A qualitative research of the conceptual learning process of the heat concept http://www.ied.edu.hk/apfslt/v17

Ekin's ideas about heat frequently changed throughout the process. Although she asserted the idea that heat is not stored in matter in the first interview, some of her statements asserted the opposite. Considering the idea of "heat loss", which is mentioned especially in basic physics courses and secondary education curriculum, and also mentioned by Ekin during interviews as well, it was found that she actually thought that matter stored heat. In reality, Ekin considered heat as a type of energy which can be stored, however, she didn't realize this in the first place. The misconception that matter stores heat is quite common. This misconception was observed in some previous studies as well (Jara-Guerrero, 1993).

The fact that some say the equation Q = m.c.∆T does not give heat, but "heat change" supports this. In reality, Ekin thought that heat was a type of energy stored in matter, the quantity of this energy changed through heat transfer, this change was calculated with the equation given above, in other words, the final heat minus the initial heat. This led to the idea that "∆T", the temperature difference, in the equation was "∆Q", the heat change. Here, Q = m.c.∆T is actually perceived as,

Q_final – Q_initial = ∆Q = m.c.T_final – m.c.T_initial = m.c. ∆T

Ekin thought that Q represented the total energy stored by the body of matter. In support of this, Ekin used this equation to calculate the heat stored by the body. She accepted the initial temperature as water's freezing temperature at 1 at pressure, 0°C. Kesidou and Duit (1993) found that students believed that temperature did not exist at 0°C. This finding is consistent with ours. However, when Ekin was reminded that not ∆Q, but Q is used in the equation, she suspected something was wrong, but her idea did not change at that moment.

Also, Ekin was sometimes influenced by the use of heat and temperature interchangeably because of misuses in everyday life. This may indicate that Ekin had difficulties with scientific thinking and mastering scientific concepts. Misconceptions involving the idea that heat and temperature are the same things are seen in the literature at every level (Arnold & Millar, 1996; Aydoğan et al., 2003; Başer, 2006; Erickson, 1980; Erickson & Tiberghien, 1985; Eryılmaz & Sürmeli, 2002; Harrison, 1996; Jara-Guerrero, 1993; Kesidou & Duit, 1993; Krajcik, 1991; Linn & Songer, 1988; Streveler et al., 2008). Jara-Guerrero (1993) observed that while students assert that heat and temperature are different concepts, they can still use them interchangeably. A similar situation can be seen here as well. Some studies show that this is due to misuses in everyday life (Driver, 1989; Campanario, 2002; Hameed et al. 1993; Harrison et al. 1999; Kolari & Savander-Ranne, 2000; Osborne & Freyberg, 1985; White, 1992). Because students hear many nouns, verbs, and adjectives related to heat and temperature (for example: heat, temperature, overheat, hot, cold, thermal, thermic, warm, freeze, warmth, to get hot, etc.) every day (Erickson & Tiberghien, 1985; Luera et al., 2005; Tiberghien, 1980). Thus, scientific terms may be confused with everyday uses.

In later weeks, Ekin described heat as a type of energy stored in matter. She even described it as the total energy arising from the motion of particles of matter. However, it is important that she emphasized the phenomenon of friction to when defining heat since the first week. It is believed that Ekin might have been influenced by frequently repeated misconceptions especially in secondary education institutions such as "the energy lost due to friction turns into heat". Because she frequently described heat as a type of energy arising from the friction caused by the vibration of particles due to their temperature. This idea is consistent with some studies on misconceptions in this area. In parallel with this finding, some studies show that students had the idea that the motion of particles is referred to as heat (Erickson, 1980; Kesidou & Duit, 1993).

Ekin had two main thoughts about heat which supported each other: "Heat is the total kinetic energy of particles" and "Heat occurs with friction due to collisions during vibration". One of these describe how heat occurs and the other described what heat is. Among the two, the idea that "heat is the total kinetic energy of particles" is close to the definition of thermal energy. The characteristic of the thermal energy concept is attributed to the heat concept and this led to the idea of heat change. Also, storage of heat was found to be related to this. The other idea may be a result of "energy lost during friction turns into heat" and "heat loss".

In the fourth week, Ekin stated that heat was not stored in matter and defined heat as the energy entered and left due to the temperature difference, which is not adequate but closer to scientific theories. This was observed in other studies as well (Taber, 2000). It can be said that the change in Ekin's ideas is a result of the information which she acquired in sessions with the PBL group. This change seems to have triggered many other changes. For example, the relationship between heat and other concepts and the thermal energy concept seem to have been the most highly affected ideas. It can also be said that this idea brought an end to the idea of "heat change". Summary of Ekin's main opinions for heat in time can be seen in Table II.

Table II. Summary of Ekin's main opinions for heat in the time

Week	What is Heat	How Emerges Heat?
1	A type of energy that sores in matter	Because of friction of particles
2	The total energy of matter's particles	Because of friction of particles
3	The total energy of matter's particles	Because of friction of particles
4	Transferred energy when there is not thermal equilibrium	If there is not thermal equilibrium
5	Transferred energy when there is not thermal equilibrium	If there is not thermal equilibrium

Although weaker in terms of dominance, the idea related to friction between particles was alive at this stage. It can be said that this idea was dependent on the definition of heat, while it also had independent components. Although one of the two heat-related misconceptions mentioned above, the idea that "heat is the total energy of particles", disappeared, the idea that "heat is the energy released due to friction", which was found to be connected with this, did not disappear completely. This made it necessary to address the idea that "heat is the energy released due to friction".

It can be said that this misconception is based on the idea that "the energy lost during friction turns into heat" and the idea of "heat loss". It is supported by Ekin's statements. There was also the idea that frictions become equal at the time of thermal equilibrium and differentiate when there is no thermal equilibrium. The fact that this idea lost its dominance when Ekin started to assert that there is a perfectly elastic collision between particles and the energy that is conversed explains this situation.

During the PBL process, she did not conduct any research on the concept of heat in first week. For this reason, at the end of the first week, she had her previous misconceptions about the concept of heat. While the second week, she began to examine the heat sources. She examined the geothermal energy more thoroughly. Therefore, she handled some information about the concepts of heat and thermal energy. The information she acquired led her to think that thermal energy and heat are the same concepts. She focused to examine geothermal energy. So, she thinks that there were a relationship between thermal energy and water. When she examined the concept of "heat loss" in the third week, she realized that her thought was not true and she changed her mind in the fourth week. The thoughts of "how energy emerges" and "what energy is" shaped to be in harmony.

During the PBL process, participants are only diverted by the teacher. Participants take responsibility for their own learning. They do this when solving the problem. For this reason, when solving the problem, the teacher has relatively less control over the progress of their research. It may not go in the right direction. The participant can reach conflicting and misleading conclusions initially, such as the case of Ekin. If they don't question the reliability of the information which they acquire, their research may lead to incorrect results.

Beginning in the first week, Ekin asserted that temperature is the reason behind heat's and thermal energy's existence. This might be due to the fact that Ekin understood temperature the best among these three concepts (heat, temperature and thermal energy). Although she is not able to define temperature precisely, she is able to describe what it is and what it is not. She also thinks that particles in the matter move and this is related to temperature. The fact that Ekin had the idea that heat is a type of energy stored in a matter because of particles and that she asserted thermal energy is related heat might be the reason why she made this association. Relationships between these three concepts remained this way until she managed to define the concepts of heat and thermal energy on a scientific basis. Streveler et al. (2003) stated that students do not understand the relationship between heat and energy and the relationship between temperature and energy. According to them, students' failure to make the connection lead to many misconceptions related to heat and temperature.

Throughout the process, Ekin never mentioned the relationship between temperature and thermal energy, E = 3(1⁄2.k.T). However, she mentioned the idea that "particles of hot matter are more active". The connection she made between the motion of particles and temperature and heat allowed her to make a similar connection between temperature and heat. She thought that heat is the total kinetic energy of particles and that temperature is an indicator related to the mean kinetic energy of particles. In other words, she made a connection between heat and temperature, which should have been made between thermal energy and temperature. This is especially evident in her idea that "the temperature does not change, but the heat increases when the matter's mass increases". In short, she confused the concepts of heat and thermal energy.

By changing her definition of heat in the fourth week, her idea about the relationship between heat and temperature changed as well. While at first, she made a connection between heat and temperature, which should have been made between temperature and thermal energy, and asserted that temperature is the source of heat, later she associated heat with "temperature difference". In other words, she asserted that there had to be a temperature difference to talk about heat. This is consistent with scientific theories.

In conceptual learning, some researchers think that some factors must change. Kalem et. al. (2002) think that some changes are needed in curricula and Leite (1999) thinks that some changes are needed in textbooks in order to teach heat and temperature concepts more effectively. But most of the researchers focus on conceptual changes and how much simplifications are needed for concepts to be learned.

Carlton (2000), in his paper; acknowledges the difficult nature of the concepts involved for most learners; points out that pupils are likely to come to lessons with their own alternative ideas in place; stresses the importance of making learners' existing ideas explicit, and using them as a starting point for constructing scientific understanding; attempts to tease out a level of presentation that is both simple enough for pupils to understand and adapt, and yet is scientifically valid. With Carlton, Taber (2000) would agree that it is sensible to teach about heat and temperature without introducing the complication of work done by changes in volume. This can be learned about later as an additional factor that does not fundamentally change the concepts of heat and temperature. However, he does not accept Carlton's approach to defining heat as the energy that has been transferred, and temperature as a measure of the concentration of heat energy. Although this leads to a simpler scheme, it also leads to logical inconsistency, and the potential for much confusion later.

During the interviews with Ekin, we examined her concept acquisition and imprinting process, as well as changes in her conceptual construct. One of the characteristics observed in Ekin was that while she provided some memorized information, she had not internalized the information in question. These were as if she memorized then as commonly used sayings. Sometimes these cliched statements such as "temperature is not a type of energy" worked, but more often than not these statements were not supported with any actual knowledge. Sometimes Ekin's answers could not go beyond being intuitive. Studies show that many students, similar to Ekin, have a readiness based on experience and intuition (Clough & Driver, 1985; Erickson, 1979; Erickson & Tiberghien, 1985; Rogan, 1988; Tiberghien, 1980). However, Ekin gave up her intuitive answers and memorized sayings, and adopted a more inquiring approach. The study conducted by Harrison et al. (1999) supports this idea. Results of their study show that students have increased responsibility for their own learning, are able to take mental risks, become more decisive in the solution of written and verbal problems, and learn how to criticize themselves throughout the process of a conceptual change.

Another characteristic observed in Ekin is that her conceptual knowledge was disconnected. Her memorized sayings and pieces of thought and information resembled independent isles. She had difficulty making connections, switching between pieces of information, and using a specific piece of knowledge in another situation. It is impossible for the student to understand the subject with this type of disconnected knowledge. This may be because she stored the information in her mind without internalizing and without associating them with her own experiences and everyday life. This prevents students from constructing their knowledge (Mäntylä, 2006).

Throughout the process, the researchers sensed that Ekin experienced flashbacks. While her idea on a certain subject seemed to have changed, she came back to her previous thoughts in the next interview. Although she made progress in general, it was in the form of a process of change with ups and downs. Also, similar to some other studies (Jara-Guerrero, 1993; Kesidou & Duit,1993; Lewis & Linn, 1994), it is found in this study that the student had certain misconceptions or incomplete information related to certain concepts. The fact that some misconceptions remained even after the PBL process shows that these misconceptions are more resistant to conceptual change (Carlton, 2000; Hewson & Hewson, 1991; Thomaz et al., 1995). According to Lewis and Linn (1994), even scientists may have such misconceptions. This is also supported by other studies (Leura, Otto, & Zewitz, 2005; Lewis & Linn, 1994).

Scientific theories define thermal energy and heat as different concepts. However, it is seen that these two concepts are sometimes used interchangeably by students. In order to prevent this misconception, the thermal energy concept should be given more emphasis in the curriculum. It may also be beneficial to teach it before the heat concept. Because students may have a gap in the total kinetic energy of particles. They can need to define it. If they don't know anything about thermal energy, they can define it as heat, the dimension of which is energy. Otherwise, this can allow students to understand the heat concept better and prevent certain misconceptions such as the idea that heat is a type of energy stored in matter. The relationships between temperature and thermal energy should be given in detail, beginning with the equation E = 3(1⁄2.k.T). Also, the temperature measured in Kelvin should be dwelt on more.

Particularly in physics courses, the idea that "the energy lost due to friction turns into heat" should be abandoned. It should suffice to say that the kinetic energy lost turns into another type of energy. However, insistently saying that it turns into heat makes it more difficult for students to understand the heat concept. A similar case applies to "heat loss" as well.

Misconceptions about heat may be related to misconceptions about other concepts. Misconceptions related to vibration, energy, momentum and general mechanical concepts may prevent students from understanding concepts related to heat and temperature. For this reason, eliminating misconceptions related to the former may be effective in eliminating misconceptions related to the latter.