Science Buddies: "Ask an Expert"

Hello.

We've tried to build a hydrometer with a straw and clay but the results to measure the salinity of water are not accurate. Any ideas as to how to build a hydrometer that would give us accurate results? Thank you!

Dear himayogi,

Thanks for reaching out. I found some alternative approaches to building a hydrometer. They are, naturally, quite similar since the concept behind each is the same.

https://www.exploratorium.edu/snacks/ey ... hydrometer
https://youtu.be/29JzFiBsbTk
https://youtu.be/qIz1BEQyHWI

In the case of any of these hydrometers, the accuracy can be improved through calibration. You probably did a "single point" calibration with distilled water. To improve upon this, you can make a "calibration curve" based on multiple measurements in solutions of known densities. If you google "how to calibrate a hydrometer," you will find a lot of resources on how to do so since hydrometers are used to measure sugar content in a certain fermented beverage.

Good luck!
Dr. Payne