scientifically correct understanding of what happens to the spaces between particles (80%), speed of the particles (89.3%) and the number of particles (55.2%) when a liquid is vaporized. On the other hand, most pre-service teachers erroneously believed the particle size decrease (48.3%) or increase (34.5%) when a liquid is vaporized.

Gas condensing: Table 1 below shows that most pre-service teachers held a scientifically correct idea that space between particles (82.8%) and speed of the particles (75.9%) decrease when a gas is condensed. Furthermore, more than half of the pre-service teachers (65.5%) also correctly indicated that the number of particles remain constant when a gas is condensed. However, some pre-service teachers erroneously believed that when a gas is condensed the size of particles increase (25%) or decrease (39.3%).

Effect of heating, and cooling on Size, Speed, Number and Spaces between particles

Heating matter: Table 2 below shows that most pre-service teachers had scientifically correct views about spaces between the particles (76.7%), speed of the particles (80.0%), and number of particles (70.0%) when matter is heated. Very few teachers (17.9%) correctly indicated that the size of particles remain constant when matter is heated. Majority of the pre-service teachers (71.4%) erroneously believed that the size of particles increase when matter is heated.

Table 2: Percentage of Responses on the effect of Heating and Cooling

 

Items

I

D

C

Heating

17

Size of particles when matter is heated

71.4

10.7

17.9*
18 Spaces between the particles when matter is heated
76.7*
16.7
6.6
19 Speed of the particles when matter is heated
80.0*
16.7
3.3
20 Number of particles when matter is heated
20.0
10.0
70.0*

Cooling

 21 Size of particles when matter is cooled
20.7
58.6
20.7*
22 Spaces between the particles when matter is cooled
7.9
80.6*
11.5
23 Speed of the particles when matter is cooled
6.7
83.3*
10.0

24

Number of particles when matter is cooled

24.1

13.8

62.1*

*% of correct responses; I=increase; D= decrease; C= constant

Cooling matter: As shown in Table 2 above, most pre-service teachers correctly indicated that both the speed of the particles (83.3%) and spaces between particles (80.6%) decrease when matter is cooled. They also correctly indicated that the number of particles remain constant (62.1%) when matter is cooled. As such, majority of the pre-service teachers exhibited sound views on the effect of cooling on the number of particles, spaces between particles and speed of the particles in a substance. However, teachers displayed poor knowledge on the effect of cooling on the size of particles as most of them indicated that the size of particles increase (20.7%) or decrease (58.6%) when matter is cooled.

Effect of Compression on Size, Speed, Number and Spaces between particles

Compressing a solid: As shown in Table 3 below, most of the pre-service teachers had scientifically correct views on the effect of compressing a solid on the four microscopic aspects of matter. For example, 57.1% said the size of particles remains constant and 73.3% said the number of particles remain the same when a solid is compressed. They also correctly believed that the speed of the particles decrease (51.7%) when a solid is compressed. Most pre-service teachers (66.7%) believed the spaces between the particles decrease when a solid is compressed. This implies that this group of teachers believed a solid can be compressed and the speed of its particles will decrease when it is compressed because such physical change will result into more reduction in spaces between particles. It is scientifically correct to say that most solids can be compressed, though the extent to which they can be compressed varies from substance to substance, and is often minute. As such, students in lower grades are likely to be taught or read in science textbooks that solids can’t be compressed. On the other hand, students in advanced college science courses, including those offered in teacher education programs, are likely to learn that solids can also be compressed. As such, teachers are expected to know that solids are compressible.

Table 3: Percentage of Responses on Compressing a Solid, Liquid and Gas

 

 

Items

I

D

C

Solid

25
26
27
28

Size of particles when a solid is compressed
Spaces between the particles when a solid is compressed
Speed of the particles when a solid is compressed
Number of particles when a solid is compressed

28.6
3.3
24.1
10.0

14.3
66.7*
51.7*
16.7

57.1*
30.0
24.2
73.3*

Liquid

29
30
31
32

Size of particles when a liquid is compressed
Spaces between the particles when a liquid is compressed
Speed of the particles when a liquid is compressed
Number of particles when a liquid is compressed

3.4
16.7
46.7
7.1

34.5
80.0*
43.3*
21.5

62.1*
3.3
10.0
71.4*

Gas

33
34
35
36

Size of particles when a gas is compressed
Spaces between the particles when a gas is compressed
Speed of the particles when a gas is compressed
Number of particles when a gas is compressed

30.0
20.0
40.0
6.6

26.7
66.7*
46.7*
26.7

43.3*
13.3
13.3*
66.7*

*% of correct responses; I=increase; D= decrease; C= constant

Compressing a liquid: Table 3 above shows that most pre-service teachers correctly believed the spaces between particles decrease (80.0%) when a liquid is compressed. They also held correct views on size of particles (62.1%) and number of particles (71.4%) remaining constant when a liquid has been compressed. On the other hand, they had an erroneous idea about the effect of compression on the speed of particles when a liquid is compressed. About 47% believed the speed of particles increase when a liquid is compressed.

Compressing a gas: As shown in Table 3 above, most pre-service teachers held correct views on spaces between particles, and number of particles when a gas is compressed. Most pre-service teachers agreed that the spaces between particles decrease (66.7%), the number of particles remain constant (66.7%), and speed decrease (46.7%) when a gas is compressed. On the other hand, 20% of the pre-service teachers believed the speed increase when a gas is compressed. Furthermore, 56.7% subscribed to an erroneous idea that the size of particles increase (30%) or decrease (26.7%) when a gas is compressed. Only 43.3% said the size of particles remain the same when a gas is compressed.

 

 

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