The main difference between salt water and fresh water is the salinity content. Both contain salt or sodium chloride, but fresh water contains only small amounts of salt. The earth’s oceans and seas are saltwater ecosystems, while lakes, rivers, streams, marshes and ponds are freshwater ecosystems. Seawater’s viscosity, or internal resistance to flow, is higher than fresh water because of differences in salinity.
The average salinity of ocean water is 3.5 percent which means that 35 grams of salt dissolve in a liter of seawater. The salinity of different bodies of water hinder organisms from thriving in both salt water and fresh water. Some plants and animals survive in one type of water but not the other.
Another considerable difference between the two is their density. Salt water has a higher density than fresh water because of the sodium chloride it contains. Furthermore, cold salt water is denser than warm salt water, but it becomes less dense when water freezes into ice. The boiling point of seawater is higher than that of pure water, and its freezing point is lower. The density of salt water is 1.025, while fresh water’s density is 1.0. Objects float more easily in salt water than in fresh water. Humans typically find it easy to float in seawater but not in fresh water.