The water that has stopped boiling will boil again after being poured with cold water. The premise is that in an instrument, such as a flask, it will boil again after pouring cold water outside the flask. After pouring cold water, the air in the flask shrinks due to cold, which leads to the decrease of air pressure in the bottle. After the air pressure is reduced, the boiling point of water is reduced, so that the water in the bottle reaches the boiling point again and boils again.

Extended data:

Boiling is a violent vaporization phenomenon that occurs simultaneously inside and on the surface of liquid at a certain temperature. The boiling point is the temperature at which the liquid boils, that is, the saturated vapor pressure of the liquid is equal to the temperature at which the external pressure is applied.

Boiling point refers to the temperature at which pure substances boil at 1 standard atmospheric pressure. Different liquids have different boiling points. The boiling point changes with the change of external pressure, and the pressure is low, so is the boiling point.

When the liquid boils, the saturated vapor pressure in the bubbles formed inside it must be equal to the external pressure, so the bubbles can grow and rise. So the boiling point is the temperature when the saturated vapor pressure of the liquid is equal to the external pressure. The boiling point of a liquid is related to the external pressure.

When the pressure on a liquid increases, its boiling point rises; When the pressure decreases; Boiling point decreases.

References:

Baidu encyclopedia-boiling heat exchange