The roles of models in understanding science

1. The roles of models in understanding science Click the links below to access the activities: • Activity 1 • Activity 2 • Activity 3 • Summary

2. Compare the maps…

3. 1 Map showing TST MTR system map Geographic map of the MTR

4. 2 Map showing TST MTR system map Geographic map of the MTR

5. 3 Map showing TST MTR system map Geographic map of the MTR

6. Map showing TST MTR system map Geographic map of the MTR

7. This is a model of the land and sea of Tsim Sha Tsui, highlighting train station exits MTR map is a model of the routes of the MTR trains.

8. A model can be regarded as a representation of an idea, an object, an event, a process or a system. Gilbert and Boulter, 1998 What is a model?

9. A model as a representation of a real object

10. A model as a representation of a system

11. A model as a representation of a process

12. A model as a representation of events

13. A model as a representation of an idea

14. When people draw maps, do they copy everything they see? If not, what criteria guide their drawing?

15. lung heart liver artery vein Figure 1 Figure 2

16. Activity 2: ? ? ? Draw pictures to illustrate the arrangement of water particles in solid, liquidandgas state.

17. gas liquid solid

18. What is used to represent each water particle in the model? Spheres are used to represent water particles

19. Information conveyed and drawbacks In order to understand the three states of matter (e.g. ice, water, steam), we used to use spheres to represent water particles. In this model, the composition of the sphere is not our concern. The composition of the sphere is not important and may confuse our understanding of the arrangement of particles in different states.

20. Does anyone not use spheres to represent water molecule/particles? Why? Why do we use spheres even though we know that water molecules are not spherical?

21. What do you value about the model that you learned in junior forms? In order to better serve its purpose, when people develop a model, it is most common that they will: • highlight the more relevant areas selectively • neglect some less important aspects

22. Activity 3: Methane molecules 3. 1. 5. 4. 6. 2. CH4

23. In a group of 3-4, • Name the type of model we used to represent methane • Describe the information that each model conveys • Describe the drawbacks of each model 3. 1. 5. 4. 6. 2. CH4

29. CH4

30. Can we have a true picture of a methane molecule when we put all the information from these models together?

31. Even seeing all of these models collectively, we still CANNOT construct a complete representation of a real methane molecule. For example, the nuclear structure (e.g. the number of neutrons), the size of the nucleus and the movement of electrons have not been considered in these previous models.

32. Conclusion Chemists or scientists use multiple types of representation or models to convey their ideas. None of these can truly and completely represent molecules. Each type of model highlights a particular set of information while neglecting other information.

33. Conclusion Therefore, it is very important to be aware of the scope and limitation of each model. A deeper understanding can result from viewing multiple representations or types of models.

34. Conclusion It may not be appropriate to judge a model that you learn in an early stage of study (e.g. particles as spheres) to be ‘wrong’. While these models suffer from their explanatory power, they have the advantage of simplicity.

35. Other examples of models in chemistry The shell and orbital models of atoms Redox reaction (in terms of oxygen/hydrogen transfer, electron gain/loss & oxidation number) Arrhenius and Bronsted-Lewis models of acid/base Prediction of the shift in equilibrium position in terms of Le Chatelier’s principle and reaction quotient.

36. 9V Ideal Gas Law PV = nRT Other examples of models

37. What have you learnt about the use of models in science?

38. What are the roles of models in science? A model can be regarded as a representation of an idea, an event, a process or a system. A model is created to test ideas. It will change or be modified to inform or assist the development of those ideas.

39. What are the roles of models in science? A model helps us to represent ideas within a defined scope. A model is NOT a direct copy of reality. When scientists develop a model, it is most common that they will highlight the more relevant areas selectivelywhile neglecting some less important aspects.