1. The microscopic nature of Matter
‘What statement would contain the most information in the fewest words? I believe it is the atomic hypothesis,… that all things are made of atoms, little particles that move around in perpetual motion, attracting or repelling one another’
(Richard Feynman, 1994)

2. Levels of representation
Macro
Micro
Symbolic

3. ‘We all hear about of atoms and molecules from our childhood from the newspapers or from television.
Students are expected to explain the properties of matter in terms of the particle nature of matter (micro approach)’
States of matter and phase changes
Kinetic theory of gases
Chemical reactions
Chemical bonding
Solution chemistry
DNA and cell biology
Matter is composed of discrete, energetic particles that are separated by space.

4. Dalton’s Atomic Theory
Matter consists of tiny indestructible particles called atoms
All atoms of a given element are identical, and have the same mass.
Atoms of different elements have different masses
The mass of an atom of an element is the same in all of the compounds.
Particles join together in simple consistent ratios when two different substances react to form a third substance. Mass is conserved in all of these reactions.

7. Kinetic Theory
A gas is composed of invisible particles with empty space between the particles.
Gas particles are evenly scattered in any enclosed space
Gas particles are constantly in motion and particle collisions are perfectly elastic.
Particles move slower in liquids and vibrate about fixed positions in solids.
Gas particles are widely spaced and there are smaller but similar sized spaces between particles in solid and liquids.

8. Common misconceptions
Matter is continuous
There is no empty spaces between particles
Molecules are in substances, rather than substances are composed of molecules.
Gas particles are static
Heated gases are lighter (so they can rise to the top of the container)
Gases have no shape and no mass
Spacing of particles in the three phases of Matter
‘Solid particles are in contact, liquid particles about one particle apart and gas particles have 3-4 particle spaces in-between’.

9. Mass is not conserved in phase changes
‘Matter is lost in changing form solid to liquid and liquid to gas’
‘There are material differences between solid, liquid and gas particles’
‘Bubbles in boiling water either are heat, oxygen or hydrogen’
- Students’ explanation of phase changes rely on what they ‘see’ and they are often unable to generalise this phenomenon to other substances.
Particles expand and contract just like the substance of which they are part
‘When substances are heated and cooled many students believe that the particles do likewise’
In the freezeing process the particles are more closely packed together
This correlates with a continuous conception of matter.

10. ‘copper atoms are red-brown because this is the colour of copper’
Macroscopic properties are attributed to particles
‘molecules in solid are heavier than molecules in the liquid phase, with molecules in the gas phase being the lighter’
‘copper atoms are red-brown because this is the colour of copper’
‘individual atoms conduct heat or electricity because the substance conducts heat or electricity’
‘atoms are malleable because the substance is malleable’
From a textbook:
‘Divide a copper penny into ever-smaller pieces. Eventually you would come upon a particle of copper that could no longer be divided, and still have the properties of copper. This particle would be an atom, the smaller particle of an element that retains the properties of that element’

11. Conceptual changes
Changing from a ‘particles-are-touching’ conception to a ‘there-is-space-between-particles’ conception, when it involves recognizing that this space is a vacuum is an ontological conceptual change.
Multiple conceptual changes are needed to bridge the gap between intuitive and scientific knowledge.
Learning necessarily proceeds via a series of intermediate steps or ‘models’, which contain aspects that are ‘incorrect’.
Many students use molecular language as a ‘veneer’ without substantially changing their conception of matter. .

12. Conceptual changes are evolutionary and do not result in the extincition of naïve conceptions.
Accomodation of the paricle theory involves a radical conceptual change that involves both epistemological and ontological aspects.
Epistemological: students need to think in new and expanded ways, in terms of evidence that includes accounts from the history and philosophy of science.
Ontological: particles are dynamic and separate.
A dynamic process explanation needs an understanding of particle interactions.
Students use substance macroscopic properties to infer what the particles are like and how they work, whwreas scientists use molecular models to explain observable quantities.

13. Issue
Is it appropariate to teach the particle theory to years students?
‘Middle school chemical science should focus on macroscopic chemical experiences that expose students to a wide range of chemical reactions and applications: acid-base chemistry, solubility and precipitation, combustion, corrosion, electrochemistry.’

14. Selected readings
Albanese, A., & Vicenti, M. (1997). Why do we believe that an atom is colourless? Reflections about the teaching of the particle model. Science and Education, 6,
de Berg, K., & Treagust, D.F. (1993). The presentation of gas properties in chemistry textbooks and as reported by science teachers. Journal of Research in Science Teaching, 30,
de Vos, W., & Verdonk, A.H. (1996). The particulate nature of matter in science education and in science. Journal of Research in Science Teaching, 33,
Duit, R. (1991). On the role of analogies and metaphors in learning science. Science Education, 75,
Garnett, P. J., Garnett, P. J., & Hackling, M. W. (1995). Students' alternative conceptions in chemistry: A review of research and implications for teaching and learning. Studies in Science Education, 25,

15. Griffiths, A. K. , &. Preston, K. R. (1992)
Griffiths, A.K., &. Preston, K.R. (1992). Grade 12 students' misconceptions relating to fundamental characteristics of atoms and molecules. Journal of Research in Science Teaching, 29,
Harrison, A. G., & Treagust, D. F. (1996). Secondary students’ mental models of atoms and molecules: Implications for teaching science. Science Education, 80,
Harrison, A.G., & Treagust, D.F. (2001) Conceptual change using multiple interpretive perspectives: Two cases in secondary school chemistry. Instructional Science, 29,
Ingham, A.M., & Gilbert, J.K. (1991). The use of analogue models by students of chemistry at higher education level. International Journal of Science Education, 13,
Krnel, D., Watson, R., & Glazar, S. A. (1998). Survey of research related to the development of the concept of 'matter'. International Journal of Science Education, 20(3),

16. Lee, O. , Eichinger, D. C. , Anderson, C. W. , Berkheimer, G. D
Lee, O., Eichinger, D.C., Anderson, C.W., Berkheimer, G.D., & Blakeslee, T.D. (1993). Changing middle school students' conceptions of matter and molecules. Journal of Research in Science Teaching, 30,
Selley, N. (2000). Students spontaneous use of a particulate model for dissolution. Research in Science Education, 30,