Build your own solar system with papier mache balloons - but use coloured paper for the final layer, get the kids to look at the size of their planet and work in teams (higher ability can manage a bigger planet!) they look super suspended from the ceiling once done and the students then research their planet and tell the class about it.
Doing density..two nice bits 1) Asked a pupil which was heavier, 1kg of feathers or 1kg of lead - caught them out (they nearly always fall for this). Then produce said items (feathers were a large bin bag of packing chips with a few masses in to make it up to weight) - placed both on balance to show same mass 2) Then brought out transparent bag full of toy balls (from early learning centre) - left a few balls in the bag - scrunched up bag to show low volume (but same number of particles - so more dense. Unscrunch bag - larger volume, same balls, so less dense
Year 8 and I spent a few happy lessons researching fossil fuels from books, the internet and multimedia science ,also from some energy posters I picked up somewhere - probably British Nuclear Fuels (sad but they are the guys with the money and the freebies). Then I challenged them to complete a proforma page as a news article on the subject of fossil fuels within one lesson - chocolate to the first three that completed it neatly and accurately - You should have seen them work on the second to last day of term!! Beautiful. To top this on the last day we played bingo with fossil fuel words and weakest link and finally finished with fill in the blanks as summary.
Radioactive half life ... popcorn ... Count out 12 (can halve and quarter it) corn kernels and heat them in a beaker. Get kids to count and time for half of them to pop! Usual half life for popcorn = 3 to 4 mins. Hot beaker works best and don't use too strong a flame without keeping it moving otherwise they burn ... don't be tempted to use too many ... can take ages and char rather than explode. Best effect if a few leap out of the beaker ...