Abstract
This article describes a non-traditional lab focused on applying Archimedes' principle in a situation that is, for students, new and unusual. Two main interconnected features of this lab are important.
Firstly, it is not a "standard" lab experiment in which students are instructed to measure something and then to interpret results. Here, a very important element is prediction.
Students have to predict the result first, calculate it using Archimedes' principle, and only then do the measurement. Secondly, it is not the teacher who tells students whether their calculation is right or wrong, it is the experiment itself.
This article presents the lab work itself (instructions and results), some methodological comments, and my experience in school.