In a pot of almost boiling water – say, 100 degrees – the molecules dance in a heated frenzy. They are livelier than those in a 30 or 50 degree cupful and are thus more apt to jump into the air. Within a few minutes, so many molecules will leave the water that it becomes cooler than the cupful that was cooler to begin with. This is why hotter water, if it is in a vessel with a wide opening, will freeze first. But if opening is narrow, vapor will have a hard time escaping. Evaporation will be inhibited and the cooler water will freeze first.
Many other factors also influence quicker freezing of hotter water. For example, hot water circulates more vigorously than cold. As a result, more of it is brought to the surface, thus speeding the loss of heat to the cool air. Also, the more water that is lost by evaporation, the less that is left behind to freeze.
- Why is steam hotter than the boiling water?
- Which liquid substance boils when it is cold?
- Why does water gurgle when it’s flowing out from a bottle?
- Why sugar dissolves faster in hot water than in cold water?
- Why hot water appears milky white when drawn from the faucet?