Heat is difficult for students to understand because it is abstract and counterintuitive resulting in misconceptions. The term heat is used in everyday life, but meanings of this term vary with the situation. Adjectives like flow, flowing, moves, moving and transfer are used causing confusion of what heat really is and how it moves or is transferred. In the context of these complexities it should not be surprising that heat transfer is an abstract confusing term to students. Through misconceptions students develop, learning of concepts associated with heat is adversely affected. This study sought to find out ways in which learner preconceptions and misconceptions on heat can be reconciled with scientific form. The study used a qualitative approach employing desk research design. Text analysis of various articles and interpretation was done to understand and explore issues related to the research problem. Articles and documents used in the study were purposively sampled, based on the researcher’s understanding of the research problem and data relevant to the purpose of the study. Findings show that science instruction should assist students to recognise and understand the functional appropriateness of personal knowledge in certain scientific contexts. Different representations of knowledge in heat transfer should be identified and clarified. It is of great importance to clarify relations and meanings of these representations to assist students to understand their own and scientific ideas.

Keywords: Heat, preconceptions, heat transfer, misconceptions

Heat is a difficult concept for students to understand because it is abstract and counterintuitive, resulting in misconceptions.¹ The term heat is used in everyday life, but meanings of this term vary with the situation. Heat is a confusing and controversial scientific term as illustrated in the history of science. For instance, early scientists conceived heat as a basic quality of a body. Later it was thought of as a kind of fluid material.² In the context of these complexities it should not be surprising that heat transfer is an abstract confusing term. This may affect learning concepts associated with heat. Abundant research evidence shows that students begin to learn science when they already have knowledge which differs with intended scientific information, yet this knowledge makes sense to them (students) [2;3]. This knowledge is called preconceptions. Alternatively, preconceptions are referred to as preconceived notions, misconceptions, non-scientific beliefs, naive theories, mixed conceptions, or conceptual misunderstandings. In science misconceptions are what a person knows and believes, which mismatches what is known to be scientifically correct. It is noted that teaching and learning of heat is associated with misconceptions, hence is an appropriate area for research [4;28].

Research in science education focuses on ways in which these student preconceptions can be reconciled with scientific form. In this context the questions to ask are: What is that thing called heat from its historical and current representation? What are the implications of diverse representations of heat transfer for school science introduction? The purpose of this study was to answer these questions.

The study used a qualitative approach employing desk research design. Text analysis of various articles and interpretation was done to understand and explore issues related to the research problem. Articles and documents used in the study were purposively sampled, based on the researcher’s understanding of the research problem and data relevant to the purpose of the study. Desk research sources included scientific journals, books, research reports, policy documents, conferences proceedings as well as theses and dissertations. To ensure validity of findings, credible sources were used. There were no date restrictions on literature search to enable wide identification of key elements related to the research problem.⁵

Historical representations of heat transfer

Analysis of literature shows that cooling of a hot body and heating of a cold body happen simultaneously as parts of the same phenomenon, and this phenomenon is described as the passage of heat from the hot to the cold body. Then, heat is something which may be transferred from one body to another, thereby reducing the quantity of heat in the first body, while increasing that in the second body by same amount. When heat is transferred to a body the temperature of the body increases, and sometimes other effects are produced like change of state from solid to liquid.⁶ Heat may pass out of one body into another just as water can poured from one vessel into another, or it may be retained in a body, just as water may be kept in a vessel. Therefore heat is referred to as a measurable quantity. However, heat is not a substance since it can be transformed into something which is mechanical work, and neither heat nor a substance. Some of the caloric properties proved inconsistent with nature. For instance, caloric was considered to have weight, and neither be created nor be destroyed. However, the most important feature was that heat flowed from hot bodies to cold bodies,⁷ as discussed below in relation with the caloric theory.

Caloric theory of heat

In the eighteenth and early nineteenth centuries, scientists imagined that all bodies contained an invisible fluid which they called caloric, which was assigned a variety of properties. Introduction of the word caloric, signified heat as a measurable quantity. The theory proposed that heat was an invisible self-repellent fluid called “caloric” that flowed from hotter to colder bodies through their pores. Being invisible, with its property of becoming fixed in solid bodies, caloric resembled gases. However, it differed with gases in that its weight could not be detected, even by finest balance.⁶ The theory suggested that when an object was heated, it absorbed caloric and released caloric when cooled. Changes in volumes and temperatures of gases when heated or cooled, and melting or freezing of substance were explained using the caloric theory of heat. However, when experiments became more sophisticated, flaws of the theory became clear by its failure to explain observed phenomena.⁸

Caloric theory of heat is now long forgotten and rarely mentioned, except as an example of primeval ignorance. However, in addition to other scientific knowledge, the caloric theory helps to show how complex the concept of heat is on both its development and understanding.⁹ All science of heat is founded on thermometry and calorimetry. Calorimetry is the measurement of heat, while thermometry is method of construction and using thermometers or measurement of temperature. Temperature of a body is a quantity which indicates how hot or how cold a body is. When a body has a higher or lower temperature than another, it means it is hotter or colder than the second body. Temperature of any body is measured by a thermometer. Measurer of warmth or thermometer and the method of constructing and using thermometers is thermometry. Heat is measured by a calorimeter. The instrument for heat measurement was named so, probably because it was invented at a time when heat was called caloric.

Diffusion of heat and heat transfer

Diffusion of heat is the process by which heat is transferred from one body to another. Invariably, diffusion of heat transfers heat from a hot body to a cold one. The process goes on till bodies are brought to the same temperature. The word diffusion suggests a fluid, implying a gas or liquid or particles of substance spreading through a liquid or space. The passage of heat in and out of the body takes place by diffusion, always from a hotter body to a colder one.⁶ Three processes of diffusion of heat are conduction, convention and radiation. The flow of heat through an unequally heated body, from places of higher to places of lower temperatures is conduction. Motion of the hot fluid carrying heat with it is called convection. In this case heat is neither flowing nor moving, but it’s being carried, implying it to be passive. Convection applies to diffusion of heat as a result of motion of the hot fluid from a region of higher temperature to region of lower temperature. As for radiation, heat is transferred as waves.⁶

Success and ultimate failure of the caloric theory

According to⁸ the caloric theory, as an important scientific idea led to several key successes which are:

1. Provision of a framework for understanding and explaining phase transitions like melting and boiling into gases. When a solid was heated, according to the caloric theory, it absorbed caloric and eventually reached a point where it could melt into a liquid. Similarly, when a liquid was heated it reached a point where it could boil into a gas. This explained the reversibility of these processes by cooling and releasing caloric.
2. The development of the concept of specific heat which is a measure of the amount of heat required to raise the temperature of a substance by 1K was developed, based on caloric theory, and
3. Prediction of temperature changes that would occur during chemical reactions was possible through understanding that the caloric would be released or absorbed during the reaction. The reaction could be determined to be exothermic (releasing heat) or endothermic (absorbing heat).

While the caloric theory was successful in explaining certain phenomena, failures which led to its abandonment in favour of the kinetic theory of heat,⁸ are:

1. Inability of the caloric theory to explain why gases had had different specific heats with solids and liquids.
2. Inability to explain heat transfer from one object to another by not clarifying the mechanism by which heat was transferred. The caloric theory only proposed that caloric was a fluid-like substance that flowed from hotter to colder bodies.
3. Failure to explain the relationship between mechanical work and heat. Experiments showed that mechanical work could be converted into heat and vice versa.⁸

Current representations of heat transfer

The kinetic theory of heat replaced the caloric theory on scientific explanation of heat in the 19^th century. Motion of atoms and molecules in a substance were said to result in heat. Experimental evidence supported this. The kinetic theory of heat is today widely accepted forming the basis for understanding of thermodynamics and heat transfer. Conceptualisation of heat as something that flows is still acceptable even today. For instance¹⁰ posit that heat flows from a body with high temperature to a body with low temperature. Like in the past⁶ three processes of diffusion of heat are conduction, convention and radiation. These three processes are discussed below.

Heat is transferred due to temperature differences in a medium or media [19;5;20;21]. Transfer of heat in a continuous substance without observable motion of matter is called conduction. Therefore conduction is transmission of energy by molecular or atomic motion. During conduction heat is transferred through vibration without atoms or molecules leaving their original position. Heat transfer by conduction requires a temperature gradient, so that heat energy transfer by conduction occurs in the direction of decreasing temperature. Conduction also occurs when electrons move from one atom to another. Heat transfer and fluid flow are related. If a macroscopic particle of a fluid moves from a hot region to a cold it carries a definite amount of heat (enthalpy), and such flow of heat is called convection. Thermal energy can be transferred between two or more fluids in contact at different temperatures.¹¹ Convection can either be natural of forced. With natural convection, fluid particles move due to buoyancy forces generated by density difference of heated and colder region of the fluid. Transfer of heat through convection occurs by movement of collective masses of atoms and molecules, hence a fluid is needed for heat transfer. During convection, actual material particles flow, whereas during conduction heat is transferred through vibration without atoms or molecules leaving their original position.

Transfer of heat through radiation occurs through electromagnetic waves which can pass through empty space / vacuum travelling at the velocity of light. Photons present in electromagnetic waves transfer heat. Atoms and molecules in heated substances move randomly emitting electromagnetic waves which carry heat to be transferred. Stephen-Boltzman Law govern the radiant heat transferred. The law says that at all temperatures above the absolute zero, a body radiates heat, irrespective of the ambient temperature.¹¹

Implications of misconceptions on heat transfer for teaching and learning

Use of phrases like:

1. Heat is a flow of energy, suggests movement of a body of fluid.
2. Heat as transfer of energy suggests heat to be passive in nature, being carried from one point / place to another.
3. Heat as movement of energy suggests heat to be a solid / body, having the ability to be mobile, that is moves on its own.

These different representations of heat transfer confuse novices in physics. Then how best can these novices be assisted to understand various conceptualisations, in relation to heat transfer?

Causes of misconceptions include students' everyday life experiences out of the classroom, including using words and specific terms in a non-scientific context.¹² Notes that scientific terms are used in different contexts, because these terms have shifted their meaning during the historical development, becoming also a possible cause of students' misconception in science.¹³

Identifies causes of students’ misconceptions as:

1. Presumed ideas which are models students formed even before they encounter a scientific concept.
2. Language and metaphors which arise from students’ daily engagements and conversation with peers gives rise to many students’ alternative concepts about a particular phenomenon. The meaning of word or phrase in daily dialect may mean something else in scientific language.¹³
3. Conceptual difficulties are challenges in understanding which arise when concepts are not directly agreeable to experience. Lack of understanding the limitations of using a concept or a law may cause over-generalisation resulting in misconceptions.
4. Teacher driven factors which include failure to give students an overview of the topic necessary for understanding and drilling for passing examinations may cause students misconceptions.¹³

To address the problem of misconceptions in physics learning, Erman (2017) suggests that educators should identify students' misconceptions before teaching any concepts and fundamentally facilitate effective communication to correct any misconceptions held by students. While heat is said to be transferred by,¹⁴ some researchers¹⁰ describe heat as flowing of energy from one place to another, suggesting fluid behaviour. Other researchers [8;11] say heat moves, suggesting that it possesses kinetic energy.³⁰ The title “Principle of Heat Flow In Fluids” of the presentation made by,²⁹ suggests that heat is a fluid which can flow, also supporting possession of kinetic energy by heat. These different ways of expressing heat transfer may develop misconceptions especially among novice physics learners.

Children are exposed every day to the colloquial term “heat” as a noun and its related forms as a verb, adverb, and adjective, resulting in confusion due to multiple forms in which the term is used. In addition, words like flow, flowing, moves, moving and transfer are used causing more confusion of what heat really is and how it moves or is transferred. Conceptual frameworks of children develop from their daily experiences, and change as they mature. However, more often than not, intuitive understanding of the world by children is at variance with scientific concepts explanations. When planning instruction it is important to understand how these naïve conceptions differ with scientific explanation and why children construct these ideas. It is therefore important that teachers identify students’ current conceptions through diagnostic assessment and plan instruction accordingly. Development of complex concepts in physics occurs in small steps and missing steps make correct explanation illusive, hence unattainable. To achieve necessary heat transfer concept development in students, instruction should be high quality age appropriate. Constructivist approaches to teaching and learning Physics using existing students’ ideas as explicit starting point for new learning, are recommended.⁴

Pre-service science teachers were found in a study by³ to have insufficient knowledge on heat energy. The pre-service science teachers had the misconception that a container deemed best to keep water warm, would not be the best container to keep ice cream cold.³ Informs that misconceptions of pre-service science teachers can be reconciled using the ED³U Conceptual Change Model,¹⁵ integrated with conditions for accommodations for the designed instruction and discussions.¹⁶ In addition,³ posits that analogies and daily life experiences can be used to help pre-service science teachers to understand concepts. Pre-service teachers science misconceptions can be reconciled through discussions with classmates. The ED³U Conceptual Change Model is represented as:

ED3U = Explore + Diagnose + Design + Discuss +Use

NB: The superscript 3 represents 3 Ds for words Diagnose, Design and Discuss respectively in the model

The model comprises five phases, in which a process can move forward or backward depending on the perceptions and understanding of students. In the first phase students explore phenomenon freely using hands-on activities, class discussions, and write ups. These activities together enable teachers to diagnose students’ individual understanding and prior knowledge towards a phenomenon. This is critical to allow teachers to understand how students perceive concepts. Appropriate strategies are designed by the teacher, then discussed with students, and lastly used to promote understanding, hence clearing misconceptions

Heat and temperature are concepts not observable, but directly related to the physical environment of living organisms, materials and objects. Therefore concepts about heat and temperature developed by students emanate from interpretation of ideas the students gain from life experiences, which include culture and language. Also textbooks and other reading materials contribute to students’ alternative conceptions on heat and temperature.⁴ At school level in a class, information gathered through diagnoses should be used by teachers to design hands-on activities, which are subsequently given to students to challenge their current knowledge. In the end students will understand concepts as intended, since their prior knowledge will have been reconciled with the expected knowledge understanding.

Prior knowledge influences how student learn by providing the context in which concepts are understood.¹⁷ Therefore when children come to school, these preconceptions and multiple uses of various words, may inhibit understanding of concepts related to heat.² What should then be the representations of thermal concepts of heat transfer in science instruction to mitigate challenges which may arise due to preconceptions on heat transfer? Students hold many intuitive ideas about heat and temperature, and these intuitive ideas do not easily change.² Therefore science instruction should assist students to recognise and understand the functional appropriateness of personal knowledge in certain scientific contexts. Different representations of knowledge on heat transfer should be identified and clarified. It is of great importance to clarify relations and meanings of these representations, to assist students to understand their own and scientific ideas.

 ¹⁸posit that heat transfer is one of the physics topics difficult to understand, but arguing that the demonstration method is effective in facilitating learning of this topic. Some researchers [22;23;24], aver that innovative strategies to facilitate learning can minimise misconceptions about heat transfer. Demonstration method can be used innovatively for easy conceptual understanding of heat transfer by secondary school learners. As a teaching approach if used innovatively, demonstration communicates an idea concretely through visual aids like flip charts, posters, powerpoint, and scientific apparatus. ²⁵posit that teachers do not only demonstrate, but participate in the learning process which motivates learners, hence enhancing understanding.

Misconceptions should be taken as stepping stones to facilitate learning, rather than obstacles which should be removed for learning to take place.²⁶ Consistent with this, science educators at higher education level and science teachers at secondary school level, should pay attention to the effects of misconceptions on understanding of concepts.²⁷ When the learner’s prior knowledge required for processing new information is not articulated due to poor bridging, it results in poor reasoning, hence misconceptions arise. For instance, daily use of the words move, transfer, follow, liquid and fluid have resulted in misconceptions of understanding some physics concepts associated with heat. Consequently, students' prior knowledge is an essential factor in successful transitional learning to develop correct scientific concepts.

Prior knowledge can facilitate learning by providing students an interpretive basis of phenomena. Similarly prior knowledge can inhibit learning through destructive interference. Consistent with this, science educators at higher education level and science teachers at secondary school level, should pay attention to the effects of misconceptions on understanding of concepts. Non-scientific thoughts held by students about a specific concept are called misconceptions. At school level in a class, information gathered through diagnoses should be used by teachers to design hands-on activities which are subsequently given to students to challenge their current or limited knowledge. In the end students will understand concepts as intended, since their prior knowledge will have been reconciled with the expected knowledge understanding. Therefore science instruction should assist students both at secondary school and higher education level, to recognise and understand the functional appropriateness of personal knowledge in certain scientific contexts. Different representations of knowledge in heat transfer should be identified and clarified. It is of great importance to clarify relations and meanings of these representations to assist students to understand their own and scientific ideas.

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