# Boil water below normal boiling temperature

3 Steps
As a fun science demonstration, we're going to boil water at about 128F or 53C, significantly below the 212F or 100C that is normally needed, in a syringe.  The water will simply come from a household hot water tap.  The trick is that the boiling temperature of a liquid goes down as the air pressure goes down--water boils when its vapor pressure exceeds the air pressure.

This is a good demonstration to show to kids at home or at a school.

What you need:
• Plastic syringe  (I used a 12mL monoject.  One can buy them cheap in large or small quantities on amazon or ebay.)
• Hot tap water, at around 125F
• Cup for the water
• Optional: Thermometer

Remove these ads by Signing Up

## Step 1: Pour water into cup

Run hot water from the tap, waiting for it to reach full temperature.  Then fill up a cup with the hot water.

Stick a thermometer into it if you like.  But don't take too long, or the water will cool off too much.
Computothought says: Aug 30, 2011. 11:09 PM
Would be interesting to do that with a large pvc equivalent of the small syringe. Might actually be useful for camping or picnics.
arpruss (author) in reply to ComputothoughtAug 31, 2011. 10:53 AM
You mean, for disinfecting water? I am not sure low-temperature boiling will disinfect. Or is there some other purpose to boiling?
Computothought in reply to arprussAug 31, 2011. 7:09 PM
You could have a can of soup or whatever suspended in the tube. when the water boils, the food in the can gets cooked (patent pending).
The Ideanator in reply to ComputothoughtSep 3, 2011. 1:13 PM
Not going to work.

The water is boiling due to the low pressure, taking that a step further, it would require a higher temperature to boil water in a higher pressure.
arpruss (author) in reply to ComputothoughtSep 1, 2011. 12:36 PM
The water is boiling at 50C. That's not enough to cook the soup.
Computothought in reply to arprussSep 1, 2011. 2:16 PM
Sure you are right, but most soups in a can are already cooked and just need some heat.
arpruss (author) in reply to ComputothoughtSep 1, 2011. 5:12 PM
But you're not actually generating any heat in this way. In fact, the boiling takes heat out of the water. So you might as well put it in the water without any low pressure tricks. Not that I wouldn't mind a use being found for this!