home > floating and sinking under5s - floating and sinking EQUIPMENT Small plastic fish tanks round glass fish bowl, golf ball, polystyrene ball all identical sizes. ACTIVITY Feel weight of each ball. Drop each ball individually into tank. CONCEPT/LANGUAGE Which ball is heaviest, lightest? Which ball sinks, floats? EQUIPMENT Two plastic guttering pipes, balls of different materials, preferably the same size e.g. plastic, hollow, solid.. wood, wool, rubber, ...