Although the word 'model' is polysemic, its most common meaning is that of a representation of an idea, object, event, process or system that is created for a specific objective (Gilbert & Boulter, 1998). The basic characteristics of a model are:• It does not represent the complete reality of the system being modelled, but only the aspects that are of interest to its user, and therefore, as they are human creations, they do not exist in the physical world. • The same reality can be represented by multiple models, depending on the interests of whoever is using the model. Gutiérrez ( 2005) defines the term 'scientific model' as a representation of a system, made up of a set of objects with certain properties or variables, and a set of laws that declare the behaviour or functions of these objects or the relationship between their variables. The essential functions of a scientific model are to explain and predict. At the same time, scientific models are considered to be representations that enable scientists to reason, and which are used to simplify or idealise complex phenomena, to help visualise abstract ideas, to support interpretations of experimental results and to help produce explanations and predictions (Justi & Gilbert, 2002).Despite the importance of building models in the development of scientific knowledge, many authors agree that there are no general rules for doing so. This non-linear process of constructing, evaluating and using models is what is known as 'scientific modelling'. As Hodson (1992) said: "the ways in which scientists work are not fixed and not entirely predictable, and involve a component that is experiencedependent in a very personal sense. These ways of working are not teachable. So, the only effective way to learn to do science is by doing science". In accordance with this viewpoint, there is a need to promote among students a more realistic image of science, trying not to portray the existence of a single scientific method but instead encouraging creativity as one of the essential skills used in the construction of scientific conceptual models at school.
This is a post-print versionof the following article: López, V., Hernández, M.I. (2015). Scratch as a computational modelling tool for teaching physics. Physics Education, 50 (3), 310-316.
