why do hot water pipes freeze more quickly than pipes carrying cold water?

Answer 1

The definition of freezing is that they reach 0C, not that they turn to a solid, that is a separate step. Hot water pipes and cold water pipes, both in an identical freezing environment will cool down at different rates because the higher the temperature gradient or difference, the faster the rate of cooling. So hot water will cool faster to 0 than cold water, although cold water will form ice faster since overall it requires less heat overall to be removed to freeze.
Note that practically the hot pipe will take longer to freeze solid since there simply needs to be more energy removed to get the solid. This question is normally asked theoretically to demonstrate (or trick a student) to teach the lesson about how larger temperature gradient have a higher cooling speed relative to the lower temperature gradient. It depends on the reason for asking this question.

Note that the Mpemba effect, while it has been observed, is only under specific experimental conditions and is far from a general phenomenon and not general enough to effect the average set of pipes in the average house basement.

Answer 2

This is false. Cold water pipes freeze faster. One could think of exceptions to this rule, eg. if water was running through the cold water pipe, but still in the hot water pipe, then the hot water pipe may freeze faster.

Answer 3

This is due to evaporation cooling,just as overhead tank water is colder in summer than in winter.However the question i feel should read warm water pipes than hot water pipes

Answer 4

Because heating water precipitates out solutes such as calcium and magnesium bicarbonate. Water that has never been heated still contains these solutes, as it freezes ice crystals form and the concentration of these solutes becomes increasingly higher. This lowers the freezing point of the water, it has to cool further before it freezes, meaning it takes longer to freeze. Hot water does not contain as much of these solutes and therefore will freeze faster.

Answer 5

In Science class years ago, I was told that a bucket of warm water would freeze more quickly than a bucket of cold water. It has something to do with the speed and distance of the molecules when they are heated. Supposedly they are more easily frozen when warm.

Answer 6

Because, hot water cools faster. It sounds weird, but it is logical.

Hot water has nothing to do but get cold, while cold water needs to warm up in order to get colder.

It's called the Mpemba effect.

Answer 7

They don't. If you look at it logically, the hot water has to lose more heat than cold water. This will take more time.

Answer 8

I have a theory, since the hot water is much hoter than the surrounding air, then the difference of the temps between the metal (which is really hot) and the surrounding air (which is alot cooler) makes the metal seem colder. (hoter temp) - (colder temp) = (differnce) (air temp) - (difference)= temp you feel