Chemistry - specific temp

Question

How much will the temperature of a cup (180 g) of coffee at 95 °C be reduced when a 45 g silver spoon (specific heat 0.24 J/g °C) at 25 °C is placed in the coffee and the two are allowed to reach the same temperature? Assume that the coffee has the same density and specific heat as water.

Answer 1

So Nadia B., set up your equation for heat transfer between the various items. Heat flow = mass*temp_change*specific_heat of each item

Since you don't KNOW the final temperature, you have to put that in as an unknown (a variable, call it T_f . So the heat loss of the coffee = the heat gain of the spoon, since as you know heat does not escape your cup (unless it runneth over, but that's a different metaphor).

Solve for T_f !

--Cheers, --Mr. d.

-- P.S. The only exception to solving as heat loss = heat gain in this way, might be if you had an external uncontrolled heat source, such as if you did this experiment with an empty dish containing the spoon, in a microwave of the type "Never operate this microwave without a wet item inside!". Then it might truly be a case of "the dish ran away with the spoon (thermally)". Also burns out the magnetron of the microwave!