Choose a selection of different materials and test whether they float or sink. (the bath or sink is a good place to test this). The objects could include things such as rocks, plastic bottles, rubber bands etc.
Once you have collected some different items, predict (make a guess) at whether you think they will float or sink.
Why do you think they will float?
Why do you think they will sink?
Now, test your objects.
Conclusion – were your predictions, right? Did any surprise you?
Why do you think they floated/sank?
If you would like to, you could write your predictions and conclusions down.