Question

A 500 g teapot and an insulated thermos are in a `20^(@)`C room. The teapot is filled with 1000 g of the boiling water. 12 tea bags are then placed into the teapot. The brewed tea is allowed to cool to `80^(@)`C, then 250 g of the tea is poured from the teapot into the thermos. The teapot is then kept on an insulated warmer that transfers 500 `cal//min` to the tea. Assume that the specific heat of brewed tea is the same as that of pure water, and that the tea bags have a very small mass compared to that of the water, and a negligible effect on the temperature. The specific heat of teapot is `0.17 J//g` K and that of water is `4.18 J//g` K. The entire procedure is done under atmospheric pressure. There are `4.18` J in one calorie.
An alternative method for keeping the tea hot would be, to place the teapot on a 10 pound block that has been heated in an oven to `300^(@)`C. A block of which of the following substances would best be able to keep the tea hot?
A. copper (specific heat `=0.39 J//gK)`
B. granite (specific heat`=0.79 J//gK)`
C. iron (specific heat `=0.45 J//g K)`
D. pewter (specific heat `=0.17 J//g K)`

Answer 1

Correct Answer - B
(a) `250gmxx4.18xx(80-75)=(ms)(75-20)`
`:.(ms)=95 J//k`
(b)Granite (maximum specific heat)
(c) as Rate `=500cal//min.:.5min=2500`cal.
`2500xx4.18=(750xx4.18+500xx0.17)Deltatheta`
Rightarrow `Deltatheta=3.24` final temperature`=83.24^(@)`C