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Teaching with models

Models are human inventions, based on an incomplete understanding of how nature works.

A model is a representation of an idea, object, event, process or system (see below for examples of types of models ).

Models and modelling play a crucial role in science practice. One justification for their inclusion in science teaching is that they contribute to an ‘authentic’ science education, where teaching reflects the nature of science as much as possible.

Learning challenges when using models

Models are human inventions, based on an incomplete understanding of how nature works. Models concentrate attention on specific aspects by using something that is familiar as a simile to explain or describe something that is not familiar.

Consequently, most models are limited or ‘wrong’ in some key aspect. This can create learning problems if students take a different meaning from the model than that intended by the teacher. For example students may:

  • learn the model rather than the concept it is meant to illustrate
  • fail to distinguish between a mental image and a ‘concrete’ model
  • lack the necessary visual imagery to understand the model
  • lack awareness of the boundary between the model and the reality the model is representing
  • mix up aspects of two or more different models
  • miss some key attributes and so misunderstand the purpose of the model
  • continue to use the least sophisticated of a range of models, even when they have been introduced to more advanced models
  • find it difficult to apply the model in different contexts.

How to overcome learning challenges

Overcoming such learning challenges requires careful teaching that focuses quite consciously on the model as an idea, object, event, process or system. A new model could be introduced in a sequence such as this:

  1. Introduce the idea that the model is intended to show and find out what ideas students already have about that event or pattern.
  2. Carry out the modelling activity.
  3. During the activity, or at the end if more appropriate, talk about how the model/modelling activity is ‘like’ what would really be happening and how it is ‘different’.
  4. The analysis of the model could also include a discussion of how the model shapes a particular view of ‘reality’. Such an analysis would focus on:
    • identification of the positive features of the model (what is deliberately chosen to represent 'reality')
    • identification of the negative features of the model (what is deliberately excluded)
    • identification of the neutral features (what is ignored or not commented on).
  5. Return to the ‘big idea’ at the end and let the students explain to you the sense they have made of the activity. Older students could analyse the model for themselves after some practice runs and their comparisons could be used to assess their new learning. Students may continue to need help do this for every new model used.

From mental model to expressed model

Mental models are used to describe and explain phenomena that cannot be experienced directly. Scientists use mental models to think through abstract ideas and theories.

Mental models become expressed models when they enter the public domain through action, speech, and writing. They are often represented as analogies and metaphors.

Examples of this process are:

Structure of the benzene molecule

The ring structure of the benzene molecule

August Kekule was puzzled by benzene, a 6-carbon molecule. There are many stories of his famous dream where he saw dancing snakes biting their own tails, and realized the benzene molecule could be seen as a ring structure rather than a straight chain. This was his mental model.

The expressed model he made as a result of his ‘dream’ helped others understand how the atoms could fit together.

The composition of atoms

When John Dalton started thinking about atoms he thought of them as if they were bowls or balls – this was his mental model.

His experiments in 1802 supported the theory that matter was made of particles and he pictured them as small billiard balls. Using this model he was able to show how each element could be represented as being made up of the same kinds of atoms, and that compounds could be explained as being made up of atoms in specific ratios – this was his expressed model.

The ‘plum pudding’ model of atom composition

J.J. Thomson studied atomic theory and cathode rays, and postulated the existence of small negative particles we now call electrons. He realised that the ‘billiard ball’ model where atoms had the same composition throughout didn’t explain the existence of electrons. His expressed model showed atoms having negative electrons dotted throughout the positive atom like plums in a pudding.

Types of expressed models

Expressed models used in science communication and teaching include: two-dimensional models, such as those found in textbook diagrams; three-dimensional models such as scaled miniatures (a smaller version of large structures); scaled enlargements (an enlarged view of something too small to be seen); and working models. For example:

Leonardo da Vinci’s “Vitruvian man”: A two-dimensional anatomical model

  • Leonardo da Vinci created many wonderful anatomical drawings (two-dimensional models) and these helped further medical understanding.
  • The internal structure of the Earth at Te Papa Tongarewa’s Awesome Forces exhibit is a scaled miniature. The model shows the layers of the Earth’s interior in what we believe to be their correct proportions.
  • The structure of a cell can be represented as a scaled enlargement.

Digital models

Digital models include animated models and simulations. Simulations allow students to simulate a situation, such as making choices about land use. Animated models may also allow students to control variables to see what impact each variable has. Digital models intended for learning are called Learning Objects. Teachers can find a wide variety of Learning Objects suitable for use with New Zealand students of all ages in Digistore/Te Pataka Matahiko . These include animated models of science concepts such as cell division and tectonic plate movement, through to simulations of decisions about land use and factors which influence the UV index.