Received from William \"Chops\" Westfield at 09/25/11 05:17 UTC:

>On Sep 24, 2011, at 8:07 PM, Jim Higgins wrote:
>
> > rate of heat loss is a function of temperature difference.
>
>Also, the milk in cup A essentially gets to warm up for two minutes, while=
=20
>the milk added to cup B stayed cold (by magic, I guess.)
>
>BillW


The rate of temperature change will be proportional to the difference betwe=
en=20
substance temperature and room temperature.

Using typical temperatures...

Cold Milk       2C
Tea Black       90C
Tea Green       75C
Room Temp       25C

Tastes vary as to the amount of milk to add.  (I prefer none.)  Let's assum=
e=20
25% milk.

Black Tea + Milk        68C
Green Tea + Milk        57C

Delta T vs room temp

Cold Milk       23C

Tea Black       65C
Black Tea + Milk        43C

Tea Green       50C
Green Tea + Milk        32C


Hot tea has a larger delta T vs room temp than the milk or the milk/tea=20
mixture, so it will lose heat faster than the mixtures and the cold milk wi=
ll=20
absorb heat slower than the hot tea loses heat.

The result is that cup B is cooler after final addition of milk.

Jim H=20


--=20
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