Task E. Make the following points:

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1 Using models to teach the particle theory Make the following points: 20 minutes Research has shown that there are differences in the ways teachers use models to explain particles, even within a single department. The purpose of this session is to explore some of the differences about the models that are used in teaching science at Key Stage 3 and point out that there is often no right or wrong answer, but that we use different models for different purposes. This session also attempts to make clear that whilst this is so, some models are better than others and that it would be helpful if teachers within a department adopted a consistent approach. Slide 3.6 Task E 10 minutes Show participants Slide 3.6 to introduce them to Task E. Ask them to draw quickly (allow no more than 1 minute) a particle picture to represent a solid, liquid and gas. Then ask them to compare notes and discuss any differences. Allow 2-3 minutes for this. Task E (part 1): Pictures of particles Draw a particle picture to represent: A solid A liquid A gas Slide 3.6 Slides 3.7/3.8 Next show participants Slide 3.7, and then Slide Misconceptions in Key Stage 3 science notes for course tutors Crown copyright 2002

2 Solid, liquid and gas picture 1 Solid Slide 3.7 Liquid Gas Solid, liquid and gas picture 2 Solid Slide 3.8 Liquid Gas Say that: Particle theory will probably be new to pupils at Key Stage 3. It is not in the programme of study at Key Stage 2, although primary teachers may have referred to it. Many textbooks tend to show solids, liquids and gases as in the first example. However, others suggest that many of the particles representing a liquid should be touching as in the second example. 24 Misconceptions in Key Stage 3 science notes for course tutors Crown copyright 2002

3 Reasons suggested for this picture are that when solids melt to form liquids their volumes are about the same, and that you cannot easily compress solids or liquids. In air (a mixture of gases) the particles are about nine diameters apart; hence gases are relatively easy to compress. Additional guidance The marking scheme for the end of the Key Stage 3 science tests allocates marks for identifying that 50% of particles should be touching in a liquid, but there is no standard set or expressed for this. Handout 3.9 Handout 3.10 Whilst this may be a useful picture to explain the solids, liquids and gases, it doesn t work with other phenomena such as expansion of solids. The particletouching model is not a correct model; rather, it is a good enough model that can be used to explain phenomena such as the comparative noncompressibility of liquids and solids. Use Handouts 3.9 and 3.10 to illustrate how a good enough model can be used in teaching particles.

4 A good enough version of the billiard ball model to explain a range of physical phenomena Handout 3.9 Basic premises All matter consists of tiny particles. Types of particle vary in their volume. Types of particle vary in their mass. A crystalline solid has a set shape and a fixed volume that is independent of that of its container. To represent this the particles in the particle model: are arranged in rows and sheets; are close together; are held together tightly; have energy and vibrate around a point; cannot easily change places. A liquid has a fixed volume and takes up the shape of its container up to the level of the surface of the liquid. To represent this the particles in the particle model: have no set pattern; are also close together; are not so tightly held together as in a solid; have more energy and move randomly; can change places. A gas takes up the whole volume of its container. If that container is open, it will diffuse into the air. To represent this the particles in the particle model: are not arranged in any way; are far apart; are very weakly held together; have much more energy and move very rapidly in all directions; constantly change places in no pattern. Note: the distance between particles in air is about nine diameters. 29 Misconceptions in Key Stage 3 science notes for course tutors Crown copyright 2002

5 Developing a sequence of good enough particle models Handout 3.10 Scientific idea Matter made of particles that are moving, very small and broadly of similar size Particles are of different size/mass When particles interact there are forces acting between them Particles are of different types. There are a set number of atoms and all other particles are made from these The types of particle interactions: A + B AB AB A + B AB + C AC + B AB + CD AC + BD Teaching model Billiard ball (Handout 3.9) Computer animations Use marbles, ball bearings, beads, etc. to illustrate Use magnetic marbles, or sticky and non-sticky balls to illustrate forces Use commercially produced models such as Molymod or Lego to illustrate different types Use Molymod type or Lego to model each reaction type and model reactions whilst they take place Can be used to explain Changes of state, solidifying, melting, evaporating Density, viscosity, movement of substances through cell membranes, Brownian motion Dissolving Elements, compounds and chemical change Patterns in chemical change: combination disassociation displacement (special case of recombination) recombination 30 Misconceptions in Key Stage 3 science notes for course tutors Crown copyright 2002