Burning snow? A conspiracy theory resurfaces

For example, in this video shared on Telegram on February 10, a man collects snow in front of his house and burns it on his gas cooker. The snowball doesn't seem to melt, then it blackens before catching fire. How can this be explained? Tristan Werkmeister from the France 24 Observers team investigated this claim. 

What can we learn from this video?

If snow gives the impression that it doesn't melt, the explanation is chemical, and is called sublimation. As explained in this video by chemistry professor Kim Hilton, water goes directly from a solid to a gaseous state: it doesn't melt, it evaporates. 

Then, if the snow blackens, it is not because of what it contains but because of the impurities in the gas, which create a carbon layer as explained in this article from NBC25 News.

Finally, pure snow cannot burn, since it is only water, confirms Jean-Michel Courty, professor of physics at Sorbonne University. So in the video showing a burning snowball, the only scientific explanation is that it contains other elements that are not necessarily toxic: the same process can occur with sugar, or with wood, paper or plastic residues collected with the snow.

It is impossible to define exactly what is in the snow without analysing it. But the "burning snow" effect does not mean that the substance itself contains toxic elements that are dangerous to humans.

A longtime conspiracy theory

This type of video is not uncommon in places where it snows: according to their authors, they are proof of the existence of chemicals in the air, such as chemtrails, a theory claiming that aeroplanes spread chemicals in the atmosphere to control the climate or poison the population.