Does salt make water boil faster? Why can't we drink ocean water? 

According to the advice of old grandmothers, salt should be added to a pot of water on the stove to make it boil faster.

This is exactly what we do when we boil pasta, for example;

So putting salt in boiling water is a necessity, but do we put it for this specific reason?

According to Live Science, the story is true in only a small part;

Because if you were to add 1 teaspoon (less than 3 grams) of salt to a liter of water, it wouldn't make much difference, and the time difference to boiling would be just seconds if any.

But if you want to make a big difference in terms of reducing the time it takes for the water to boil, you really have to put in a lot of salt, which is not suitable for human use.

As for Rebecca Morris, a writer at Martha Stewart, she says - chemically - that salt raises the boiling point of water, but the amount of salt used in cooking water is so small that it does not affect the timing.

But what is true is that you have to put salt in the pasta water in order to make it taste palatable, because it needs a reasonable amount of salt that is easily absorbed by the boiling water.

How does water boil?

It takes a great deal of energy to boil water, and it takes one calorie of energy to raise the temperature of one gram of water by one degree Celsius.

For water to boil, its vapor pressure must equal atmospheric pressure, Leslie Ann Giddings, an assistant professor of chemistry and biochemistry at Middlebury College in Vermont, tells Live Science.

This is partly why water boils at a lower temperature on Mount Everest than it does at sea level;

At 8,800 meters above Mount Everest there is less air, or less pressure, putting pressure on the water and it boils here faster.

Let's imagine a pot of water on a stove burning at sea level, Giddings says. When salt is added it makes it difficult for the water molecules to escape from the pot and enter the gas phase that occurs when the water boils;

This gives salt water a higher boiling point.

Giddings explains that, on the other hand, the heat capacity - the amount of heat needed to raise the temperature of a substance by one degree Celsius - will be less for salt water than for fresh water;

This means that less heat is needed to increase the temperature of salt water by 1 degree Celsius compared to fresh water.

"Salt water will rise faster than pure water, but it will still have a higher boiling point, and the mass will be greater when you add salt to the same volume of water, so that doesn't mean that salt water boils faster," Giddings says.

But the story changes if you don't have the same volume of water.

Let's imagine two bowls: bowl A and bowl B. Bowl A is filled with 100 grams of water, while bowl B has 80 grams of water and 20 grams of salt.

In Pot A, 100g of water has a high heat capacity, which means that it takes a lot of energy to boil this water.

By contrast, the salt in Pot B has now melted, and the dissolved salt has a lower heat capacity than pure water, according to Mike Daman, director of the division of inorganic materials at the Southwest Research Institute in San Antonio, Texas.

Furthermore, bowl B contains only 80 grams of water, which means it has less water for heating than bowl A.

Explaining this, Daman wrote, 20% of salt water would heat up 25% faster than pure water, and would win the race to the boiling point;

So pot B will boil faster than pot A because it has less water and more salt.

Salt is necessary for pasta water to give it a palatable flavour.

But a 20% salt water solution is too salty to use in cooking or anything else, so seawater itself contains only about 3.5% salt, yet we can't cook with it or drink it.

Why can't we drink salt water?

In addition to the fact that it doesn't taste good, drinking salt water is a bad idea because it causes dehydration, Andrea Thompson says in her article for Live Science.

And if you took a few gulps of ocean water, for example, your body would have to pee more than it drank to get rid of all that extra salt, leaving you thirstier than you used to.

Seawater can be desalinated to reduce salt levels to where it is palatable, but this technique is energy intensive.

But this does not mean that some animals have developed ways to overcome the problem of excess salt in sea water;

Like albatrosses, they have special saline glands just behind their eye cavities, which absorb salt from the water the bird swallows and then secrete it into a saline solution that drains through the tip of its beak.