Does water really freeze at 0°C?

Supercooled water freezing on an ice cube
Supercooled water freezing on an ice cube. Source

Last 6 October (6·10·23) I celebrated the Day of the Mole (one mole is equal to 6 · 1023 molecules) at the School of Industrial Engineers of the Polytechnic University of Madrid. It was a small symposium on didactics and history of science, organised by the specialist group in these areas within the Spanish Royal Societies of Physics and Chemistry (Grupo Especializado en Didáctica e Historia de la Física y la Química or GEDH). My contribution to the programme was a presentation on the life of Elmer Imes. Other participants shared their teaching strategies, carried out experiments... We all had a great time on an unforgettable day.

Participants in the Day of the Mole
Participants in the Day of the Mole

One of the best parts of the day was the guided tour of the Altos de Hipódromo that the students at the School offered us over lunch. The Altos del Hipódromo is one of the most important places in Spanish culture (and I include science in culture). On this small hill in Madrid is the Palace of Arts and Industry, the building that houses the School of Industrial Engineers and the National Museum of Natural Sciences under its immense dome; the Residencia de Estudiantes, where figures such as Luis Buñuel, Salvador Dalí, Federico García Lorca, Severo Ochoa and many others lived and grew up (the women lived in the Residencia de Señoritas, on the other side of the Castellana); and the Rockefeller Institute, the cradle of modern Spanish physics and physical chemistry, where Blas Cabrera, Miguel Catalán and Arturo Duperier carried out their research.

The Transatlantic Pavilion of the Residencia de Estudiantes
The Transatlantic Pavilion of the Residencia de Estudiantes

The weather was very pleasant for October and we all ended up eating in the canteen at the engineering school. I must digress here to say how happy I was to be eating in a university canteen again. There is no such concept in Scottish universities as a place to socialise with peers while enjoying good, affordable food (and drink) and I miss it very much.

The organiser of Day of the Mole and the visit to Hippodrome Heights, Gabriel Pinto, is also the editor of Faraday Journal, the GEDH's physics and chemistry newsletter. At the end of the visit to the Altos, walking with him, I promised to write an article for the journal.

Original cover of Faraday Journal
Original cover of Faraday Journal

The journal was originally founded in 1928 by Modesto Bargalló (1894-1981), one of the pioneers of 20th century popular science in Spain, with the aim of promoting knowledge of the didactics and history of science among teachers of the time. Modesto had to go into exile in Mexico after the Spanish Civil War, where he continued his popular science work, researching the history of chemistry in Latin America (here is a fantastic website in Spanish about him).

Modesto Bargalló (1894-1981)
Modesto Bargalló (1894-1981)

In 2021, the Grupo de Didáctica e Historia revived the journal and turned it into a benchmark where you can find entertaining and rigorous popularisation articles and, frankly, with much more original topics than the ones we are inundated with by the fashionable popularisers (here is the link to all the issues of the journal).

My article tries to correct what is probably the most common mistake people make after studying physics at school: the temperature at which water freezes is 0ºC. I talk about supercooled water, los Toreros Muertos (a Spanish pop band) and the world record I hold for lowering the temperature of water without turning it into ice. The article is on page 23 of issue 41, June 2024. You can access the full journal (sadly, it is only in Spanish) via the following link:

Does water really freeze at 0°C?
As always... I hope you like it!
Posted on 11 July, 2024