To know and compare the difference between the density of the fresh water and salt water or sea water require a graduated cylinder, balance, and weighing machine. The graduated cylinders are the containers that have markings on them to measure the volume of the liquid.
First, fill the cylinder with 1000 ml of fresh water which is the measure of the volume. now weight the cylinder filled with the fresh water and then find the difference between filled and empty container divide the mass of the fresh water by its volume, the result is the density of fresh water.
Repeat the process with salt water or sea water. The answer would be sea water has more density than fresh water.
