This is an activity in which students add marbles to a small plastic cup until it sinks. After some preliminary investigation, students make a prediction of how many marbles their cup should hold before it sinks and then test their prediction. They calculate the density and weight of the cup + marbles with each addition. Analysis and extension questions on the back guide their thinking.
I use this with my 9th grade general science classes as well as lower level conceptual physics classes. Math required is multiplying and dividing.
Unless your stockroom contains 3oz plastic cups and marbles, you'll need to obtain those separately.
Included are some teacher notes as page 1. This lab fits on the front and back of a single sheet.