Salt Questions · Science, chemistry & environment
How does salt water affect the density of water?
Short answer
Dissolving salt makes water denser, because the salt adds mass without increasing the volume much. Fresh water has a density of about 1.000 g/cm³; average seawater is about 1.025 g/cm³; saturated brine is about 1.2 g/cm³. Denser water pushes up harder on objects, which is why things float more easily in salt water.
Density, g per cm³
Bars start at zero; differences look small but matter for buoyancy.
Why salt adds density
When salt dissolves, its ions fit snugly among water molecules, so the solution's volume grows only slightly while its mass increases noticeably.
Density compared
| Fresh water | ≈ 1.000 g/cm³ |
|---|---|
| Seawater | ≈ 1.025 g/cm³ |
| Saturated brine | ≈ 1.20 g/cm³ |
| Dead Sea | ≈ 1.24 g/cm³ |
The egg experiment
An egg sinks in fresh water. Stir in salt, a tablespoon at a time, and it floats once the water is denser than the egg.
In nature
Denser salty water sinks below fresh water, helping drive deep ocean currents, and it's why ships float higher in the sea than in rivers.
Related on The Salt Almanac
More science, chemistry & environment questions
- Why do things float easier in the Dead Sea?
- What is the difference between organic and inorganic salt in chemistry?
- What is the chemical formula for table salt?
- Why does salt melt ice on roads in the winter?
- Is salt an element, a compound, or a mixture?
- How does salt water conduct electricity?
Cite this page
For school projects and reports. Teachers often prefer the original sources too: see the list below.
The Salt Almanac. (2026, November 8). How does salt water affect the density of water. https://saltalmanac.com/answers/how-does-salt-water-affect-the-density-of-water
“How does salt water affect the density of water.” The Salt Almanac, 8 Nov. 2026, saltalmanac.com/answers/how-does-salt-water-affect-the-density-of-water. Accessed [today's date].
“How does salt water affect the density of water.” The Salt Almanac. Last modified November 8, 2026. https://saltalmanac.com/answers/how-does-salt-water-affect-the-density-of-water.
Original sources
- Wikipedia. Seawater. https://en.wikipedia.org/wiki/Seawater
- Wikipedia. Dead Sea. https://en.wikipedia.org/wiki/Dead_Sea