How To Boil Water at Room Temperature Without Heating It

Splashy surface of water on pan
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You can boil water at room temperature without heating it. This is because boiling is about pressure, not just temperature. Here's an easy way to see this for yourself.

Simple Materials

  • water
  • syringe

You can get a syringe at any pharmacy or lab. You don't need the needle, so it's safe project, even for kids.

How To Boil Water Without Heating It

  1. Use the plunger to pull up a bit of water into the syringe. Don't fill it -- you need airspace in order for this to work. You just need enough water that you can observe it.
  2. Next, you need to seal the bottom of the syringe so that it won't be able to suck up more air or water. You can put your fingertip over the opening, seal it with a cap (if one came with the syringe), or press a piece of plastic against the hole.
  3. Now you'll boil the water. All you need to do is pull back as quickly as you can on the syringe plunger. It may take a couple of tries to perfect the technique, so you can keep the syringe still enough to watch the water. See it boil?

How It Works

The boiling point of water or any other liquid depends on vapor pressure. As you lower the pressure, the boiling point of the water drops. You can see this if you compare the boiling point of water at sea level with the boiling point of water on a mountain. The water on the mountain boils at a lower temperature, which is why you see high-altitude instructions on baking recipes!

When you pull back on the plunger, you increase the amount of volume inside the syringe. However, the contents of the syringe can't change because you have sealed it. The air inside the tube acts as gases do and the molecules spread out to fill the whole space. The atmospheric pressure inside the syringe drops, creating a partial vacuum. The vapor pressure of the water becomes high enough compared to the atmospheric pressure that the water molecules can easily pass from the liquid phase into the vapor phase. This is boiling.

Compare it with the normal boiling point of water. Pretty cool. Any time you lower the pressure around a liquid, you lower its boiling point. If you increase the pressure, you raise the boiling point. The relationship is not linear, so you would need to consult a phase diagram to predict how great the effect of a pressure change would be.