Maximizing Displacement: Mass, Volume and Density
Summary
After discussing the concepts of mass, volume and density, the students will be presented with a scenario where they are in a boat full of rocks that is contained in a cylinder of water. The cylinder is filling with poison gas and they have 10 minutes to get out. The top of the cylinder is 4 feet above their reach. The task is to devise a way to use the rocks to elevate their boat 4 feet so they can escape.
CollapseLearning Goals
This is a problem-solving activity. They are told up front that simply throwing all of the rocks overboard will not displace enough water to escape. So the goal is to have the students devise creative approaches using the rocks to maximize their elevation to escape.
Context for Use
I see this as a one period lab that follows a lesson on mass, volume, density, and displacement. Groups of two would work with a small boat, some small rocks and a beaker of water. It can be done without specialized equipment and can be adapted to almost any classroom environment.
Description and Teaching Materials
The students are given a small boat, a pile of small rocks and a beaker that the boat will fit in. They will scale the sizes to represent a 4 foot distance to elevate to escape the beaker. Then they will use the concepts of mass, density, volume and displacement to devise ways to use the rocks in the boat to get themselves up to the top to escape. It will be set up such that piling the rocks will not be enough and throwing them all overboard will not be enough to get them out. By understanding that, while in the boat, the rocks displace water according to their mass and when in the water they displace water according to their volume, they will have to come up with a combination solution that will get them out of the beaker. It is a problem-solving approach that demonstrates the concepts of mass, volume, and density and how they relate to displacement.
Teaching Notes and Tips
The solution will be a combination of throwing certain rocks overboard to maximize water displcement while keeping the correct rocks to pile up in the boat in order to get yourself 4 feet higher to escape. Sharp students will recognize that the best solution is to overturn the boat to raise the base that you are standing on.
Assessment
In the lab write up, the students should describe their problem-solving process, how they used the concepts of mass, volume, and displacement in devising their solution, and, finally, how successful they were.
Standards
We don't have to worry about Mn Science Standards at Community Christian School but I am told that the following standards are addressed by this activity:
IIA4, IIA6, IIA7
IIA4, IIA6, IIA7