Physics Think and Solve

Question

Part A

The specific heat capacity of steel is 450 J/kg⋅∘C. Find the amount of heat that is needed to raise the temperature of a 14-kg piece of steel from 0 ∘C to 80 ∘C.

Part B

How does this compare with the heat needed to raise the temperature of the same mass of water through the same temperature difference? (For water, c = 4190 J/kg⋅∘C.)

Answer 1

A) Q = mC∆T

Q = heat

m = mass = 14 kg

C = sp. heat = 450 J/kgºC

∆T = 80 - 0 = 80º

Solve equation: Q = (14 kg)(450 J/kgºC)(80º) = answer in joules

B) You can either re-do the calculation using 4190 in place of 450, or you can reason that since it takes much more energy to raise 1 kg water by 1 degree(4190 J/kg/degree vs 450 J/kg/degree), it will take more heat to raise the temperature of the same mass of water through the same temperature difference. In fact it will take 9.3 times as much heat (4190/450).