Boiling Water at Room Temperature

Materials: ★★☆ Available in most school laboratories or specialist stores
Difficulty: ★☆☆ Can be easily done by most teenagers
Safety: ★★☆ Some safety precautions required to perform safely

Categories: Particles and States of Matter, Pressure and Fluids

Alternative titles: Boyle-ing Water

Summary

By pulling back the plunger on a water-filled syringe with the tip sealed, the pressure inside is reduced. This causes the water to boil at room temperature, demonstrating how boiling depends on pressure as well as temperature.

Procedure

Fill a clear plastic syringe about one-quarter full with tap water, minimizing the amount of trapped air.
Place a finger firmly over the syringe tip to seal it.
Pull the plunger back to increase the volume inside. Notice that bubbles appear, and with enough pull, the water boils even though it is at room temperature.
Release the plunger to let it snap back in, creating nucleation sites for easier boiling in later attempts.
Repeat pulling back the plunger. Observe that boiling happens more readily once bubbles have already formed.
Optional: Try with carbonated water and compare how carbon dioxide bubbles form quickly under reduced pressure.

Links

Boiling in a Syringe - FlinnScientific:

📄 Boyle-ing Water - Exploratorium: https://www.exploratorium.edu/snacks/boyle-ing-water

Variations

Heat the water slightly, but use a safe temperature to touch.
Use a vacuum pump instead of a syringe to reduce pressure more dramatically.
Try the experiment with different liquids and compare their boiling responses.
Demonstrate the concept of the triple point by discussing conditions where water can freeze and boil simultaneously.
Compare plain tap water with distilled water to observe differences in bubble formation.

Safety Precautions

Ensure the syringe is plastic, not glass, to prevent breakage under force.
Do not pull the plunger out completely, as water may spill.

Questions to Consider

Why does reducing pressure cause water to boil at room temperature? (Because boiling occurs when vapor pressure equals surrounding pressure, and lowering external pressure makes this easier.)
Why are bubbles more likely to form after snapping the plunger back once? (Because seed bubbles act as nucleation sites.)
How does this demonstration relate to Boyle’s Law? (Increasing volume decreases pressure, following the inverse relationship.)
Where in everyday life might you encounter water boiling at low temperatures? (High-altitude cooking, vacuum distillation, or conditions on Mars.)