Know the boiling point of water to prepare coffee

Oct 1, 2019 | Curiosities

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What is the boiling point of water?

The answer to this question is simple. The boiling point of water is 100°C or 212°F at sea level (1 atmosphere).

However, this value is not constant and varies depending on atmospheric pressure. But the atmospheric pressure depends on the height. Therefore, the boiling point of water varies according to the height.

Water boils at a lower temperature as the altitude increases. If we boil water both at the top of a very high mountain and at its base, the water at the top will boil at a lower temperature than the base.

The boiling point of water also depends on the purity of the water. Water containing impurities (such as salt) boils at a higher temperature than pure water. This phenomenon is known as Boiling point elevation (ebullioscopy), which is one of the colligative properties of matter.

However, we will not concentrate on this phenomenon, because to raise the boiling point of water 1°C (33.8°F), we must add 58 grams of table salt (NaCl) per liter of water, and this is not useful when preparing coffee.

Ebullición del agua - Water boiling

Water vapor due to water boiling

Why is it important to know the boiling point of water?

Water temperature has always been a topic of debate and study when preparing coffee. This is why baristas put all their effort into finding the ideal temperature for the correct extraction of the coffee.

Not all coffee beans are equal, depending on traceability information; a coffee may require a higher or lower water temperature for proper extraction.

Experts recommend heating the water to a temperature of about 90°C ± 5°C (194°F ± 41°F). Seeing these values, some may think that the important thing is that the water does not boil. However, in some places on the planet, the water may already be boiling at that temperature.

As is the case in the city of La Paz, in Bolivia, where the boiling point of water is approximately 88°C (190.4°F) and this can be a challenge when preparing a coffee.

Ebullición del agua - Water boiling - know

Water boiler

The boiling point of water at different places

The boiling point of water can be determined mathematically, for different places, knowing their altitude.

Using the barometric equation.

Water boiling barometrica

And the Clausius Clapeyron equation.

Water boiling Clausius Clapeyron
The boiling point of water can be determined, for different altitudes.
Ebullición del agua - Water boiling - graph

Graph of the boiling point of water as a function of altitude

With the above equations and taking the altitudes of some cities, the following water boiling temperature values are obtained.

City

Altitude (m)

T (°C)

T (°F)

La Paz – Bolivia3.64088.0190.4
Quito – Ecuador2.85090.6195.1
Bogota – Colombia2.64091.3196.4
Mexico DF2.25092.6198.7
Caracas – Venezuela90097.1206.7
Madrid – Spain66797.8208.1
Santiago – Chile57098.1208.6
Lima – Peru15499.5211.1
Buenos Aires – Argentina2599.9211.9
London – England11100211.9

 

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