Density Determination with a Balance: A Simple Guide
How a lab balance with a density kit measures the density of solids and liquids using Archimedes' principle, and what to watch out for.
Density is mass divided by volume. A balance cannot measure volume directly, but with a density kit it can find it using Archimedes' principle: a body in a liquid loses weight equal to the weight of the liquid it displaces.
For a solid
- Weigh the solid in air.
- Weigh it again while it is fully immersed in a liquid of known density, usually water.
- The difference tells the volume of liquid displaced, so the software or a simple formula gives the density.
For a liquid
Weigh a reference body (a sinker) of known volume in air and then in the liquid. The weight loss gives the liquid density.
Tips for good results
- Remove air bubbles from the solid, they make it look lighter.
- Record the liquid temperature, because density changes with it.
- Use a balance with a below-balance hook or a density kit.
- Wet the wire or hanger the same way every time.
- Use a fine balance. See analytical vs precision.
See our laboratory balances and ask us on WhatsApp whether a density kit is available for the model you want, and read the weighing technique guide. Also see what to buy for a lab.
