Question

How can water be boiled without heating?

Answer 1

The boiling point of a liquid depends on both temperature and pressure. As pressure increases, so does the boiling temperature. Pressure cookers are used in cooking to raise the temperature at which liquids within will boil. Conversely, the lower atmospheric pressure on a mountain top makes it harder to get boiling water hot enough for good tea or coffee.

Boiling occurs when a liquid's molecules have enough energy to break free from surrounding molecules. Think of higher pressure as making that escape more difficult by offering a counteracting force.

Water boils under normal atmospheric pressure at 212°F (100°C). Imagine it at 221°F (105°C) but NOT boiling in a pressurized container. If the pressure is quickly reduced, the 221°F (105°C) water at normal pressure will now boil.

For another example, put water at room temperature into a vacuum chamber and begin removing the air. Eventually, the boiling temperature will fall below the water temperature and boiling will begin without heating.