# Modelling in middle years sciences

By Sarah Phillips At its heart, science is about understanding how matter and energy interact with each other. As simple as it may sound, the number and variety of interactions, and the many scales of time, place and size over which those interactions operate make science a highly complex endeavour. Because of this complexity, models are essential tools for scientists and science students alike.

Scientists use models in a variety of ways. They might create a 2- or 3- dimensional model to explain a phenomenon, or to generate a hypothesis about how different components in a system interact with each other. Scientists also construct mathematical models to find and describe relationships in the quantitative data that they gather through experimentation. These models can be tested and refined through further experimentation. Eventually, such models can be accepted as rules or generalizations, like Boyle’s Law or Newton’s laws of motion. Science students learn about the models, rules and generalization that have been established by scientists, but they can also learn with models. This happens when students use existing models to understand and explain the world around them, and when they construct their own models.

### Students use existing models to make sense of phenomena

For example, students could use the particle model of matter to explain why sugar dissolves more quickly in hot water than in cold water.

### Students can also construct models to explain phenomena

For example, students might use a graph of the data they gathered in an experiment in order to show how the current in a circuit changes as the voltage is increased. By prompting students to visualize processes that are complex and/or invisible, models help students to understand and explain phenomena. Moreover, models can help students to move from concrete observations and experience to abstract processes and relationships.

“Models are bridges that connect concrete learning by using physical objects to correspond to abstract ideas. Moving from concrete to abstract thinking means perceiving the likeness of parts in a situation that at first glance may appear to be unlike each other. Models provide a means for making this transition and support students in constructing relationships that form the basis for using graphs, tables and formulas.” (Carrejo & Reinhartz 2014, p. 11)

Regardless of whether students are using existing models or developing their own, how the models are used is essential to their value. Models are common features in many science projects, such as 3D models of volcanoes, models depicting the differences between plant and animal cells, models depicting the flow of energy and nutrients in a local ecosystem. While such projects involve models, they do not necessarily engage students in the kind of thinking associated with modelling.

Modelling involves the use of models to illustrate, explain and/or predict phenomena. Building a model that shows the parts of a volcano is not a modelling activity unless students use the model to explain something about the volcano, such as how it was formed or what causes an eruption.

 Model Sample modelling activity 3D Volcano Using the model to explain the causes of volcanic eruptions Diagram of a plant cell and animal cell Using the models to illustrate the differences between plant and animal cells. Food web Using the model to predict what would happen if a predator was removed from the ecosystem

As a related concept in our Middle Years Programme (MYP) science courses, models are defined as “representations used for testing scientific theories or proposals that can be accurately repeated and validated; simulations used for explaining or predicting processes which may not be observable or to understand the dynamics of multiple underlying phenomena of a complex system”. This definition draws a clear connection between the model and its application to testing, explaining and predicting. As such, modelling is embedded in the MYP sciences framework.

Modelling is also connected to many of the MYP sciences objectives. The operational framework proposed by Schwarz et al. (2009) offers a basis for drawing connections:

 Elements of modelling practice* Examples Related MYP sciences objectives “students construct models consistent with prior evidence and theories to illustrate, explain, or predict phenomena.” Draw a model to show how various factors could affect plant growth; use the model to formulate a testable hypothesis Bi: explain a problem or question to be tested by a scientific investigation Bii: formulate a testable hypothesis and explain it using scientific reasoning Use a model to summarize and explain the data and observations from an experiment Cii: interpret data and explain results using scientific reasoning “Students use models to illustrate, explain, and predict phenomena.” Use a Bohr model to explain the difference between ionic and covalent bonding Ai: explain scientific knowledge Use the particle model of matter to predict what will happen to the density of an object as its temperature changes Bii: formulate a testable hypothesis and explain it using scientific reasoning “Students compare and evaluate the ability of different models to accurately represent and account for patterns in phenomena, and to predict new phenomena.” Consider how established scientific models have been revised over time Ai: Explain scientific knowledge Compare different models of the atom (Rutherford, Bohr, Lewis etc.) to evaluate how well each represents ionic and covalent bonding Aiii: analyse and evaluate information to make scientifically supported judgments Compare the data gathered through experimentation against different graph types (linear, exponential, quadratic) to determine which is the best fit Cii: interpret data and explain results using scientific reasoning “Students revise models to increase their explanatory and predictive power, taking into account additional evidence or aspects of a phenomenon.” Use the data gathered in the experiment to revise the model that was used to generate the hypothesis Ciii: evaluate the validity of a hypothesis based on the outcome of the scientific investigation

*from Schwarz et al. 2009, p. 635

The digital interface used in MYP on-screen assessment provides a variety of tools that allow students to engage in modelling activities in ways that would not be possible in paper-based examinations. In the demonstration video for the MYP sciences examination, you can see that candidates are able to use simulations and a variety of data analysis tools to develop hypotheses and explain their findings with reference to mathematical models.

The use of models in MYP sciences classes helps students to learn about science while also developing their ability to think and work as scientists do. Modelling activities are closely connected to the MYP sciences objectives and can be used to support students’ learning in the classroom and in the laboratory.