MODELS IN SCIENCE TEACHING & LEARNING What are models ? A model is a representation of an object, event or idea. This representation creates a vehicle.

MODELS IN SCIENCE TEACHING & LEARNING

What are models ?A model is a representation of an object, event or idea. This representation creates a vehicle through which the object, event or idea can be conceptualized and understood. Models are important in science teaching, as major tools for teaching and learning. Models are one of the main products of science – the progress of science is normally marked by the production of a series of models, each associated with a distinctive theory. Modeling is a major element in scientific methodology

DIFFERENT TYPES OF MODELS Mental model – that each of us visualizes in our mind; Expressed model – when we try to explain or present in another

form our mental model; Consensus model – an expressed model which has gained

acceptance within the scientific community; Historical model – a consensus model which has been

superseded at the ‘cutting edge’ of science e.g. the ‘plum pudding’ model of an atom is an historical model superseded by ‘orbiting electrons’ model.

A teaching model is one specifically produced to teach a difficult consensus or historical model.The last four models can be put forward in a number of different ways including as objects, symbolic or mathematical representations, diagrams, spoken explanations or a mixture ofthese.

Discuss 2D and 3D Models in chemistry teaching

SIX CHARACTERISTICS OF GOOD MODELS

Structurally complete in the relationship of its elements - ie has all the essential elements of the target idea;

Coherent and appropriate in its level of detail; Considerate in its form – appropriate vocabulary and

form of presentation; Concrete in its representation – the relationship of all

parts of the model are obvious; Provides clear conceptual explanation – the associated

theory can be explained through the model; Highlights the correct comparatives between the model

and the target idea – the scope and limitations of the model are pointed out.

These ‘6Cs’ can be used to evaluate the effectiveness of a model in exploring the target idea.

REASONS FOR USING MODELS To help pupils visualize a structure or process; To help less able pupils to remember a concept or

idea; To simplify a difficult concept or idea; Because the pupils failed to understand a concept or

idea on an earlier occasion; To help the pupils link an unfamiliar idea with a

familiar one, particularly in an imaginative way; To entertain or to provide a variety of approach; Because the pupils were encountering a concept or

idea for the first time. (Jarman, 1996)

ANALOGICAL MODELS Analogies are valuable thinking tools in helping students to

learn and understand an unknown phenomenon in terms of the well known ones. They help in mental processing of abstract concepts which most of the times are the reasons why students find science very difficult to understand. . In science, for example, analogical reasoning is a common place, a well respected way of thinking and modelling and often used as a device in communications Far back in 19th century, electrons were pictured as behaving like light and waves. Water waves are known and familiar experiences to chiildren who go near and throw objects into a river. This was used as one to one mapping to illustrate the behaviour of electrons which are abstract, unknown and quite difficult to comprehend using waves that sudents are familiar with

Categorizing Models/Chemical EquilibriumAssessing the efficacy of analogical teaching involves thinkingabout the mode of analogy representation, their classification, andthe conceptual demands different models place on learners.The representational mode of chemistry model presentation can be concrete (e.g., ball-and-stick molecules), verbal (e.g., analogical stories like those reported in this study), mathematical (e.g., graphs of reaction profiles), visual (e.g., STM images and 2D Lewis diagrams), and mixed mode (Boulter & Buckley, 2000; Gilbert, Boulter, & Elmer, 2000). A hidden mode is the personal mental models that are generated or modified by teacher and textbook models. Mental models are dynamic cognitive interpretations of targetconcepts and often are unstable, incomplete, or ‘‘mentalmuddles’’ (Greca & Moreira, 2000)..

CLASSIFICATION OF TEXTBOOK ANALOGIES

Classification. Curtis and Reigeluth (1984) classified textbook analogies under three types, based on each analogy’s degree of elaboration. The most common is simple analogy where thewriter says something like ‘‘activation energy is like ahill,’’ and leaves the student to interpret how activation energy is like ahill. Type two, enriched analogy, includes the grounds for the likeness; for example, ‘‘assembling a car is like the mechanism of a chemical reaction, because both cases proceed step by step.’’ The difference lies in telling the students how the analog is like the target. Type three, extended analogy, comprises multiple simple and/or multiple enriched analogies that describe and explain the same target. The elaborated ‘‘super-rubber balls in a box’’ analogy is an extended analogy as are several of the equilibrium analogies reported in this study.

ANALOGUES HAVE TWO PARTSAnalogy is made up of two parts, the target analogue,

which is the domain to be explained, and the base analogue, which is the domain that serves as a source of knowledge.

The analogue domain is the one that exists in the memorry, from which the analogy is drawn, and the target domain which contains the science concept to be learned, the instructional objective of the analogy.

From the example given earlier, water waves is the domain analogue while electron behavior is the target analogue. We use the domain to explain the target.

TEACHING WITH ANALOGIESWhen using analogy,teachers regularly preface their

explanation with colloqual expressions such as “It’s just like ....”, “It’s the same as .....”, “It’s no different than.....”, and “Think of it as ...”.

In textbooks too, authors use more formal expressions like “Similarly ...”, “Likewise ...”, “Along related line ...”, “In comparison to ...”, and “In contrast with ...”

When you hear phrases like these what is being used is analogy which sometimes can be called mental models. What the teachers and the authors are saying in these expresions is “Let me give you an analogy”.

EXAMPLES IN TEACHING ATOMIC STRUCTURE

Topics Teachers’ analogy

Target concepts Mapping

Atomic structure and Periodicity

Crumb/particle of chalk

Combination of crumbs

A boy and a girl

Union between a man

and a woman marrying

Solar system with the

sun at the center and

the planets revolving

Particulate nature of

matter

Molecule, atom + atom

Cation and anion

Electrovalency

Electrons revolving in

orbits around the

nucleus.

Chalk particles are

very large

compared to atoms

or molecules

Mapping could be

established after

further explanation

to reduce

misconception.

There are more

than one electron

in some

MORE EXAMPLESTopics Teachers’

AnaloguesTarget Concepts

Mapping

Kinetic theory of matter

Spraying insecticide/

air freshner in a

toilet/ Perfume on

the body

Pressing piston on

air in bicycle pump.

Pressing becomes

difficult due pressure

Diffusion of

gases/ Random

movement

Pressure/Volume

relationship

Analogue and target structures match.

Gas molecules are the target. Gas pressure is as a result of collision of molecules against the walls of container. Mapping can be established on further explanation.

Analogies used by four chemistry teachers across 43 lessons

ANALOGUE TARGET

Reaction rates

Students hurdling hurdles of different

heights

The student dance

Coconut shy

Climbing through a Swiss mountain

pass

Pushing a car around a side road

Chipmunks storing food before winter

Rates of various reactions having

different activation energies

Increasing in molecular velocities

causing an increasing number of

collisions

Effect of increasing concentration on

the number of successful collisions

Effect of catalysts on reaction

Mechanism and rate

Ease of catalyzed reaction mechanism

Exothermic and endothermic reactions

ANALOG TARGET

Chemical Equilibrium

Breaking apart a pen and its cap

Water flowing in and out of a

sink

Gravitational effects on a body

Elastic band returning to its

original size

People moving in and out of a

shop

Person walking up a down

Escalator

Energy required to break chemical bonds

Constant dynamic properties in a steady state open system

Tendency of a chemical system to revert to equilibrium

Rates of forward and reverse

reactions for equilibrium

Competing forward and reverse

rates of reaction

RECOMMENDATIONS FOR USE OF ANALOGY Use models at the beginning of a topic or integrated fully into

the teaching of key ideas. Where analogies are used, check pupils’ understanding of the

analogy itself before using it to explain the key idea. Show similarities and differences of the model to the target

idea – i.e. highlight the strengths and limitations of the model. Give pupils practice in developing their own models and use

them to explain ideas. Highlight the strengths and limitations of their models

Encourage pupils to explore the use of (their) models in explaining related ideas – does the model still hold?

When using concrete models (e.g. drawings/ 3D models of atoms, bonding etc), 3D models seem to lead to greater understanding and retention of key ideas compared to 2D.

Enjoy using models – they provide an interesting, visual and stimulating way of understanding chemical ideas! Models can really help and motivate low achieving pupils.

MORE ABOUT MODELSA scientific model is a set of ideas that

describes a natural process.In Biology, the meiotic model describes the process by which alleles segregate and independently assort during gamete formation. Given this model and some background knowledge about certain genes of interest, it is possible to predict the possible allele combinations resulting from meiosis in a given sex cell or class of sex cells. The processes of meiosis and fertilization are frequently represented using Punnett squares

Models can be used to explain and predict natural phenomena.

One can use the simple dominance model to explain and predictInheritance phenomena in given organisms. One could explainwhy a true-breeding tall pea plant crossed with a true-breedingshort pea plant always produces tall progeny and also why thesetall progeny, when cross-bred with one another, produce tall andshort progeny in a 3:1 ratio. Using the simple dominance model,an explanation for such phenomena would take the form ofSpecifying genotype to phenotype mappings (the relationshipsbetween alleles is already specified in the model as one of simpledominance) and describing how parent organisms with a givengenotype might contribute particular alleles to their offspring, viameiotic processes, leading to organisms with particulargenotypes (and the consequent phenotypes).

Models are consistently assessed on the basis of empirical and conceptual criteria.

Specifically, scientists assess whether a particular model canexplain all of the data at hand and predict the results of futureexperiments (empirical assessment). They also evaluate how wellA model fits with other accepted models and knowledge(conceptual assessment—see Figure 3 for a summary). Forexample, since the meiotic model is at some level a component of he simple dominance model, it is important that there be noconceptual conflicts between them. Models that fail to satisfysome or all of the assessment criteria are discarded or (morecommonly) revised until they are deemed acceptable. In practice,models are continuously revised as they are used to probe newphenomena and collect additional data.

Models are useful as guides to future research.Once constructed, models influence and constrain the kinds of questionsscientists ask about the natural world and the types of evidence they seek insupport of particular arguments. They guide a researcher’s perception of whatis involved in the natural processes of the world. The belief of early geneticiststhat genotypes controlled discrete phenotypes only led them to see organismsas mere aggregates of discontinuous traits. Important research for thesescientists included identifying just which characteristics could be identified astraits’ and how such traits 6were inherited. Later, when geneticists began torecognize the complexity of inheritance phenomena, they revised their earliermodels in order to account for inheritance of continuous characteristics as

well. Their revised models led to new conceptions of how inheritance worked and, subsequently, new research questions as well.