Asia-Pacific Forum on Science Learning and Teaching, Volume 6, Issue 1, Article 3 (June, 2005)
Suat ÜNAL & Bayram COŞTU
Problematic issue for students: Does it sink or float?
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Results and discussion

The frequencies and percentages of the students’ responses to SFCT items are represented in Table 1.

Table 1. The frequencies and the percentages of the students’ responses to SFCT (n=108)

Item
Correct choice
A
B
C
D
No response
f
%
f
%
f
%
f
%
f
%
1
D
-
-
-
-
10
9
98
91
-
-
2
C
16
15
7
66
16
15
4
4
-
-
3
A
59
55
10
9
18
17
21
19
-
-
4
A
44
41
49
45
6
6
9
8
-
-
5
B
-
-
57
53
7
6
44
41
-
-
6
B
20
19
48
44
12
11
28
26
-
-
7
D
43
40
14
13
8
7
43
40
-
-
8
C
-
-
12
11
64
59
32
30
-
-
9
A
38
35
32
30
21
19
17
16
-
-
10
A
44
41
27
25
8
7
25
23
4
4
11
D
17
16
38
35
34
31
19
18
-
-
12
B
5
5
67
62
25
23
11
10
-
-
13
C
33
31
25
23
36
33
12
11
2
2
14
D
39
36
27
25
12
11
30
28
-
-
15
B
17
16
15
14
42
39
34
31
-
-
16
C
16
15
17
16
54
50
14
13
7
6
17
A
34
31
19
18
45
42
10
9
-
-
18
A
67
62
14
13
-
-
24
22
3
3
19
D
20
19
12
11
13
12
63
58
-
-
20
B
20
19
51
47
35
32
2
2
-
-

* The frequencies and the percentages of student choosing the correct answer are shown in bold.

From the analyses of the students’ responses to the test items 2, 7, 15 and 20, it is clear that most of the students had the misconception that weight or mass determines whether an object sinks or floats. The percentages of the students who had this misconception were in the range of 40-66% for different items (see Table 2). It is possible to conclude that students probably construct some non-scientific rules guided by their limited daily life experiences. This misconception may stem from both students’ lack of knowledge and their inaccurate generalization.

Another misconception revealed in the study was that the volume of an object determines whether it will sink or float (see items 1, 2, 15 and 20 in Table 2). The percentages of the students whose choice includes this misconception were in the range of 19-55% for different items. This misconception may also result from students’ lack of the concept of density and their over generalization of experiences in daily life.

The majority of the students think that the volume of a liquid in a container determines whether an object sinks or floats. This misconception was revealed from the students’ responses to items 9, 16 and 17. The percentage of the students whose choice on those items includes this misconception, were 35%, 50% and 69% respectively. According to the students who had this misconception, when the level of the liquid in a container is increased, a sinking object will float and the volume of its sinking part will decrease. This misconception may also stem from students’ previous experiences. Although a child could not float a toy boat in a bowl because of its height, he could float it in a pool. Therefore, students erroneously conclude that the volume of a liquid in a container determines whether an object sinks or floats.

Table 2. The percentage of students who gave the correct response and those who had misconceptions for each item

Item No Students Giving Correct Responses (%) Propositional Statements (Content of Test Items) Students' Misconceptions and Difficulties
1 91 Deciding whether an object sinks or floats by regarding its position in a liquid *Objects which are hanging on in a liquid are named as sinking objects because they are covered by the liquid (9%)
2 15 Identification of the factors influencing whether an object sinks or floats in a liquid

*Volume determines if an object will sink or float (19%)

*Weight determines if an object will sink or float (66%)

*The volume of the liquid determines if an object will sink or float (70%)
3 55 Description of the concept of density

*Density is the weight of an object (9%)

*Density is the weight of an object in a liquid (17%)

*Density is the force that pushes an object up (19%)
4 41 Comparison of different objects’ densities by regarding their positions in a liquid

*The density of an object hanging in a liquid is equal to that of a floating object (8%)

*The density of an object hanging in a liquid is equal to the density of a sinking object (6%)

*The density of a floating object is more than that of a sinking object and an object hanging in a liquid (45%)
5 53 Making a connection between the buoyancy which affects an object and the weight of the liquid overflowing

*The density of an object hanging in a liquid is less than the density of the liquid (6%)

*The buoyancy of an object which is hanging in a liquid is more than the weight of the liquid overflowing (41%)
6 44 Comparison of the densities of different objects, whose masses are the same but volumes and buoyancies are different from each other

*The density of an object hanging in a liquid is equal to that of a floating object (19%)

*When two objects at the same mass are put into a liquid, the buoyancy on the object hanging in the liquid is more than that on floating object (26%)
7 40 Understanding the reasons why objects may have different positions in a liquid, although they are made of the same matter and their masses and densities are equal

*The mass of an object determines whether it will sink or float (40%)

*When two objects of the same mass are put into a liquid, a geometrical shaped one will float, but the other having no geometrical shape will sink (13%)
8 59 Determination of the processes to make a floating object sink

*When the container is shaken, the floating object will sink (11%)

*If you make a hole through the object, it will sink (41%)
9 35 Comprehension of the reason why an object may have different positions in two different liquids

*Because the volume of the liquid affects buoyancy, the volume of the sinking part of the objects in a container filled with a little liquid is more than another with more liquid (46%)

*Because the volume of the liquid in the container is little and insufficient, the volume of the sinking part of an object is more than that in another container (35%)
10 41 Calculation and comparison of the buoyancies of objects whose weight and volume of the sinking parts are the same

*The greater the floating part (out of water) of an object, the greater its buoyancy (30%)

*When comparing buoyancies affecting three objects one of which sinks, another floats and the other hangs in a liquid, the buoyancy of the sinking object is more than the others (25%)

*Not making the connection between the volume of sinking part of an object and its buoyancy (59%)

11 18 Putting the solutions (liquids) in order, according to their densities by regarding of solvent and solute quantities *Making wrong connections between the solvent and solute quantities of solutions and their densities (82%)
12 62 Identification and comparison of the densities of different liquids, which don't mix with each other, by regarding their positions in a container * Making wrong connections between the densities of different liquids and their positions in a container (38%)
13 33 Interpretation of how the volume of the sinking part of an object and its buoyancy changes when a liquid which is less dense is poured into the container filled with a more dense liquid

*When the densities of the liquid changes, the buoyancy of an object changes too (54%)

*The volume of the sinking part of an object becomes less when a liquid which is less dense is poured into the container filled with a more dense liquid (34%)
14 28 Interpretation of how the water level in a container and the positions of the objects change when two objects, one of which is put on top of the other, and then put into the liquid one by one

*When two objects, one of which is put on the top of the other, is put into the liquid one by one, the position of the object which is beneath does not change (47%)

*When two objects, one of which is put on the top of the other, are then put into the liquid one by one, the water level in the container does not change (36%)
15 14 Understanding the reasons why objects may have different positions in a liquid

*Weight determines if an object will sink or float (47%)

*Volume determines if an object will sink or float (55%)
16 50 Understanding that the volume of a liquid in a container does not affect the position of the object in the liquid and its floatation

*When the volume of a liquid in a container is increased, the volume of the sinking part of an object will decrease (15%)

*When the volume of a liquid in a container is increased, the volume of the sinking part of an object will increase, too (19%)

* When the volume of a liquid in a container is decreased, a floating object will sink (13%)
17 31 Understanding the reasons why objects at the same volume may have different positions in a liquid

*The volume of a liquid in a container determines whether an object sinks or floats (69%)

*Objects which have a hole will sink in the course of time because the liquid fills the hole (51%)
18 62 Interpretation of the last positions of two objects in a liquid when they are tied together by regarding their earlier positions in the liquid *No interpretation of the position of objects, which are tied to each other, in a liquid by considering their earlier positions in the liquid (38%)
19 58 Interpretation of the densities of new objects which are formed by sticking an object on another object with regard to their positions in a liquid *Objects which are covered by the liquid have always the same density (23%)
20 47 Identification of the positions of the pieces of the object in the liquid when a floating object is cut into parts of different sizes

*When a floating object is cut into two parts, the volume of the smaller sinking part will become less (53%)

*When a floating object is cut into two parts, the bigger piece will sink or the volume of the sinking part will increase (51%)

*In some of the test items (e.g. items 2, 8, 9, 10), total percentages may not be %100 because two or more choices include the same misconception. Therefore, in grouping misconceptions and calculating their percentages, the choices of the test items were used more than once.

It was found that students had difficulties in understanding the concept of density. It was very clear from the students’ responses to test items 3, 11, 12 and 14 (see Table 2) that the students could not understand it and thus, had some misconceptions. For example, more than 38% of students had difficulties in describing density and also definitions of densities of different objects. In addition to this, some students did not consider the density of the liquid when determining whether an object would sink or float (see items 8, 9 and 13 in Table 2). The percentages of the students whose choices were wrong for these items were 41%, 65% and 65% respectively.

Students’ responses to items 4, 6 and 19 showed that they could not compare the density of different objects by regarding their positions in a liquid (see Table 2). The percentages of the students whose choices include misconceptions in this area were 59%, 56% and 42% respectively. The most common misconception held by the students in this area was that the density of an object hanging in a liquid is equal to that of a floating object or a sinking object. Moreover, some students made an incorrect connection between densities of the objects and their position in the liquid.

Another misconception revealed from the students’ responses to the test items 3, 5, 6, 9 and 10 was that the students did not have a sound understanding of buoyancy. For example some students reported that the buoyancy of an object hanging in a liquid is more than the weight of the liquid overflowing. In addition, some students had the misconception that when two objects are put into a liquid, the buoyancy of the object hanging in the liquid is more than that of the floating object. In other words, students cannot make the connection between the volume of the sinking part of an object and its buoyancy.

It was revealed from the students’ responses to test items 8 and 17 that found that some students believe that objects with holes will sink in the course of time, because the liquid fills the hole. This misconception was revealed from the students’ responses to items 8 and 17 (41% and 51% respectively).

Students’ responses to item 20 showed that some students could not identify the positions of the pieces in a liquid when a floating object is cut into parts of different size. Some students (53%) indicated that when a floating object is cut into two parts, the volume of the sinking part of the smaller piece will become less. Furthermore, 51% of them also reported that when a floating object is cut into two parts, the bigger piece will sink or the volume of the sinking part will increase.

 

Copyright (C) 2005 HKIEd APFSLT. Volume 6, Issue 1, Article 3 (June, 2005). All Rights Reserved.