[Physics] Does tea made with boiling water cool faster than tea made with boiled (but still hot) water

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I always make tea with boiling water – not water that is almost boiling, not water that has boiled and stopped boiling a few seconds earlier – in my opinion, for the best tea flavour the water must be boiling as it comes out of the kettle into the pot (or cup).

My wife is not so obsessive, and will often leave the kettle to switch itself off, then, after as long as a minute, pour the water onto the tea (she does admit that tea made by me is far superior to the tea she makes).
Anyway, I've found that tea made by be (boiling water) cools to a drinkable temperature faster than tea made by her (boiled, then very slightly cooled water). But that seems scientifically impossible – or could it be explained in the same way that warm water freezes (when put in a domestic freezer) quicker than cold water? Just clutching at physics straws here!

Maybe the whole thing is my imagination.

Best Answer

There is a reasonable chance that your tea is cooling faster.

This is somewhat counter-intuitive, but it's because the only variable here isn't the temperature.

Evaporation is also very important in the cooling of the tea. The kettle probably has much less available area to release the steam, so the air above is saturated. This will lead to a much slower rate of evaporation, compared to when the boiling water is exposed to open dry air. This would mean if you poured the same amount of water into each tea, yours would lose more mass through evaporation which could be the deciding factor.

The rate of evaporation depends on the surface area and vapour saturation in the air. A kettle has a small opening to exchange it's saturated air with the surroundings, while the open cup can easily move away the saturated air through natural convective currents and new fresh air can come in to take it's place.

If you put some sort of loose covering on your cup that emulated a kettle while it cools for the first few seconds (be careful to make sure steam can still get out, just not as easily) you should see it remain quite a bit warmer.

Edit: Adjusted the answer to reflect brought up in Vectorjohn's answer. I was getting too invested into evaporation and lost track of why I brought it up in the first place. It changes the mass of the tea you have to cool if you pour both to the same level.