the experiment for Finding the extension of the rubber with the stand and the measuring rule and all .
Or perhaps you might as well make a model which for example something pretty easy is the desity chapter .
make a boat of paper pr any other perhaps rough material *mathalan cartoon willa fileen ..etc* , actually make two of them .
then insert one in FRESH water and the other in SALT water .and mark the points and this basically shows you the following principle :
body sinks LESS in HIGH dense liquid ,and body sinks MORE in LESS dense liquid .
I hope I helped