A metal piece of thermal capacity 40 JK-1, absorbs 800 J of heat. Calculate the rise in the temperature of this metal piece.
Topic: Thermal capacity
Answer
Given: thermal capacity C = 40 J K⁻¹, heat absorbed Q = 800 J
Thermal capacity is the heat needed to raise the temperature by 1 K: C = Q ÷ ΔT
Rearranging: ΔT = Q ÷ C = 800 ÷ 40 = 20 K
Rise in temperature = 20 K (a rise of 20 °C)
Because thermal capacity already includes the mass of the object, you need neither the mass nor the specific heat capacity here — and neither is given, which is the clue.
Divide, do not multiply: 800 × 40 = 32 000 is not a temperature. Check with the units — joules divided by joules per kelvin leaves kelvin ✓.
A RISE of 20 K is the same as a rise of 20 °C, because the two scales have degrees of the same size. They differ only in where zero sits, and a difference of temperature is unaffected by that.