• Question: When I think of evaporation I think of water boiling at 100 degrees centigrade but is it true that water actually boils at 100 degrees farenhite ?

    Asked by mrenglishblonde to Donna, Jo, Mark, Stuart, timcraggs on 21 Jun 2010 in Categories: .
    • Photo: Donna MacCallum

      Donna MacCallum answered on 18 Jun 2010:

      Hi Blondie – great question! Under normal pressure water boils at 99.97 degrees celsius, but liquids can begin evaporating before they boil (so this can occur at lower temperatures) – this only occurs for the liquid closest to the surface

    • Photo: Joanna Buckley

      Joanna Buckley answered on 18 Jun 2010:

      Hi again 🙂

      You’re right! Water boils just a shade under 100 degrees centigrade (212°F) but water evaporates all the time. Next time we have a warm day and a really heavy rain shower, go outside just after it’s stopped raining (not before… you’ll get soaked and blame me!) and see what happens. You’ll notice steam rising and it’s not boliing then.

      100 degrees farenheit is about 38 degrees, close to body temperature and you can get things boliing even at low temperature by increasing their pressure. That’s how old fashioned pressure cookers used to work. You wouldn’t have to heat them up as much to cook your food because the high pressure decreases the boiling point.

    • Photo: Mark Lancaster

      Mark Lancaster answered on 21 Jun 2010:

      Evaporation occurs below boiling point – evaporation only affects molecules close to the surface – they get kicked out by collisions with other molecules and these rogue collisions can give enough of a kick even if the temperature is below boiling point. Boiling affects all the molecules

Comments