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Asia-Pacific Forum
on Science Learning and Teaching, Volume 11, Issue 2, Article 14 (Dec., 2010) |
The results about gender differences are shown in Table 1.
Table 1. T-test results of the overall score of the students by gender
Gender
n
x̄
S
df
t
p
Male
124
12.66
3.77
147
1.958
0.052
Female
174
11.47
3.57
As shown in Table 1, overall scores of undergraduate students do not have a statistically meaningful difference according to gender (t(147)=1.958, p>0.05). Due to these results, male and female undergraduate students have a similar level of knowledge about traffic based environmental problems.
The students answers about the relationship of car exhaust gasses with environmental problems are summarized in Table 2, where f is the frequency.
Table 2. The questions about the effects of car exhaust on environmental problems
EXPRESSIONS
True
False
No idea
f
%
f
%
f
%
Vehicle exhaust increases global warming (making the greenhouse effect worse)
286
96.0
2
0.7
10
3.4
Vehicle exhaust causes more acid rain
246
82.6
3
0.2
50
16.8
Vehicle exhaust damages the ozone layer
268
89.9
14
4.7
16
5.4
The majority of the students correctly realized that car emissions contribute to the greenhouse effect (96%) and to acid rain (83%). However, the majority of the students (90%) erroneously thought that vehicles also endanger the ozone layer. In a similar study that was performed among trainee teachers, two thirds of the students erroneously thought that cars damage the ozone layer (Hillman et al., 1996).
Previous studies in different countries have shown that although students correctly linked vehicle emissions with greenhouse effect and acid rain, they also incorrectly associated cars with ozone layer depletion. This misconception was common for students of different grade levels, ages and genders (Boyes and Stanisstreet, 1993; Boyes and Stanisstreet, 1994; Boyes et al., 1995; Leeson et al., 1996, 1997; Batterham et al., 1996; Dove, 1996; Hillman, et al., 1996; Boyes and Stanisstreet, 1997; Dimitriou, 2001, 2002, 2003; Khalid, 2001; Daskolia et al., 2006).
Motor vehicles are the most predominant source of carbon monoxide (Fisher et al., 2002) and three-forths (75%) of the students realized that car exhaust emissions include carbon monoxide, which is an odorless gas formed as a result of incomplete combustion of carbon containing fuels, including petrol and diesel (Fisher et al., 2002). It is interesting that only two-fifths (40%) of the students understood that cars emit carbon dioxide. Cars were considered a source of nitrogen oxide by relatively fewer (17%) students, but in fact motor vehicles are usually the major source of nitrogen oxides (Fisher et al., 2002). More than a third (34%) thought that car exhausts contain sulphur dioxide. In reality, although cars do emit some sulphur dioxide, exhaust emissions are responsible for only a small proportion of the atmospheric load of sulphur dioxide (Hillman et al., 1996; Boyes and Stanisstreet, 1997). In fact, car exhaust does contain water vapor, however only a quarter of students agreed with this idea. 44% of the students evaluated acid vapor as a component of vehicle exhaust emissions. As might be expected, most of the students (84%) realized that car exhaust produces heat. On the other hand, about a third (31%) of the students erroneously thought that cars emit chlorofluorocarbon gases (CFCs). Many of the students (56%) responded in the “do not know” category here; and less than a seventh (13%) strongly rejected this idea.
Most of the students (80%) understood that carbon monoxide makes the greenhouse effect worse. 69% of them knew that carbon dioxide contributes to global warming. Only, 38% of the students realized that nitrogen oxide is responsible for global warming. More than half (52%) erroneously thought that sulphur dioxide causes the greenhouse effect. A similar proportion (53%) saw CFCs as a greenhouse gas. Almost half of the students (48%) based their answer on the erroneous idea that heat from car exhaust contributes to the greenhouse effect. More than two-third (69%) of the students considered acid vapor a cause of global warming.
Few (17%) saw water vapor as a factor for increasing the greenhouse effect. According to Hillman et al. (1996) and Boyes and Stanisstreet (1997), “it might be the reason that students imagine water as something which is 'clean' or even 'pure' and so an unlikely candidate for a 'pollutant'. In fact, water vapor does contribute to the greenhouse effect, although the water vapor in the atmosphere originating from vehicle exhausts forms only a small proportion of that in the atmosphere compared with that provided by evaporation of the oceans and other surface water.”
Three-fourths (76%) of the students erroneously held the idea that carbon monoxide is responsible for acid rain. More than half (55%) saw carbon dioxide as a factor for more acid rain. Nearly half of the students (48%) thought that CFCs cause acid rain. Although only less than a tenth (9%) saw water vapor as a cause of acid rain, most (79%) imagined that acid vapor contributes to acid rain. About a quarter (23%) of the students thought that heat causes acid rain. Half (50%) of the students knew that sulphur dioxide contributes to acid rain and a third (%35) held the idea that nitrogen oxide is factor for acid rain.
The results showed that the majority of the total sample of the students (79%) erroneously thought that carbon monoxide damages the ozone layer. 57% of the students saw carbon dioxide as a factor of ozone layer damage. More than half (52%) believed that sulphur dioxide damages the ozone layer. Data about erroneous ideas on the factors of ozone layer damage breaks down to: 35% for nitrogen oxide, 9% for water vapor, 73% for acid vapor and 32% for heat. More than half (56%) of the students knew that CFCs contribute to ozone layer destruction.
The detailed answers of the students were presented in Table 3 (components of car exhaust emissions) and Table 4 (the relationship between gasses and global environmental problems).
Table 3. Questions about components of car exhaust emissions
EXPRESSIONS
True
False
No idea
f
%
f
%
f
%
Car exhaust emits carbon monoxide (CO)
222
74.5
28
9.4
48
16.1
Car exhaust emits carbon dioxide (CO2)
118
39.6
110
36.9
70
23.5
Car exhaust emits chlorofluorocarbons (CFCs)
92
30.9
40
13.4
166
55.7
Car exhaust emits sulphur dioxide (SO2)
112
34.2
28
9.4
168
56.4
Car exhaust emits nitrogen oxide
50
16.8
54
18.1
184
65.1
Car exhaust emitst water vapor
76
25.5
112
34.2
120
40.3
Car exhaust emits acid vapor (acid gases)
130
43.6
46
15.4
122
40.9
Car exhaust emits heat
250
83.9
14
4.7
34
11.4
Table 4. Questions about the relationship between gasses and the environmental problems
EXPRESSIONS
True
False
No idea
f
%
f
%
f
%
Carbon monoxide gases increase global warming
238
79.9
12
4.0
48
16.1
Carbon monoxide gases cause more acid rain
226
75.8
22
7.4
50
16.8
Carbon monoxide gases damage the ozone layer
234
78.5
12
4.0
52
17.4
Carbon dioxide gases increase global warming
206
69.1
40
13.4
52
17.4
Carbon dioxide gases cause more acid rain
164
55.0
58
19.5
76
25.5
Carbon dioxide gases damage the ozone layer
170
57.0
78
26.2
50
16.8
CFC gases increase global warming
158
53.0
12
4.0
128
43.0
CFC gases cause more acid rain
144
48.3
14
4.7
140
47.0
CFC gases damage the ozone layer
168
56.4
16
5.4
114
38.3
Sulphur dioxide gases increase global warming
154
51.7
16
5.4
128
43.0
Sulphur dioxide gases cause more acid rain
148
49.7
22
7.4
128
43.0
Sulphur dioxide gases damage the ozone layer
156
52.3
24
8.1
118
39.6
Nitrogen oxide gases increase global warming
114
38.3
16
5.4
168
56.4
Nitrogen oxide gases cause more acid rain
104
34.9
16
5.4
178
59.7
Nitrogen oxide gases damage the ozone layer
104
34.9
28
9.4
166
55.7
Water vapor increases global warming
52
17.4
196
65.8
50
16.8
Water vapor causes more acid rain
28
9.4
210
70.5
60
20.1
Water vapor damages the ozone layer
28
9.4
204
68.5
66
22.1
Acid vapor increases global warming
206
69.1
26
8.7
66
22.1
Acid vapor causes more acid rain
234
78.5
10
3.4
54
18.1
Acid vapor damages the ozone layer
218
73.2
26
8.7
54
18.1
Heat increases global warming
144
48.3
66
22.1
88
29.5
Heat causes more acid rain
68
22.8
104
34.9
126
42.3
Heat damages the ozone layer
96
32.2
92
30.9
110
36.9
It is interesting that, in addition to the common misconceptions, some of the trainee teachers made logical errors that seem to be based on poor understanding of gases and their environmental effects. The misconceptions and paradoxical ideas (logical errors) of the students are summarized as follows:
Misconceptions about global warming:
A quarter of the students who saw cars a source of global warming accepted that this might happen via CFCs. Although CFCs make the greenhouse effect worse, cars do not emit CFCs. The same proportion of students thought that cars contribute to global warming via sulphur dioxide. In reality, sulphur dioxide from car exhaust is a small proportion of the total atmospheric load, and sulphur dioxide is not a greenhouse gas.
The major misconception, held by more than two-fifths of the students who realized that cars increase global warming, is that heat from car exhaust causes the greenhouse effect. In the previous research, similar misconception were found (Hillman et al., 1996; Boyes and Stanisstreet, 1997).
Logical errors about global warming:
4% of the students had a logical error specified by the following route (I? II? III);
(I) Cars give out sulphur dioxide; (II) Sulphur dioxide contributes to global warming; (III) Cars do not contribute to global warming.
Misconceptions about acid rain:
Half (52%) erroneously thought that CO from car exhaust causes acid rain. A quarter (23%) accepted that cars cause acid rain via carbon dioxide. A third (30%) of the students held the idea that acid vapor, which is emitted by cars, cause acid rain. Only a few (7%) thought that cars cause acid rain by emitting water vapor. A small number (14%) imagined that heat from car exhaust causes acid rain. A fifth (%20) of the students erroneously held the idea that cars contribute to acid rain by emitting CFCs.
Logical errors about acid rain:
4% of the students had a logical error specified by the following route (I? II? III);
(I) Cars emit heat; (II) Heat causes acid rain; (III) Cars don’t cause acid rain.8% of the students had a logical error specified by the following route (I? II? III);
(I) Cars emit carbon monoxide; (II) Carbon monoxide causes acid rain; (III) Cars don’t cause acid rain.4% of the students had a logical error specified by the following route (I? II? III);
(I) Cars emit CFCs; (II) CFCs cause acid rain; (III) Cars don’t cause acid rain.5% of the students had a logical error specified by the following route (I? II? III);
(I) Cars emit acid vapor; (II) Acid vapor causes acid rain; (III) Cars don’t cause acid rain.Misconceptions about the ozone layer:
The majority of the students held the erroneous view that car exhaust damages the ozone layer. The dominant idea (61%) appeared to be that carbon monoxide from car exhaust is responsible for ozone layer damage. More than a quarter (28%) accepted the idea that carbon dioxide from car exhaust causes ozone layer damage. A fifth of the students (21%) saw sulphur dioxide from car exhaust as a factor of ozone layer damage. Only 13% thought that cars damage the ozone layer via nitrogen oxide. Few (4%) imagined that water vapor from car exhaust damages the ozone layer. A third (34%) accepted the acid vapor route (cars→acid vapor→ozone layer damage). A quarter believed that cars damage the ozone layer by giving out heat.
Logical errors about the ozone layer:
3% of the students had a logical error specified by the following route (I? II? III);
(I) Cars emit heat; (II) Heat damages the ozone layer; (III) Cars don’t damage the ozone layer.4% of the students had a logical error specified by the following route (I? II? III);
(I) Cars emit carbon monoxide; (II) Carbon monoxide damages the ozone layer; (III) Cars don’t damage the ozone layer.3% of the students had a logical error specified by the following route (I? II? III);
(I) Cars emit CFCs; (II) CFCs damage the ozone layer; (III) Cars don’t damage the ozone layer.2% of the students had a logical error by the following route (I? II? III);
(I) Cars give out acid vapor; (II) Acid vapor damages the ozone layer; (III) Cars don’t damage the ozone layer.The limitation of this study is that, as in most of the similar studies, the results obtained from the present study cannot be generalized to a large population because of the small sample of students. Also, the results, which are based only on a questionnaire, cannot enable the researchers to deeply understand the students' perceptions. Air pollution is a problem that irritates society. There are different attitudes in the world to cope with this problem that integrate principles of sustainable development.
