Types of Model in Science/Document
Why is using a range of models effective?
A small-scale survey was reported in School science review in March 2000 (Trgidgo and Ratcliffe ‘The use of modelling for improving pupils learning about cells’), which involved two parallel groups of mixed-ability Year 7 pupils. Both groups used the same orientation exercises, elicitation of prior knowledge followed by exposition using whole-class teaching and a worksheet. The approach taken with each group was then changed. Group 1 used 2-D illustrations and drawings to label diagrams and locate various organelles. The other group produced 3-D models using the same stimulus. Modelling cells with the 3-D group presented some interesting teaching opportunities. The pupils made tissues by stacking their cells, made in small plastic bags, in a large clear perspex box. A single cell (constructed using a clear perspex box, visking tubing and green plasticine – chloroplasts) was placed on the overhead projector. This bore a remarkable resemblance to the real thing.
This illustration shows some cells made in a similar way. You may recognise them from the Science Key Stage 3 training unit ‘Misconceptions’.
When the pupils had finished their learning in this topic, both groups were given the same end-of-unit test. Some general patterns emerged from the results of the test. The 3-D modellers:
- achieved accepted responses more often;
- expressed new learning in their answers more frequently;
- were more likely to apply their knowledge to new and novel situations;
- held fewer misconceptions;
- successfully used difficult terminology.
Although this was only a small-scale study the teachers involved were convinced that using 3-D models was instrumental in the deeper understanding of the pupils. They also stated ‘further more, lower attainers in the 3-D group had a better grasp of the overall concept than high attainers from the 2-D group’. For the full version of this report see School Science Review, March 2000, 81(296) pages 54–59.
This study would lead us to believe that constructing models of this type enhances pupils’ learning and understanding. This type of model using the definitions given earlier would be described as a teaching model.
When to use different models
Models can take many different forms, not just the three broad categories mentioned earlier and each one can be used for a different illustrative purpose.
Different types of modelling Look at this list of models:
- Scientific model
- Consensus model
- Historical model
- Teaching model
- Verbal model (analogy)
- Materials model (physical objects/models)
- Visual models (graphs, flow charts, diagrams)
- Symbolic model (mathematical, formulaic)
Using your scheme of work for the module you are about to teach, look through the activities that you have planned and begin to categorise the models that you will use. If you see an opportunity to add a model that you have not thought of, include it.
If you teach two parallel classes, try using models with one class and not with the other. Pair with another teacher and try the two approaches between you. Be prepared to analyse the results of pupils’ learning in the two groups to look for strengths and weaknesses in the methods you have used.
When you are using a model of any type with groups of pupils you should make it clear to them that it is a model that you are using. Be explicit about the model as you cannot guarantee that the way you see a model, or want the pupils to see it, is the same way that the pupils do. Introduce the idea that models can change over time and that models need only be ‘good enough’ to explain a particular concept or idea to meet the needs at that time. Explain that in science once a model does not illustrate or explain a concept or idea adequately any more, it should be changed. Scientists (and science teachers) do this all the time. In Key Stage 3, teachers are being asked to introduce the idea of a model in Year 7, refine and challenge the model in Year 8 and then ask pupils to begin to come up with their own models in Year 9. An example of this could be to introduce 3-D cells models in
Year 7; consider in Year 8 how these models are not really effective at explaining how the products of digestion are absorbed in the cells of the small intestines. In Year 9 pupils can be asked to produce a model to help illustrate respiration in cells. You will see that this principle is supported by the yearly teaching objective in the five key ideas in science (Framework for science 2002).
The programmes of study for both Key Stage 3 and 4 identify some models and theories. Very few abstract ideas are introduced at Key Stage 2, this being a major difference between Key Stage 2 and 3. The introduction of abstract ideas in Key Stage 3 requires modelling for and with pupils so they can progress to the higher levels of the national curriculum. Abstract ideas and models begin to feature significantly in the level descriptions at levels 5, 6 and 7.
Planning to use models The list below illustrates outcomes for learning at different levels for each attainment target. They illustrate the need for effective modelling with pupils.
- Work with a colleague and look through your departmental scheme of work for Key Stage 3.
- Does what you have planned to teach allow pupils to understand and use models appropriately in each of the three years?
Extracts from the attainment targets
Science 1 Level 5 ‘Pupils describe how experimental evidence and creative thinking have been combined to provide a scientific explanation.’
Level 6 ‘Pupils describe evidence for some accepted scientific ideas …’ Level 7 ‘Pupils describe some predictions based on scientific theories …’
Science 2 Level 5 ‘Pupils understand the importance of classification.’
Level 6 ‘They use scientific knowledge and understanding … to describe life processes.’
Level 7 ‘They construct models to show feeding relationships.’
Science 3
Level 5 ‘They use properties of materials to distinguish between metals and non metals.’
Level 6 ‘They recognise that matter is made up of particles and describe differences between the arrangement and movement of particles in solids, liquids and gases.’
Level 7 ‘They use the particle model to explain …’ ‘They recognise elements and compounds can be represented by symbols and formulae.’
Science 4
Level 5 ‘They use some abstract ideas …’ ‘They use simple models to explain effects that are caused by the movement of the Earth …’
Level 6 ‘They use abstract ideas in some descriptions and explanations …’ Level 7 ‘They make calculations, using correct units of moments, speed and pressure ...’
Summary of these features
At level 5 pupils begin to use some abstract ideas and models to describe and explain familiar phenomena.
At level 6 pupils use abstract ideas in some descriptions and explanations and recognise the principle features of models of cell, particle, energy transfer, force and interdependence to describe some phenomena.
At level 7 pupils link ideas together, construct and use a range of abstract ideas and models in descriptions and explanations.
Reflection time Before pupils start to develop their understanding of the key ideas, particularly energy and particles, it would help them to understand why scientists construct models. Perhaps a session in Year 7 about ‘How scientists think’ rather than ‘what scientists do’ would help.
How could you incorporate this into Year 7? The central heating system is not a relevant model to use to teach about electrical circuits because both the teaching model – the central heating system and the concept of current are both unfamiliar to the learners hence confusion! A better model might be traffic flow or demonstrating the flow of water (This is a good way to highlight limitations of the model).
What model could you use to stimulate the imagination of those pupils with no interest in cars? The model of particles being all the same is a ‘good enough’ model to explain changes of state but needs modifying to teach dissolving and density.
How could you modify the model? You need to consider whether the use of models is required. For example, the concrete thinker who is not thinking in an abstract way is likely to find the use of models to visualise abstract ideas challenging. However, to use models to explain things that are too large (the solar system) or not accessible (human organs) is well matched to these pupils’ ability. These are good starting places to highlight the importance of models to these pupils. It is likely that work on cells will be easier for these pupils to understand than energy.
What models do you use to teach cells and energy? Learners need to be aware that models provide simple pictures that are ‘good enough’ to help them understand more complex ideas and a range of phenomena. These simple models either need to be made more sophisticated or changed.
| Review |
| The purpose of models and the use of modelling as a process of thinking needs to be made explicit.
The teaching model needs to be relevant to the individual learner. The teaching model should be matched to pupils’ ability and maturity. By using modelling techniques, individual learners should be taught the scope and limitation of the models. |
| Developing models |
| Look at the following example of how a model (for the way in which light travels) can be changed and refined. The straight-line model is good enough to explain refraction and reflection but not for other light phenomena.
|
Developing a Model of Light
| Scientific Idea | Scientific model | Teaching model | Can be used to explain |
| Light travels from the source in rays | Key stage 3 – Light travels in straight lines | String can be used to represent light travelling in straight lines. Pencil laser light is made visible by dust particles | How and why shadow is formed |
| Light transfers energy from the source to the receiver | Key stage 3 – Energy transfer/radiation | Use money analogy to show transfer | Light radiation transfers energy |
| Light reflected and scattered from different surfaces | Key stage 3 – Light rays travel in straight lines and are reflected according to precise rules | Table-tennis balls used to show light bouncing off plane surfaces.
Table tennis ball thrown at egg boxes can show scattering light. |
Reflection, laws of reflection.
Scattering of light. |
| When light passes from one medium to another it is refracted | Key Stage 3 – the density of a medium with respect to the transfer of energy | Rows of soldiers marching into mud
Wheels on an axle travelling from floor to carpet Plastic tube rolling down a slope which is split, shiny and rough |
Refraction of light Light beam bends towards the normal when light reduces speed |
| White light consists of a mixture of colours | Key Stage 3 – different colours of light travel in straight lines at different speeds in different mediums | Colour wheel and Colour mixing
Pass white light through a prism |
White light is made up from red, green and blue. Rainbows, dispersion, recombination |
| Light can be absorbed and reflected by different coloured materials | Key Stage 3 – different colours of light travel in straight lines at different speeds in different mediums | A carefully explained demonstration using coloured light filters | Why objects appear different colours under different conditions |
| Light filters can absorb some colours and transmit others | Key Stage 3 – different colours of light travel in straight lines at different speeds in different mediums | A carefully explained demonstration (viewing different coloured lights through spectacles with different coloured lenses) following on from reflection and absorption of different coloured materials. | How white light and other coloured light can change colour after filtering |
| Polarisation | Key Stage 4 – wave model | Slinky with rows of posts | |
| Diffraction | Key Stage 4 – wave fronts | Ripple tank 3 cm wave kit | |
| Interference | Key Stage 4 – |
