Will Salt Water Dry Up?

Water is a crucial component for all forms of life. Without it, life as we know it could not continue. It’s distinct from other chemicals due to its unusual features. When salt is added, a lot of different things happen chemically and physically. In this piece, I’ll explain whether or not seawater evaporates.

Thus, it begs the question: does saltwater evaporate? As you probably guessed, salt crystals form as saltwater evaporates. And the rate of evaporation of the salt solution is reduced by the addition of salt to pure water. Because the salt solution’s saturation vapour pressure is dropping, this is what happens. Vapor pressure differential between the air in contact with the salt solution and the air at some altitude is directly proportional to the rate of evaporation.

Salts (sodium chloride, magnesium chloride, and potassium chloride) are naturally occurring components of many types of water. It has been found experimentally that the amount of salt in the water has a significant impact on the rate of evaporation.

Evaporation is the phase transition from a liquid to a gas caused by an increase in temperature or a decrease in pressure.

When a substance is in a liquid condition, some percentage of its molecules will escape as vapour. Some environmental conditions, such as pressure, temperature, humidity, etc., affect the rate of evaporation.

In a similar vein, saltwater, which is a solution in a liquid state, loses its molecules in the form of vapours at temperatures and vapour pressures above those at which the solution is liquid.

The water molecules around the salt particles in a salt solution prevent the salt from re-crystallizing.

When water evaporates, some of the water molecules go up in smoke, while others stay to keep the salt crystals apart. All the water evaporates, leaving behind the salt crystals, which then recrystallize.

Science Experiment With Salt Water

High school chemistry lab practicals typically include a salt crystallisation experiment. The goal is to achieve crystallisation of the salt solution.

Evaporating seawater is the method of choice to obtain salt crystals. Here are the measures to take to carry out this experiment.

Put some salt into a pan of water and stir it around until it’s totally dissolved.

Prepare a baking sheet with the dark paper. The water molecules are given more energy, allowing them to evaporate more quickly, thanks to the dark hue of the sheet.

Place the baking sheet with the salt solution in it in a warm area, such as the sun or a window.

Over the course of a few hours, the water level will drop as the solution evaporates off the water molecules.

If you let it sit for a few hours and keep track of what happens, you’ll notice that the water evaporates and crystallised salt is left behind.

The salt is also processed from seawater. Extraction of salt from saltwater is performed on a massive scale. The idea, though, remains the same.

How does salt influence the rate at which water evaporates?

When everything else is equal, the evaporation rate of salt water is lower than that of fresh water under typical conditions.

The following factors account for this:

As salts like NaCl are added to water, the vapour pressure drops. This means that less water will evaporate from the surface of the solution. So, the more salt there is, the less water will evaporate.

It’s crucial to keep in mind that surface evaporation is the fundamental process at work here. This indicates that only the molecules near the solution’s surface are susceptible to evaporation.

Na ions and Cl ions, both present in NaCl aqueous solution, share the available surface area. The number of H2O molecules on the surface is therefore decreased (liquid-air boundary). As a result, when salt is added to water, less water evaporates.

Do salty ocean waters evaporate?

Water on Earth circulates primarily through aqueous ecosystems. There is a great deal of ocean coverage. About 71% of Earth’s surface is taken up by oceans.

They supply 97% of the world’s fresh water. And the ice caps and glaciers account for the remaining 3% to 5% of the world’s water supply. Freshwater makes up less than 1% of the world’s total water supply.

A variety of salts can be found in seawater. Sulfate (SO24), chloride (Cl), potassium (K+), sodium (Na+), calcium (Ca2+), and magnesium (Mg2+) are the most common of the six primary salt ions. The term salinity is used to describe the amount of salt in ocean water (S).

The salt in saltwater is not bound to the water in any way chemically. It is simply mixed with saltwater.

When all other parameters are held constant, evaporation from saltwater is far slower than from freshwater. The vapour pressure of seawater is reduced by the salts contained in saltwater, causing less evaporation to occur.

To leave behind trace amounts of salt, seawater evaporates only to leave behind pure water molecules.

The rusting of cars owned by locals is a good indicator of how much salt is in the air around the sea.

What about evaporation rates, do saltwater pools lose water quicker?

The salinity of pool water reduces the rate of evaporation, which is something to keep in mind. The salt particles in the pool reduce the vapour pressure of the salt water and take up residence on the salt water’s surface (air-liquid boundary).

And remember, in a salty solution, only the pure water molecules near the surface evaporate or escape.

Since portion of the surface area is occupied by the salt particles, there are fewer H2O molecules present, and hence fewer H2O molecules can escape as vapours.

Because of this, saltwater pools have a lower evaporation rate than their freshwater counterparts. Evaporation rates are always lower if the water is more salty.

Read more: Can You Heat Glass?

Misha Khatri
Misha Khatri is an emeritus professor in the University of Notre Dame's Department of Chemistry and Biochemistry. He graduated from Northern Illinois University with a BSc in Chemistry and Mathematics and a PhD in Physical Analytical Chemistry from the University of Utah.


Please enter your comment!
Please enter your name here

Read More