Question

why hot water became cold after some time and cold water became hot after some time?​

Answer 1

Answer:

Evaporation. One explanation of the effect is that as the hot water cools, it loses mass to evaporation. With less mass, the liquid has to lose less heat to cool, and so it cools faster. With this explanation, the hot water freezes first, but only because there's less of it to freeze.

Explanation:

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Answer 2

Answer:

Because it takes cold water some time to reach the temperature of hot water, cold water clearly takes longer to boil than hot water does. ... When water is hotter than 80 degrees C, the rate of cooling by rapid vaporization is very high because each evaporating gram draws at least 540 calories from the water left behind.