Does salt actually make water boil faster than usual?

According to an old folktale, there was a wife while cooking, she noticed that when adding salt to a pot of water placed on the stove, the water boiled faster than usual. So does salt make the water boil faster?

" This story is real, but the difference between them is insignificant, " an expert told Live Science.

" If adding 1 tablespoon of salt (less than 3 grams) to 1 liter of water, it will not be much different from when you boil water normally" - Lesley-Ann Giddings - an assistant professor of chemistry and biochemistry at the school Middlebury University in Vermont said .

"Transformation: If that happens, the difference in boiling time is merely a few seconds " - Giddings added.

It takes a lot of energy to boil water. In fact, you need 1 calorie of energy to heat 1g of water to 1 degree C ( 1.8 degrees F ).

" To boil water, its vapor pressure must be equal to atmospheric pressure. It is only part of explaining why why boiling water on Mount Everest has a lower temperature than boiled water. "It is because there is less air or less pressure, pushing the water on the top of the mountain at 8,800 meters (29,000 ft), " Giddings said.

" However, we can imagine a kettle placed on a fire at sea level. When adding salt, it will make it difficult for water molecules to escape from the kettle and into the gas phase. This makes the water boil, so salt water will boil at higher temperatures, "Giddings added.

" There are many answers that explain that, " noted Giddings.

She explained: " Heat capacity - the amount of heat needed to increase the temperature of a substance to 1 degree C - freshwater will be lower than saltwater. This means that saltwater does not resist change. temperature like fresh water, in other words, less heat, so the salt water temperature is increased to 1 degree Celsius compared to fresh water ".

" The saltwater temperature becomes hotter than pure water. However, it still has a higher boiling point, and a larger volume when adding salt to the same volume of water. that salt water boils faster, "said Giddings.

But the story changes that if you give two different amounts of water - that is, if you put a smaller amount of water in a kettle and add more salt. Imagine that there are 2 warm water: warm A and warm B. Warm A is poured 100g of water while warm B only has 80g of water and 20g of salt.

100g of warm water A will have a higher temperature, meaning it requires a significant amount of energy to keep the warm water boiling. In contrast, warm salt B is dissolved and dissolved salts have a lower heat capacity than pure water, according to a Mike Dammann article , Inorganic Process Manager at the Southwest Research Institute in San Antonio. , Texas.

" Moreover, warm B only has 80g of water, less water has to be heated than pot A. 20% of salt water will be heated faster than about 25% of pure water and have a faster boiling speed " - Dammann wrote in one Online explanation.

" So warm B will boil faster than warm A because it contains less water and more salt, " Dammann said.

" But the aqueous solution with 20% salt is quite salty, the seawater contains only 3.5% salt . Most people cannot use seawater to cook because it is too salty. " Giddings said.

" In fact, you will have to add a lot of salt to the water to see the difference in taking less time to boil salt water, " Giddings said.

For a better understanding, see the boiling time between pure water and salt water: