A fundamental target of chemistry education is for students to develop an understanding of the concept of matter and its particulate nature. Yet a number of studies have shown that students find it difficult to understand the concept and to apply it consistently when explaining chemical phenomena (e.g. Nakhleh and Samarapungavan, 1999; Talanquer, 2009). This study aims to explore how young children develop their understanding of the particulate nature of matter.
This is an important question, as few studies concern primary school children (Krnel, Watson and Glažar, 2005; Liu and Lesniak, 2005) and the research literature so far offers mixed answers as to the age at which children can understand the particle model (e.g. Fensham, 1994; Harrison and Treagust, 2002; Novak and Musonda, 1991; Papageorgiou and Johnson, 2005).
Students’ understanding of scientific concepts
Students’ understanding of scientific concepts has been extensively studied in science education research. Researchers in the field tend to agree that understandings are personal constructs that depend on the quantity and quality of a person’s knowledge and how ideas are connected with each other (Barlett, 1932; Nickerson, 1985; Smith, 1991; Taber, 2013).
Following a systematic review of children’s understandings of matter, Hadenfeldt, Liu and Neumann (2014) developed a five-level model that captures students’ progression in understanding the structure and composition of matter: (1) matter is divisible but continuous, (2) particles are entities embedded in matter, (3) particles are the last divisible unit and constitute the building blocks of matter, (4) differentiation between molecules and atoms and (5) explanation and description of the structure of complex molecules.
Similarly, Talanquer (2009) suggested a model that describes how learners go through certain stages while developing their understanding of matter. Novice learners view matter as continuous with no underlying structure and as they get introduced to the particle model they develop the assumption of granularity of matter (substances are made up of little pieces of the same material or they have atoms or particles embedded). The next stage is the corpuscularity assumption, in which learners conceive substances as a collection of particles of the same size and shape made of a distinctive type that are no more divisible. Only advanced learners assume that there is empty space between particles in a substance (Vacuum assumption).
Research in this area has shown that students’ progression of understanding is not linear and is unlikely to be the same for each student, as it is dependent on the specific content and context of the task that students undertake (Hadenfeldt, Liu and Neumann, 2014). Furthermore, there is significant variability in students’ understandings of the composition of matter even within the same age group (Talanquer, 2009). The present study provides empirical evidence that could support or refine the aforementioned suggested models for investigating and potentially improving students’ progression towards understanding matter. Moreover, the present study provides valuable insight into the ongoing debate in the research community regarding the early introduction of the particulate nature of matter in schools (e.g. Harrison and Treagust, 2002; Novak and Musonda, 1991; Papageorgiou and Johnson, 2005). Additionally, it has important implications for teaching practice, as a detailed descriptions of children’s understandings can help educators to recognise potential barriers to, and opportunities for facilitating learning of the concept of matter, and provide them with the means to design more effective courses.
Design and procedures
108 children (27 5-year-olds, 27 7-year-olds, 27 9-year-olds, 27 11-year-olds) from four primary schools in England participated in this study. Students spanned all attainment levels. The dataset was collected as part of the Young Children’s Reasoning about Everyday Chemistry project (Quinn, Ellefson, Schlottmann and Taber, 2013); an inter-disciplinary project that combines paradigms from cognitive psychology, education and chemistry and aims to explore children’s knowledge of how substances mix prior to systematic chemistry instruction.
Students participated in one-to-one interviews that took place in their schools. Researchers showed children a glass of water and a container with sugar. The interview protocol was adopted from Nakhleh and Samarapungavan (1999) and included six questions on students’ models of water and sugar composition. Students were asked the following questions:
- What is water/sugar made of?
- Is it made of one piece or lots of little pieces?
- Think of the smallest pieces. Are they all the same or are they different?
- Can you see the smallest bits? What are the little bits like?
- What shape are they?
- Are they all the same shape?
Interviews were recorded and transcribed and then analysed qualitatively using thematic analysis as introduced by Braun and Clark (2006). Thematic analysis is the process of identifying patterns and themes in the data. Four main themes were identified that fully captured the data-set. The list below presents these four themes, showing children’s understanding of the composition of matter. The themes are organised from the least to the most sophisticated. Each theme is presented with a short description and examples from students’ interviews.
- Macrocontinuous – Statements that refer to a continuous view of matter and its composition as one big piece. For example: ‘water is just one piece really, you can’t really make water’ and
‘sugar is made of flour… it is made of one piece’.
- Macroparticulate – Statements that refer to visible little particles, of different shapes and sizes. For example: ‘water is made of little pieces… Yes, I can see them… Sometimes they look like sausages and sometimes like balls’ and ‘sugar is made of lots of little pieces… I can see them… They are a bit square-ish. And are quite, they are in the middle of a cuboid and sphere’.
- Microparticulate – Statements that refer to invisible pieces, usually of different shapes and sizes. Macroproperties are often attributed (softness, little drops, crystal bits). For example:‘water is made of lots of little pieces… they are probably different… I cannot see them… they are circles’ and ‘sugar is made up of little, little granules. Little bits of sugar which are all formed together to make one big bit of sugar… You can if you look really closely with a magnifying glass. But it will probably be really hard to see them just normally’.
- Molecular – Statements that refer to invisible same spherical bits and utilise the words molecules and atoms. For example: ‘water is made of molecules…they are all the same… they have a circle shape’ and ‘sugar is made of molecules…you cannot see the little bits Unless you had an electronic microscope… they can be any shape’.
Results and discussion
Figure 1 presents the conceptual progression patterns for the composition of water and sugar. The three most important findings that have implications for teaching practice are discussed below:
Overall, it seems that there are two different conceptual progression patterns for the composition of water and sugar. Primary school children find it easier to make a shift from macro-level to micro-level views for water than for sugar. As children grow older they gradually refer to invisible pieces of water of different shapes and sizes. Fewer children talk about visible particles. However, regarding sugar, it seems that most children in all year-groups understood the composition of sugar as macroparticulate (composed of visible pieces) and only some 11-year-olds referred to invisible particles of sugar.
In terms of curriculum development, this finding seems to suggest that students are more familiar with water (liquid) than sugar (solid) and thus, students should potentially get introduced to the states of matter with an initial focus on the concept of liquid, and more specifically, water. This conclusion is supported by previous research findings, as it has been found that students often use water as a prototype for liquids when they talk about liquids’ properties (Krnel, Watson and Glazar, 1998). Thus, teachers could initially focus on water when introducing students to the particle model and gradually move to solids, especially after Year 4, when students are more prepared to think in the micro-level.
The second finding is that primary school children generally did not develop a molecular view of water or sugar apart from some exceptions for 9- and 11-year-olds. As the particle model is not part of the primary school science curriculum, most primary school students are not taught about the particle theory before secondary school. The students who did talk about molecules and atoms in their explanations have probably acquired the relevant knowledge from informal sources of education such as documentaries, science museums, popular science books etc.
Concerning the debate as to whether the particle theory should be introduced in primary school, the findings seem to suggest that most of the 11-year-olds in this study have a microparticulate level of understanding the composition of matter and thus the introduction of the idea of molecules and atoms could potentially be within their conceptual reach. Papageorgiou and Johnston (2001) reported that the introduction of these ideas should be questionable if children have not developed a basic understanding of the states of matter. This study has shown that children develop a different understanding of water and sugar, while after the age of nine they start using more technical terms as solids, liquids, substance etc. Thus, potentially a simple particle model could be introduced to 11-year-olds, probably using water as an entry point (Stavy & Stachel, 1985).
The third prominent finding is that even within the same year-group, there is a significant variability in students’ understandings of the composition of matter and their progress does not appear to be a linear process as supported by previous literature (Talanquer, 2009). For instance, 11-year-olds in the present study expressed all four different views of the composition of matter varying from a macro-continuous to a molecular one.
The interview protocol used in this study could potentially be used to help teachers assess their students’ current levels of knowledge, and help them to plan their lessons and curricula accordingly.
Considering children’s progress in their understanding of the composition of matter, it seems that as children grow older they progress from a macroparticulate view to a microparticulate view of matter for water. For sugar, the progress is slower and most children have a macroparticulate view of its composition, probably because of its granular texture. A molecular understanding of matter does not appear to emerge during the primary school years, which is not surprising given that the particle model is not part of the English Science curriculum for primary school years. Overall, it seems that children start appreciating the particle nature of liquids sooner than solids.
Maria Tsapali is a PhD Candidate in Education and Psychology at the Faculty of Education, University of Cambridge
The Young Children’s Reasoning about Everyday Chemistry Project (Reference: RPG-115) is funded by The Leverhulme Trust. Polly Basak, Hyunji Kim, Julia Hill, Gina Plant Cabrita, KatjaRieger, Sarah Lauper and Matthew Cairnduff assisted in data collection.