Take home lab experiment – Ranking of common fluids by density

This is a very simple take home lab to get students started into the semester. They are asked to use three different techniques to rank a range of common fluids (that can be found in one’s home) by their density . There are a broad range of approaches to this including directly measuring their density, using buoyancy, using multi-fluid manometers, or simply stacking them up. However, there are also some tricks to this as well. For example, it is easy to end up with two or more of the fluids being miscible making it hard to float one on the other. It is also a great introduction to quantifying errors. Many common fluids are quite close in density so often the student groups would get different rankings from their different experiments. This illustrates that even simple measurements have error/uncertainty associated with them. This provides a great motivation for discussing measurement errors and resulting calculation uncertainty (though at the start of the semester I typically only discuss measurement error and move onto error analysis later).

As with all the take home lab write ups I will not publish detailed methods for conducting the tests. I still use them in class and want my students to figure it out on their own. The instructions I give to students are below.

Introduction

As we have seen in class different fluids have different densities. Density is a fluid property that varies with temperature (and pressure but not very much). Accurately measuring the density of a given fluid can be done in many ways and you are welcome to research this as part of this assignment.

1. Identify 5 common fluids that you find in everyday life (kitchens are a good place to start)
2. Run a series of experiments to establish their relative densities (that is, rank them by their density)
3. Use three different experimental techniques to establish this ranking.
4. Write a brief report that
1. Is 2 pages max including photos of you running your experiments
2. Describes the experiments you used to establish your rankings
3. Includes a table of fluids ranked by density

Rules

1. You may not use equipment in the fluids lab or any other scientific lab equipment
2. You should only use items that are commonly available in your home
3. If you need to go to a store to buy something please come and see me first. I may be able to lend you something or I will buy it and then lend it to you. You will need to explain why you need it and it should be cheap.

Due in 2 weeks

An index of all the demonstrations posted on this blog can be found here. Don’t forget to follow @nbkaye on twitter for updates to this blog. If you have a demonstration that you use in class that you would like to share on this blog please email me (nbkaye@clemson.edu). I also welcome comments (through the comments section or via email) on improving the demonstrations.