Does salt speed up the boiling of cooking water? Why does drinking salty water make us thirsty? | SCIENCE

If you are going to drink a few sips of ocean water, for example, your body will have to urinate more than it drank to get rid of all that extra salt, leaving you more thirsty than before.

On the advice of old grandmothers, salt should be poured into a pot of water on the stove to boil faster. This is exactly what we do when we cook pasta, for example; So putting salt in boiling water is a must, but do we put it for this specific reason?

According to Live Science, the story is only true in a small part; Because if you were to add 1 teaspoon (less than 3 grams) of salt to a liter of water, there would not be much difference and the time difference until boiling would be only seconds if any.

But if you want to make a big difference in terms of reducing the time it takes to boil water, 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 increases the boiling point of water, but the amount of salt used in cooking water is so small that it does not affect time.

But what is true is that pasta water must be salted in order to have a pleasant taste because it needs a reasonable amount of salt that is easily absorbed by the boiling water.

How does water boil?

It takes a lot of energy to boil water and 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 be equal to atmospheric pressure, says Leslie Ann Giddings, an assistant professor of chemistry and biochemistry at Middlebury College in Vermont, for Live Science.

This is partly why water boils at a lower temperature on Mount Everest than at sea level; At 8800 meters above Mount Everest there is less air, or less pressure, exerting pressure on the water and here it boils faster.

Let’s imagine a pot of water on a stove burning at sea level, Giddings says. When salt is added, this makes it difficult for water molecules to come out of the pot and enter the gas phase that occurs when water boils; This gives the 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 raise the temperature of salt water by 1 degree Celsius compared to fresh water.

“Salt water will rise faster than pure water, but it will have a higher boiling point and the mass will be greater when you add salt to the same volume of water, so that does not mean that water salty boils faster. ” says Giddings.

But the story changes if you do not have the same volume of water. Let us imagine two cups: 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, 100 g of water has a high heat capacity, which means that it takes a lot of energy to boil this water. In contrast, the salt in pot B is now melted and the dissolved salt has a lower heat capacity than pure water, according to Mike Daman, director of inorganic materials division at the Southwest Research Institute in San Antonio, Texas.

Moreover, bowl B contains only 80 grams of water, which means that there is less water for heating than bowl A.

Explaining this, Daman wrote, 20% of salt water would heat up 25% faster than pure water and 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 the pasta water to give it a pleasant aroma.

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

Why can’t we drink salt water?

Aside from the fact that it does not taste good, drinking salt water is a bad idea because it causes dehydration, says Andrea Thompson in her Live Science article.

And if you are going to drink a few sips of ocean water, for example, your body will have to urinate more than it drank to get rid of all that extra salt, leaving you more thirsty than ever.

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

But this does not mean that some animals have developed ways to overcome the problem of excess salt in seawater; Like albatrosses, they have special saline glands just behind the eye sockets, which absorb salt from the water that the bird swallows and then secrete it into a saline solution that drains through the tip of its beak.

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