Determining If an Electric Kettle Filled With Alcohol Will Ever Automatically Turn Itself Off

Prolific science vlogger and author, Steve Mould responded to a viewer asking if an electric kettle filled with alcohol will ever turn itself off. Mould started off by predicting that the kettle wouldn't automatically shut itself off due to the fact that alcohol has a lower boiling point than water.

It's an interesting question, isn't it? Because electric kettles turn off automatically when water reaches boiling point, but alcohol, specifically the chemical ethanol has a lower boiling point than water. So my prediction is that a kettle full of ethanol will not turn off automatically. It will boil dry because that mechanism that turns the kettle off automatically would never kick in because it's based on temperature.

Unfortunately for Mould, his prediction proved wrong due to the safety precautions within the different kettles he tried. So he took each one apart, noting that the first kettle had a tube that connected to a bimetallic strip that switched the kettle off. This design detects vapor rather than temperature.

So what's the purpose of this design? Well, it's actually really clever because it detects the presence of boiling in general, not a specific temperature. Like you could have a liquid in there, that's at 100 degrees, but if it's not boiling, then it's not producing vapor. And there's nopressure to force that vapor down the tube to the bimetallic strip.

The second kettle confused Mould a bit more, as he didn't understand how it detected either temperature or vapor.

I'm just wrong, it's weird though because I just don't understand how this kettle works. It doesn't make sense to me because surely if this little kettle is able to bring water to the boil, this thermal switch can't shut off before 100C and yet it seems to be.

As it turns out, an electric kettle filled with alcohol will automatically shut itself off if it creates enough steam.