Science Buddies: "Ask an Expert"

Apologies if this is in the wrong place.

My daughter asked me this question after watching a Bear Grylls program where the made water safe to drink by boiling it first.

She'd been taught at school about the boiling point of water (100C), and that this can be reduced by reducing the atmospheric pressure. However, in terms of water purification, if you reduced the atmospheric pressure and boiled water at a lower temp, say 70C, would it then become safe to drink?

Is it the boiling of the water that renders it safe, or the temperature it's boiled at?

Thanks

Stephen (flustered Dad!)

Hi Stephen,

Heating the water to high temperatures is what makes it safe to drink by killing any microorganisms that might be present. If you were boiling the water at lower atmospheric pressure, for example at high elevation, you would need to boil it for a longer period of time to be sure to sterilize it since the temperature would be lower.

Audrey