Hi. I received a letter inviting me to an interview, with the lesson to be taught: "20 minutes presenting a topic that is based on a point on the range 'Sustainable Earth' in the National Curriculum, namely: The properties of solids, liquids and gases and how the particle model can be used to explain these properties. The pupils have already studied the unit this year, so applicants are asked to extend the pupils and talks about the effects such as expansion, diffusion or change state." Sorry all this messaged is squished up. I STILL don't know how to do paragraphing on here!! So, anyway, my questions are what is it do you think the pupils have studied if they haven't done change of state? The lesson is to be taught to a higher ability y8 group. From the information above, would you assume that they've done melting, condensing, freezing etc? I can't really organise in my head what to teach, where to pitch it? I had an idea about diffusion, but then think maybe freezing and melting etc would be easier. Was thinking I could do the balloons in a box of ice, box of hot water? A 'thermometer' to show that the liquid is expanding. What do you think? Any ideas a very greatly appreciated!! Thanks.