4 ms·
But cooling rate is proportional to the temperature difference (see Newton's law of cooling). Thus the hotter water may start cooling faster, once it reaches th
by muti 6y ago
But cooling rate is proportional to the temperature difference (see Newton's law of cooling). Thus the hotter water may start cooling faster, once it reaches the initial temperature of the cooler water, it would cool at the same rate as the cooler water did initially. It then couldn't possibly reach freezing point earlier.
But in some conditions it does, which is the surprising result.
- sliken 6y agoHot water freezing faster in an ice cube tray is commonly reported, a bunch of reasons could explain it. Evaporation can reduce the volume of water, and the smaller volume freezes faster. A hot tray will settle into any ice build up in the freezer (which is common) increasing the rate of heat exchange. Hot water will create currents in the air and water (driven by the higher water temperature) which help the exchange. On the flip side lower temperature differences will often cause a stagnant layer that will reduce the temp exchange, much like sitting in a cold pool which gets better if you want a few seconds... until you move again. The reported experiment reduces the variables by using glass instead of water, so there's no internal flow, but that doesn't stop the airflows generated in the air.