Energy is releases from there, that's mean barium thiocyanate is much stable than barium hydroxide. That's why energy dropped. Why it is dropped in such large ...
Background 2
Students’ understanding about natural phenomena frequently inconsistent with what the scientific community understands and the intended learning outcomes of chemistry programmes summarized in substantive literature (e.g. Barke, Al Hazari, & Yitbarek, 2009; Barker, 2000; Garnett, Garnett, and Hackling,1995) unable to differentiate between chemical reactions and physical change fail to recognize the conservation of mass chemical reactions as transmutational processes
Background 3
“if science education is to provide more than simple knowledge of science content, that is, of specific facts and laws of science, then it must elicit how students acquire and use mental models to think of the physical world and how these models evolve with age” (Borges & Gilbert, 1999, p. 99) Studies of students’ mental model may offer a better understanding of students’ alternative conceptions (Franco et al., 1999)
Model and Mental Model 4
Research Purpose 5
To explore the nature and types of students’ mental models about chemical reactions Research questions
What are different types of students’ mental models of chemical reactions? In what way are these mental models are different to each other?
Research Method 6
Cross-age study carried out for the data collection 67 participants were interviewed – 36 secondary school students (Form 1, 4 and 6) and 31 university students (1st and 4th year) in Malaysia Interview-about-Instances (IAI) (Gilbert, Watts & Osborne, 1985) Also involve sketching
The IAI
P
Conservation of mass Process of chemical reaction
P
P P
Chromate-dichromate equilibrium
P
An endothermic reaction
Dissolution of salt and sugar
Notion of chemical reaction
Combustion
Ice melting
P
Focus topics
Zinc-acid reaction
Rusting
Chemical Phenomena
Lead iodide precipitation
7
P
Energy change in chemical reaction
P
P
Spontaneity
P
P
Reversibility
P
P
P
The chemical phenomena 8
Salt
Metal corroding
Ice turning to water
Sugar
Water Mixing sugar and salt together into a glass of water
Analysis of data 9
The interviews were transcribed, participants validated and translated The data is coded and assembled according into inventories (based on Erickson,1979) Thematic coding by comparing data to find similarities and differences
Distribution of the mental models 10
Category A1
A2
A3
A4
A5
B1
B2
C1
C2
C3
Total
Student n
%
n
%
n
%
n
%
n
%
n
%
n
%
n
%
n
%
n
%
Senior University
0
0
0
0
0
0
0
0
0
0
5
29
0
0
4
24
1
6
7
41
17
Junior University
0
0
0
0
1
7
0
0
0
0
0
0
3
21
3
21
3
21
4
29
14
Form 6
0
0
0
0
1
8
0
0
0
0
4
33
2
17
3
25
0
0
2
17
12
Form 4
2
17
3
25
5
42
1
8
0
0
1
8
0
0
0
0
0
0
0
0
12
Form 1
1
8
1
8
5
42
4
33
1
8
0
0
0
0
0
0
0
0
0
0
12
Total
3
5
4
6
13
19
5
8
1
2
9
13
5
8
10
15
4
6
13
19
67
Mental Model Type A 11
Response of chemical substances towards other chemical substances or other agents “We know that chemicals [like metal] interacts with our surroundings. There is something causes it to happen.”(SO040)
Does not include kinetic theory of particles nor chemical bonding explanation The explanation of energy change in chemical reaction based on the heat gain or loss “it has heat energy” (SF053); “when you heat a substance, and leave it at room temperature, the heat will be absorb to surroundings.” (SO033 )
Mental Model Type B 12
As response of chemical reaction towards reacting agents that forms new substances Involve rearrangement of atoms in forming the new substances “When zinc is mixed with the HCl, chlorine will react with the zinc. The bond will be broken. There are two chlorine so it is easier to react. Zinc can hold two. Hydrogen turns into ions, but doesn’t exist in single atom. H plus with H plus will become one hydrogen molecule.” (UF008)
Mental Model Type C 13
Integration between kinetic theory of particles and chemical bonding I imagine zinc as simple sphere, and hydrogen chloride as another sets sphere. So these two [Zn and HCl], will undergo collision, and meantime transfer of electrons will occur. So, hydrogen will transfer two of these, transfers over electron from zinc. Zinc donate electrons, there by forcing H become H plus. Cl minus to recombine with zinc, to form zinc chloride. (SS030)
Mental Model Type C 14
Energy change based on the net energy transfer happened in bond breaking and formation The bonds formed after oxidation is stronger than those there are presence in butane. Therefore, the heat required to be absorb for reaction to occur is less than heat release due to the formation of the new bonds. … this energy is absorbed, use to break the bond and initiate reaction with butane. As time progresses, this energy used up, and this energy become negative energy, as is released due to bond formation. (SS030)
Mental Model Type C 15
Mental Model Subtype C2 when confronted with the endothermic reaction failed to apply the net energy but thinking energy looses to the surrounding. “This process is also an exothermic reaction. So, once the reaction occurs, it will release the energy to the surrounding and it becomes very cold. Because it has already looses the energy to the surroundings. It releases heat to the surroundings. Therefore the energy content become lesser and also become cold.” (UF016)
Mental Model Type C 16
Stability as the driving force of the reaction Energy is releases from there, that’s mean barium thiocyanate is much stable than barium hydroxide. That’s why energy dropped. Why it is dropped in such large scale is because barium thiocyanate, from these process we can see the barium thiocyanate is stable, and we know that ammonia and water are both stable. That’s why when they formed, a much stable product, just like combustion they form much stable product, they release much energy to the surroundings, that’s why it itself is in negative temperature. (UO064)
Conclusion 17
Chemical bonding as ‘enabling’ model for understanding of the chemical phenomena in term of rearrangement of atoms and energy change Students’ mental models seem to be developing from causality oriented models towards teleological oriented model Models of energy as ‘threshold model’ for students to be able to a fully understanding of chemical reactions as change of matter and energy
Thank you Questions or comments?
