Which one is hotter?

Question

(a)how many joules are required to heat 100. g copper (s=0.389 J/g×K) from 10.℃ to 100.℃?

(b)The same quantity of the heat as in (a) is added to 100.g of aluminum (s=0.908 J/g×K) at 100.℃. Which gets hotter, the copper of aluminum?

I know how to do (a), but i am confused with (b).

someone please help me...T__T

Answer 1

You know how to do a, that's good.  You do the reverse in b.  In A, you used the temperature difference times the mass, times the heat capacity, to get the heat input in joules.

In b, you could take the heat in joules (the amount you calculated in A) and divide by the new heat capacity of aluminum (joules/(joules/g*K) = g*K) and then divide by the mass to get the temperature difference.

OR  you can look at the   heat capacities and say: " the heat capacity of aluminum is higher, and the amount of heat and the masses of the two samples are the same.  Since it takes more heat to change aluminum's temperature, copper will be hotter".    And you don't have to calculate a thing.  

Answer 2

(a)how many joules are required to heat 100. g copper (s=0.389 J/g×K) from 10.℃ to 100.℃?

dH = m C dT

dH = 100g (0.389)(90)

dH = 3501 Joules

your answer is(3sigfigs): 3.50e2 joules

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(b)The same quantity of the heat as in (a) is added to 100.g of aluminum (s=0.908 J/g×K) at 100.℃. Which gets hotter, the copper of aluminum?

copper is hotter, it takes .908/.389 =  2.33 times as much heat to get Al to the same hotter temp as it does Cu