Y10 very low ability Polymers: we made a poly-pupil by having 8 separate pupils linking arms up front. Sounds crap and only lasted 5 minutes but it got the restless ones out of their seats legitimately for those 5 minutes. To start off, I linked a couple of paper clips together to demonstrate monomers polymerising. Easy peasy. Then, in true Blue Peter styley, produced one I had made earlier - a whole 900 paperclips long, to represent a poly(ethene) chain, which was then strung up around the room. I used coloured paperclips, which make for a more attractive model.
Chemistry related activities 'Dissolve 1/2 ounce of alum into 1/2 pint of vinegar Dip a fine tipped brush into the solution and write your message on the shell of an egg. Let dry completely; then boil for 15 minutes. Writing cannot be seen on the shell, but is on the inside of the egg.' Having a whiteboard that is magnetic, (discovered that by chance) I use bright plastic-covered magnets (Staples - £1.99? - cheaper from some of the usual suppliers) to represent atoms in equations. The students love it and find it easier to remember as they can come up & move 'atoms' around.