Chemical Reactions and Equations

Why is Sea Water Salty?

Why is Sea Water Salty?

“Why is sea water salty” is a question that has made people curious since time immemorial. Seawater refers to the water available in the oceans on the Earth. Seawater is a mixture of pure water and minerals like salts, dissolved gases, organic substances, and undissolved particles.

Pure water is 96.5 % and minerals are 3.5%. Its physical properties are determined by 96.5% pure water present. In this article, we student will learn about seawater and will get the answer to the popular query that why is sea water salty?

why is sea water salty

How Much Salt is in The Ocean?

Seawater contains 3.5% of salts, dissolved gasses, organic substances, and undissolved particulate matter. The presence of salts influences the most physical properties of seawater like density, compressibility, freezing point, temperature, etc. Two main properties whose determination takes place by the amount of salt in the sea are conductivity and osmotic pressure.

Salinity is the sum of all dissolved salts in grams per kilogram of seawater. In practice, it is difficult to measure. It allows the determination of salt content through some measurements.

Determination of salinity takes place through its most important component, chloride. This chloride content as defined in 1902 as the total amount in grams of chlorine ions contained in one kilogram of seawater.

Factors Explaining Why is Sea Water Salty

Now the question is from where did all this salt come from? Its simple answer is that salts in the ocean come from rocks on land. Some main sources of salt in seawater are as follows:

1. Rain:

The rain that falls on the land, contains some dissolved carbon dioxide from the air. Due to this, the rainwater becomes slightly acidic with carbonic acid. Also, the rain physically erodes the rock and the acids chemically break down the rocks and carry salts and minerals along in a dissolved state as ions.

The ions in the runoff are carried to the various streams and rivers and finally to the ocean. Many of such dissolved ions are used by organisms in the ocean and hence are removed.

But, others are not used up and are left for long periods of time. So, their concentrations increase over time.

Rivers and surface runoff:

Rivers and surface runoff are not the only sources of dissolved salts. Hydrothermal vents on the crest of oceanic ridges also contribute dissolved minerals to the oceans.

These vents are the exit point on the ocean floor through which seawater that has seeped into the rocks of the oceanic crust has become hotter. Therefore it has dissolved some of the minerals from the crust and flows back into the ocean.

With the hot water, large amounts of dissolved minerals also come. Thus, this process has a very important effect on the salinity of the ocean.

 Submarine volcanism:

Another process that provides salts to the oceans is submarine volcanism. That is the eruption of volcanoes underwater. This is similar to the previous process in which seawater is reacting with hot rock and dissolving some of the mineral constituents.

Solved Question for You

Q: Why can’t we drink seawater?

Ans: Seawater is toxic because our body fails eventually when it has to try to get rid of the salt that comes from seawater. Our body gets rid of excess salt by having the kidneys produce urine. But it needs freshwater to dilute this salt in our body.

Normally that is not a problem, as we are always drinking water and eating food with water. Also, the tissue in our body contains freshwater which can be used.

But if there is too much salt in our body, our kidneys cannot get enough fresh water to dilute the salt and body will fail. So, we can’t drink seawater.

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