The students in the class conducted an experiment to observe which objects float and which objects sink in water. They brought various objects like rocks, paper, plastic bottles, corks, leaves, and flowers to test. Through observing which objects floated and which sank, they discussed that rocks sank because they are heavier than water, while corks and plastic bottles floated because they contain air. The students decided to continue the experiment by bringing more objects and recording their observations on a class list to classify each object as floating or sinking.